Methods and systems for optical detection using a biomimetic electrochemical eye

Abstract

This application provides a biomimetic electrochemical eye device and its manufacturing method, an artificial vision system, a method for manufacturing an electrochemical detector, and a method for manufacturing an integrated electrochemical image sensor. The biomimetic electrochemical eye device includes: a first hemispherical film layer, the first hemispherical film layer comprising: a hemispherical membrane including a plurality of through-holes, and a plurality of nanowires formed in the plurality of through-holes, the nanowires being made of a material with photoelectric effect; a second hemispherical film layer, the second hemispherical film layer comprising: a first hemispherical shell, and a metal film layer located on the concave side of the first hemispherical shell; an ionic liquid filling a spherical cavity formed by the first hemispherical film layer and the second hemispherical film layer; and a plurality of back contacts connected to the plurality of nanowires from the back side of the first hemispherical film layer opposite to the concave side of the first hemispherical film layer.

Description

[0001] Cross-references to related applications

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 100,942, filed April 9, 2020, which is incorporated herein by reference. Technical Field

[0003] This application relates to the field of optical inspection, and more specifically, to methods and systems for optical inspection using a bionic electrochemical eye. Background Technology

[0004] The biological eye is arguably the most important sensory organ for the vast majority of animals on Earth. In fact, the human brain uses the eyes to acquire more than 80% of its information about its surroundings. The human eye, with its concave hemispherical retina and light management components, is particularly remarkable for its exceptional characteristics, including a wide field of view (FOV) of up to 150°, high resolution of 1 arcmin per line at the fovea, and excellent adaptability to the optical environment. In particular, the dome shape of the retina has the advantage of reducing the complexity of the optical system by directly compensating for aberrations from the curved focal plane.

[0005] Just as the human eye mimics the human eye, artificial vision systems play a crucial role in autonomous technologies such as robotics. However, currently used commercial charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) image sensors in artificial vision systems primarily employ planar device structures formed through mainstream planar microfabrication processes, making the fabrication of hemispherical devices difficult. In other words, most image sensors currently manufactured and used in artificial vision systems are planar (e.g., 2D) rather than hemispherical (e.g., 3D and shaped like a human eye). Because they are not hemispherical, these sensors lack many of the unique device characteristics and the aforementioned advantages of a human eye-like shape. Furthermore, particularly for humanoid robots, vision systems seek to be designed to resemble the human eye as closely as possible in appearance to enable friendly human-robot interactions. Therefore, there remains a technological need for designs of hemispherical image sensors that mimic the human retina. Summary of the Invention

[0006] Embodiments of this application disclose a biomimetic electrochemical eye device, which includes:

[0007] A first hemispherical membrane layer, comprising:

[0008] A hemispherical membrane comprising multiple through-holes, and

[0009] Multiple nanowires formed in the plurality of through-holes, the nanowires being made of a material having a photoelectric effect;

[0010] The second hemispherical membrane layer comprises:

[0011] The first hemispherical shell, and

[0012] A metal film layer located on the concave side of the first hemispherical shell;

[0013] An ionic liquid, which fills a spherical cavity formed by the first hemispherical film layer and the second hemispherical film layer; and

[0014] Multiple back contacts are connected to the multiple nanowires from the back side of the first hemispherical film layer opposite to the concave side of the first hemispherical film layer.

[0015] In some embodiments, each of the plurality of back contacts is individually connected to at least one of the plurality of nanowires.

[0016] In some embodiments, each of the plurality of back contacts is a liquid metal wire.

[0017] In some embodiments, each of the plurality of back contacts includes a conductive microneedle.

[0018] In some embodiments, each of the plurality of nanowires includes a first portion wholly located in the through-hole and a second portion partially protruding outward from the back side of the first hemispherical film layer, the first portion and the second portion being made of different materials, and the conductive microneedle being connected to the second portion of the at least one nanowire.

[0019] In some embodiments, each of the plurality of back contacts includes a conductive wire, and the conductive microneedles electrically connect the conductive wire to the at least one nanowire.

[0020] In some embodiments, the conductive microneedles are connected to four of the plurality of nanowires that form a pixel.

[0021] In some embodiments, the biomimetic electrochemical eye device further includes a second hemispherical housing, wherein the second hemispherical housing is attached to the back side of the first hemispherical film layer, the second hemispherical housing includes a plurality of through holes arranged in an array, and the plurality of back contacts are connected to the plurality of nanowires through the plurality of through holes of the second hemispherical housing.

[0022] In some embodiments, the second hemispherical film layer has an opening at its center, and the lens is embedded in the opening.

[0023] In some embodiments, adjacent nanowires in the plurality of nanowires are spaced 500 nm apart, and the plurality of nanowires have a spacing of 4.6 × 10⁻⁶ nm. 8 cm -2 The density.

[0024] In some embodiments, the ionic liquid comprises 10 v% of 1-butyl-3-methylimidazolium iodide.

[0025] Embodiments of this application also disclose an artificial vision system, comprising: the aforementioned bionic electrochemical eye device, a circuit system connected to the bionic electrochemical eye device, and a computing device connected to the circuit system and configured to process data.

[0026] In some embodiments, the circuit system includes a multiplexer, a voltage source, an ammeter, and ground.

[0027] Embodiments of this application also disclose a method for manufacturing an electrochemical detector in a hemispherical artificial retina, comprising:

[0028] A hemispherical membrane with multiple pores is formed, wherein a blocking layer is provided on one side of the hemispherical membrane to block the multiple pores;

[0029] At least a portion of the barrier layer is removed to form at least a portion of the plurality of holes as through-holes through the hemispherical membrane;

[0030] Nanowires are grown in the through-holes, wherein the nanowires are made of a material with photoelectric effect.

[0031] In some embodiments, forming a hemispherical film having a plurality of pores includes forming the hemispherical film by anodizing and etching processes.

[0032] In some embodiments, removing at least a portion of the barrier layer includes etching at least a portion of the barrier layer using a focused ion beam.

