Optic electronic devices and methods for optical epicardial pacing

Abstract

The present disclosure relates to optoelectronic devices and methods for optical epicardial pacing and endoscopic delivery devices and methods for translational photostimulation.

Description

OPTIC ELECTRONIC DEVICES AND METHODS FOR OPTICAL EPICARDIALPACINGGOVERNMENT FUNDING STATEMENT

[0001] This invention was made with government support under 2105321, 2128140, and 2121044 awarded by the National Science Foundation, W91 INF-21-1-0090 awarded by the Army Research Laboratory - Army Research Office, FA9550-20-1-0387 awarded by the Air Force Office of Scientific Research, and EB034289 awarded by the National Institutes of Health. The government has certain rights in the invention.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application Nos. 63 / 601,414, filed November 21, 2023, 63 / 555,582, filed February 20, 2024, and 63 / 564,215, filed March 12, 2024, the disclosures of which are hereby incorporated by reference in their entirety.BACKGROUND OF THE DISCLOSURE

[0003] Random-access bioelectrical modulation, an intrinsic process in cellular and tissue architectures, is essential for precise spatiotemporal regulation in biological systems. For example, retinal photoreceptors and skin mechanoreceptors, when accessed by light and force, elicit localized responses. In cardiac systems, innervation of different areas of the heart modulates the cardiac conduction. Leadless flexible bioelectronics1 3that modulate bioelectrical signaling in a manner similar to the body's own regulatory mechanisms would present new treatment paths for neurodegenerative and cardiac diseases6,7. Optically mediated genetic systems can achieve high spatiotemporal resolution and tunability with random-access capabilities for cellular and tissue stimulation and exploration of multiscale biological processes8,9. For clinical translation, recent non-genetic photodiode-based optoelectronic devices, which convert light into electrical currents, efficiently modulate cells and tissues at optical power levels comparable to those used in optogenetics10 13. Micropatterned pixelated optoelectrodes that enable localized stimulation with high resolution demonstrate significant potential for retinal prosthesis14 , 7.Nonetheless, the translational potential of monolithic photoelectrochemical devices that facilitate random-access biostimulation hinges on clear characterization of the photostimulation responseprofile, in terms of precision, accuracy, and resolution, and applicability in large-brained mammals.

[0004] Biological systems, especially neural systems, exhibit mesoscale bioelectrical heterogeneity. In neuronal networks, individual neurons can generate both current sources and sinks, resulting in a globally charge-balanced network with locally heterogeneous extracellular potentials in the form of dipoles and even n-poles18. Although spatially resolved and controllable charge polarity domains have been reported in faceted crystals19, heterodimers20, and other microfabricated devices, random-access and leadless dipole formation on a monolithic surface has not been demonstrated. At the molecular level, neuronal excitation primarily involves fast sodium inward currents, slow calcium inward currents, and fast or slow potassium currents. These ionic currents are analogous to the photocurrent generated by a photocathode under light illumination, which can be divided into fast capacitive cathodic and anodic currents and long- lasting faradaic currents. Bioelectronics devices designed to mirror the role of the multiscale nervous system are in essence neuromorphic devices21 23. In the development of artificial systems for computing and sensing, neuromorphic systems emulate the structure and functionality of biological neural networks.24 29As such, a random-access device that targets optical (or bioelectrical) stimuli to the epicardial surfaces, or other components of the cardiac conduction system, to modulate activity in a manner analogous to biological regulation can be broadly considered a neuromorphic photoelectrochemical device.

[0005] Photogenerated carriers and their dynamics in photoelectrochemical materials play a crucial role in shaping photocurrent distribution profiles. In solar energy harvesting, singlecrystalline silicon or perovskites30are preferred over their polycrystalline counterparts. Elimination of grain boundary recombination leads to increased carrier lifetimes and, consequently, enhanced collection efficiency.31,32In contrast, random-access photostimulation benefits from tightly confined carrier diffusion.

[0006] Additionally, pacemaker therapy significantly enhances patient well-being and has been linked to lower mortality rates. However, even with considerable advancements, existing pacemaker treatments carry notable risks. Complications with standard endocardial pacing often stem from the implanted leads within veins or issues with the subcutaneous generator pocket. These lead-related issues can result in venous blockages, damage to the heart's tricuspid valve, and infections of the heart's inner lining, which have an associated mortality risk between 12%and 31%. While modern endocardial leadless pacemakers eliminate problems related to leads, they encounter different issues such as complications from the insertion point in the thigh's major vein, challenges in repositioning the device once implanted, and a significant risk of puncturing the heart which can lead to fluid accumulation around the organ. Epicardial pacing, which involves attaching the pacemaker leads to the outside of the heart, is typically reserved for patients who cannot have internal vein access, like growing children or those with specific heart deformities. However, this method is prone to lead failures due to blockage or wire breakage, making it less reliable for consistent dual-chamber pacing.SUMMARY OF THE DISCLOSURE

[0007] As shown and described herein, the present disclosure relates to optic electronic devices and methods for optical epicardial pacing as well as endoscopic delivery devices and methods for translational photostimulation. In an embodiment of the present disclosure, a method for modulating activity of cardiac tissue is disclosed. The method includes contacting a cardiac tissue with a silicon device such that the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate. The method also includes exposing the silicon device to light from a light emitter at a periodic rate to cause activation of the silicon device and simulation of the cardiac tissue such that the silicon device is exposed to light at a particular point on the silicon device to cause the silicon device to induce a current in an area within about 2 millimeters of the particular point.

[0008] In various such embodiments, the silicon substrate comprises a layer of p-type silicon.

[0009] In various such embodiments, the plurality of nanoscale pores are etched into the layer of p-type silicon.

[0010] In various such embodiments, the plurality of nanoscale pores etched into the silicon substrate are created by metal-assisted chemical etching, stain-etching, or a combination of metal-assisted chemical etching and stain-etching.

[0011] In various such embodiments, the combination of metal-assisted chemical etching and stain etching includes submerging the silicon substrate in a solution including silver nitrate such that the solution further includes one or more acids, removing the silver from the silicon substrate by submerging the silicon substrate in nitric acid, and exposing the silicon substrate to oxygen plasma to create the silicon device with the plurality of nanoscale pores etched thereon.

[0012] In various such embodiments, the plurality of nanoscale pores are evenly distributed on the silicon substrate.

[0013] In various such embodiments, each nanoscale pore is between about 1 nm and about 900 nm in width.

[0014] In various such embodiments, the light emitter is configured to emit light at the periodic rate ranging from about 0.5 pulses per second to about 6 pulses per second.

[0015] In various such embodiments, the duration for each light pulse ranges from about 0.5 milliseconds to about 15 milliseconds.

[0016] In various such embodiments, the light emitter is further configured to provide light at a wavelength ranging from about 400 to about 900 nm and at a power ranging from about 1 mW to about 1W.

[0017] In various such embodiments, the light emitter is configured to emit light and not emit light for different time periods.

[0018] In various such embodiments, the silicon device further comprises a supporting substrate such that the supporting substrate comprises poly dimethyl siloxane.

[0019] In various such embodiments, the light emitter is a first light emitter, wherein the system further comprises a second light emitter such that the first light emitter and the second light emitter provide light at different wavelengths.

[0020] In various such embodiments, the silicon device adheres to the cardiac tissue by capillary force.

[0021] In various such embodiments, the silicon device adheres to the cardiac tissue without sutures or adhesives.

[0022] In various such embodiments, the silicon device adheres to the cardiac tissue with sutures or adhesives.

[0023] In various such embodiments, wherein the light emitter is not directly connected to the silicon device.

[0024] In various such embodiments, the cardiac tissue is a heart comprising a left ventricle and a right ventricle.

[0025] In various such embodiments, exposing the silicon device to light causes the silicon device to induce the heart to beat.

[0026] In various such embodiments, the periodic rate is between about 30 beats per minute and about 360 beats per minute.

[0027] In various such embodiments, the silicon device is placed on a left ventricular wall and a right ventricular wall of the heart.

[0028] In various such embodiments, exposing the silicon device to light comprises exposing the silicon device to light at a first wavelength and a second wavelength.

[0029] In various such embodiments, exposing the silicon device to light at the first wavelength causes simulation of the left ventricle.

[0030] In various such embodiments, exposing the silicon device to light at the second wavelength causes simulation of the right ventricle.

[0031] In various such embodiments, the first wavelength is between about 600 nm and about 700 nm and wherein the second wavelength is between about 400 nm and about 500 nm.

[0032] In various such embodiments, simulation of the cardiac tissue induces a calcium influx proximate to the particular point at which the light was directed.

[0033] In various such embodiments, the light has an optical intensity of between about 0.05 mW / mm2 and about 100 mW / mm2.

[0034] In various such embodiments, the area in which current is induced is an effective photostimulation area such that the effective photostimulation area does not exceed 2 millimeters from a light spot center of the light emitted from the light emitter.

[0035] In various such embodiments, a light spot size of the light emitted from the light emitter to the area on the silicon device has a diameter of between about 5 micrometers and about 1000 micrometers.

[0036] In various such embodiments, the silicon substrate comprises a layer of p-type silicon such that the plurality of nanoscale pores are etched into the layer of p-type silicon, each nanoscale pore is between 1 nm and 900 nm in width, and the silicon device further includes a supporting substrate comprising polydimethylsiloxane and a structure that can be coupled with epicardial flexible multielectrode array (MEA) for simultaneous electrical recording during the optical pacing such that exposing the silicon device to light from the light emitter causes the silicon device to send an electric signal to the cardiac tissue.

[0037] In various such embodiments, the structure is an origami or kirigami structure.

[0038] In another embodiment of the present disclosure, a system is disclosed. The system includes a silicon device such that the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate. The system also includes a light emitter configured to emit light at a periodic rate. The system further includes a controller that is operably coupled to the light emitter such the controller comprises one or more processors. The controller is programmed to perform controller operations including: operating the light emitter to provide a plurality of pulses of light at the periodic rate to cause activation of the silicon device and stimulation of cardiac tissue, operating the light emitter to provide a plurality of pulses comprises exposing the silicon device to light at a particular point on the silicon device to cause the silicon device to induce a current at an area within about 2 millimeters of a light spot center of the light emitted from the light emitter.

[0039] In a further embodiment of the present disclosure, a computing device is disclosed. The computing device is configured to carry out a plurality of operations including contacting a cardiac tissue with a silicon device such that the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate and exposing the silicon device to light from a light emitter at a periodic rate to cause activation of the silicon device and simulation of the cardiac tissue such that the silicon device is exposed to light at a particular point on the silicon device to cause the silicon device to induce a current at an area within about 2 millimeters of a light spot center of the light emitted from the light emitter.

[0040] In an embodiment of the present disclosure, a porous silicon (Por-Si) device is disclosed. The Por-Si device includes a membrane having a nanoporous semiconductor layer, a nonporous semiconductor layer that form a heterojunction, and a flexible substrate comprising one or more polymers such that the flexible substrate is in contact with the nonporous semiconductor layer.

[0041] In various such embodiments, the Por-Si device is fabricated by stain etching.

[0042] In various such embodiments, the Por-Si device is passivated with TiO2 after the stain etching.

[0043] In various such embodiments, the TiO2 has a thickness between about 1 nm and about 50 nm.

[0044] In various such embodiments, the Por-Si device is fabricated by silver-assisted porosification.

[0045] In various such embodiments, the Por-Si device is passivated with TiO2 after the silver- assisted porosification.

[0046] In various such embodiments, the TiO2 has a thickness between about 1 nm and about 50 nm.

[0047] In various such embodiments, the Por-Si device is fabricated by metal-assisted chemical etching (MACE).

[0048] In various such embodiments, the Por-Si device is passivated with TiO2 after the MACE.

[0049] In various such embodiments, the TiO2 has a thickness between about 1 nm and about 50 nm.

[0050] In another embodiment of the present disclosure, a delivery device is disclosed. The delivery device includes a catheter body comprising a delivery end, an interior retention space within a portion of the catheter body such that the interior retention space is configured to receive a silicon device prior to use of the delivery device, and a plurality of deployable arms within the catheter body and surrounding the interior retention space such that the plurality of deployable arms are configured to extend from the delivery end of the catheter body and flare in an outward direction to deliver the silicon device during use of the delivery device.

[0051] In a further embodiment of the present disclosure, a method is disclosed. The method includes introducing a delivery device into a small incision in a target body such that the delivery device includes a catheter body comprising a delivery end, an interior retention space within a portion of the catheter body, such that the interior retention space is configured to receive a silicon device prior to use of the delivery device and the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate, and a plurality of deployable arms within the catheter body and surrounding the interior retention space. The method includes deploying the silicon device from the interior retention space of the delivery device via the plurality of deployable arms of the delivery device. The method includes placing, by the deploy able arms of the delivery device, the silicon device on an epicardial surface within the target body. The method includes retracting the delivery device through the small incision.

[0052] In various such embodiments, deploying the silicon device from the interior retention space of the delivery device via the plurality of deployable arms of the delivery device furtherincludes radial extension of the plurality of deployable arms from the delivery end of the catheter body of the delivery device to deploy the silicon device in preparation for placement.

[0053] In various such embodiments, the method includes introducing an optical fibre-coupled endoscope into the small incision, illuminating, via the optical fibre-coupled endoscope, a portion of the silicon device, and stimulating, via the silicon device, a desired site on the epicardial surface.

[0054] In various such embodiments, illuminating, via the optical fibre-coupled endoscope, the portion of the silicon device comprises exposing the silicon device to light from a light emitter of the optical fibre-coupled endoscope at a periodic rate to cause activation of the silicon device.

[0055] In various such embodiments, the target body is an animal.

[0056] In various such embodiments, the animal is a mammal.

[0057] In various such embodiments, the mammal is a human.BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figures 1 A-1E depict neuromorphic photoelectrochemical devices with multiscale biomimetic designs facilitate random-access and multiscale photostimulation.

[0059] Figures 2A-2I depict spatiotemporal evaluation of device precision, accuracy, resolution, and kinetics.

[0060] Figures 3A-3T depict random-access in vitro, ex vivo, and in vivo photostimulation in multiscale cardiac systems.

[0061] Figures 4A-4J depict translational photostimulation on a live pig heart.

[0062] Figure 5 depicts a table of devices and optical systems used for biological experiments.

[0063] Figures 6A-6D depict fabrication and imaging of multiscale silicon-based photoelectrochemical devices.

[0064] Figures 7A-7D depict the physicochemical process with photocurrent generation upon localized light illumination on a photoelectrochemical device.

[0065] Figures 8A-8C depict three methods were presented to fabricate Por-Si.

[0066] Figures 9A-9C depict representative photocurrent transient measured on four Si-based devices.

[0067] Figure 10 depicts graphs assessing photocurrent stability in 1000-cycle continuous measurements.

[0068] Figures 1 1 A-l 1C depict assessing photocurrent accuracy, precision, and localization in patch-clamp measurement setup

[0069] Figure 12 depicts a plot of photocurrent magnitudes bar graph measured on the edge, center and comer positions of the four Si-based devices.

[0070] Figure 13 depicts SEM images of the PIN-Si (Au) at center, edge and corner locations.

[0071] Figure 14 depicts photocurrent heatmaps measured under corner illumination display varied outcomes.

[0072] Figure 15 depicts 81 normalized photocurrent traces measured under edge illumination for sPN-Si.

[0073] Figure 16 depicts 81 normalized photocurrent traces measured under edge illumination for PIN-Si.

[0074] Figure 17 depicts 81 normalized photocurrent traces measured under edge illumination for PIN-Si (Au).

[0075] Figure 18 depicts 81 normalized photocurrent traces measured under edge illumination for Por-Si.

[0076] Figure 19 depicts 81 normalized photocurrent traces measured under corner illumination for sPN-Si.

[0077] Figure 20 depicts 81 normalized photocurrent traces measured under corner illumination for PIN-Si.

[0078] Figure 21 depicts 81 normalized photocurrent traces measured under corner illumination for PIN- Si (Au).

[0079] Figure 22 depicts 81 normalized photocurrent traces measured under corner illumination for Por-Si.

[0080] Figure 23 depicts 81 normalized photocurrent traces measured under center illumination for sPN-Si.

[0081] Figure 24 depicts 81 normalized photocurrent traces measured under center illumination for PIN-Si.

[0082] Figure 25 depicts 81 normalized photocurrent traces measured under center illumination for PIN- Si (Au).

