Fabrication of high-precision, large-area acoustic trapping devices

Abstract

A method of fabricating an acoustic trapping device is provided herein. The method includes depositing a gas permeable membrane on a coated substrate. The method includes transmitting a pulsed laser beam through the gas permeable membrane and into the coated substrate. The gas permeable membrane is optically transparent to the laser beam. The method includes forming at least one trap positioned within the coated substrate and beneath the gas permeable membrane by creating a localized chemical or physical phase change reaction beneath the gas permeable membrane.

Description

Docket No. 206030-0340-00WGFABRICATION OF HIGH-PRECISION, LARGE- AREA ACOUSTIC TRAPPING DEVICESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Provisional Patent Application No. 63 / 727,233, filed on December 3, 2024, incorporated herein by reference in its entirety.FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

[0002] This invention was made with government support under 2345571 awarded by the National Science Foundation (NSF). The government has certain rights in the invention.BACKGROUND

[0003] Compliant Membrane Acoustic Patterning (CMAP) technology offers a substantial advancement over traditional acoustic manipulation methods. Unlike bulk or surface acoustic waves, which often lack sufficient resolution and precise control for microparticle and cell positioning, CMAP leverages an air-cavity-based membrane structure that enables subwavelength resolution of acoustic traps.

[0004] In the original CMAP device, however, patterning resolution was limited to approximately 30 pm. Achieving higher resolution patterning with the initial fabrication methods proved challenging. Early attempts involved the precise control of pressing pressure during the molding process to create thin polydimethylsiloxane (PDMS) films, which became increasingly difficult as the dimensions decreased. Other attempts used transfer printing of thin PDMS films but encountered similar limitations in which the mechanical deformation of PDMS during transfer, pressing, and peeling steps hampered the creation of high-resolution patterns.Additionally, maintaining uniform pressure across large areas further complicated the fabrication of fine features.

[0005] Recent advancements in CMAP technology achieved single-cell resolution trapping through the formation of PDMS air cavities using spherical beads in the fabrication process. This bead-based fabrication approach creates a tapered PDMS membrane structure that, when acoustically actuated, establishes precise traps for single-cell capture in the liquid medium near the surface at the center of each air cavity. However, the resulting air cavity locations andDocket No. 206030-0340-00WG densities are dictated by the random distribution of the beads' initial placement. The lack of precise control in trap positioning and pattern density constrains the potential for consistent, high-density, and well-patterned single-cell manipulation and analysis applications in future implementations. The present invention addresses these needs.SUMMARY

[0006] The present disclosure relates generally to acoustic devices, and more particularly, to processes of fabricating a high-density single cell trapping device with trap positions precisely controlled.

[0007] A process of fabricating an acoustic trapping device is provided herein. The process includes depositing a gas permeable membrane on a coated substrate. The process includes transmitting a pulsed laser beam through the gas permeable membrane and into the coated substrate. The gas permeable membrane is optically transparent to the laser beam. The process includes forming at least one trap positioned within the coated substrate and beneath the gas permeable membrane by creating a localized chemical or physical phase change reaction beneath the gas permeable membrane.

[0008] A variety of additional aspects will be set forth in the description that follows. The aspects can relate to individual features and to combination of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the embodiments disclosed herein are based.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The following drawings are illustrative of particular embodiments of the present disclosure and therefore do not limit the scope of the present disclosure. The drawings are not to scale and are intended for use in conjunction with the explanations in the following detailed description.

[0010] FIG. 1A is a cross-sectional view illustrating an example structure of a high-density single cell trapping device.

[0011] FIG. IB is a cross-sectional view illustrating the formation of trap positions within the example structure of FIG. 1A.Docket No. 206030-0340-00WG

[0012] FIG. 2 illustrates the flowchart of a fabrication process for forming trap positions within a high-density single cell trapping device.DETAILED DESCRIPTION

[0013] The following discussion omits or only briefly describes conventional features of cell trapping devices and fabrication methods thereof that are apparent to those skilled in the art. Those of ordinary skill may thus recognize that other elements may be desirable and / or necessary to implement the devices, systems, and methods described herein. In the interest of not obscuring the presentation of embodiments of the present disclosure, some processing steps or operations that are known in the art may have been combined together for presentation and for illustration purposes and in some instances may have not been described in detail. In other instances, some processing steps or operations that are known in the art may not be described at all. It is noted that various examples are described in detail with reference to the drawings. Reference to these various examples does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are intended to be non-limiting and merely set forth some of the many possible implementations for the appended claims. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. As such, it is understood that the detailed description is exemplary and explanatory only and is not restrictive of the broad inventive concepts upon which the examples disclosed herein are based.

[0014] Unless otherwise specifically defined herein, all terms are to be given their broadest reasonable interpretation. This includes meanings implied from the specification as well as meanings understood by those skilled in the art and / or as defined in dictionaries, treatises, etc.