[0033] Embodiments of this application also disclose a method for manufacturing an integrated electrochemical image sensor in a hemispherical artificial retina, comprising:

[0034] A hemispherical membrane with multiple pores is formed, wherein a blocking layer is provided on a first side of the hemispherical membrane to block the multiple pores;

[0035] Remove the barrier layer to form the plurality of holes as through-holes through the hemispherical membrane;

[0036] A first nanowire is grown in the through-hole of the hemispherical membrane such that the first nanowire fills the portion of the through-hole near the first side, wherein the first nanowire is made of a conductive material;

[0037] A portion of the hemispherical membrane is removed from the first side, such that a portion of the first nanowire is exposed to the outside of the hemispherical membrane;

[0038] A second nanowire is grown in the through-hole of the hemispherical film, such that the second nanowire fills the remaining portion of the through-hole, wherein the second nanowire is made of a material with photoelectric effect;

[0039] The conductive microneedles are placed on the hemispherical membrane from the first side, such that each conductive microneedle is electrically connected to at least one of the first nanowires, and the conductive microneedles are fixed and encapsulated using an encapsulation material.

[0040] Connect a conductive wire to the conductive microneedle to electrically connect the conductive microneedle to an external device.

[0041] In some embodiments, forming a hemispherical film having a plurality of pores includes forming the hemispherical film by anodizing and etching processes.

[0042] In some embodiments, the first nanowire comprises nickel and the second nanowire comprises perovskite.

[0043] Embodiments of this application also disclose a method for manufacturing a spherical biomimetic electrochemical eye device, comprising:

[0044] Forming the first hemispherical aluminum shell;

[0045] A hemispherical porous alumina film substrate is formed on the concave side of the first hemispherical aluminum shell;

[0046] Remove the barrier layer located on one side of the porous alumina film substrate and remove the first hemispherical aluminum shell to form an independent porous alumina film substrate having a through hole through the porous alumina film substrate.

[0047] Perovskite nanowires are grown in the through-holes of the independent porous alumina film substrate.

[0048] An adhesion layer is formed on the back surface opposite to the concave side of the independent porous alumina film substrate;

[0049] A hemispherical polydimethylsiloxane shell with an array of through holes is formed;

[0050] The independent porous alumina film substrate is bonded to the polydimethylsiloxane shell through the adhesive layer;

[0051] Liquid metal is injected into a hose to form a liquid metal line;

[0052] One end of the liquid metal wire is electrically connected to the perovskite nanowire through the through-hole array of the polydimethylsiloxane shell, so as to electrically connect the perovskite nanowire to an external device.

[0053] A second hemispherical aluminum shell with a circular opening at the center is formed, a tungsten film is formed on the concave side of the second hemispherical aluminum shell, and a light-transmitting hole is installed at the circular opening;

[0054] The second hemispherical aluminum shell and the independent porous alumina film substrate are paired and bonded together to form a spherical cavity between them;

[0055] An ionic liquid is injected into the spherical cavity, and the lens is glued to the light-transmitting hole on the second hemispherical aluminum shell to seal the spherical cavity. Attached Figure Description

[0056] Figure 1 A schematic diagram of a human imaging system is shown.

[0057] Figure 2 A schematic diagram of a spherical biomimetic electrochemical eye (EC-EYE) imaging system is shown.

[0058] Figure 3A An exploded view of EC-EYE is shown.

[0059] Figure 3B and Figure 3C Showing from Figure 3A Different perspectives of the assembled version of EC-EYE.

[0060] Figure 4A and Figure 4B Showing from Figure 3A Images of some of the components of the EC-EYE.

[0061] Figures 5A to 5D It shows the use of Figure 3A The light detection performance characteristics of each pixel in the EC-EYE.

[0062] Figure 6A and Figure 6B An EC-EYE with single and multiple nanowire (NW)-based electrochemical (EC) detectors is shown, along with fabrication processes for single and multiple NW-based EC detectors.

[0063] Figure 7 A scanning electron microscope (SEM) image showing the controlled growth of nanowires (NW) is shown.

[0064] Figures 8A to 8CThe diagram shows the EC-EYE with microneedle contacts, the manufacturing process of the microneedle array contacts, and a view of the device structure after the microneedle array contacts have been manufactured.

[0065] Figure 9 Showing from Figure 3A Different perspectives on EC-EYE.

[0066] Figures 10A to 10C An exemplary system and exemplary circuit diagram for capturing images using EC-EYE are shown, as well as an image captured using EC-EYE.

[0067] Figure 11 A comparison of FOV between EC-EYE and planar image sensors is shown.

[0068] Figure 12 This is a schematic diagram of an exemplary system for capturing one or more images using EC-EYE.

[0069] Figure 13 An exemplary procedure for capturing images using EC-EYE is shown. Detailed Implementation

[0070] Exemplary embodiments of this application provide an artificial vision system comprising a spherical biomimetic electrochemical eye (EC-EYE) having a hemispherical retina made of a high-density semiconductor nanowire (NW) array, and a method for using the artificial vision system. Further exemplary embodiments of this application provide systems and methods for growing or fabricating EC-EYEs using vapor-phase methods. For example, semiconductor NW arrays can be fabricated using any material with photoelectric effects (e.g., but not limited to metal halide perovskites, silicon (Si), germanium (Ge), indium phosphide (InP), gallium arsenide (GaAs), and / or other suitable materials, components, or elements). Hereinafter, EC-EYEs will be described as being fabricated using metal halide perovskites in order to describe the device structure and operating mechanism. However, in other examples, EC-EYEs can be made of Si, Ge, and / or other materials with photoelectric effects. In the EC-EYE, an ionic liquid electrolyte can be used as a front common contact to connect to the NW, and a liquid metal (LM) wire can be used as a back contact to connect to the NW photodetector (or NW), mimicking the nerve fibers behind the retina in the human body. Device characteristics and advantages can emerge, such as high responsivity, reasonable response speed, low detection limit, and wide field of view (FOV). In other words, due to the shape (e.g., hemispherical) and / or design of the EC-EYE's retina, the EC-EYE can have and / or acquire advantages commonly associated with the human eye. Furthermore, the EC-EYE can demonstrate the basic functions of the human eye in acquiring image patterns. In addition to its structural similarity to the human eye, the NW density of a hemispherical artificial retina is much higher than the density of photoreceptors in the human retina, and therefore, a hemispherical artificial retina can potentially achieve higher image resolution, which can be supported by implementing a single, ultra-miniature photodetector.