[0083] Figure 26 depicts 81 normalized photocurrent traces measured under center illumination for Por-Si.

[0084] Figure 27 depicts photocurrent localization profiles and photocurrents at full width at half maximum (FWHM) for four distinct silicon-based devices under illumination with varying spot sizes

[0085] Figure 28 depicts the proportion of cathodic sites on the silicon-based devices under corner illumination

[0086] Figures 29A-29C depict spatiotemporal mapping of photocurrents with time-resolved heatmaps.

[0087] Figure 30 depicts cardiomyocytes stimulation using a monolithic device.

[0088] Figure 31 depicts photocurrent characterization and ex vivo heart pacing proof-of- concept using various monolithic silicon (Si)-membrane devices with a 5 mm x 5 mm membrane size.

[0089] Figure 32 depicts an investigation of Por-Si device size for photocurrent and ex vivo heart stimulation.

[0090] Figure 33 depicts AutoCAD design schematics of the 16-channel MEA for use in ex vivo heart electrical signal recordings.

[0091] Figure 34 depicts an experimental design for a bidirectional investigation of randomaccess ex vivo rat heart photostimulation.

[0092] Figure 35 depicts in vivo rat heart pacing under 1.22 mW / mm2 pulsed illumination intensity.

[0093] Figure 36 depicts in vivo mouse heart pacing.

[0094] Figure 37 depicts histology images for Por-Si membranes implanted in the subcutaneous region of mice for 7 days.

[0095] Figure 38 depicts a monolithic Por-Si device demonstrated the ability to pace the right ventricle (RV), left ventricle (LV), and biventricular (BiV) regions.

[0096] Figure 39 depicts design and implementation of a 30-channel MEA for recording and analyzing electrical signals obtained from various sites on the epicardial surface.

[0097] Figure 40 depicts representative ECG traces obtained from the 30-channel MEA display pig heart activity both with and without pacing.

[0098] Figure 41 depicts an assessment of ECG peak delays in longitudinal and transversal directions with and without pacing.

[0099] Figures 42A-42F depict AutoCAD design schematics for various monolithic Si devices used in biological experiments.

[0100] Figure 43 depicts BET adsorption-desorption experiments disclose a mesoporous type IV material property for porous-Si particles.

[0101] Figures 44A-44E depict a minimally invasive approach for closed-thoracic modulation.

[0102] Figures 45A-45C depict a design of the minimally invasive device delivery system.

[0103] Figure 46 depicts an advanced catheter-like device designs for Si membrane delivery, microsurgeries, and optical pacing platforms.

[0104] Figures 47A-47I depicts optoelectronic membrane devices with various sizes and designs.

[0105] Figures 48A-48H depicts multisite in vivo pig heart pacing.DETAILED DESCRIPTION

[0106] All publications, including but not limited to patents and patent applications, cited in this specification are herein incorporated by reference as though set forth in their entirety in the present application.

[0107] As utilized in accordance with the present disclosure, unless otherwise indicated, all technical and scientific terms shall be understood to have the meaning commonly understood by one of ordinary skill in the art. Unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular.

[0108] Throughout this specification, unless the context specifically indicates otherwise, the terms “comprise” and “include” and variations thereof (e.g., “comprises,” “comprising,” “includes,” and “including”) will be understood to indicate the inclusion of a stated component, feature, element, or step or group of components, features, elements or steps but not the exclusion of any other component, feature, element, or step or group of components, features, elements, or steps. Any of the terms “comprising,” “consisting essentially of,” and “consisting of’ may be replaced with either of the other two terms, while retaining their ordinary meanings.

[0109] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise.

[0110] In some embodiments, percentages disclosed herein can vary in amount by ±10, 20, or 30% from values disclosed and remain within the scope of the contemplated disclosure.[0U1] Unless otherwise indicated or otherwise evident from the context and understanding of one of ordinary skill in the art, values herein that are expressed as ranges can assume any specific value or sub-range within the stated ranges in different embodiments of the disclosure, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise.

[0112] As used herein, ranges and amounts can be expressed as “about” a particular value or range. About also includes the exact amount. For example, “about 5%” means “about 5%” and also “5% .” The term “about” can also refer to ± 10% of a given value or range of values. Therefore, about 5% also means 4.5% - 5.5%, for example.

[0113] As used herein, the terms “or” and “and / or” are utilized to describe multiple components in combination or exclusive of one another. For example, “x, y, and / or z” can refer to “x” alone, “y” alone, “z” alone, “x, y, and z,” “(x and y) or z,” “x or (y and z),” or “x or y or z.”I. OVERVIEW

[0114] In general, the present disclosure relates to optic electronic devices and methods for optical epicardial pacing. In addition, also contemplated herein are endoscopic delivery devices for such optic electronic devices and methods for translational photostimulation. Additional aspects of the present disclosure are discussed below.

[0115] Electrode-based electrical stimulation underpins several clinical bioelectronic devices, including deep brain stimulators and cardiac pacemakers. Random-access, a feature of high- fidelity and efficient regulation in biological systems, however, is limited even in high-density electrode arrays due to persistent spatial access constraints. Optogenetics provides optically controlled random accesses with high-spatiotemporal capabilities, but its clinical application poses challenges.

[0116] Random-access photostimulation of cardiac systems using a non-genetic neuromorphic platform based on semiconductor-enabled biomodulation interfaces is disclosed herein. Through spatiotemporal profiling of photoelectrochemical currents, the precision, accuracy, and resolution of photostimulation in four leadless silicon-based monolithic photoelectrochemical devices isassessed. The random-access capabilities of the neuromorphic system(s) via optical overdrive pacing of cultured cardiomyocytes targeting multiple regions and spatial extents, isolated rat hearts within a Langendorff apparatus, and rat hearts in an in vivo ischemia model are discussed. To demonstrate cardiac control under clinical conditions, the first optical pacing of a pig heart in vivo was performed. The results indicate the clinical potential of the leadless, lightweight, random-access photostimulation platform as, for example, a cardiac pacemaker in cardiac resynchronization therapy, where lead-placement complications are common.II. THE MONOLITHIC SILICON DEVICE AND ASSOCIATED METHODS

[0117] In some embodiments, a monolithic silicon device for random access, multisite and multiscale translational photostimulation applications is disclosed.

[0118] Many suitable flexible substrates are known in the art. In certain embodiments as otherwise described herein, the flexible substrate comprises one or more polymers, and the one or more polymers is selected from a biocompatible polymer, a biodegradable polymer, an extracellular matrix protein, and a combination thereof. For example, in some embodiments, the polymer is polydimethylsiloxane, poly(methyl methacrylate), polylactic-co-glycolic acid, poly(ethylene glycol) diacrylate, collagen, or gelatin (e.g., is polymethylsiloxane). In particular embodiments, the flexible substrate comprises poly dimethyl siloxane, or is a polydimethylsiloxane substrate.

[0119] In some embodiments, the flexible substrate may be porous. In certain embodiments, the flexible substrate has an open porosity of at least about 10%. For example, the flexible substrate has an open porosity of at least about 20%, or 30%, or 40%, or 45%, or 50%, or 55%, or even 60%. In various embodiments, the flexible substrate has an open porosity of no more than 80%, or no more than 75%. In some embodiments as otherwise described herein, the nanoporous semiconductor layer comprises pores having cavities and / or channels. In other embodiments, the flexible substrate is non-porous.

[0120] To demonstrate the utility of such materials in optically induced biomodulation, ex vivo heart pacing and in vivo sciatic nerve stimulation were performed. Flexible crystalline silicon membranes were fabricated that transduce light pulses with low optical densities to allow overdrive heart pacing and nerve bundle activation leading to skeletal muscle contraction. It isbelieved that this new class of pure-silicon optical biological modulator may have therapeutic applications, such as cardiac pacing and peripheral nerve regeneration.

[0121] The nanoporous semiconductor layer can be prepared from any suitable semiconductor material, including purified silicon. Silicon, such as silicon wafer or silicon-on- insulator wafer, is widely available commercially, for example from Nova Electronic Materials (Flower Mound, TX, USA). In various embodiments, the silicon is p-type silicon.

[0122] It has been surprisingly determined that nanoporous semiconductor layers afford enhanced photocurrents which can be effectively used in various modes of biomodulation. Accordingly, in certain embodiments as otherwise describe herein, the nanoporous semiconductor layer is mesoporous, wherein the nanoporous semiconductor layer has a pore size in the range of 2 nm to 50 nm, for example in the range of 1 nm to 25 nm, usually 2 to 10 nm.

[0123] The nanoporous semiconductor layer as otherwise described herein can be provided in a variety of suitable thicknesses according to the device characteristics. In certain embodiments as otherwise described herein, the nanoporous semiconductor layer has an average thickness in a range of about 500 nm to 3 pm, for example in the range of 700 nm to 1.5 pm, or in the range of 800 nm to 1.2 pm, or in a thickness of about 1 pm.

[0124] As described herein, nanoporous semiconductor may be prepared according to various methods. Three fabrication techniques, as described below, significantly broaden the functional and structural range of manufacturing porous silicon (Por-Si), thereby enhancing the versatility and performance of Por-Si-based devices and optimizing optical properties for biomedical applications. After the formation of the nanoporous and nonporous semiconductor, the semiconductor wafer may be joined with the flexible substrate. For example, in the semiconductor wafer way be pressed onto a pre-formed substrate, or the substrate may be cast onto the semiconductor wafer. In particular embodiments, PDMS substrate is cast on the semiconductor wafer. Other methods of substrate formation will be apparent to a person of skill in the art in light of the disclosure herein.Fabrication1. Stain Etching

[0125] This method employs nitric acid (HNOs) as an oxidizing agent to drive the oxidation of silicon, followed by hydrofluoric acid (HF) to dissolve the oxidized layer. This dual action results in the formation of nanoscale pores within the silicon substrate, generating a porousarchitecture that can be finely tuned by adjusting etching parameters. Such nanoscale porosity is essential for applications requiring high surface area, precise control of light interaction, and compatibility with biological environments.2. Silver-Assisted Porosification

[0126] By introducing silver nitrate (AgNCh) into the etching process, silver nanoparticles are formed continuously on the silicon surface, which act as catalytic sites for porosification. This process gives rise to hierarchical porous structures, significantly enhancing light absorption — a phenomenon commonly referred to as "black silicon" due to its high optical absorbance. This structure is especially valuable for applications in optoelectronics and photobiomodulation, where efficient light capture and delivery are critical.3. Metal-Assisted Chemical Etching (MACE)

[0127] In this method, silver nanoparticles are strategically deposited on the silicon surface to define specific etching locations. Subsequent etching in an HF and hydrogen peroxide (H2O2) solution leads to the formation of complex, hierarchical porous structures that combine Ag- catalyzed pores with those created by HF / H2O2. This approach produces a robust form of black silicon with multi-scale porosity, optimizing the material for both light absorption and enhanced surface interactions.Passivation

[0128] To improve the stability and longevity of Por-Si devices, particularly for biological applications, passivation using atomic-layer deposition (ALD) of titanium dioxide (TiCh) is possible. This passivation layer significantly enhances the in vitro stability of Por-Si devices for biological applications. The tested passivated devices exhibited sustained functionality, effectively pacing cardiomyocytes for over 48 hours in physiological conditions with comparable optical intensities to fresh, unpassivated samples. Furthermore, the preliminary in vivo data indicates that TiCh-passivated Por-Si devices demonstrate stability for at least six months, a substantial improvement over unpassivated counterparts. This extended durability, facilitated by TiCh passivation, underscores the potential of Por-Si devices in long-term biomedical applications, such as chronic implants for cardiac or neural modulation, where sustained performance and material stability are paramount.

[0129] Through this multi-method fabrication and passivation approach, the development of Por-Si is advanced as a versatile platform for bioelectronic interfaces and other light-sensitive, implantable applications.Por-Si membrane for epicardial surface placement

[0130] As disclosed above, a new class of biocompatible and flexible optoelectronic devices for optical epicardial pacing in vivo is discussed, and the porosity-based heterojunction option has been determined to achieve the best localization upon photostimulation of tissues.

[0131] As the membrane device is placed on the epicardial surface, its position outside the heart without any direct connection to the heart interior eliminates potential risks associated with placement of intravenous cardiac leads, including vein stenosis and lead extraction complications.

[0132] Additionally, the Por-Si membrane devices are capable of stimulating multiple sites with appropriate timing, offering a leadless route to cardiac resynchronization therapy. Optical biointerfaces based on flexible biocompatible / biodegradable semiconductors may launch a new generation of pacemakers.

[0133] The photostimulation tools (semiconductor-based heterojunctions) can be placed at any location on the heart, free of lead -associated limitations, providing a new route to leadless epicardial CRT (or single chamber) pacing and improved treatment in patients with anatomical constraints where intravenous access is limited. By illuminating different spots on the silicon material of the membrane device, achieving random-access, multi-site photostimulation can be completed on-demand. The membrane devices also avoid the scale-up issues affecting existing electrical cardiac pacemakers (with / without leads), as scalable top-down processes for semiconductor fabrication are well established in the semiconductor industry.Device for membrane installation

[0134] In order to install the membrane devices disclosed above, a device for membrane installation also needed to be created.

[0135] Traditionally, open-thoracic surgery is used for implanting functional epicardial devices, often resulting in patient discomfort, post-operative trauma, and prolonged recovery times. Here, a minimally invasive clinical procedure was developed using a custom endoscopic delivery device as described herein, with which closed-thoracic operations and endoscopic optical stimulation were demonstrated. The results indicate clinical potential of the leadless,lightweight, and multi site photostimulation platform as a pacemaker in cardiac resynchronization therapy, where lead-placement complications are common. The disclosed delivery method also extends beyond the optoelectronic membrane discussed deploying a variety of flexible electronics and tissue-regeneration scaffolds.

[0136] A minimally invasive device delivery technique was devised for optical cardiac modulation, using a pig heart model to emulate clinical surgical procedures (Figs. 44A-44B; Figs. 45-46).

[0137] Use of the device requires only a small incision, 0.5-1 cm in diameter between two ribs (Fig. 44A, left). This approach avoids invasive cutting and spreading of ribs and associated postoperative trauma. Before device insertion, a microsurgical procedure exposes a diminutive window (1.5 - 2 cm) on the pericardium. The delivery device catheter is introduced by the means of the incision, enabling unrolling and secure placement of the Si membrane device on the epicardial surface (Fig. 44C).

[0138] Once the delivery device is retracted, an optical fibre-coupled endoscope is introduced through the incision, for visually guided optical stimulation (Fig. 44A, right; Fig. 44D). In a trial, this procedure was proficiently executed, and the entire procedure was completed in a closed- thoracic setting, resulting in the first minimally invasive optical stimulation of an in vivo pig heart (Fig. 44E).

[0139] These findings reinforced the conceptual integrity of the approach, indicating translational potential for minimally invasive cardiac interventions in clinical settings. It is believed that this demonstration of non-genetic optoelectronic heart pacing in a pig and the minimally invasive operation lays the groundwork for translational semiconductor-based photostimulation.

[0140] Furthermore, the total weight of the pacemaker devices, as disclosed, including the polymeric substrates used to support the Si membranes, is 2-3 orders of magnitude lower than that of conventional pacemaker devices and, therefore, therapeutically advantageous to enhancing patient outcome.Multisite in vivo pig heart stimulation

[0141] The minimally-invasive delivery tool allows the deployment of the optoelectronic membrane devices with various sizes and designs (Fig. 4).