[0071] Figure 1 and Figure 2 A human imaging system was shown. Figure 1 ) and EC-EYE imaging system ( Figure 2 An illustrative comparison. Specifically, Figure 1 and Figure 2Each section comprises three parts, and each part illustrates a different image. Section 102 illustrates the human visual system, which is a comprehensive system with two eyeballs for optical sensing, millions of nerve fibers for data transmission, and a brain for data processing. The human brain has an astonishing capacity for parallel processing. For example, neural electrical signals from approximately one million nerve fibers can be processed simultaneously, and thus image processing / recognition can be achieved in a very short time. The internal structure of the human eye shown in section 104 includes a lens 108, a spherical cavity, vitreous fluid 110, a hemispherical retina 112, and nerve fibers 114. In this structure, vitreous fluid 110 is a transparent gel-like tissue filling the eyeball behind the lens 108, and the retina 112 is the core component for converting optical images into neural electrical signals. The hemispherical shape simplifies the optical design of the eye, resulting in an ultra-large FOV of approximately 155° with wide visual perception of the surrounding environment. Section 106 illustrates the human retina with photoreceptors 118, neurons 120, and an optic nerve layer 116 including the optic nerve. Approximately 100 to 120 million photoreceptors 118 and / or rod and cone cells are densely and vertically assembled in a quasi-hexagonal manner within the retina 112. These photoreceptor units 118 have a density of approximately 10 million per square centimeter, and the average spacing between the photoreceptor units 118 is 3 μm, resulting in a high imaging resolution comparable to that of prior art CCD / CMOS sensors. However, the nerve fiber layer is located on the anterior surface of the human retina, leading to light loss and blind spot problems. For example, light loss may exist through the optic nerve layer 116. Since the nerve fibers travel in front of the retina 112, there is a “via” through which the fibers pass through the retina 112. This “via” can be a blind spot on the retina 112 where there are no photoreceptors 118.

[0072] Reference Figure 2Section 202 illustrates the entire EC-EYE imaging system including the EC-EYE, section 204 illustrates the EC-EYE, and section 206 illustrates the perovskite NW and its crystal structure in a porous alumina film (PAM) template. Specifically, sections 202, 204, and 206 illustrate schematic diagrams of a biomimetic vision system including a lens 208, a retina 210 (e.g., an NW retina), and fine liquid metal (LM) wires (e.g., LM fibers) 214 as electrical contacts. The retina 210 may include a photodetector array 212 (e.g., NW photoreceptors) on a hemispherical substrate. The lens 208, the photodetector array 212 on the hemispherical substrate, and the fine LM wires 214 assembly mimic the lens, retina, and nerve fibers behind the retina of a biological eye, respectively. The artificial retina is fabricated from a high-density array 212 of perovskite NWs. In some cases, perovskite NWs are grown inside a hemispherical porous alumina film (PAM) using a vapor phase process. Additionally and / or alternatively, certain components of the EC-EYE can be manufactured and / or produced using 3D printing and / or liquid metal patterning. The manufacturing / production process is described below.

[0073] Figure 3A It shows Figure 2 An exploded view of the EC-EYE. For example, refer to... Figure 3AAn exploded view of the EC-EYE 300 is shown. The EC-EYE 300 includes a lens 302, an aperture 304, an aluminum (Al) shell sclera and a tungsten (W) film contact 306, an ionic liquid body fluid 308, an indium adhesion layer 310, a polydimethylsiloxane (PDMS) orbital 312, a non-volatile (NW) array retina 314, and liquid metal (LM) nerve fibers 316. The NW 314 (e.g., the NW array retina) serves as a photosensitive working electrode. The tungsten (W) film 306 on the aluminum (Al) hemispherical shell serves as a counter electrode. Between the two electrodes (e.g., 314 and 306), an ionic liquid (e.g., an ionic liquid body fluid 308) is used to fill the spherical cavity as an electrolyte, mimicking the vitreous fluid in the human eye. An aperture 304 is also present as a corresponding portion of the pupil in the human eye. Flexible LM lines 316 (e.g., eutectic gallium indium (EGaIn) LM lines) in a soft rubber tube are used for signal transmission between the NW 314 (e.g., an NW array retina) and external circuitry (e.g., a processor, controller, and / or other types of computing devices described below that can be used to process images captured by the EC-EYE 300). Individual photodetectors can be addressed and measured by selecting corresponding LM lines from the liquid metal nerve fibers 316. This is analogous to the working principle of the human retina, where each set of photoreceptors is individually connected to each nerve fiber, enabling suppression of inter-pixel interference and high-speed parallel processing of neural electrical signals. Additionally and / or alternatively, the LM lines 316 are located behind the sensing material (e.g., the NW array 314), thus avoiding the light loss and blind spot problems mentioned earlier in the human retina. In some examples, a 10×10 photodetector array (e.g., the NW array 314) can be fabricated with a spacing of 1.6 millimeters (mm). In some variations, the minimum size of each sensing pixel within the NW array 314 can be limited by the diameter of the LM line 316, which can be a few micrometers (μm) or larger. In other variations, to further reduce the pixel size (which increases spatial imaging resolution), an alternative method of fabricating the sensor pixel array can be used, in which each pixel has an area of ​​approximately 1 μm. 2 Furthermore, metal microneedles are used. This alternative method is described in further detail below. In embodiments of this application, each pixel may include at least one NW in the NW array 314, and each LM line 316 may be connected to a pixel.

[0074] Photosensitive NW 314 can be grown in a hemispherical template, thus forming a unique structure similar to the human retina in a single step. Lead formamidinium iodide (FAPbI3) is suitable as a model material for NW growth due to its excellent photoelectric properties and appropriate stability. However, in other examples, other suitable materials can be used as model materials for NW 314 growth. The NW growth and property details are further described below. In other variations, gas-liquid-solid processes can also be used to grow other types of inorganic NWs made of Si, Ge, GaAs, etc., and used in EC-EYE 300.

[0075] Figure 3B and Figure 3C Showing from Figure 3A Different perspectives of the assembled version of the EC-EYE. Specifically, Figure 3B Showing from Figure 3A The side view of the assembled EC-EYE shows an indicator 318 to indicate one centimeter (cm). Figure 3C Showing from Figure 3A A top view of the assembled EC-EYE, showing indicator 320 to indicate five millimeters (mm).

[0076] Figure 4A and Figure 4B More details are shown from Figure 3A Some of the various components of EC-EYE. For example, Figure 4A and Figure 4B Each has two parts, and each part shows a different image of a component from the EC-EYE 300. (See reference...) Figure 4A Section 402 is a low-resolution cross-sectional scanning electron microscope (SEM) image of a hemispherical PAM / NW (e.g., NW array retina 314). An indicator 412 is shown to indicate 2 mm. Section 404 is a cross-sectional SEM image of the NW 314 within the PAM. Specifically, section 404 is a close-up image of the rectangular portion 410 indicated in section 402. The SEM images of the hemispherical PAM and NW 314 shown in sections 402 and 404 are located at the bottom of the nanochannel. (See reference...) Figure 4B Section 406 shows a high-resolution transmission electron microscope (HRTEM) image of a single-crystal perovskite NW array 314. Specifically, the single-crystal NWs have a spacing of 500 nm and a diameter of 4.6 × 10⁻⁶ nm. 8 cm -2The density, which is much higher than that of photoreceptors in the human retina, demonstrates the potential and / or capability to achieve high imaging resolution based on appropriate electrical contact. Indicator 416 is shown indicating 3 nm. Section 408 shows an image of the PDMS eye socket 312 used to aid in alignment of the LM line 316. Indicator 418 is shown indicating 5 mm.

[0077] Figures 5A to 5D It shows the use of Figure 3A The light detection performance characteristics of each pixel in the EC-EYE 300. For example, Figure 5A An exemplary schematic diagram of a single-pixel measurement performed by the EC-EYE 300 is shown. Specifically, Figure 5A The diagram illustrates an EC-EYE 300, a single LM line 502 containing liquid metal, and circuitry (e.g., ground, power supply (e.g., a battery or battery pack), and / or an ammeter / current meter). The EC-EYE 300 can be used to capture measurements of individual pixels. In other words, each LM line in the LM line 316 (e.g., line 502) can capture measurements of a single pixel. For example, a collimated beam 504 is focused onto a pixel at the center of the retina of the EC-EYE 300.

[0078] Figure 5B The band structure of the EC-EYE 300 is shown, and the charge-carrier separation path under photoexcitation is further illustrated. In some cases, the EC-EYE 300 can capture image pixels at a bias voltage of -3 volts (V).

[0079] Figure 5C The current-voltage (I / V) characteristic is shown, which exhibits the characteristics of... Figure 5B The asymmetric photoresponse is caused by asymmetric charge transport across the NW sides. Electrochemical properties indicate that the iodide / triiodide (I) ion / triiodide ratio is affected. - / I 3- The redox reactions of the two phases occur at the NW / electrolyte and tungsten film / electrolyte interfaces, and ion transport within the electrolyte contributes to the photoresponse. Inset 506 shows the transient response of EC-EYE 300 to chopped light. The relatively fast and highly reproducible response indicates that EC-EYE 300 possesses excellent photocurrent stability and reproducibility. The response time and recovery time are approximately 32.0 ms and 40.8 ms, respectively. Furthermore, electrochemical analysis of the critical NW / electrolyte interface reveals that the response time of EC-EYE 300 can depend on the kinetics of various ion types at this interface. Electrochemical impedance spectroscopy (EIS) measurements indicate that structural optimization of EC-EYE 300 and increased ionic liquid concentration can significantly reduce the charge transfer resistance (R) at the NW / electrolyte interface. ctThis results in the EC-EYE 300's response and recovery times being reduced to 19.2ms and 23.9ms, respectively, which is much faster than the response and recovery times of human photoreceptors in the range of 40ms to 150ms.

[0080] EC-EYE 300 can be improved by reducing R. ct To achieve a relatively fast and highly repeatable response speed, EC-EYE 300 can be optimized, for example, by removing the subchannel layer between the NW and the metal electrode (e.g., liquid metal). The subchannel layer refers to the fine pore layer between the NW and the liquid metal. After PAM fabrication, a U-shaped oxide insulating layer (i.e., a barrier layer) can be formed at the bottom. A barrier layer thinning process prior to NW growth results in the formation of fine subchannels at the bottom of the PAM. For NW growth, the barrier layer thinning process can include thinning the barrier layer to approximately 3 nanometers using a progressively decreasing anodic oxidation voltage. The barrier layer can include an alumina layer. During the barrier layer thinning process, large channels gradually split into multiple smaller channels (i.e., the subchannel layer mentioned above). Smaller channels have smaller diameters and therefore higher resistance, thus increasing the overall resistance. NWs grown in this subchannel layer can have smaller diameters and higher resistance than NWs in the main channels. Therefore, removing the subchannel layer reduces resistance and optimizes EC-EYE 300. Therefore, the EIS measurement results indicate that the R of EC-EYE 300 ct In darkness and light (50 microwatts (μW) cm) -2 (cm -2 The response times are 5.56 megohms and 1.89 megohms. The response and recovery times of the EC-EYE 300 are 32 ms and 40.8 ms, respectively. In some examples, a gentle ion milling process can be used to remove the subchannel layer to facilitate carrier transport in the NW. For such examples, considering both dark and light conditions, R... ct The Ω values ​​can be significantly reduced to 1.31 MΩ and 0.92 MΩ, indicating an accelerated charge transfer process. Consequently, the response and recovery rates of EC-EYE (response time t) can be improved. reponse = 21.8ms, recovery time t recovery =29.9ms).

[0081] Additionally and / or alternatively, improve I - / I 3- The concentration of the redox pair (e.g., increasing the concentration of 1-butyl-3-methylimidazolium iodide (BMIMI) from 1 v% to 10 v%) further promotes the charge transfer rate. Using these increased concentrations, EIS measurements indicate that R ctThe impedance has been further reduced to 1.28 megohms and 0.4 megohms under dark and light conditions, respectively. Response time and recovery time have been reduced to 19.2 ms and 23.9 ms, respectively.

[0082] Figure 5D The image shows the photocurrent and responsivity of individual pixels in relation to illumination intensity, obtained using the EC-EYE 300. Figure 5D The illumination light intensity shown has a range from 0.3 μW / cm². -2 Up to 50 milliwatts (mW) cm -2 The photocurrent has a wide dynamic range and conforms to the quasi-linear power law relationship (I~P). 0.69 (I) represents the photocurrent, and P represents the irradiance. When the illumination intensity is reduced, the responsivity can increase, and can reach up to 303.2 mAW. -1 This is the highest reported among photoelectrochemical (PEC) photodetectors. At the lowest measured radiation level, the average number of photons received per second from a single NW can be estimated at 86 photons. This sensitivity is comparable to that of human cone cells. The corresponding specific detectivity can be calculated for 0.3 μW / cm². -2 The incident light is ~1.1×10 9 Jones. The spectral responsivity shows a broadband response with a clear cutoff at 810 nm. The stability and repeatability of individual pixels were tested for nine hours under continuous chopper light at two hertz (Hz) to confirm its durability. In other words, this shows that despite drift for both dark current and photocurrent, there is no significant performance degradation of EC-EYE 300 after 64,800 cycles.