[0142] Here, the large-sized device (9.6 mm x 79.6 mm) secured on epicardial surfaces spanning different regions for multisite pig heart stimulation (Fig. 48) is shown. When the device is placed between the left and right ventricle, during multisite pacing over different sites of the device (Fig. 48A, pl-p9), the recorded surface ECG waveforms reflect a gradient shift in muscle-activation sequences from the right to the left ventricle (Fig. 48B). Biventricular pacing can be exemplified by concurrently focusing two light beams on separate points on the left and right ventricles (Fig. 48B, pl + p9). Comparable spatial control over cardiac activation in other regions of the heart surface are shown in Figs. 48C-48H.Minimally invasive delivery device fabrication

[0143] Delivery tubes and substrates (Fig. 45) are designed using AutoCAD 2023. The delivery tubes were fabricated with the Creality Halot-One Resin 3D Printer and then cured for 10 minutes using the Creality UW-01 Washing & Curing Machine. For the delivery substrates, we utilized the Universal Laser Cutter VLS4.60 to shape them from a 100 pm PET sheet. The Si membrane was attached to the PET substrate using a combination of double-sided tape and a water-soluble tape from 3Q. Before deployment, the Si membrane device was kept in a rolled configuration.Closed-thoracic in vivo pig heart stimulation

[0144] A sheep cadaver model was first used to validate the feasibility of the device delivery protocol, as shown in Fig. 44C. The device was smoothly deployed on the non-beating sheep heart. In the in vivo pig heart experiment, an adult female pig was thoroughly anesthetized and prepped in a manner consistent with the open-thoracic in vivo pacing procedure. An incision was made between the 3rd and 4th or the 4th and 5th intercostal spaces using a surgical electroceutical pen to access the heart ventricle. Using surgical scissors, a small window (1.5 - 2 cm) was created in the pericardium. An endoscope could be introduced to assist with the procedure. The delivery device was then inserted through the incision until the beat of the ventricle was felt. This was followed by the injection of the rolled Si membrane, ensuring it formed a conformal contact with the ventricle. The natural fluid on the heart surface provided adequate moisture for device release. Alternatively, saline solution could be introduced via the tube to aid in adhesive dissolution. Once the Si membrane device was attached to the heart ventricle, the delivery device was removed. A 0.5 mm commercial PMMA fiber optics-coupled endoscope (Oiiwak) was then introduced for visually guided photostimulation. The surface ECGrecorded with commercial adhesive electrode pad through Intantech RHD2216-chip head stage. Signal recordings were collected at a sampling rate of 2 kS s-1 within a frequency bandwidth of 0.6-100 Hz.Further considerations towards minimally-invasive optical pacing in clinical applications

[0145] Safe access to the heart is important. In the current approach to minimally-invasive cardiac pacing tool described herein, an optical fiber needs to be inserted through the catheter to point at the desired location of the heart surface. This technique recognizes the potential complications of interfering with nearby organs, particularly the lungs. To mitigate these risks, the practice incorporates independent lung ventilation. Specifically, it involves deflating the lung on the side where the device is being positioned, coupled with the intentional induction of pneumothorax using a specialized tool. Meanwhile, patients’ stability will be maintained through positive pressure ventilation. Additionally, introducing CO2 gas into the chest cavity serves to displace the diaphragm. The displacement creates a more conducive working space for the minimally invasive procedures, such as the implantation of the device and optical fiber. These procedural steps have been seamlessly integrated into current medical practice, prioritizing procedural safety. Furthermore, integrating this approach into robotic and minimally invasive cardiac surgeries potentially minimizes the risk of injury and maximizes accuracy and precision in accessing the heart.

[0146] Infections need to be prevented. Another concern is the potential infections induced by the existence of the optical fiber. A future endeavor involves the pursuit of biocompatible fiber optics, like those used in the existing ventricular assist devices with reduced diameters. The key to this reduced infection risk lies in their specialized coatings, which are designed to adhere to subcutaneous tissue and skin, thereby safeguarding against infections at the fiber insertion sites. Many ongoing efforts in implantable optical fibers have shown great promise in biomedical applications. Additionally, the miniaturized design of the fiber optic systems makes it feasible to develop a subcutaneously implanted device much smaller than current pacemakers.

[0147] Accurate multisite pacing on the beating heart needs to be considered. The heart’s beating motions may pose certain challenges that limit the light beam’s ability to target precise areas with our current prototypes. The issue can be addressed by the state-of-the-art electroanatomic mapping systems, which facilitate real-time locating within the beating heart. A catheter device, coupled with a laser ablation source, has been used for ablating the source ofarrhythmia with a control accuracy of 5 mm in the beating heart. Integrating the cutting-edge technology with the photostimulation approach, which potentially shares a similar laser system, could enable precise multisite pacing. Furthermore, exploring the potential of augmenting our system with advancements in computer vision and robotic surgery represents a new avenue. These technologies show significant promise in tracking organ movements and targeting specific areas with high precision. Such integration could significantly enhance the device's functionality, enabling it to adapt to the heart's movements in real-time and deliver targeted treatment with accuracy.

[0148] Scar tissue formation and fibrosis also needs to be considered. Scar tissue management in scientific research and clinical settings has been benefited by the development and use of various sealants specifically designed to prevent these complications, through reducing surgical trauma, inflammation and adhesion and promoting hemostasis and tissue healing. These sealants have become a standard practice in addressing such concerns effectively. Furthermore, mild scar formation and adhesion can be beneficial in securing the position of the photostimulation device, alleviating the impact of heart and body movement over time. In case fibrosis envelops the device, which might happen during the lifetime of the implantation, an increased light intensity would be necessary for the successful heart pacing. The current devices, having been optimized with the use of deep-red light (625 - 635 nm), may experience a 10-fold decrease in optical intensity after penetrating a 1 - 2 mm thick tissue. Though higher intensities of deep-red light may be administered, this issue can be alternatively addressed by the use of near-infrared (NIR) light for the enhanced tissue penetration, as demonstrated by the Tian lab in a prior publication. In our present emphasis on acute and short-term cardiac treatments, the applications are particularly suited to specific contexts such as managing postoperative arrhythmias, addressing disruptions in normal heart conduction following catheter ablation, and dealing with urgent cardiac conditions that necessitate immediate surgical intervention. In such scenarios, the likelihood of encountering extensive scarring and fibrosis is minimal.III. DEVELOPMENT OF THE MONOLITHIC SILICON DEVICE AND ASSOCIATED METHODS

[0149] In some embodiments, the spatiotemporal profiles of photocurrent generation and dynamics in four variations of monolithic Si-based photoelectrochemical devices (for example,as shown in Figure 1C) were assessed to delineate random-access capability. Owing to their capacity for multiscale configurations (Fig. ID; Fig. 6), each Si-based monolithic device can interface with a wide array of biological targets. Random-access multiscale cardiac modulation in in vitro cultured neonatal rat cardiomyocytes (CMs) and ex vivo and in vivo rat heart models is discussed. We performed a tissue-penetrating photostimulation experiment in a mouse heart in vivo to illustrate the feasibility of non-invasive stimulation. Finally, we demonstrated cardiac control in a live pig heart experiment under clinical thoracic-opening conditions (Figure IE).

[0150] The neuromorphic photoelectrochemical devices exhibit random-access responses, spatially resolved polarity, and dynamic ionic currents, which replicate the biological neural activation process. Beyond biointerface research, the capacity for random-access manipulation of photoelectrochemical current polarity on a monolithic semiconductor surface will have wide- ranging implications in the domains of energy science and catalysis.

[0151] As noted above, Figures 1A-1E depicts neuromorphic photoelectrochemical devices with multiscale biomimetic designs facilitate random-access and multiscale photostimulation. Figure 1A depicts neuronal processes in biology. As shown in the left panel of Figure 1A, biological systems such as retinal photoreceptors and skin mechanoreceptors elicit randomaccess localized tissue stimulation. Innervation of the heart with autonomic nervous systems (ANS) facilitates cardiac function control at multiple sites. As shown in the middle panel of Figure 1A, a single neuron can act as both a current source and sink. As shown in the right panel of Figure 1 A, in a typical neuron activation, rapid inward sodium current, slow inward calcium current, and rapid outward potassium current contribute to cellular depolarization and repolarization.

[0152] Figure IB depicts material characteristics necessary for neuromorphic photostimulation. In the left panel of Figure IB, high-resolution photostimulation for randomaccess biological modulation is depicted. As shown in the middle panel of Figure IB, spatially resolved polarity enables biomimetic charge balance, allowing cathodic and anodic processes to occur on the same material surface. Further, as shown in the right of Figure IB, biomimetic iontransport processes, comprising fast cathodic (inward), slow faradaic (inward), and fast anodic (outward) processes, are supported.

[0153] Figure 1C depicts junction design and screening for development of random-access neuromorphic photoelectrochemical devices. Scanning electron microscopy images, transmissionelectron microscopy images, and diffraction patterns display representative cross-sections of the four contemplated semiconductor junction structures shown.

[0154] Figure ID depicts embodiments of Silicon (Si)-based photoelectrochemical devices such as those contemplated for use herein. Such can be adapted to have various forms and shapes to interface with diverse biological systems. For instance, in a biological system 100, an Si-based photoelectrochemical device 102 can be disposed on a tissue 104, (for example, an organ), and the light from a light emitter 106 can stimulate a particular point of a Si-based photoelectrochemical device 102 to achieve a clinically relevant result, such as electrical activation of the tissue. Additional contemplated silicon devices that are contemplated for use herein include those described in U.S. Patent Application No. 63 / 282,955, which is incorporated by reference herein.

[0155] Figure IE depicts a contemplated monolithic silicon platform 110 capable of interfacing with multiscale cardiac systems, ranging from a single cardiomyocyte 112 to rodent heart tissues 114 and 116 and large mammalian cardiac systems 118. Multiscale cardiac systems used in this study enable mechanistic studies and proof-of-concept demonstrations and highlight translational potential.

[0156] Figures 2A-2I depict spatiotemporal evaluation of device precision, accuracy, resolution, and kinetics. Figure 2A depicts four distinct semiconductor configurations and their predicted carrier diffusion distances under localized illumination. In single-crystalline PN (sPN- Si), nanocrystalline p-, intrinsic-, n-type (PIN-Si), and gold-decorated PIN (PIN-Si (Au)), the cathodic process is dominated by electrons as majority carriers. In the porosity-based heterojunction (Por-Si), the cathodic process involves minority carriers.

[0157] Figure 2B depicts an analogy between the current intensity distribution in high- resolution photostimulation and light intensity distribution (optical microscopy) in high- resolution imaging. Stimulation emission depletion (STED) and Por-Si-based photostimulation represent two similar depletion-based approaches for surpassing the resolution barrier.

[0158] Figure 2C depicts a precision evaluation that includes 9-point photocurrent measurements at the center, edge, and corner of each device. Smaller variance in the 9-point results indicates more precise random-access photostimulation across different device locations. For instance, silicon device 200 is showing the results for a Spn-Si evaluation, silicon device 210is showing the results for a PIN-Si evaluation, silicon device 220 is showing the results for a PIN-Si (Au) evaluation, and silicon device 230 is showing the results for a Por-Si evaluation.

[0159] In Figure 2D, accuracy is evaluated by mapping the photocurrent profde on the monolithic device to determine photocurrent magnitude and polarity distributions relative to the illumination spot (center). We calculated how accurately photocurrent hotspot aligned with stimulation location. The light gray dot indicates light spot and location. The black cross represents photocurrent maximum. Error (Err) defines the extent to which the photocurrent maximum deviates from the illumination center. Detailed calculations can be found later in the disclosure.

[0160] In Figure 2E, photocurrent resolution can be determined by mapping the normalized photocurrent against the illumination center.

[0161] Figure 2F depicts photocurrent profiles of the four Si-based devices with various spot sizes. Higher resolution signifies more localized photostimulation and a tunable stimulation zone controlled by the light spot size.

[0162] Figure 2G shows the photocurrent profiles under backside and dual-spot illumination. The normalized and absolute photocurrent linear distributions of Por-Si membranes showed good alignment when light was projected from both the front and backside of the sample. The plot indicates no-loss of photocurrent magnitude in the back (rear) illumination scenario (upper right panel). Photocurrent resolution assessment with dual-spot illumination (both with 1 mm spot size) from the backside at varying separation distances showed the emergence of two distinct photocurrent peaks (lower panel), underscoring the high spatial resolution attainable for multisite stimulation. This data also demonstrates that high spatial resolution can be achieved with both topside and backside light illumination.

[0163] In the left panel of Figure 2H, two static heatmaps demonstrating the photocurrent distribution of Por-Si on horizontal and vertical planes are shown. In the right panel of Figure 2H, spatiotemporal mapping of monolithic Por-Si photocurrent with time-resolved heatmaps reveal bipolarity evolution and diffusion during charge (light on) and discharge (light off) when illumination is directed to the device bottom-left corner. The data indicate that the photocurrent is generated within a localized domain around the light illumination spot.

[0164] As noted above, Figure 3A-3T illustrate random-access in vitro ex vivo, and in vivo photostimulation in multiscale cardiac systems. Figure 3 A depicts experimental setup of in vitrocardiomyocyte (CM) photostimulation. CMs were cultured on a glass-bottomed dish and placed on a motorized stage during experiments. A 488 nm excitation wavelength was used for calcium imaging with a 515 nm emission peak. A 635 nm laser was focused through the objective. The active side of the photoelectrochemical Si device interfaces with the CM monolayer and light source. Inset shows fluorescent calcium image of in vitro cultured CMs, where cells were labeled with Ca 520 AM (AAT Bioquest).

[0165] Figure 3B depicts dF / Fplot showing neonatal rat CM optical pacing at 1 Hz (4 mW, 1- ms pulse, 80-pm spot). Inert device: pristine p-type silicon. The cells could be paced with the presence of active devices, but not with inert device or light only. The calcium traces demonstrate the successful achievement of optical pacing.

[0166] Figure 3C depicts a plot of excited cell area after photostimulation with various spot sizes within one frame (83 ms). Statistically significant differences in activated cell area demonstrate highly localized and tunable random-access photostimulation based on laser spot size. N = 8 independent photostimulation locations were evaluated for each laser spot size. Boxes bind the interquartile range (IQR) divided by the median; whiskers extend 1.5 times IQR.

[0167] Figure 3D depicts in vitro pacing of neonatal rat CMs using monolithic silicon devices with addition of drugs. The top panel is the control. Nifedipine is a L-type calcium channel blocker, which decreased the calcium amplitude upon pacing in a dose dependent manner (middle panel). Isoproterenol is a beta-adrenergic agonist which improves contractility and other functions of cardiac systems. It leads to increased calcium amplitude upon pacing (bottom panel). This demonstration suggests that photostimulation using the devices and methods disclosed here can be an effect tool for studying the effects of new (and existing) drugs on cardiac function.

[0168] Figure 3E depicts in vitro pacing of adult rat CMs using monolithic silicon devices at different frequencies, showing the capability of modulating more mature cellular systems. The previously presented data illustrated optical pacing in cultured neonatal cardiomyocytes, which are not fully mature. In contrast, the data shown here involves adult heart cells isolated using a different protocol.

[0169] In Figure 3F, time-resolved dF / F fluorescent images show calcium wave generation and propagation upon stimulation with different spot sizes. A 10 ms laser pulse was appliedimmediately after the 0 ms image. The data demonstrate that the number of cells can be easily controlled by adjusting the illumination area.

[0170] Figure 3G depicts the spatiotemporal activation of CMs by photostimulation visualized by membrane voltage dyes. Using a 4x objective, photostimulation (200 pm spot, 8 mW, 1 ms) was applied immediately after the frame labeled 43 ms” (upper left panel) at various sites (activation points 1-7) indicated by the arrows to achieve spatial activation of the CMs. Cells activated at "0 ms" closely corresponded with the light stimulation site. The spatiotemporal maps further revealed variations in voltage propagation across the CM monolayer based on the excitation locations. The rightmost figures display the activation map, or isochrone, for each activation point.

[0171] Figure 3H depicts the pacing of an ex vivo rat heart using a monolithic silicon membrane at varying optical intensities which illustrates full capture, partial capture, and non-capture. The optical intensities to induce reliable pacing were found to be as low as 0.51 mW / mm2, a value not previously reported. The data illustrate the threshold for photostimulation.

[0172] In Figure 31, an isochrone map (right panel) displays electrical signal activation delay on the ex vivo rat heart upon photostimulation of eight different locations on an open window- structured monolithic Si device (left panel). Random-access photostimulation overrides the heart's electrical conduction. For instance, the system 300 includes a Si device 302 having a base substrate 304, a plurality of nanoscale pores 306 etched into the base substrate, and a plurality of points 308 upon which photostimulation may be targeted.

[0173] Figure 3 J is a photograph of left anterior descending artery (LAD) ligation-induced ventricular ischemia. Figure 3K depicts a plot of ECG waveforms before and after LAD ligation. Acute heart ischemia results in increased heart rate and stronger breathing cycles, indicated by periodic fluctuations of the baseline. Figure 3L depicts optoelectronic pacing on LAD-ligated heart with varying light intensities. Pacing frequency was 6 Hz, and pulse duration was 10 ms. Figure 3M depicts a zoom-in plot showing stable and consistent synchronization at 0.73 mW / mm2in the LAD-ligated heart. Figure 3N depicts photostimulation success rate LAD- ligated heart at different intensities. 100% reliability was achieved for intensities above 0.84 mW / mm2. N = 3 independent rats and devices were used. N > 20 QRS complexes were evaluated per rat per photostimulation intensity. The data demonstrate the successful implementation of optical pacing in a diseased in vivo model.

[0174] Figure 30 depicts that rat heart optoelectronic pacing at 1 .22 mW / mm2for 5 minutes at 10-ms pulse duration (-1800 paced QRS complexes) demonstrated a 100% success rate. The data demonstrated reliable and stable ischemic heart pacing during continuous optical stimulation, and the recordings were obtained from the various points indicated in Figure 3P.

[0175] Figure 3P is a schematic illustration of one potential embodiment how placement of a contemplated device on an animal (e.g., human) heart could be performed and possible laser spot location for random-access epicardial photostimulation. As shown in Figure 3P, a schematic heart with a silicon device installed 310 includes a first laser spot 312, a second laser spot 314, a third laser spot 316, a fourth laser spot 318, and a fifth laser spot 320, upon which random-access epicardial photostimulation can occur.

[0176] Figure 3Q depicts that multi-site photostimulation on the epicardial surface can generate different QRS shapes in the heart, indicating the potential for random-access photostimulation on live human hearts. The recordings were obtained from the various points indicated in Figure 3P.

[0177] Figure 3R is a photograph showing biventricular photostimulation on a single monolithic Si device using two spatially separated laser sources with wavelengths of 635 nm and 473 nm. As shown in Figure 3R, the system 330 includes a silicon device 332 installed on an epicardial surface, and two laser source outputs 334 and 336, respectively, that are output from separated laser sources. In various such embodiments, the laser source with a wavelength of 635 nm is a first light emitter and the laser source with a second wavelength of 473 nm is a second light emitter. In most cases, only one beam of light is necessary, and a use can choose between the first light emitter and the second light emitter for the desired application.

[0178] In Figure 3S, ECG traces show biventricular pacing upon simultaneous optoelectronic pacing on left and right ventricles.

[0179] Figure 3T depicts a comparison of QRS durations among sinus rhythm and various pacing conditions. N = 10 QRS durations were evaluated for each condition. Boxes bind the IQR divided by the median; whiskers extend 1.5 times IQR. Statistics are calculated using two-tailed independent samples t-test. n.s. > 0.05. ****p < 0.0001.

[0180] As noted above, Figure 4A-4J illustrate devices and methods for translational photostimulation on a live pig heart. It is believed that such devices and methods are application to other animals, such as humans. Figure 4A depicts a schematic illustration 400 of an adult pig (-100 kg) 402 in an open-thoracic cardiac pacing experiment. Setup includes a health-monitoring station 414, an anesthesia ventilation system 416, a workstation 404 controlling the laser source 406, which is connected by a connection 410, and a recording hub connected 408 to an epicardial flexible multielectrode array (MEA, not shown) by a connection 412.

[0181] Figure 4B is a photograph 420 that shows placement of a monolithic Si membrane 424 conformally attached to the ventricular wall 422 and a flexible MEA 426 for recording electrical signals directly from the heart surface.

[0182] Figure 4C depicts a printed original ECG grid paper that displays the transition from normal to paced ECG waveforms under photostimulation.

[0183] Figure 4D depicts representative plots that demonstrate overriding of the original heartbeat to a designated frequency and paced QRS complexes.

[0184] Figure 4E depicts snapshots of a ventricular pacing event upon photostimulation of the desired region 432. The epicardial surface (dashed line 436) moved down upon laser stimulation from the laser emitter 434, indicating systole caused by electrical stimulation, followed by diastole right before the next photostimulation.

[0185] In Figure 4F, heart contraction events were plotted as vertical displacement, with synchronized movement following photostimulation at 2 Hz.

[0186] In Figure 4G, photostimulated ECG waveforms (under pacing) exhibit significantly longer QRS durations compared to sinus rhythm. Boxes bind the IQR divided by the median; whiskers extend 1.5 times the IQR.

[0187] In Figure 4H, an ECG isochrone displays the activation delay between left and right ventricular muscles. For each isochrone map, five ECG peaks were averaged from three independent recordings, Npeaks = 15.

[0188] Figure 41 depicts a plot of ECG signal delay diagonally along the MEA from the pacing location. Two diagonal channels in the 30-channel MEA from three independent recordings were used for the plot, N = 6.

[0189] Figure 4J depicts time-resolved heatmaps that show electric signal propagation measured from -7000 to 7000 pV) originating from the pacing location (arrow).

[0190] As noted above, Figure 5 depicts a table of devices and optical systems used for biological experiments discussed and shown herein. The pulse time was 10 ms unless otherwise specified.

[0191] As noted above, Figures 6A-6D depict fabrication and imaging of multiscale silicon- based photoelectrochemical devices. The silicon devices can be fabricated in various forms, such as microparticles, microstructures, hierarchical patterns, and monolithic films.

[0192] Figure 6A depicts a SEM image, TEM image, and photograph of Por-Si microparticles (from left to right, respectively).

[0193] Figure 6B depicts Optical, SEM, and LEXT images of Si microstructural patterns made by reactive ion etching (RIE). The silicon pattern 600 includes teardrop-shaped nanoscale pores 602 etched into the silicon substrate.

[0194] Figure 6C depicts RIE and stain-etching enabled hierarchical Por-Si structures. The silicon pattern 610 includes rounded-shaped nanoscale pores 612 etched into the silicon substrate, hexagonal-shaped nanoscale pores 614 etched into the silicon substrate, rectangularshaped and / or square-shaped nanoscale pores 616 etched into the silicon substrate, and triangular-shaped nanoscale pores 618 etched into the silicon substrate. Additional shapes of pores are contemplated herein.

[0195] Figure 6D depicts optical and photographic images 620 of monolithic Por-Si membranes 622, 624, and 626, respectively.

[0196] As noted above, Figures 7A-7D depict the physicochemical process of photocurrent generation upon localized light illumination on a photoelectrochemical device.

[0197] Figure 7A depicts that, first, carrier separation occurs due to the built-up potentials across the p-n junction.

[0198] Figure 7B depicts that, next, the separated carriers diffuse radially away from the illumination center and reach the electrode-electrolyte interface.

[0199] Figure 7C depicts that, consequently, charge carriers accumulate at the electrodeelectrolyte interface, inducing ionic movements, which leads to the formation of an electrochemical double layer (EDL) and generates a transient charging capacitive current.

[0200] Figure 7D depicts ionic current arising from ion concentration differences also contributes to the photocurrent measured away from the light spot.

[0201] As noted above, Figures 8A-8C depicts three methods that can be used to fabricate Por- Si.

[0202] Figure 8A depicts stain etching employs HNO3 as the oxidation agent and HF to remove oxidized silicon, creating nanoscale pores.

[0203] Figure 8B depicts, in the presence of AgNCh, Ag nanoparticles continuously form on silicon surfaces, catalyzing porosification. This process results in hierarchical porous structures that enhance light absorption, a phenomenon known as black silicon.

[0204] Figure 8C depicts that during the metal-assisted chemical etching (MACE) process, Ag nanoparticles are deposited to predefine etching locations. This leads to the formation of hierarchical porous structures with Ag-catalyzed pores and HF / HzCh-created pores, resulting in light-absorptive black silicon.

[0205] As noted above, Figures 9A-9C depict representative photocurrent transient measured on four Si-based devices.

[0206] Figure 9A depicts PIN-Si (Au) and Por-Si showed much higher photocurrent than sPN- Si and PIN-Si.

[0207] Figures 9B-9C depict that, while the photocurrent values of PIN-Si (Au) and Por-Si are similar, Por-Si has a significantly larger total injected cathodic charge.

[0208] As noted above, Figure 10 depicts graphs assessing photocurrent stability in 1000-cycle continuous measurements. The normalized photocurrent of the four types of Si devices showed good retaining photocurrents after the 1000th measurement. sPN-Si and PIN-Si showed nearly constant photocurrents, PIN-Si (Au) showed about 85% remaining photocurrent and Por-Si showed about 90% remaining photocurrent after 1000 excitation.

[0209] As noted above, Figures 11A-11C depict assessing photocurrent accuracy, precision, and localization in patch-clamp measurement setup.

[0210] Figure 11 A depicts photocurrents from nine distinct locations, as depicted in the graph, were employed to gauge the accuracy of random-access photostimulation. The system 1100 includes a silicon device 1102, having photocurrents in nine distinct locations 1104, being acted on by the photocurrent delivery device 1106.

[0211] Figure 1 IB depicts an 81-point measurement that was conducted on a 5 mm x 5 mm device, illuminating the corner, edge, and central points. The comer and edge illumination results were utilized to assess photocurrent precision and potential off-target outcomes. The central illumination outcome demonstrated the photocurrent resolution for the four devices. As depicted in system 1110, a silicon device 1112, having 81 target locations thereon, was subjected to illumination by an illumination device 1114. The illumination device 1114 was set to aim for a desired location 1116 of the 81 target locations, namely a lower corner desired location (leftpanel), a leftmost edge desired location (middle panel), and a central desired location (right panel), respectively.

[0212] Figure 11C depicts photocurrent localization profdes that were characterized based on the distance from the light spot. The system 1120 includes a silicon device 1122, having photocurrents in a desired location 1126, being acted on by the photocurrent delivery device 1124.

[0213] As noted above, Figure 12 depicts a plot of photocurrent magnitudes bar graph measured on the edge, center, and corner positions of the four Si-based devices. The PIN-Si and Por-Si showed high photocurrent accuracy with uniform photocurrents displayed on various device locations.

[0214] As noted above, Figure 13 depicts SEM images of the PIN-Si (Au) at center, edge, and corner locations. The SEM images were captured on different locations on the PIN-Si soaked in 1% HF and 1 mM HAuCh for 2 min. The images showed non-uniform Au nanoparticle deposition profdes, which may lead to decreased photocurrent precision at different locations for PIN-Si (Au).

[0215] As noted above, Figure 14 depicts photocurrent heatmaps measured under corner illumination display varied outcomes. The sPN-Si exhibited a 100% error, with the photocurrent maximum occurring at the device center. Conversely, PIN-Si, PIN-Si (Au), and Por-Si demonstrated high precision, with the illumination and photocurrent maximum being well- aligned.

[0216] Figure 15 depicts 81 normalized photocurrent traces measured under edge illumination for sPN-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a“time(s)” x-axis spanning 0.21 to 0.22.

[0217] Figure 16 depicts 81 normalized photocurrent traces measured under edge illumination for PIN-Si. The dot indicates the illumination location. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0218] Figure 17 depicts 81 normalized photocurrent traces measured under edge illumination for PIN-Si (Au). The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a“time(s)” x-axis spanning 0.21 to 0.22.

[0219] Figure 18 depicts 81 normalized photocurrent traces measured under edge illumination for Por-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a“time(s)” x-axis spanning 0.21 to 0.22.

[0220] Figure 19 depicts 81 normalized photocurrent traces measured under corner illumination for sPN-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0221] Figure 20 depicts 81 normalized photocurrent traces measured under corner illumination for PIN-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0222] Figure 21 depicts 81 normalized photocurrent traces measured under corner illumination for PIN- Si (Au). The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0223] Figure 22 depicts 81 normalized photocurrent traces measured under corner illumination for Por-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0224] Figure 23 depicts 81 normalized photocurrent traces measured under center illumination for sPN-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0225] Figure 24 depicts 81 normalized photocurrent traces measured under center illumination for PIN-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0226] Figure 25 depicts 81 normalized photocurrent traces measured under center illumination for PIN- Si (Au). The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0227] Figure 26 depicts 81 normalized photocurrent traces measured under center illumination for Por-Si. The dot indicates the illumination location. Each of the 81 graphs includes a “Normalized current” y-axis spanning -0.5 to 1.0 and a “time(s)” x-axis spanning 0.21 to 0.22.

[0228] As noted above, Figure 27 depicts photocurrent localization profiles and photocurrents at full width at half maximum (FWHM) for four distinct silicon-based devices under illumination with varying spot sizes. Por-Si device demonstrated best photocurrent resolution and tunable FWHM with varying light spot size.

[0229] As noted above, Figure 28 depicts the proportion of cathodic sites on the silicon-based devices under corner illumination. A decreased cathodic proportion suggests improved photocurrent localization and enhanced polarity separation for anodic charges to return on the same side.

[0230] As noted above, Figures 29A-29C depict spatiotemporal mapping of photocurrents with time-resolved heatmaps. Figure 29A depicts PIN-Si (Au). Figure 29B depicts PIN-Si. Figure 29C depicts sPN-Si. Photocurrent bipolarity evolution was revealed on PIN-Si (Au) and PIN-Si. sPN-Si showed unipolar photocurrent profile on the same side of monolithic device, indicating long electron diffusion length and lack of “depletion” from holes. The illumination is directed to the bottom-left corner.

[0231] As noted above, Figure 30 depicts cardiomyocytes stimulation using a monolithic device. Random-access photostimulation was successfully implemented on a monolithic porous silicon (Por-Si) device, which induced calcium influx in cardiomyocytes at respective illuminated locations. The colored crosses in the images indicate the location (spot) of light stimulation (upper panel). As shown in the upper panel, the distance between Spot 1 and Spot 2 is 1540 pm, the distance between Spot 2 and Spot 3 is 686 pm, the distance between Spot 3 and Spot 4 is 1157 pm, the distance between Spot 4 and Spot 5 is 14219 pm, and the distance between Spot 5 back to Spot 1 is 507 pm. Spot illumination is conducted between -83 ms and 83 ms with a 200 pm spot size per spot location (lower panel).

[0232] As noted above, Figures 31 A-3 ID depict photocurrent characterization and ex vivo heart pacing proof-of-concept using various monolithic silicon (Si)-membrane devices with a 5 mm x 5 mm membrane size. Figure 31 A depicts a photocurrent box plot for PIN, PIN-Au, andPor-Si membranes. Figure 3 IB depicts total injected charge box plot for PIN, PTN-Au, and Por- Si membranes, determined by integrating the cathodic photocurrent peak upon illumination.

[0233] Figure 31C depicts representative photocurrent transient for the three devices.

[0234] Figure 3 ID depicts ex vivo heart pacing performed using the three different devices.

[0235] As noted above, Figures 32A-32D depict an investigation of Por-Si device size for photocurrent and ex vivo heart stimulation. Figure 32A depicts increasing device size led to larger photocurrents at the same optical intensity, potentially due to an increased charge-return area. Figure 32B depicts etching reduced device thickness, with an optimal etching time of 20-60 seconds for achieving maximal photocurrents. Figure 32C depicts an increased device size resulted in a lower threshold intensity required to elicit heart pacing. A spot size of 2.25 mm and three devices for each size were tested on the same rat heart. Figure 32D depicts, as the light spot size approached the device size (medium, 3.4 mm), the threshold intensity increased, possibly due to a lack of anodic charge-returning area, which limits overall cathodic charge injection. The data shown in Figures 32C and 32D were experiments performed on N = 3 different devices on the same heart.

[0236] As noted above, Figure 33 depicts AutoCAD design schematics of the 16-channel MEA 3300 for use in ex vivo heart electrical signal recordings. Layer 1 3302 is a substrate made of 8 pm SU-8. Layer 2 3306 is a metallization layer composed of 5 nm and 100 nm Au. Layer 3 3304 is an encapsulation layer made of 6 pm SU-8.

[0237] As noted above, Figure 34 depicts an experimental design for a bidirectional investigation of random-access ex vivo rat heart photostimulation. The silicon device 3400 includes a base 3402 and 16 target points 3404 for photostimulation. By stimulating various locations, unique ECG traces and peak delays are produced. These can be depicted as an activation delay map, enabling the examination of conduction pathways within the heart.

[0238] As noted above, Figure 35 depicts in vivo rat heart pacing under 1.22 mW / mm2pulsed illumination intensity. A detailed zoom-in view illustrating stable cardiac pacing in a live rat heart with ischemia, maintained for over 5 minutes.

[0239] As noted above, Figure 36 depicts in vivo mouse heart pacing. Photostimulation using a Por-Si device facilitated in vivo mouse heart pacing through both open-thoracic and through- thoracic approaches, suggesting potential for non-invasive photostimulation applications.

[0240] As noted above, Figure 37 depicts histology images for Por-Si membranes implanted in the subcutaneous region of mice for 7 days. The black arrow indicates the debris from Por-Si membrane after implantation. Minimal inflammation was observed, indicating favorable biocompatibility.