[0083] As mentioned above, one of the many advantages of using a high-density NW array 314 for artificial retinas is their potential for high imaging resolution. While the aforementioned LM fiber contact 316 is conveniently connected to the NW 314, and the image resolution is already comparable to many existing bionic eyes in use, in some cases the EC-EYE 300 can be further enhanced to reduce pixel size to the single-digit micrometer level. For example, Figures 6A to 6B and 8A to Figure 8C Additional and / or alternative examples of the EC-EYE 300 for achieving ultra-small pixel sizes are shown. For example... Figure 6A As shown, individual NWs can be deterministically grown within a single nanochannel opened by a focused ion beam (FIB), resulting in a lateral dimension of 500 nanometers (nm) and a micrometer diameter of ~0.22 micrometers. 2 (μm 2 The area occupied by a single pixel.

[0084] Figure 6BThe process 600 for fabricating single and multiple NW-based electrochemical (EC) detectors is shown in more detail. For example, a separate planar PAM is fabricated via a standard two-step anodizing process followed by mercuric chloride (II) (HgCl2) etching. At stage 606, the separate PAM can be transferred to a focused ion beam (FIB) to selectively etch away the barrier layer. To facilitate etching, the chip (i.e., the PAM after the previous stages) can be bonded to an Al substrate with the barrier layer side facing upwards. At stage 608, after FIB etching (e.g., etching voltage: 30 kV, etching current: 26 nA), a 500 nm thick Cu layer can be deposited onto one side of the barrier layer to serve as an electrode for subsequent lead (Pb) electrochemical deposition. Then, at stage 610, the chip can be moved into a tube furnace for perovskite NW growth. Copper (Cu) wires can then be bonded to the Cu side of the PAM using carbon paste, and the entire chip can be fixed to a glass substrate using UV epoxy resin. After curing, at stage 612, an ionic liquid can be dropped onto the top of the PAM. Additionally and / or alternatively, a tungsten probe can be inserted into the ionic liquid for photoelectric measurements. A bias voltage of -3V and a current of 50mW / cm² can be used. 2 The light intensity is measured by the light response.

[0085] Use and Figure 6A and Figure 6B The same method shown can also be used to create four NW pixels and use them to capture images. Figure 7 SEM images showing controlled growth of NWs are presented, including the number and location of NWs. Specifically, Figure 7 Top-view and cross-sectional SEM images of PAM at different stages are shown. For example, stage 702 is before FIB etching, stage 704 fills a single nanowire, and stage 706 fills four nanowires. (Return to reference) Figure 6A The optical response of the two devices (e.g., a single NW and four NWs) is also shown.

[0086] Alternatively, or in addition to using LM line 316, microneedles (nickel (Ni) microneedles) can be used to reduce pixel size to the single-digit micrometer level. Figures 8A to 8C A schematic diagram showing the connection of Ni microneedle contacts to the NW array 314 and the process for fabricating the microneedle contacts is illustrated. For example, Figure 8AAn EC-EYE300 coupled to a copper (Cu) wire signal transmission line is schematically shown. The lateral dimension of the contact area can be 2 mm. For example, to form an array of ultra-small pixels, Ni microneedles can be vertically assembled on top of a PAM via a magnetic field, and thus each microneedle can address four NWs forming a pixel with a lateral dimension of approximately 1 μm and a spacing of 200 μm. Indicator 818 shows 5 micrometers. In embodiments of this application, each pixel may include at least one NW in an NW array 314, and each microneedle may be connected to one pixel.

[0087] Figure 8BA schematic fabrication process for an integrated electrochemical image sensor based on a magnetic field-assisted microneedle array contact is shown. Stage 802 shows a freestanding PAM with through-holes. For example, a 40 μm thick freestanding PAM can be fabricated by standard anodizing, sodium hydroxide (NaOH) etching, and mercuric chloride (II) (HgCl2) solution etching. Ion milling can be used to remove the barrier layer to achieve the through-hole PAM. Then, Stage 804 shows Pb and Ni NWs grown in the PAM. For example, a 1 μm thick copper (Cu) film can be thermally evaporated onto the through-hole PAM to serve as electrodes for subsequent Ni and Pb electrochemical deposition. Stage 806 shows the perovskite NWs grown in the PAM and the Ni NWs exposed by reactive ion etching (RIE). For example, to expose the Ni NWs, the copper layer can be removed by ion milling, and the PAM can be partially etched away by reactive ion etching (RIE). The exposed Ni nanowires can be about 3 μm long. The chip can be moved into a tube furnace for the growth of the perovskite NWs. Next, stage 808 shows a magnetic field-assisted assembly of Ni microneedles on Ni NW / PAM. For example, the PAM chip can be fixed on an electromagnet with the Ni nanowires facing upwards. Simultaneously, a 50 μm diameter Ni microwire can be sharpened in a mixed acid solution (100 ml of 0.25 M hydrochloric acid (HCl) aqueous solution + 100 ml of ethylene glycol (EG)) under a bias voltage of 1 V, where the Ni microwire serves as the working electrode and the tungsten coil serves as the counter electrode. The resulting Ni microwire with a sharp tip can be the aforementioned Ni microneedles, and the radius of curvature of the sharp tip is in the range of 100 nm to 200 nm. The Ni microneedles can then be gently deposited onto the PAM substrate with the magnetic field turned on. Due to the magnetic force, the ferromagnetic Ni microneedles can bond to the Ni NW to form an effective electrical contact with the NW. To facilitate Ni microneedle deposition, a mask with a 10 × 10 hole array (hole diameter: 100 μm, spacing: 200 μm) can be used to align the Ni microneedles. Phase 810 illustrates an epoxy-encapsulated device. For example, after drop-through, UV epoxy resin can be dripped between the mask and the PAM substrate. Enamelled copper wire with a diameter of 60 μm can be inserted into the hole to form an electrical contact bridging the Ni microneedles to an external PCB board. Phase 812 illustrates a device with an ionic liquid for measurement.