[0241] As noted above, Figure 38 depicts a monolithic Por-Si device demonstrated the ability to pace the right ventricle (RV), left ventricle (LV), and biventricular (BiV) regions. Evaluation of QRS complex durations revealed a shortened QRS duration during BiV pacing.

[0242] As noted above, Figure 39 depicts design and implementation 3900 of a 30-channel MEA 3904 for recording and analyzing electrical signals obtained from various sites on the epicardial surface 3902 using electrode array 3906. MEA 3904 was placed spanning the upper left and right ventricle in the epicardial surface 3902 of the design and implementation 3900. Longitudinal, transversal, and diagonal directions were denoted.

[0243] As noted above, Figure 40 depicts representative ECG traces obtained from the 30- channel MEA display pig heart activity both with and without pacing. Pacing ECG at 2 Hz were observed upon stimulation. Each of the 30 graphs shown includes an “ECG (pV)” y-axis and a “time(s)” x-axis spanning 0 to 4, with pacing turned on just after 2 seconds. Graph numbers 1, 6, 7, and 11 span, on the y-axis, from 0 to 5000. Graph numbers 2-4, 8, 9, 12-14, 16-20, 22-25, and 28-30 span, on the y-axis, from -5000 to 5000. Graph numbers 5, 10, 15, 21, and 27 span, on the y-axis, from -5000 to 0. Graph number 26 spans, on the y-axis, from -2500 to 2500.

[0244] As noted above, Figure 41 depicts an assessment of ECG peak delays in longitudinal and transversal directions with and without pacing. Pacing was observed to increase ECG peak delay times in both longitudinal and transversal directions

[0245] As noted above, Figures 42A-42F depict AutoCAD design schematics for various monolithic Si devices used in biological experiments contemplated and / or disclosed herein. Figures 42A-42C were used for ex vivo heart pacing experiments, and represent a design schematic 4200 for monolithic Si devices 4202.

[0246] Figure 42D was used for random-access ex vivo heart experiment, and represents a design schematic 4210 for a monolithic Si device 4212.

[0247] Figure 42E was used for in vivo mouse and rat heart experiments, and represent a design schematic 4220 for monolithic Si devices 4222, 4224, and 4226.

[0248] Figure 42F was used for in vivo pig heart experiment, with the relevant unit being: mm, and represents a design schematic 4230 for monolithic Si devices 4232.

[0249] As noted above, Figure 43 depicts BET (Brunauer-Emmett-Teller) adsorptiondesorption experiments disclose a mesoporous type IV material property for porous-Si particles. An increased surface area was detected for porous-Si compared to pristine silicon microparticles.

[0250] As noted above, Figure 44 depicts a minimally invasive approach for closed-thoracic modulation. Figure 44A depicts a schematic representation depicting an incision through the intercostal space, followed by catheter-based delivery of the Si device (i) and subsequent optical fiber photostimulation (ii). The system 4400 includes a test subject 4402 having a heart 4404. Closed-thoracic modulation region 4406 of the test subject 4402 includes an environmental region above the test subject 4402, the skin of the test subject 4402, the ribs of the test subject 4402, and the heart 4404 of the test subject 4402. In these scenarios, a silicon device 4408 is placed onto the epicardial tissue of the heart 4404 of the test subject 4402 by creating an incision in the skin of the test subject 4402 and inserting a delivery device 4410 into the incision in the skin of the test subject 4402, through the skin of the test subject 4402, between respective ribs of the test subject 4402, deploying, via a plurality of arms 4412 of the delivery device 4410, the silicon device 4408, placing the silicon device 4408 onto the epicardial tissue of the heart 4404 of the test subject 4402, and removing the delivery device 4410 through the incision in the skin of the test subject 4402. While this scenario shows and describes a minimally invasive approach for closed-thoracic modulation in a pig, it is believed that the same or similar approaches can be applied to other animals. In one embodiment, it is contemplated that it could be therapeutically effective in humans.

[0251] The top of Figure 44B depicts a photograph illustrating an embodiment of a flexible membrane device housed within the custom delivery device, and the bottom of Figure 44B depicts the unrolling and release of the device upon trigger-pulling. The inset shows the actual Si membrane device attached to the substrate. The depicted delivery device 4420 includes a handoperated base 4424, an elongated catheter 4426 extending from the hand-operated base 4424, and a plurality of arms 4428 deployable from the elongated catheter 4426 to deliver a silicon device 4422.

[0252] Figure 44C depicts endoscopic and side-view photographs of the device delivery process within a sheep cadaver for preliminary investigations before the actual pig heart in vivoexperiment. The system 4430 includes epicardial tissue 4432 onto which a silicon device 4434 is able to be placed by inserting a delivery device 4436 and deploying, via a plurality of arms 4440 held within an interior retention space 4438 of the delivery device 4432, the silicon device 4434, placing the silicon device 4434 onto the epicardial tissue 4432, and removing the delivery device 4436.

[0253] Figure 44D depicts photographs of optical fiber-coupled endoscope and endoscopic views during the minimally invasive pig heart pacing process. After the process described in Figure 44C, the following process described in Figure 44D may begin. The system 4450 includes an endoscope 4452 having an optical fiber 4454 may be inserted near the epicardial tissue 4432 and the silicon device 4434 such that the optical fiber 4454 may target a portion of the device 4456 during photostimulation of the system 4450.

[0254] Figure 44E depicts paced ECG waveforms derived from a fully closed-thoracic procedure using 1 ms optical pulses. An uncollimated fiber optics was employed for this proof- of-concept study, yielding optical intensities between 1 - 100 mW / mm2. The results highlight the procedure's substantial promise for future optimization and clinical translation.

[0255] As noted above, Figure 45 depicts a design of the minimally invasive device delivery system. Figure 45A depicts individual components of the delivery device. The backbone of the device can modified from other available devices, such as, for example, a Smith & Nephew delivery device. The depicted delivery device 4500 includes a hand-operated base 4504, an elongated catheter 4506 extending from the hand-operated base 4504, and a plurality of arms 4510 deployable from within an interior retention space 4508 of the delivery device 4504 to deliver a silicon device 4502.

[0256] Figure 45B depicts a CAD design 4520 of the adapter tubes 4522 and 4524, respectively.

[0257] Figure 45C depicts a CAD design of the delivery substrate and potential adhesives.

[0258] As noted above, Figure 46 depicts an advanced catheter-like device 4600 design for Si membrane delivery, microsurgeries, and optical pacing platforms. The integration of multiple components can be the next generation of minimally invasive cardiac modulation tools. The device 4600 can include a silicon membrane delivery outer shell 4602, a microsurgery space 4604 in the middle, and an optical fiber delivery 4606 inner region. Optical fibers 4610 made of polymer (encased in a hollow sheath 4608 as seen in the top central panel) with bendable tips4612 (top central panel) offer increased flexibility for precise optical modulation across multiple sites. While the hollow sheath 4608 can be attached via glue or suturing after device deployment, the bendable fiber tips 4612 can still maneuver through the sheath 4608, adjusting the light's position on the tissue surface.

[0259] We target several key functionalities in our device design and implementation: (1) Precision access: The design allows for entry into surgical sites through minuscule incisions, minimizing tissue trauma and promoting faster recovery. (2) Minimally-invasive facilitation: The tubing of the device is optimized to support intricate surgical maneuvers (such as epicardial tissue removal and suturing), ensuring precision and safety during operations. (3) Si-based membrane deployment: The instruments are equipped with mechanisms to adeptly deploy and orient silicon-based membranes, ensuring optimal positioning and functionality. (4) Optical fiber positioning: Specialized inner channels and guides are incorporated to accurately position optical fibers, ensuring targeted and efficient photostimulation. Notably, the tips of the optical fibers have pre-defined curvature, and their angular and translational positions can be adjusted in vivo. Upon the delivery of the optical fibers, they exhibit free rotation inside the external sheath. However, to inhibit fiber displacement during the chronic in vivo experiments, the external sheath should be anchored to the in vivo tissues either by suturing or adhesive. (5) In vivo photostimulation capability: Beyond mere positioning, the instruments are designed to actively execute photostimulation within living organisms, ensuring real-time therapeutic interventions. This comprehensive approach to design ensures that the instruments are not only functional but also enhance the efficacy and safety of photostimulation procedures. Our initial findings indicate the feasibility of all the previously mentioned attributes. A salient feature of this system is the arbitrary control of illumination. By maneuvering the catheter through the endoscope and utilizing rotatable optical fibers with angled tips, we will achieve targeted and efficient photostimulation. This design ensures that optical fibers can be precisely positioned to stimulate various cardiac locations, such as the left and right ventricles, emulating natural cardiac rhythms.

[0260] As noted above, Figures 47A-47I depicts optoelectronic membrane devices with various sizes and designs. Figures 47A-47C depict use for ex vivo heart pacing experiments, and represent a design schematic 4700 for monolithic Si devices 4702. Figure 47D depicts use for multisite ex vivo heart experiment, and represents a design schematic 4710 for a monolithic Si device 4712. Figure 47E depicts use for in vivo mouse and rat heart experiments, and representsa design schematic 4720 for monolithic Si devices 4722, 4724, and 4726, respectively. Figure 47F depicts use for multisite rat heart pacing was used for in vivo pig heart experiment, and represents a design schematic 4730 for a monolithic Si device 4732. Figure 47G depicts use for in vivo pig heart experiment, and represents a design schematic 4740 for a monolithic Si devices 4742. Figure 47H depicts use for minimally invasive pig heart modulation, and represents a design schematic 4750 for a monolithic Si device 4752. Figure 471 depicts used for multisite pig heart modulation, and represents a design schematic 4760 for a monolithic Si devices 4762. Units: mm.

[0261] As noted above, Figures 48A-48H depict a multisite in vivo pig heart pacing experiment. The images and plots shown are representative of three pacing trials from one pig heart. Figure 48A depicts device placement on the pig heart, designed for multisite optical pacing across both left and right ventricles. The device measures 0.96 cm x 7.96 cm, with each pacing point evenly spaced by approximately 0.9 cm. The system 4800 includes a silicon device 4804 being placed on epicardial tissue 4802 having a plurality of target photostimulation points 4806. Figure 48B depicts representative evoked ECG waveforms following multisite photostimulation. LV, left ventricle; RV, right ventricle. Figures 48C-48H depict multisite spatial modulation of pig heart tissues: horizontally on the left ventricle (Figs. 48C-48D) (The system 4810 includes a silicon device 4814 being placed on epicardial tissue 4812 having a plurality of target photostimulation points 4816); longitudinally on the right ventricle (Figs. 48E-48F) (The system 4820 includes a silicon device 4824 being placed on epicardial tissue 4822 having a plurality of target photostimulation points 4826); longitudinally on the left ventricle (Figs. 48G-48H) (The system 4830 includes a silicon device 4834 being placed on epicardial tissue 4832 having a plurality of target photostimulation points 4836). All multisite modulations used 25 mW mm-2 intensity and 1-ms pulse duration.

[0262] The Examples that follow are further illustrations of specific embodiments of the disclosure, and various uses thereof. They are set forth for explanatory purposes only and should not be construed as limiting the scope of the disclosure in any way.SPECIFIC EXAMPLESExample 1: Spatiotemporal profiling reveals random-access photostimulation capabilities

[0263] Spatiotemporal profiling of photocurrent generation and ion diffusion as a novel approach to assess random-access capability in semiconductor-saline systems was introduced, using a customized patch-clamp setup. Upon focused spot illumination, photogenerated carriers in semiconductor-electrolyte systems underwent a series of processes: 1) photocarrier generation and separation, 2) solid-state carrier diffusion, 3) capacitive and electrochemical processes at the electrode-electrolyte interface, and 4) ion diffusion due to concentration difference (Fig. 7). Temporal information from the first two solid-state processes fell in the pico- and micro-second range and is beyond the scope; however, these processes provide valuable insight into the spatial distribution of charge accumulation onset on our devices. The latter two processes involved aqueous-state chemical dynamics on the device and can be characterized with milli- and microsecond temporal resolution using our patch-clamp technique.

[0264] Four Si-based photodiode devices with distinct configurations were designed and fabricated. Fig. 2A illustrates the electron (cathodic) and hole (anodic) diffusion processes from the light beam center for the different configurations. The governing equations for carrier diffusion length and diffusion time can be expressed as equations (1) and (2):Carrier diffusion length: Le= jDeTe(1)1 1 1 1 1Effective carrier lifetime: — = — I - 1 - 1 — (2)TeTbTGBTsTa

[0265] Where Derepresents the diffusion coefficient and is the effective carrier lifetime; n, TGB, Ts, and Tarefers to the contribution from bulk, grain boundary, surface, and Auger recombination, respectively, to carrier lifetime. The charge-balanced process, i.e., the anodic current, from the four Si-based devices in saline will also display different spatiotemporal profiles and may help confine the cathodic domains via 'depletion'.

[0266] In the first device, high-purity single-crystalline p-n Si (sPN-Si), carrier recombination primarily arises from bulk (~ Tb). With minimal defects present, carriers freely diffuse to the device edge for collection by the solution. The second device, p-i-n type Si (PIN-Si), comprises polycrystalline intrinsic (i-) and n-type layers with nanosized grains produced by chemical vapor deposition (CVD) over a single-crystalline p-type Si layer. Electron-hole recombination due to defects and grain boundaries (~ TGB) limits photocarrier diffusion in the top n-type Si layer. The third device, Au nanoparticle-decorated p-i-n Si (PIN-Si (Au)), employs Au for photoelectrochemical current enhancement and improved photostimulation.13Increased surface recombination (~ TSand Auger recombination, due to the incorporation of Au nanoparticles onthe Si surface (~ rfl),33may further reduce electron diffusion in the top Si layer and improve photocurrent localization. It is worth noting that the cathodic process in these first three devices all leverage majority carrier diffusion in the n-type Si top layers, resulting in intrinsically longer electron diffusion lengths (i.e., more delocalized in photoelectrochemical reactions). The final device configuration, a porosity-based heterojunction (Por-Si), employs a minority carrier- mediated photocathodic process, as the entire material is p-type Si. This heterojunction can be fabricated through several facile wet chemical etching processes (Fig. 8). Electrons diffuse as minority carriers in the nanoporous Si layer and the diffusion length may be further reduced by bulk recombination (~ Th) and surface recombination (~ T.?). It was hypothesized that Por-Si may yield the best photostimulation localization and, consequently, the best random-access capability.

[0267] Multiple photoelectrochemical current measurements were performed to investigate both static and dynamic profiles. The concept of photostimulation localization in the four Si devices bears a logical resemblance to the point spread function-based resolution argument found in various imaging methodologies (Fig. 2B). The absolute photocurrent magnitude of the four devices under identical illumination and recording conditions (Fig. 9) follows the sequence: Por- Si > PIN-Si (Au) > sPN-Si > PIN-Si. The photocurrent amplitude have been improved through surface treatments with oxygen plasma and nitric acid (Figure 21). In photostability assessments, all four devices maintained >85% of their respective initial photocurrent values after 1000 cycles of illumination (Fig. 10).

[0268] The precision (Fig. 2C), accuracy (Fig. 2D), and resolution (Fig. 2E) of photostimulation in the four devices was assessed by spatially mapping the maximum (photocathodic) or minimum (photoanodic) photocurrent peaks during the ON-stage of illumination across the Si surfaces (see below for details). Precision was defined as the consistency of photoelectrochemical output across different photostimulation locations on a given monolithic device; all devices were subject to the same illumination and recording conditions (Fig. 2C; Fig. 11 A & 12). Both PIN-Si and Por-Si displayed minimal standard deviations (s.d.) in their photocurrents, 0.043 and 0.026, respectively, suggesting consistent photostimulation strength during a random-access process. In contrast, PIN-Si (Au) and sPN-Si exhibited reduced uniformity in their recorded photoelectrochemical currents, with s.d. values of 0.193 and 0.145, respectively. The variability in PIN-Si (Au) may be attributed to the non- uniform distribution of nanocluster-gold deposition on the Si surface (Fig. 13). The diminishedphotocurrents observed at the edges and corners of sPN-Si devices result from charge compensation by leaky anodic currents from device boundaries (i.e., where the p-type Si is exposed).

[0269] Accuracy was characterized as the alignment between the center of the illuminated region and the maximum (or peak) of the photoelectrochemical current (Fig. 2D; Fig. 1 IB, left and middle), with emphasis on light strikes near the device edge or corner. Upon edge and corner illumination, sPN-Si exhibited errors of 75% and 100%, respectively (Fig. 2D; Fig. 14). The offset between the optical and photoelectrochemical centers indicates a compensating photoelectrochemical anodic current originating from the p-n junction boundaries at the exposed device edge. Conversely, PIN-Si, PIN-Si (Au), and Por-Si maintained alignment between the photoelectrochemical current and optical excitation centers for both edge and corner excitation (Fig. 2D; Fig. 14). Photocurrent traces on individual points were also plotted (Edge: Fig 15 - 18; Corner: Fig. 19 - 22) to show center offsets.

[0270] High spatial resolution of photoelectrochemical processes is also essential to determining photocurrent localization and, consequently, selective random-access photostimulation. Upon illumination of the center of monolithic Si devices, we observed a radial distribution of photoelectrochemical currents (Fig. 2E; Fig. 1 IB, right; Fig. 23 - 26; Figure 2G). As depicted by the intensity heat map, the area enclosed by the photoelectrochemical current half-maximum, also quantified as photoelectrochemical current full-width-half-maximum (FWHM) (Fig. 27), successively decreased in the order of sPN-Si > PIN-Si > PIN-Si (Au) > Por- Si. This successive decrease, with the lowest FWHM observed in Por-Si, is in line with the photoelectrochemical current localization originally outlined for each device configuration (Fig. 2A). The normalized photocurrent profiles under varying light spot sizes were also analyzed, ranging from 750 pm to 35 pm (Fig. 2F; Fig. 11C; Fig. 27). Por-Si exhibited the most pronounced change in photoelectrochemical current FWHM with modifications in laser spot size (Fig. 27), signifying a higher degree of optically tunable resolution.

[0271] The localized photocurrent distributions and distinct spatially resolved polarities of Por- Si under comer illumination are shown in the left of Fig. 2H. The observation of opposite polarities on the same surface of the Si device implies that the photogenerated holes (majority carriers in p-type Si) diffuse further than the electrons, facilitating anodic charge injection through the peripheral porous region, and corroborating the proposed model (Fig. 2A). A similarphenomenon was observed in PIN-Si and PIN-Si (Au) devices, potentially due to leakage of anodic current from grain boundaries. Conversely, the sPN-Si device exhibited a unipolar charge distribution on the same surface, which can be attributed to the extended carrier lifetime in single crystalline materials. In line with these results, decreased cathodic proportions and increased anodic proportions were observed for the three devices with localized photocurrent (Fig. 28). The phenomenon of spatially resolved bipolarity suggests that the light spot location will effectively determine the cathode (and anode), thereby achieving random-access photopatteming of stimulation sites. Charge balancing on the same side on the biointerface, enabled by the spatially resolved bipolarity, will also eliminate the need for a return electrode in bioelectrical stimulation.

[0272] Assessment of maximum or minimum currents during the ON-stage of illumination provides crucial insights into the precision, accuracy, and resolution of photocurrent generation. However, this information does not adequately portray the dynamic behavior. To elucidate the spatiotemporal characteristics of photocurrent dynamics across the Si surface, we mapped currents originating at distinct locations and time points for both ON- and OFF-stages of the illumination cycle. To amplify the polarity contrast, we normalized the currents to the local photocurrent maximum or minimum (See further disclosure for more information). Spatiotemporal maps for Por-Si (the right of Fig. 2H) show that at ~ 0.3 ms illumination, a cathodic charge injection emerges (Fig. 7, step 8), followed by cathodic current diffusion until ~ 0.7 ms (Fig. 7, step 9). The generation and evolution of the border between cathodic and anodic domains exhibits a localized pattern, aligning with the static measurements (the left of Fig. 2H). Illumination was switched off after 10 ms. Analogously, a polarity reversal from the area of the localized photocurrent was observed ~ 0.3 ms following the cessation of light, signifying discharging dynamics. Spatiotemporal profiles for PIN-Si (Au) and PIN-Si displayed similar photocurrent bipolarity dynamics with less localized cathodic domains and sPN-Si showed unipolar cathodic current profile on the device surface (Fig. 29).

[0273] Through spatiotemporal profiling and screening, it was determined that, of the four configurations, Por-Si possessed the optimal photostimulation strength, precision, accuracy, and resolution, as well as better bipolarity domains for charge balance. These findings indicated the potential of the Por-Si device for random-access and multiscale photostimulation in vitro, ex vivo and in vivo.Example 2: Random-access photostimulation of cardiomyocytes in vitro

[0274] Photostimulation was performed on CMs cultured on glass-bottom dishes using monolithic Por-Si chips (Fig. 3A). This approach differs from commonly used methods that require cell seeding directly on the materials34 38. In this "insert-and-play" alternative, the device is dropped into the cell culture medium where it naturally lands and interacts with the CMs. Although this method does not yield a seamless cellular integration, it facilitates closer measurement correlations between patch-clamp experiments and biological modulation scenarios, and avoids complications arising from photothermal or photoacoustic effects that may be significant in tight biointerfaces13,36,39. The reduced photoelectrochemical current due to fluid separation between cells and the Por-Si chip is unlikely to pose a problem, as the current does not decrease by more than 50% even when the separation is increased from 10 pm to 250 pm, as demonstrated by the x-z mapping (Fig. 2H).

[0275] Stimulation-induced calcium influx and calcium wave propagation was examined using fluorescent calcium dye. Optical pacing elicited synchronized contractions at 1 Hz with a 1 ms delivered pulse (Fig. 3B). To note, previous work with Si nanowire-based CM interfaces yielded optical training effects but not overdrive pacing40. Random-access stimulation at various locations on the device resulted in immediate calcium influx and propagation surrounding the illumination spot (Fig. 30). To ensure control over the stimulation area, the spot size was adjusted from 200 pm to 10 pm and successfully reduced the excited cellular area from hundreds of cells down to a single cell within the imaging frame time of 83 ms (Fig. 3C). The initial area of excitation (Fig. 3D, 83 ms) correlated strongly with the photostimulation location, where optically activated cells initiated intercellular calcium propagation (Fig. 3D, 167 ms and 250 ms). Following light stimulation, we observed localized photostimulation effect in the randomly oriented cell culture, inducing membrane-voltage distributions and propagation patterns distinct from those observed without stimulation (Figure 3G). This controlled-area photostimulation provides direct support for the highly resolved and adjustable photoelectrochemical current profde on the Por-Si monolithic device (Figure 2) and encouraged further investigation of random-access photostimulation in tissue contexts. The monolithic photoelectrochemical device can also be applied to intracellular Ca2+dynamics and drug-related experiments, including nifedipine and isoproterenol (Figure 3D), as well as to efficiently modulate more mature adult cardiomyocytes (Figure 3E).Example 3: Random-access, multisite photostimulation of isolated rat heart ex vivo

[0276] To investigate random-access stimulation in a more intricate and organized biological context, monolithic membranes composed of PIN-Si, PIN-Si (Au), and Por-Si were interfaced with isolated rat hearts in a Langendorff setup. The optical pacing capabilities of the membranes were assessed with respective photocurrents produced by a 10 ms pulse (Fig. 31A-31C). The PIN-Si membrane failed to override the heartbeat, even at a light intensity of 177 mW / mm2(Fig. 3 ID). The increased photoelectrochemical current of PIN- Si (Au) achieved pacing of the isolated heart at 4 Hz using an optical intensity of 141 mW / mm2(Fig. 3 ID). With Por-Si, the required intensity for stable pacing was reduced to 0.166 mW / mm2(Fig. 3 ID). Stable pacing of the heart at 6 Hz was also observed at low optical intensities (< 0.5 mW / mm2). A systematic investigation on membrane designs and pacing conditions, such as device structures and laser spot sizes, have been investigated, which affects threshold optical intensity that elicits pacing (Fig. 32; Fig. 42A-42C).

[0277] The Por-Si device was further engineered to feature an open window, which accommodated a flexible 16-channel multi-electrode array (MEA) (Fig. 33). The conformability of the two devices to the epicardium facilitated bidirectional stimulation and recording.Photostimulation was performed on eight symmetric points on the Por-Si frame (Fig. 3E; Fig. 34; Fig. 42D). Using 1-ms light pulse trains, the isolated heart can be paced with an optical intensity as low as 0.51 mW / mm2(Figure 3H). The recorded electrical signals in the cardiac tissue displayed varying delays in activation of the cardiac muscle, as shown in the isochrone maps (Figure 31). This result indicates that the monolithic device can execute leadless random-access photostimulation, effectively controlling the activation initiation point on cardiac tissue via the light spot location. The cardiac rhythm in the ex vivo isolated heart used for perfusion purposes deviates from the sinus rhythm, as the atrial tissues have been removed. In intact in vivo cardiac tissue, the sinoatrial node governs the sinus rhythm. In the following sections, we explore photostimulation of cardiac tissue in vivo.Example 4: Random-access, multisite, and biventricular cardiac pacing in rodent models in vivo

[0278] The in vivo heart pacing experiment is more complex, as cardiac activity is influenced by the ANS and involves inter-organ interactions41. To demonstrate reliable pacing in a compromised heart, left anterior descending artery (LAD) ligation was performed in a rat modelto induce acute ischemia (Fig. 3J). Following ligation, electrocardiogram (ECG) traces suggested an increased heartbeat, potentially a compensatory response to ischemia, as well as fluctuating baselines indicative of pronounced breathing patterns (Fig. 3K). The Por-Si device reliably paced ischemic in vivo cardiac tissue at 360 beats-per-minute (b.p.m.), with optical intensities comparatively lower than optogenetic approaches where an intensity of > 1 mW7mm2would generally be required9(Fig. 3L-I). Consistent photoactivated QRS complexes were observable at optical intensities of 0.73 mW / mm2and above (Fig. 3N). Furthermore, consistent pacing at 360 b.p.m. for over 5 minutes, with more than 1800 photoactivated QRS complexes, was achieved at an optical intensity of 1.22 mW / mm2(Fig. 30; Fig. 35). To explore the potential for non- invasive trans-thoracic pacing, the Por-Si device was implemented in an in vivo mouse heart and the thorax was subsequently closed. Pacing at 360 b.p.m. was achieved with an intensity of 62.7 mW / mm2through the chest (Fig. 36), a relatively lower power than that used in trans-thorax or transcranial optogenetics with irradiances over 100 mW / mm2842. In in vivo compatibility experiments, no significant inflammation was observed after a 7-day Por-Si film implantation (Fig. 37).

[0279] To assess random-access photostimulation on the in vivo rat heart, the device was designed to span both the left and right epicardial surfaces (Fig. 3P). Photostimulation at five distinct locations on the monolithic device evoked varied QRS complexes, corresponding to a gradient in the activation sequence from the left ventricle (point 1) to the right ventricle (point 5), with characteristic QRS complexes (Fig. 3Q). This result indicates that random-access photostimulation can be achieved on any exposed epicardial surfaces using monolithic Por-Si devices. Biventricular pacing is a clinically established cardiac resynchronization therapy (CRT) for ventricular dyssynchrony43. Two laser sources (635 nm and 473 nm) were utilized for simultaneous pacing of the left and right ventricles, using a single monolithic Por-Si device. Biventricular photostimulation generated ECG waveforms in line with previous studies on rats employing epicardial leads and clinically acquired data from patients with pacemakers44,45(Fig. 3R-O). The concurrent activation of the left and right ventricles resulted in QRS durations not significantly different from the sinus rhythm, suggesting a potential route to optical CRT43(Fig. 3T; Fig. 38).Example 5: Non-genetic optical pacing of a live pig heart in vivo

[0280] A pioneering application of a non-genetic optoelectronic technique for modulating cardiac activity in a live porcine model is presented, with anatomical and functional resemblance to the human heart, to replicate the clinical scenario (Fig. 4A). Optical cardiac pacing, currently implemented using genetic modifications, has not been reported in large animal models to the best of our knowledge. Given the experimental complexity, high costs, and ethical dilemmas of optogenetic approaches, their translation into clinical applications is challenging. Following median sternotomy on the anesthetized animal, the Por-Si device was placed on the epicardial wall of the right ventricle, conforming easily to the curvilinear ventricular wall without the need for sutures or adhesives (Fig. 4B; Fig. 42F). Upon optical pacing (~23 mW / mm2, 10 ms pulse), distinct ventricular pacing waveforms were captured on clinical ECG grid paper (Fig. 4C). The sinus rhythm ECG displayed a resting heart rate of ~71 b.p.m. Pacing with 2 Hz laser pulses resulted in an override heart rate of -120 b.p.m. (Fig. 4D). A snapshot from a pacing video shows a single optical pacing event under 2 Hz pacing with 18 mW / mm2and 10 ms pulse (Fig. 4E). Upon illumination, the Por-Si device induced a depolarization current, causing the heart to contract. Heart displacement traces showed that heart contractions synchronized with the pacing frequencies (Fig. 4F). Initial and terminal pulse train observations may exhibit minor synchronization discrepancies, potentially attributed to suboptimal optical intensities at 18 mW / mm2. However, by elevating the optical intensity, it is feasible to attain a more deterministic pacing approach, mitigating these synchronization inconsistencies (25.2 mW / mm2, 40 ms pulse). The recorded ECG waveforms indicated that the sinus rhythm had a QRS duration of less than 120 ms, corresponding to normal heart conduction conditions. Upon left ventricular pacing, the QRS complex widened to over 120 ms due to the time difference between left and right ventricular contraction events (Fig. 4G).

[0281] A flexible 30-channel MEA was positioned on the epicardium, covering a mapping area of 40 mm * 32 mm and majority electrodes were on the upper part of right ventricle, to directly record epicardial electrical signals (Fig. 4B; Fig. 39). The pacing optoelectrode was placed on the left ventricle, anatomically bottom-right relative to the MEA, and recordings were captured with 30 individual channels (Fig. 40). Recorded multichannel signals revealed that the paced cardiac tissue overrode the original heart conduction pathway, leading to a propagation of electrical signal induced from the left ventricular surface to the surrounding tissues (Fig. 4H).The propagation direction was also indicated by the ECG peak delay in the diagonal direction along the MEA (Fig. 41), as well as in the longitudinal and transversal directions (Fig. 41; Fig. 41). A time-resolved static heat map depicting peak intensity over time showed the electrical signal propagation on the epicardial surface (Fig. 4J). It is believed that this demonstration of non-genetic optoelectronic heart pacing in a pig has laid the groundwork for translational semiconductor-based photostimulation. Additionally, the pacemaker devices disclosed, including the polymeric substrates used to support the Si membranes, have a total device weight that is 2-3 orders of magnitude lower than conventional pacemaker devices currently available in the market. This substantial reduction in weight offers the potential for numerous therapeutic advantages for patients, which may enhance patient outcomes and overall quality of life.Outlook

[0282] In this study, four different Si-based photoelectrochemical devices were characterized and their spatiotemporal photocurrent profiles in physiological environments analyzed. A neurom orphic porous Si-based monolithic device was introduced possessing charge injection capabilities, as well as the accuracy, precision, and resolution necessary for random-access photostimulation. The spatiotemporal profiling of photoelectrochemical outputs reported here alone has the potential to launch future research exploring diverse devices in energy and catalysis research domains.

[0283] This multiscale neuromorphic device facilitates low-power (Figure 5), random-access, and multiscale biological modulation, spanning from individual CMs to an entire pig heart, without necessitating predefined electrode patterning. In contrast to conventional, bulky pacemakers, the monolithic and pixel-less membrane design disclosed herein significantly reduces the footprint and crosstalk at biointerfaces. Future work towards clinical trials will necessitate development of a microsurgical technique for minimally invasive delivery of optoelectronic devices to cardiac tissue, along with fiberscope-guided multisite optoelectronic therapy. Furthermore, integration of a tunable device lifetime, a property of Si, will allow for on- demand bioresorption.MethodsFabrication of photoelectrochemical silicon chips

[0284] sPN-Si. sPN-Si (Orientation (1 11), n-type layer, 44.5 ± 1 pm, 1.1 ohm cm; p-type layer, 381 pm, 0.004 - 0.008 ohm cm) was obtained from Nova Electronic Materials and diced using a Disco DAD3240 dicing saw for direct characterizations.