[0088] Figure 8C It shows that in the already used Figure 8B The following are different views of the fabrication apparatus structure described in the figure. For example, view 814 is a top view of the apparatus structure, and view 816 is a side view of the apparatus structure. As shown, the apparatus includes Ni microneedles, Ni NW, PAM, perovskite NW, ionic liquid, and sealing substrate.

[0089] After describing the characteristics of each sensor pixel, the functionality of the complete imaging system will be described below. Figure 9 Different perspectives of the EC-EYE 300 are shown. For example, perspective 902 shows a side view of an EC-EYE (e.g., EC-EYE 300) with liquid metal fibers (e.g., LM nerve fibers 316). Perspective 904 shows a front view of an EC-EYE mounted on a printed circuit board (PCB). Perspective 906 shows a rear view of an EC-EYE with liquid metal lines / fibers. Furthermore, perspective 906 also shows a multiplexer electrically coupled to the LM lines / fibers. Although... Figure 9 The example shown includes a PCB, but in other cases the PCB may be optional (e.g., an EC-EYE may be used without a PCB).

[0090] Figure 10A An exemplary system 1000 for capturing images using EC-EYE is shown. For example, EC-EYE 300 includes an LM line 316. The LM line 316 is connected via a PCB to a controllable 100×1 multiplexer 1002. The PCB and multiplexer 1002 are located in... Figure 9 As shown in the figure. System 1000 also includes a galvanometer 1004 (e.g., an ammeter), a computing device 1006 for data processing, a voltage source 1008, and ground 1010. Figure 10B A circuit diagram 1020 of system 1000 is shown. For example, circuit diagram 1020 also includes a multiplexer 1002, a current meter 1004, a computing device 1006, a voltage source 1008, and ground 1010. In addition, each of the pixels (e.g., “pixel 00” to “pixel 99”) represents a different LM line from LM line 316.

[0091] By projecting an optical pattern, the EC-EYE 300 can record, identify, and / or acquire the photocurrent of each sensor pixel. In some examples, to reconstruct the optical pattern projected onto the EC-EYE 300, the photocurrent values ​​can be converted to a grayscale value between 0 and 255. The equation used for grayscale conversion is as follows:

[0092] G = (I Light -I Dark ) / (I Full -I Dark Equation (1) is (1) × 255

[0093] Where G is the grayscale value, I Full -I Dark The dynamic range of the difference between the full illumination current and the dark current of a pixel is given. Figure 10CThe character “A” and its projection on a plane are shown using EC-EYE 300 and System 1000 imaging.

[0094] Compared to planar image sensors based on a crossbar structure, the EC-EYE 300 can provide higher contrast with sharper edges because each individual pixel is better isolated from its neighboring pixels. In some cases, instead of using the EC-EYE 300 with LM contacts 316, small EC image sensors with microneedle contacts can also be fabricated as described above and used to capture images. In some examples, a high-precision robotic arm enhanced with piezoelectric actuators, aided by a magnetic field and a high-resolution optical monitoring system, can be used to alight Ni microneedles onto a hemispherical PAM.

[0095] Figure 11 A comparison of the field of view (FOV) between the EC-EYE 300 and a planar image sensor is shown. For example, compared to the planar image sensor, the hemispherical shape of the EC-EYE 300's retina ensures a more consistent distance between pixels and the lens, resulting in a wider FOV and better focusing across all pixels. For instance, the top layer 1102 is hemispherical, thus the distance from the lens to the center of the top layer 1102 is more consistent with the distance from the lens to the edges / corners of the top layer 1102. The bottom layer 1104, from the planar image sensor, shows that the distance from the lens to the center of the bottom layer 1104 is inconsistent with the distance from the lens to the edges / corners of the bottom layer 1104. The EC-EYE with a hemispherical retina in this application has a diagonal field of view of ~100.1°, while the planar device has a diagonal field of view of only 69.8°. Furthermore, by optimizing the pixel distribution and the shape of the PAM beyond the hemisphere, the field of view can be further improved to a static FOV (approximately 130°) close to that of a single human eye, without taking into account eye / head movement.

[0096] As disclosed herein, images are captured using a bionic eye (e.g., EC-EYE 300) with a hemispherical retina made of a high-density photosensitive nanowire. The structure of EC-EYE 300 can be highly similar to that of the human eye, while possessing the ability to achieve higher imaging resolution based on the aforementioned example and enhancements. The developed process can address the bottleneck challenges of fabricating optoelectronic devices on non-planar substrates with high integration density. Furthermore, EC-EYE 300 can be used in a wide range of technological applications, such as scientific instruments, consumer electronics, robotics, etc.

[0097] Figure 12This is a schematic diagram of an exemplary system 1200 for capturing one or more images using an EC-EYE. For example, system 1200 includes an EC-EYE 1202, a circuit system 1204, and / or a computing device 1206 having a display device 1208. Although entities within system 1200 may be described below and / or depicted in the figures as a single entity, it will be understood that the entities and functions discussed herein may be implemented by and / or comprise one or more entities. For example, in some cases, display device 1208 may be a separate entity from computing device 1206. In other words, computing device 1206 may be one or more controllers and / or processors configured to perform image processing based on information from EC-EYE 1202 and / or circuit system 1204.

[0098] In some cases, System 1200 can be Figure 10A The block diagram of system 1000 is shown. In other words, EC-EYE 1202 may be EC-EYE 300, computing device 1206 may be computing device 1006, and circuit system 1204 may include multiplexer 1002, voltage source 1008, ammeter 1004, and ground 1010. In other cases, system 1200 may include one or more components / entities from system 1000, and / or may also include one or more additional and / or alternative components / entities not shown in system 1000.

[0099] EC-EYE 1202 can be designed to and / or include functions similar to those of EC-EYE 300 described above. For example, EC-EYE 1202 may include NW array retina (e.g., NW array retina 314), LM nerve fibers (e.g., LM nerve fibers 316), and / or the above-mentioned... Figures 2 to 11 The additional / alternative components described herein. EC-EYE 1202 can be configured to capture and / or acquire images and provide that information to computing device 1206 via circuitry system 1204. For example, each of the LM nerve fibers can be electrically coupled to an NW from the NW array retina. The NW can acquire information (e.g., one or more pixels) and then provide the information to circuitry system 1204.