[0285] PIN-Si. PIN-Si was prepared using the chemical vapor deposition (CVD) method. A p- type Si wafer or a silicon-on-insulator (SOI) wafer was used as the substrate for deposition of intrinsic and n-type layers. Before deposition, the substrate was cut into 4 cm x 2 cm and cleaned in an ultrasonic bath for 3 minutes in acetone and 3 minutes in isopropyl alcohol (IP A), and then rinsed with deionized (DI) water. The wafer was soaked in 10% hydrofluoric acid (HF) for 5 min to remove the native oxide and then placed inside a quartz tube for evacuation. The i- and n-type layers were deposited under 650°C with 15 torr chamber pressure for 20 min. Flow rates of H2 and SiH4 were set as 60 and 0.3 seem for the i-layer. The same settings were used for the n-layer with an extra 1.5 seem flow rate for the dopant gas, PH3 (1000 ppm in H2).

[0286] PIN-Si (Au). The PIN-Si chip was decorated with gold nanoparticles using electroless deposition. The PIN-Si chip was first dipped in 10% HF for 3 min to remove any potential oxide layer. It was then dipped in an electroless-deposition solution composed of 1% HF and 1 mM HAuCh for 2 min.

[0287] Por-Si. Three techniques for creating nanoscale pores in p-type Si (orientation (100), resistivity 0.001 - 0.005 ohm cm, Nova Electronic Materials) is presented, including metal- assisted chemical etching (MACE), stain-etching, and a combination of both methods. Prior to etching, the wafers were diced using a Disco DAD3240 dicing saw and subsequently cleaned in an ultrasonic bath for 3 minutes in acetone and 3 minutes in IPA. For MACE, Si chips were first dipped in 10% HF for 3 min. It was then immersed in an electroless deposition solution containing 1% HF and 1 mM silver nitrate (AgNCh) for 2 minutes, and then rinsed with DI water. The silver-decorated Si chips were then submerged in an etching solution comprised of 50% HF and 30% hydrogen peroxide (H2O2) at a 20: 1 volume ratio for 3 minutes. Afterward, the Si chips were soaked in concentrated nitric acid (HNO3) for 2 minutes to remove the silver. For stain-etching, the process was slightly modified from previously reported procedures.12The Si chips were immersed in a mixture of HF and HNO3 at a volume ratio of 100: 1 for 1 minute, followed by soaking in concentrated HNO3 for 1 minute to activate the surface. For the combined stain-MACE process, the Si chips were submerged in a solution of HF and HNO3 with a 100:1 volume ratio, as well as 1 mM AgNCh, for 3 minutes. The chips were then soaked inconcentrated HNO3 for 2 minutes to remove the silver. The as-prepared Por-Si samples were exposed to 400 W oxygen plasma at a flow rate of 50 seem for 10 minutes in a Plasma-Therm inductively coupled plasma fluoride etcher, without radiofrequency bias.Fabrication of monolithic Si membrane

[0288] SOI wafers (p++; device, 7 ± 1 pm, <0.005 ohm cm; handle, 300 ± 10 pm, 1 - 30 ohm cm; buried oxide, 1 pm) were sourced from Ultrasil. The photomask was designed using AutoCAD software and can be found in Fig. 42. The fabrication process adhered to standard lithography techniques. A thick positive resist AZ40XT-1 ID (MicroChemicals) served as a mask for reactive ion etching. Patterns were exposed using the Heidelberg MLA150 direct writer, and the uncovered SOI was removed using an SF6 / CHF3 (20 seem: 50 seem) reactive ion etching process (inductively coupled plasma, 600 W; radiofrequency, 60 W) in a Plasma- Therm inductively coupled plasma fluoride etcher, with an etching rate of - 660 nm min The photoresist was stripped using AZ NMP (MicroChemicals), and the wafers were cleaned in an ultrasonic bath for 3 minutes in acetone, followed by 3 minutes in IP A, and dried using compressed nitrogen. Samples were immersed in concentrated buffered HF (Thermal Scientific) overnight (-12 hours) to eliminate buried oxide layers. Membranes, along with the handle wafer, were subsequently rinsed twice for 1 minute each in separate DI water baths to remove any residual HF. Wafers were then soaked in an IPA bath for 1 minute and transferred to an acetone bath to facilitate interactions between the membranes and handle wafer. Lastly, free-floating membranes were moved to a fresh IPA bath using filter paper and stored at 4°C before undergoing further processing. An optional supporting substrate for Si membranes, to facilitate device handling, was made of PDMS (10: 1, Sylgard 184) coated PET (Sigma-Aldrich) with thickness - 5 pm and 12.5 pm respectively.Fabrication of 16-channel MEA for rat heart recording

[0289] Fabrication of the flexible 16-channel recording electrodes was conducted on a p-type wet oxide Si wafer (NOVA Electronic Materials) which served as the substrate. The wafer was evaporated with 50 nm nickel which served as the sacrificial layer. The first SU-8 layer (SU-8 3005, MicroChemicals), with thickness -8 pm, was patterned using direct writer photolithography (MLA150, Heidelberg), providing a flexible substrate for the electrode. Subsequently, metal layers consisting of 5 nm Cr and 100 nm Au were evaporated onto the first layer using an electron-beam evaporator (EvoVac, Angstrom Engineering). This was done on apatterned AZ nLOF 2070 (MicroChemicals) photoresist mask, followed by a lift-off in AZ NMP (MicroChemicals) to remove the photoresist. The third encapsulation layer (SU-8 3005, MicroChemicals), with thickness ~6 pm, was then patterned to encapsulate the metal interconnects, exposing only the sensing pads for interfacing with cardiac tissues and the bottom pads for external connections. Finally, the device underwent a lift-off process in a HC1 solution, which removed the sacrificial nickel layer for device release.Fabrication of 30-channel MEA for pig heart recording

[0290] A polyimide film (25 pm, McMaster-Carr) was employed as the substrate for the MEA. Following a 3-minute ultrasonic bath cleaning in acetone and IP A, the film was initially bonded to an Si wafer substrate using AZ nLOF 2070 (MicroChemicals) photoresist and cured at 110°C for 5 minutes. Subsequently, AZ nLOF 2020 (MicroChemicals) was spin-coated so it could be exposed and defined as the sensing pad and interconnect regions. Metal layers, comprising 5 nm Cr and 100 nm Au, were evaporated onto the first layer utilizing an electron-beam evaporator (EvoVac, Angstrom Engineering), succeeded by a lift-off in AZ NMP (MicroChemicals) to eliminate the photoresist. A water-releasable tape was patterned using a laser cutter and adhered to the 30 sensing pads. PDMS mixed with PDMS base (Sylgard 184, Dow) and PDMS cure (Sylgard 184, Dow) in a 10: 1 ratio was then spin-coated onto the flexible MEA film at 4000 rpm and cured at 80°C for 2 hours to form the encapsulation layer. To expose the 30 sensing pads, the MEA was immersed in warm (50°C) water, facilitating the release of the water-dissolvable tape.Standard photocurrent measurements

[0291] Photocurrent measurements were generally conducted in accordance with previously established methods. A custom-made patch-clamp setup, integrated with an upright microscope (Olympus, BX61WI) featuring *20 / 0.5 and *40 / 0.5 numerical aperture water-immersion objectives, was employed to measure photocurrents. Light pulses were introduced through episcopic illumination, utilizing a dichroic mirror (for 625 nm LED, FF660-Di02-25x36, Semrock) or Thorlabs protected silver mirrors (for 635 nm laser, PF10-03-P01, PFR10-P01). Clamp voltage and current were recorded using silver chloride electrodes and amplified by an AxoPatch 200B amplifier (Molecular Devices). Voltage-clamp levels and light pulsing were digitally regulated using transistor-transistor logic or analog signals sent from a Digidata 1550 digitizer (Molecular Devices), controlled with Clampex software (Molecular Devices). Glass pipettes were created using a P-97 micropipette puller (Sutter Instrument), typically featuring aresistance of 1-4 MO, and filled with 1 x PBS. For a standard measurement, the material was positioned at the center of the field of view in a petri dish filled with 1 x PBS. The pipette tip was brought close to the material surface (<10 pm) and the measurement sequence was initiated. The sequence lasted 400 ms, with an initial voltage level of - 0.5 mV between 100 - 300 ms. At 200 ms, a 10 ms light pulse was administered to provoke a photoresponse from the material. The holding current was adjusted so that the current at the first voltage level was near 0 pA (typically below 2,000 pA).Photocurrent precision measurements

[0292] The precision of four distinct Si devices was evaluated by measuring nine individual points on 5 mm x 5 mm chips (Fig. 11). Points one, three, seven, and nine were located at the corners; points two, four, six, and eight were situated at the edges; and point five was at the device center. Precision maps were generated by averaging the results from four independent samples for each Si device. The standard deviation (s.d.) was computed using the population s.d. derived from the nine measured points. A 625 nm collimated LED with 20 mW power provided the illumination, and the spot size measured -750 pm.Photocurrent spatiotemporal mapping

[0293] In this study, photocurrent mapping with illumination at the device center (Fig. 2e), edge (Fig. 2D), and corner (Fig. 2H; Fig. 14) is presented. Each map was constructed using 81 measurements, with each point separated by 0.5 mm in a 9 x 9 array on the 5 mm x 5 mm chip (Fig. 11). For the center-illumination photocurrent measurement, light was illuminated at point 41 for a total of 81 times. For each illumination the photocurrent was recorded at one individual point by controlling the micropipette location. This process was similarly performed for edgeillumination (point 37) and comer illumination (point 73).

[0294] In the static heat maps presented in Fig. 2D to the left of Figure 2H and Fig. 14, the peak photocurrent values (upon illumination) at each measurement point are displayed. The color scale was normalized to the point with the highest photocurrent. In the dynamic photocurrent map (the right of Fig. 2H), the color of each individual pixel is normalized to their respective maximum and minimum values in the 20 ms recording (10 ms light-on and 10 ms light-off), better illustrating the polarity distribution and switch. A 625 nm collimated LED with 20 mW power was used for illumination, and the spot size measured -750 pm.

[0295] The error value presented in photocurrent accuracy measurement was calculated by:

[0296] Where pmaxis the coordinate with maximum photocurrent, pa is the point coordinate with illumination and pcenter is the coordinate at center.Photocurrent localization profiling

[0297] Resolution profiling (Fig. 2F; Fig. 27) was used to illustrate the photocurrent localization capability of the four Si devices. A 750 pm light spot was generated using a *20 / 0.5 numerical aperture water-immersion objective in conjunction with a 625 nm collimated LED. A 120 pm light spot was produced using the same objective but employing a 635 nm laser (Laserglow). By adjusting the lens position with a *40 / 0.5 objective, a 35 pm light spot was obtained. The optical power levels for the 750 pm, 120 pm, and 35 pm spots were 20 mW, 20.5 mW, and 16.5 mW, respectively.

[0298] The light spot was centered on the device, and a micropipette was used to record the current localization profile, starting at a distance of 2 mm from the device center on one side and finishing at 2 mm from the other side, covering a total span of 4 mm across the device center. For Por-Si illuminated with 120 pm and 35 pm spots, a step size of 0.025 mm was employed, while a step size of 0.05 mm was used for the others. The photocurrent full width at half maximum (FWHM) was calculated by summing the distances at which the photocurrent reached half of its maximum value.Electron microscopy

[0299] A transmission electron microscope (JEOL, JEM-3010) and an aberration-corrected scanning transmission electron microscope (JEOL, JEM-ARM200F) were used to image the cross-sectional structures of both the pristine PIN-Si junction and the Por-Si heterojunction. Selected area electron diffraction (SAED) patterns were taken using the JEM-3010. Cross- sectional specimens for transmission electron microscopy (TEM) were prepared by controlled tripod polishing followed by liquid-nitrogen-cooled Ar ion millings using a Fischione 1050 TEM mill (Fischione Instruments). A 4 kV ion milling was used to further thin the specimen and a final 0.5 kV milling was performed to remove surface damages. Scanning electron microscopy was carried out using a Merlin microscope (Carl Zeiss). Samples were affixed to aluminum sample holders with copper or carbon tapes. To prepare for cross-sectional imaging, the backsideof the sample was scratched with a diamond scribe, and the sample was then broken in half and mounted on a 90-degree sample holder using copper or carbon tapes.Cardiomyocytes culture

[0300] Hearts were excised from neonatal rats (postnatal day 1-3) into ice-cold Hank’s Balanced Salt Solution (HBSS; without Ca2+or Mg2+). Hearts were cut in half, rinsed with ice- cold HBSSx3 to remove blood, and then minced into 1-2 mm small pieces. A Pierce Primary Cardiomyocyte Isolation Kit (Thermo Fisher Scientific) was used to digest the tissue, according to manufacturer’s protocol. After digestion, tissues were disrupted by vigorous pipetting ><25-35, and the suspended cells were pre-plated for 2 hours to allow fibroblasts to adhere to the tissue culture plate. The cell suspension was collected and the enriched CM population was seeded onto a glass-bottomed dish pretreated with gelatin / fibronectin (Sigma, gelatin: 0.02%; fibronectin: 5 pg / mL). Cells were allowed to sit in culture media (DMEM high glucose plus 10% fetal bovine serum (FBS), 1% GlutaMAX and 1% penicillin-streptomycin) for 24 h, and then the media was changed to CM-specific media (DMEM high glucose plus 10% FBS, 1% penicillinstreptomycin and 0.1% CM growth supplement).Ex vivo random-access isolated heart stimulation

[0301] The isolated heart preparation followed previously described methods. Briefly, adult male rats (400-500 g body weight) were heparinized and anesthetized using open-drop exposure to isoflurane in a bell jar setup. The heart was excised and immersed in ice-cold HBSS buffer before cannulating the aorta in preparation for a Langendorff setup. An oxygenated HEPES- buffered Tyrode's solution was perfused through the cannulated aorta after passing through a heating coil and bubble trap (Radnoti). The heart was positioned in a water-jacketed beaker (Fisher Scientific). The system temperature was kept constant at 37°C. Perfusion pressure was kept at 80-100 mmHg. To reduce the atrioventricular node pace, the sinoatrial node and atria were removed. Perfusion and left ventricular pressure were monitored using a BP- 100 probe (iWorx) connected to the perfusion line and a water-filled balloon (Radnoti) inserted into the left ventricle, respectively. For ECG recordings, needle electrodes were positioned on the left ventricular wall and aorta, grounded on the cannula and connected to a C-ISO-256 preamplifier (iWorx). All signals (perfusion, left ventricular pressure, and ECG) were amplified using an IA- 400D amplifier (iWorx) and interfaced with a computer using a Digidata 1550 digitizer with Clampex software (Molecular Devices). For proof-of-concept pacing tests (Fig. 31), themonolithic Si membrane was placed on the left ventricular wall and adhered to the heart with capillary force. Stimulation and recording were controlled using the Digidata 1550 digitizer. For random-access photostimulation, the open-windowed Si membrane (Fig. 34) was placed on the epicardial surface spanning left and right ventricles. A 635 nm laser with 1 mW / mm2optical intensity was used. A 1 ms pulse was used to better decouple the photocurrent artifacts and ECG signals from the recording. The flexible 16-channel MEA was placed within the window to perform multichannel recording and mapping. The MEA was connected to a zero-insertion-force connector linked to an Intantech RHD2132-chip headstage through an 18-pin electrode adapter board. Signals were recorded at 20 kS s ' in the 0.1-2000 Hz bandwidth.In vivo rat heart stimulation with left anterior descending artery ligation

[0302] Adult rats (10 - 24 weeks, males and females, 400 - 500 g) were deeply anaesthetized with isoflurane (2 - 4%). The tongue was gently pulled sideways, and forceps were used to insert a tracheal cannula connected with a ventilation system (Harvard Small Animal Ventilator Model 683). The parameters of ventilation were set by following the publication "Ventilation standards for small mammals". The fur was removed from the chest, right and left clavicle, and left hip using surgical clippers and hair removal cream. The ECG electrodes were placed on the left clavicle, right clavicle, and left hip. The costal cartilages were cut along the left side of the sternum between the 3rd and 5th intercostal ribs to expose the left ventricle. The pericardium was gently cleared away from the surface using forceps and cotton swabs. A small-animal rib spreader was used to open the thoracic space. A surgical needle with suture wire (8 / 0) was used to ligate the left anterior descending artery to induce ischemia; the ventricular wall became pale in appearance right after ligation. The Si membrane was then attached to the epicardial surface.In vivo mouse heart experiments with non-invasive stimulation

[0303] The surgical procedure for exposing the mouse heart is similar to that of the rat heart experiment. The ventilator was set at a tidal volume of 7 ml / kg and a ventilation rate of 140 strokes / min. After Si device implantation, a tissue adhesive was applied to immobilize the device to the epicardial surface. The thorax opening was closed with 5 / 0 surgical sutures. A 635 nm laser was illuminated through the closed chest for non-invasive photostimulation.In vivo pig heart stimulation

[0304] An adult female pig was deeply anesthetized using inhalant anesthesia administered via a vaporizer connected to a ventilator. The animal's vital signs, including ECG, heart rate, end-tidal CO2, blood oxygen saturation (SPO2), respiratory rate, blood pressure, and temperature, were continuously monitored at a monitoring station. The pig was positioned in the supine position, and a median sternotomy was performed to expose the heart. After opening the pericardium, the Si membrane device was placed on the right ventricular wall of the cardiac tissue. Epicardial recordings were obtained by interfacing the cardiac tissues with an MEA positioned mostly on the upper part of right ventricle. The MEA was connected to a zeroinsertion-force connector, which was then linked to an Intantech RHD2132-chip headstage (32 channels) via a 36-pin electrode adapter board. Signal recordings were collected at a sampling rate of 20 kS s ' within a frequency bandwidth of 0.1-2000 Hz.Multichannel ECG isochronal maps

[0305] The recordings from the 16-channel MEA on the ex vivo rat heart and the 30-channel MEA on the in vivo pig heart were analyzed by customized python scripts. Gaussian interpolation was used to enhance readability.Animal subjects

[0306] CD / SD rats were originally obtained from Charles River and were housed and bred in the animal facility at the University of Chicago. C57BL / 6J mice (6 - 8 weeks) were purchased from JAX. The animal room was maintained at a humidity of 40 - 60% and a temperature of 18 - 23 °C under a 12-h-light / 12-h-dark cycle. The animals were allowed free access to food and water.

[0307] Female domestic swine were obtained from a USDA Class A vendor and were housed in accordance with the Guide for the Care and Use of Laboratory Animals under a protocol approved by the University of Chicago’s Institutional Animal Care and Use Committee.Data processing and statistics

[0308] Data analysis was performed with Python scripts using the NumPy, Matplotlib, SciPy and Pandas libraries. Plotting was performed with Origin and Python Matplotlib. Statistics were calculated using the scipy. stats library unless otherwise clarified. For s.d. calculations, population s.d. was used for Fig. 2C while others employed sample s.d.. Images were processed using ImageJ software. The fluorescence dF / F videos and images were processed using imageJ and available online macro https: / / gist.github.com / ackman678 / l l 155761. Tracking of pig heart surface movement utilized imageJ Manual Tracking plugin.Preparation of Por-Si microparticles

[0309] The Por-Si microparticles were prepared for imaging, cytotoxicity and biocompatibility test purposes. Por-Si microparticles were prepared from a p-type wafer (orientation (100), resistivity 0.001 - 0.005 ohm cm, Nova Electronic Materials). The wafer was ground using a mortar and pestle to generate microscale particles. A metal sieve (#230) was utilized to separate microparticles with dimensions smaller than 63 pm. Subsequently, the particles were confined in a syringe containing the same etching solution employed for Por-Si chip fabrication. Following a 5-minute etching process within the syringe, the microparticles were collected on a filter paper, thoroughly washed with deionized (DI) water, and preserved in isopropyl alcohol (IP A) at 4°C for future applications. The porous Si particles showed increased surface area compared to the non-porous counterparts. (Fig. 43).BET characterization

[0310] The powder sample is degassed at 120 °C under vacuum for 12 hours to remove any adsorbed gas or moisture. Nitrogen adsorption at 77 K was used to determine the specific surface area, pore volume, and average pore size, using the BET (Brunauer-Emmett-Teller) method. The analyses were performed using a 3Ilex Adsorption Analyzer (Micromeritics Instrument Corporation, USA). This method is based on determination of the volumes of gas adsorbed and desorbed at different relative pressures.Evaluation of in vivo biocompatibility in mice

[0311] Monolithic silicon membranes were surgically implanted under the dorsal skin of 6- to 8-week-old C57BL / 6J mice through incisions, which were later closed with sutures. After 7 days, mice were euthanized, and skin tissue surrounding the implant site was excised and fixed with buffered formalin for histology. The excised tissues were processed and stained with hematoxylin and eosin for histopathological evaluation at the University of Chicago human tissue resource center.Transmission electron microscopy of Si microparticles

[0312] For transmission electron microscopy (TEM) characterization, por-Si microparticle suspension was dropped onto copper grids (lacey formvar / carbon, Ted Pella). Morphology and crystallinity of microparticles were observed on their edge areas with Tecnai F30 (FEI) at 300 kV.Optical materials microscopy

[0313] Color optical microscopy and 3D profiling was performed on the Olympus OLS5000 LEXT system.Surface ECG recordings on the anesthetized live rat.

[0314] ECG measurements on live rats involved with Arduino Uno board and ECG sensor AD8232 (DFRobot). Data was extracted using Teraterm software. To facilitate the coupling between skin and ECG electrode, the commercial adhesive pad could be replaced by our custom- made hydrogels for better signal-to-noise ratio. The amplitude reading was converted to voltage values for better interpretation. Arduino utilizes a 10-bit analog-to-digital converter from 5 V analog input, so the following conversion equation is used:

[0315] It should be noted that the amplitude values were not used for any direct quantitative analysis to match the values reported in clinical ECG readings.Hydrogel synthesis for electrode-skin interface

[0316] To prepare the hydrogel precursor solution, 4 wt% chitosan (448869, Sigma-Aldrich) and 4 wt% L-ascorbic acid (A92902 solution, Sigma-Aldrich) were dissolved in lx PBS overnight. The gelatin powder (Type A, G2500, Sigma-Aldrich) from porcine skin was then gradually added into the mixed solution at 45 °C for 1 hour with vigorous stirring. The final concentration of the gelatin in the mixed solution was 12 wt%. The interfacial hydrogel can be generated after the in-situ gelation of the solution at the rat skin surface.

[0317] The embodiments illustratively described herein suitably can be practiced in the absence of any element or elements, limitation or limitations that are not specifically disclosed herein. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the embodiments claimed. Thus, it should be understood that although the present description has been specifically disclosed by embodiments, optional features, modification, and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of these embodiments as defined by thedescription and the appended claims. Although some aspects of the present disclosure can be identified herein as particularly advantageous, it is contemplated that the present disclosure is not limited to these particular aspects of the disclosure.

[0318] Claims or descriptions that include “or” between one or more members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context. The disclosure includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process. The disclosure includes embodiments in which more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process.

[0319] Furthermore, the disclosure encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, and descriptive terms from one or more of the listed claims is introduced into another claim. For example, any claim that is dependent on another claim can be modified to include one or more limitations found in any other claim that is dependent on the same base claim. Where elements are presented as lists, e.g., in Markush group format, each subgroup of the elements is also disclosed, and any element(s) can be removed from the group.

[0320] It should it be understood that, in general, where the disclosure, or aspects of the disclosure, is / are referred to as comprising particular elements and / or features, certain embodiments of the disclosure or aspects of the disclosure consist, or consist essentially of, such elements and / or features. For purposes of simplicity, those embodiments have not been specifically set forth herein.References1. Jiang, Y. et al. Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing. Nat. Biotechnol. (2022) doi: 10.1038 / s41587-022- 01528-3.2. Maya-Vetencourt, J. F. et al. A fully organic retinal prosthesis restores vision in a rat model of degenerative blindness. Nat. Mater. 16, 681-689 (2017).3. Ferlauto, L. et al. Design and validation of a foldable and photovoltaic wide-field epiretinalprosthesis. Nat. Commun. 9, (2018).4. Mickle, A. D. etal. 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Claims

CLAIMS1. A method for modulating activity of cardiac tissue, the method comprising: contacting a cardiac tissue with a silicon device, wherein the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate; and exposing the silicon device to light from a light emitter at a periodic rate to cause activation of the silicon device and simulation of the cardiac tissue, wherein the silicon device is exposed to light at a particular point on the silicon device to cause the silicon device to induce a current in an area within about 2 millimeters of the particular point.

2. The method of claim 1, wherein the silicon substrate comprises a layer of p-type silicon.

3. The method of claim 2, wherein the plurality of nanoscale pores are etched into the layer of p-type silicon.

4. The method of claim 3, wherein the plurality of nanoscale pores are etched into the silicon substrate by metal-assisted chemical etching, stain-etching, or a combination of metal-assisted chemical etching and stain-etching.

5. The method of claim 4, wherein the combination of metal-assisted chemical etching and stain etching comprises: submerging the silicon substrate in a solution including silver nitrate, wherein the solution further includes one or more acids; removing the silver from the silicon substrate by submerging the silicon substrate in nitric acid; and exposing the silicon substrate to oxygen plasma to create the silicon device with the plurality of nanoscale pores etched thereon.

6. The method of claim 1, wherein the plurality of nanoscale pores are evenly distributed on the silicon substrate.

7. The method of claim 6, wherein each nanoscale pore is between about 1 nm and about 900 nm in width.

8. The method of claim 1, wherein the light emitter is configured to emit light at a periodic rate ranging from about 0.5 pulses per second to about 6 pulses per second.

9. The method of claim 8, wherein the duration for each light pulse ranges from about 0.5 milliseconds to about 15 milliseconds.

10. The method of claim 8, wherein the light emitter is further configured to provide light at a wavelength ranging from about 400 to about 900 nm and at a power ranging from about 1 mW to about 1 W.

11. The method of claim 1, wherein the light emitter is configured to emit light and not emit light for different time periods.

12. The method of claim 1, wherein the silicon device further comprises a supporting substrate, wherein the supporting substrate comprises polydimethylsiloxane.

13. The method of claim 1, wherein the light emitter is a first light emitter, wherein the system further comprising a second light emitter, wherein the first light emitter and the second light emitter provide light at different wavelengths.

14. The method of claim 1, wherein the silicon device adheres to the cardiac tissue by capillary force.

15. The method of claim 1, wherein the silicon device adheres to the cardiac tissue without sutures or adhesives.

16. The method of claim 1, wherein the silicon device adheres to the cardiac tissue with sutures or adhesives.

17. The method of claim 1, wherein the light emitter is not directly connected to the silicon device.

18. The method of claim 1, wherein the cardiac tissue is a heart comprising a left ventricle and a right ventricle.

19. The method of claim 18, wherein the silicon device is placed on a left or right ventricular wall of the heart.

20. The method of claim 19, wherein exposing the silicon device to light causes the silicon device to induce the heart to beat.

21. The method of claim 20, wherein the periodic rate is between about 30 beats per minute and about 360 beats per minute.

22. The method of claim 18, wherein the silicon device is placed on a left ventricular wall and a right ventricular wall of the heart.

23. The method of claim 22, wherein exposing the silicon device to light comprises exposing the silicon device to light at a first wavelength and a second wavelength.

24. The method of claim 23, wherein exposing the silicon device to light at the first wavelength causes simulation of the left ventricle.

25. The method of claim 23, wherein exposing the silicon device to light at the second wavelength causes simulation of the right ventricle.

26. The method of claim 23, wherein the first wavelength is between about 600 nm and about 700 nm and wherein the second wavelength is between about 400 nm and about 500 nm.

27. The method of claim 1, wherein simulation of the cardiac tissue induces a calcium influx proximate to the particular point at which the light was directed.

28. The method of claim 1, wherein the light has an optical intensity of between about 0.05 mW / mm2and about 100 mW / mm2.

29. The method of claim 1, wherein the area in which current is induced is an effective photostimulation area, and wherein the effective photostimulation area does not exceed 2 millimeters from a light spot center of the light emitted from the light emitter.

30. The method of claim 1, wherein a light spot size of the light emitted from the light emitter to the area on the silicon device has a diameter of between about 5 micrometers and about 1000 micrometers.

31. The method of claim 1, wherein the silicon substrate comprises a layer of p-type silicon, wherein the plurality of nanoscale pores are etched into the layer of p-type silicon, wherein each nanoscale pore is between 1 nm and 900 nm in width, and wherein the silicon device further comprises: a supporting substrate comprising polydimethylsiloxane; and a structure that can be coupled with epicardial flexible multi el ectrode array (MEA) for simultaneous electrical recording during the optical pacing, wherein exposing the silicon device to light from the light emitter causes the silicon device to send an electric signal to the cardiac tissue.

32. The method of claim 31, wherein the structure is an origami or kirigami structure.

33. A system, comprising: a silicon device, wherein the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate; a light emitter configured to emit light at a periodic rate; anda controller that is operably coupled to the light emitter, wherein the controller comprises one or more processors, wherein the controller is programmed to perform controller operations including: operating the light emitter to provide a plurality of pulses of light at the periodic rate to cause activation of the silicon device and stimulation of cardiac tissue, wherein operating the light emitter to provide a plurality of pulses comprises exposing the silicon device to light at a particular point on the silicon device to cause the silicon device to induce a current at an area within about 2 millimeters of a light spot center of the light emitted from the light emitter.

34. A computing device configured to carry out a plurality of operations, the operations comprising: contacting a cardiac tissue with a silicon device, wherein the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate; and exposing the silicon device to light from a light emitter at a periodic rate to cause activation of the silicon device and simulation of the cardiac tissue, wherein the silicon device is exposed to light at a particular point on the silicon device to cause the silicon device to induce a current at an area within about 2 millimeters of a light spot center of the light emitted from the light emitter.

35. A porous silicon (Por-Si) device, comprising: a membrane comprising: a nanoporous semiconductor layer and a nonporous semiconductor layer that form a heterojunction; and a flexible substrate comprising one or more polymers, wherein the flexible substrate is in contact with the nonporous semiconductor layer.

36. The Por-Si device of claim 35, wherein the Por-Si device is fabricated by stain etching.

37. The Por-Si device of claim 36, wherein the Por-Si device is passivated with TiO2 after the stain etching.

38. The Por-Si device of claim 37, wherein the TiO2 has a thickness between about 1 nm and about 50 nm.

39. The Por-Si device of claim 35, wherein the Por-Si device is fabricated by silver-assisted porosification.

40. The Por-Si device of claim 39, wherein the Por-Si device is passivated with TiO2 after the silver-assisted porosification.

41. The Por-Si device of claim 40, wherein the TiO2 has a thickness between about 1 nm and about 50 nm.

42. The Por-Si device of claim 35, wherein the Por-Si device is fabricated by metal-assisted chemical etching (MACE).

43. The Por-Si device of claim 42, wherein the Por-Si device is passivated with TiO2 after the MACE.

44. The Por-Si device of claim 43, wherein the TiO2 has a thickness between about 1 nm and about 50 nm.

45. A delivery device, comprising: a catheter body comprising a delivery end; an interior retention space within a portion of the catheter body, wherein the interior retention space is configured to receive a silicon device prior to use of the delivery device; and a plurality of deployable arms within the catheter body and surrounding the interior retention space, wherein the plurality of deployable arms are configured to extend from the delivery end of the catheter body and flare in an outward direction to deliver the silicon device during use of the delivery device.

46. A method, comprising: a) introducing a delivery device into a small incision in a target body, wherein the delivery device comprises: a catheter body comprising a delivery end, an interior retention space within a portion of the catheter body, wherein the interior retention space is configured to receive a silicon device prior to use of the delivery device, wherein the silicon device comprises a plurality of nanoscale pores etched into a silicon substrate, and a plurality of deployable arms within the catheter body and surrounding the interior retention space; b) deploying the silicon device from the interior retention space of the delivery device via the plurality of deployable arms of the delivery device; c) placing, by the deployable arms of the delivery device, the silicon device on an epicardial surface within the target body; and d) retracting the delivery device through the small incision.

47. The method of claim 46, wherein deploying the silicon device from the interior retention space of the delivery device via the plurality of deployable arms of the delivery device further comprises radial extension of the plurality of deployable arms from the delivery end of the catheter body of the delivery device to deploy the silicon device in preparation for placement.

48. The method of claim 46, further comprising: introducing an optical fibre-coupled endoscope into the small incision; illuminating, via the optical fibre-coupled endoscope, a portion of the silicon device; and stimulating, via the silicon device, a desired site on the epicardial surface.

49. The method of claim 48, wherein illuminating, via the optical fibre-coupled endoscope, the portion of the silicon device comprises exposing the silicon device to light from a light emitter of the optical fibre-coupled endoscope at a periodic rate to cause activation of the silicon device.

50. The method of claim 46, wherein the target body comprises an animal.

51. The method of claim 50, wherein the animal comprises a mammal.

52. The method of claim 51, wherein the mammal is a human.

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