[0100] In some examples, the EC-EYE 1202 may include one and / or multiple NW-based EC detectors. The EC-EYE 1202 can use one and / or multiple NW-based EC detectors to acquire / capture images.

[0101] In some variants, the EC-EYE 1202 may include microneedles (e.g., Ni microneedles). The EC-EYE 1202 can use microneedles to acquire / capture images.

[0102] The EC-EYE 1202 is electrically coupled to the circuit system 1204. In some cases, the circuit system 1204 may be wired to the computing device 1206. In other cases, the circuit system 1204 may include a multiplexer, a galvanometer, a power supply, ground, and / or additional circuit system components. The circuit system 1204 electrically couples the EC-EYE 1202 to the computing device 1206.

[0103] The computing device 1206 may be, and / or includes, but is not limited to, a desktop computer, a laptop computer, an Internet of Things (IoT) device, or any other type of computing device that typically includes one or more communication components, one or more processing components, and / or one or more memory components. In some variations, the computing device 1206 may be implemented as an engine, software function, and / or application. In other words, the functionality of the computing device 1206 may be implemented as software instructions stored in storage (e.g., memory) and executed by one or more processors.

[0104] The computing device 1206 can receive information from the EC-EYE 1202 via the circuit system 1204. Using the information, the computing device 1206 can generate an image and then display the image on the display device 1208.

[0105] In some examples, computing device 1206 includes a processor, such as a central processing unit (CPU), a controller, and / or logic, which executes computer-executable instructions for performing the functions, processes, and / or methods described herein. In some cases, the computer-executable instructions are stored locally and accessed from a non-transitory computer-readable medium.

[0106] Figure 13 An exemplary process 1300 for capturing images using EC-EYE is shown. Process 1300 can be performed by any type of system including EC-EYE (e.g., system 1000 and / or system 1200).

[0107] At box 1302, the system may use EC-EYE (e.g., EC-EYE 1202 and / or EC-EYE 300) to capture one or more images.

[0108] At box 1304, the system can process the image.

[0109] At frame 1306, the system enables the image to be displayed on the display device.

[0110] In some variations, spherical EC-EYEs (e.g., EC-EYE 300) can be fabricated as follows. The fabrication process can begin by deforming a thick (500 μm) Al sheet on a set of hemispherical molds to create a hemispherical Al shell (e.g., Al shell 306). The hemispherical Al shell (e.g., Al shell 306) can then undergo a standard two-step anodizing process to form a PAM with a thickness of 40 μm and nanochannel spacing and diameter of 500 nm and 120 nm, respectively, on the Al surface. A barrier layer thinning process and Pb electrodeposition can be performed to obtain Pb nanoclusters at the bottom of the PAM channels. The outer layer of the PAM and residual Al can then be etched away to obtain freestanding PAMs with Pb, which can then be transferred to a tube furnace for ~5 μm long perovskite NW growth (e.g., for NW array 314). Then, a 20 nm thick indium layer (e.g., indium adhesion layer 310) can be fabricated by evaporating a 20 nm thick indium layer onto the back surface of the PAM to serve as an adhesion layer. Due to the discontinuous morphology of the indium layer, it does not cause short circuits between pixels. To obtain an LM contact array (e.g., LM fiber 316), a hedgehog-shaped mold can be 3D printed from which a complementary PDMS cavity (e.g., PDMS eye cavity 312) with a 10 × 10 hole array (hole size: 700 μm, spacing: 1.6 mm) can be cast. EGaIn LM can then be injected into a thin tube (inner diameter: 400 μm, outer diameter: 700 μm) to form an LM line (e.g., LM fiber 316). 100 tubes can then be inserted into the holes on the PDMS cavity (e.g., PDMS eye cavity 312), and the entire cavity can be attached to the PAM / NW surface to form a 10 × 10 photodetector array (e.g., LM nerve fiber 316). These long flexible tubes can be directly connected to a printed circuit board (PCB), thus avoiding complex wire bonding processes. A circular hole can be drilled in another Al shell, which can then be covered with a tungsten film (e.g., W film contact 306) used as the counter electrode for the EC-EYE. After installing the light-transmitting hole (e.g., light-transmitting hole 304), the Al shell can then be secured to the front side of the PAM using epoxy resin. An ionic liquid (e.g., ionic liquid 308) (e.g., 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIMTFSI) mixed with 1v% of 1-butyl-3-methylimidazolium iodide (BMIMI)) can then be injected, and the lens (e.g., lens 302) can then be glued to the hole in the Al shell to seal the device. After curing, the EC-EYE device 300 is complete.

[0111] All references cited in this article (including publications, patent applications and patents) are incorporated herein by reference to the extent that each reference is individually and specifically indicated to be incorporated herein by reference and discussed in its entirety.

[0112] The terms “a,” “an,” “the,” “at least one,” and similar designations used in the context of describing the invention (especially in the context of the appended claims) shall be construed as covering both the singular and plural, unless otherwise stated herein or obviously contradicted by the context. Unless otherwise stated herein or obviously contradicted by the context, the use of the term “at least one” (e.g., “at least one of A and B”) preceding a list of one or more items shall be construed as referring to one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B). The terms “comprising,” “having,” “including,” and “containing” shall be construed as open-ended terms (i.e., meaning “including but not limited to”), unless otherwise stated. Unless otherwise stated herein, the description of ranges of values ​​herein is intended only as a shorthand method for individually referring to each individual value falling within that range, and each individual value is incorporated into the specification as if it were individually described herein. Unless otherwise stated herein or obviously contradicted by the context, all methods described herein may be performed in any suitable order. Unless otherwise required, the use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better illustrate the invention and not to limit its scope. The language in the specification should not be construed as indicating that any unclaimed element is necessary for the practice of the invention.

[0113] This document describes preferred embodiments of the invention, including the best modes known to the inventors for carrying out the invention. Variations of those preferred embodiments will be apparent to those skilled in the art after reading the foregoing description. The inventors expect those skilled in the art to appropriately employ these variations, and the inventors intend that the invention be practiced in ways different from those specifically described herein. Therefore, the invention includes all modifications and equivalents of the subject matter recited in the appended claims as permitted by applicable law. Furthermore, the invention includes any combination of the foregoing elements in all possible variations, unless otherwise stated herein or clearly contradicted by the context.

Claims

1. A biomimetic electrochemical eye device, comprising: A first hemispherical membrane layer, comprising: A hemispherical membrane comprising multiple through-holes, and Multiple nanowires formed in the plurality of through-holes, the nanowires being made of a material having a photoelectric effect; The second hemispherical membrane layer comprises: The first hemispherical shell, and A metal film layer located on the concave side of the first hemispherical shell; An ionic liquid, which fills a spherical cavity formed by the first hemispherical film layer and the second hemispherical film layer; and Multiple back contacts are connected to the multiple nanowires from the back side of the first hemispherical film layer opposite to the concave side of the first hemispherical film layer.

2. The biomimetic electrochemical ocular device of claim 1, wherein, Each of the plurality of back contacts is individually connected to at least one of the plurality of nanowires.

3. The biomimetic electrochemical eye device according to claim 2, wherein, Each of the plurality of back contacts is a liquid metal wire.

4. The biomimetic electrochemical eye device according to claim 2, wherein, Each of the plurality of back contacts includes a conductive microneedle.

5. The biomimetic electrochemical eye device according to claim 4, wherein, Each of the plurality of nanowires includes a first portion entirely located within the through-hole and a second portion partially protruding outward from the back side of the first hemispherical film layer, the first portion and the second portion being made of different materials, and The conductive microneedle is connected to a second portion of the at least one nanowire.

6. The biomimetic electrochemical eye device according to claim 5, wherein, Each of the plurality of back contacts includes a conductive wire, and the conductive microneedles electrically connect the conductive wire to the at least one nanowire.

7. The biomimetic electrochemical eye device according to claim 6, wherein, The conductive microneedles are connected to four nanowires that form a pixel among the plurality of nanowires.

8. The biomimetic electrochemical eye device according to claim 1 further includes a second hemispherical shell, wherein, The second hemispherical shell is attached to the back side of the first hemispherical film layer. The second hemispherical shell includes a plurality of through holes arranged in an array, and the plurality of back contacts are connected to the plurality of nanowires through the plurality of through holes of the second hemispherical shell.

9. The biomimetic electrochemical eye device according to claim 1, wherein, The second hemispherical film layer has an opening at its center, and the lens is embedded in the opening.

10. The biomimetic electrochemical eye device according to claim 1, wherein, The plurality of nanowires have a spacing of 500 nm between adjacent nanowires and a density of 4.6 x 10 8 cm -2 -2.

11. The biomimetic electrochemical eye device according to claim 1, wherein, The ionic liquid includes 10 v% of 1-butyl-3-methylimidazolium iodide.

12. An artificial vision system, comprising: The biomimetic electrochemical eye device according to any one of claims 1 to 11, the circuit system connected to the biomimetic electrochemical eye device, and the computing device connected to the circuit system and configured to process data.

13. The artificial vision system according to claim 12, wherein the circuit system comprises a multiplexer, a voltage source, an ammeter, and ground.

14. A method for manufacturing an electrochemical detector in a hemispherical artificial retina, comprising: A hemispherical membrane with multiple pores is formed, wherein a blocking layer is provided on one side of the hemispherical membrane to block the multiple pores; At least a portion of the barrier layer is removed to form at least a portion of the plurality of holes as through-holes through the hemispherical membrane; Nanowires are grown in the through-holes, wherein the nanowires are made of a material with photoelectric effect.

15. The method according to claim 14, wherein, Forming a hemispherical film with multiple pores includes forming the hemispherical film by anodizing and etching processes.

16. The method of claim 14, wherein, Removing at least a portion of the barrier layer includes etching at least a portion of the barrier layer using a focused ion beam.

17. A method for fabricating an integrated electrochemical image sensor in a hemispherical artificial retina, comprising: A hemispherical membrane with multiple pores is formed, wherein a blocking layer is provided on a first side of the hemispherical membrane to block the multiple pores; Remove the barrier layer to form the plurality of holes as through-holes through the hemispherical membrane; A first nanowire is grown in the through-hole of the hemispherical membrane such that the first nanowire fills the portion of the through-hole near the first side, wherein the first nanowire is made of a conductive material. A portion of the hemispherical membrane is removed from the first side, such that a portion of the first nanowire is exposed to the outside of the hemispherical membrane; A second nanowire is grown in the through-hole of the hemispherical film, such that the second nanowire fills the remaining portion of the through-hole, wherein the second nanowire is made of a material with photoelectric effect; The conductive microneedles are placed on the hemispherical membrane from the first side, such that each conductive microneedle is electrically connected to at least one of the first nanowires, and the conductive microneedles are fixed and encapsulated using an encapsulation material. Connect a conductive wire to the conductive microneedle to electrically connect the conductive microneedle to an external device.

18. The method according to claim 17, wherein, Forming a hemispherical film with multiple pores includes forming the hemispherical film by anodizing and etching processes.

19. The method according to claim 17, wherein, The first nanowire comprises nickel and the second nanowire comprises perovskite.

20. A method for manufacturing a spherical biomimetic electrochemical eye device, comprising: Forming the first hemispherical aluminum shell; A hemispherical porous alumina film substrate is formed on the concave side of the first hemispherical aluminum shell; Remove the barrier layer located on one side of the porous alumina film substrate and remove the first hemispherical aluminum shell to form an independent porous alumina film substrate having a through hole through the porous alumina film substrate. Perovskite nanowires are grown in the through-holes of the independent porous alumina film substrate. An adhesion layer is formed on the back surface opposite to the concave side of the independent porous alumina film substrate; A hemispherical polydimethylsiloxane shell with an array of through holes is formed; The independent porous alumina film substrate is bonded to the polydimethylsiloxane shell through the adhesive layer; Liquid metal is injected into a hose to form a liquid metal line; One end of the liquid metal wire is electrically connected to the perovskite nanowire through the through-hole array of the polydimethylsiloxane shell, so as to electrically connect the perovskite nanowire to an external device. A second hemispherical aluminum shell with a circular opening at the center is formed, a tungsten film is formed on the concave side of the second hemispherical aluminum shell, and a light-transmitting hole is installed at the circular opening; The second hemispherical aluminum shell and the independent porous alumina film substrate are paired and bonded together to form a spherical cavity between them; An ionic liquid is injected into the spherical cavity, and the lens is glued to the light-transmitting hole on the second hemispherical aluminum shell to seal the spherical cavity.

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