[0015] It is noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified. The terms “includes” and / or “including,” when used in this specification, specify the presence of stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.Docket No. 206030-0340-00WG

[0016] Relative terms such as “horizontal,” “vertical,” “up,” “down,” “top,” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then-described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation in actuality. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. It should be understood that when an element such as a layer, region, or substrate is referred to as being “on”, “over”, “beneath”, “below”, or “under” another element, it may be present on or below the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on”, “directly over”, “directly beneath”, “directly below”, or “directly contacting” another element, there may be no intervening elements present. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The phrases “operatively” or “operably connected” indicates such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship.

[0017] Reference throughout the specification to “exemplary”, “one example”, “an example” or “some examples” means that a particular feature, structure, or characteristic described in connection with at least one example of the subject matter disclosed. Thus, the appearance of the phrases “in one example”, “in an example” or “in some examples” in various places throughout the specification is not necessarily referring to the same example. Further, the particular features, structures or characteristics of “one example”, “an example” or “some examples” may be combined in any suitable manner with each other to form additional examples of such combinations. It is intended that examples of the disclosed subject matter cover modifications and variations thereof. Terms such as “first,” “second,” “third,” etc., merely identify one of a number of portions, components, steps, operations, functions, and / or points of reference as disclosed herein, and likewise do not necessarily limit embodiments of the present disclosure to any particular configuration or orientation.Docket No. 206030-0340-00WG

[0018] Moreover, throughout this disclosure, various aspects can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, 6, and any whole and partial increments there between. This applies regardless of the breadth of the range. As used herein, the term “about” in reference to a measurable value, such as an amount, a temporal duration, and the like, is meant to encompass a specified value and / or variations of plus or minus 20%, plus or minus 10%, plus or minus 5%, plus or minus 1%, and plus or minus 0.1% of the specified value, as such variations are appropriate.

[0019] Current acoustic manipulation methods often lack sufficient resolution and precise control for microparticle and cell positioning. The disclosure provided herein allows for the formation of arbitrarily shaped, localized pressure fields in aqueous environments close to the surface of the device. That is, the device and fabrication processes described herein provide a level of spatial control that conventional methods cannot achieve.

[0020] FIG. 1A is a cross-sectional view illustrating an example structure of single cell trapping device 100. FIG. IB is a cross-sectional view illustrating the formation of traps positioned within the device 100. FIG. 2 illustrates the flowchart of a fabrication process 200 for forming traps within the trapping device 100.

[0021] The device 100 may include a base layer 102 and membrane 104. The base layer 102 may be substrate coated in, for example, but not limited to, graphite or any other like material that under optical illumination becomes a gas, such as carbon nanotubes, graphene, and the like. The process of becoming a gas via optical illumination may be a chemical reaction, such as a burning process when using a graphite-coated substrate, or a physical phase change process, such as water changing into vapor or gel changing into vapor. In one or more cases, the base layer 102 may be mounted on a motorized stage and / or incorporated into a scanning mirror system.

[0022] The membrane 104 may be formed from, for example, but not limited to, polydimethylsiloxane (PDMS) or other gas permeable polymer materials. PDMS has impedanceDocket No. 206030-0340-00WG properties, closely matching that of water, minimizing wave reflection and ensuring efficient acoustic energy transmission. Further, PDMS permits gas exchange, allowing oxygen from the surrounding environment to reach the base layer 102 and enabling the formation of carbon dioxide as a byproduct during, for example, laser heating. As such, the gas permeability of PDMS supports a controlled burning effect on, for example, the graphite of the base layer 102, leading to the formation of a trap (e.g., traps 108a, 108b) with high spatial precision positioned below the PDMS membrane 104. A trap may be, for example, a membrane-bound air cavity formed directly below the membrane 104 and positioned within the base layer 102. The thickness of the membrane 104 may be about 5pm to about 0.1 m thick. The membrane 104 may be formed from other materials that have a Young’s modulus (E) similar to that of PDMS in the range of about 0.01 MPa to 10 MPa.

[0023] In one or more cases, a membrane may be deposited on a base layer (at 202 of FIG. 2). For example, as illustrated in FIG. 1A, the membrane 104, such as a PDMS membrane, is deposited on the surface of the base layer 102 via spin-coating or another deposition technique to deposit thin fdms, such as, but not limited to, spray coating, other room temperature PECVD coating, or other chemical vapor deposition or physical vapor deposition techniques.

[0024] Light may be transmitted through the membrane and into the base layer (at 204 of FIG. 2). In one or more cases, the membrane 104 may be optically transparent to certain wavelengths of light. For instance, the membrane 104 may be optically transparent to a laser beam (e.g., laser beam 106) of a laser (not shown). The laser may be, for example, a near-infrared (NIR) laser. The NIR laser may emit a pulsed laser beam having, for example, a wavelength of about 1030nm or other wavelengths transparent to the membrane 104. As the membrane 104, such as a PDMS membrane, is optically transparent to the beam of the NIR laser, the beam may pass through the PDMS membrane and directly to the underlying base layer 102 without damaging the PDMS membrane itself.

[0025] A trap may be formed within the base layer beneath the membrane (at 206 of FIG. 2). For example, as illustrated in FIG. IB, the laser beam 106 is transmitted through the membrane 104 to heat a portion of the base layer 102 to form trap 108b. In one or more cases, the trap, such as trap 108b, may be sized to trap beads that are about 10 pm. In some cases, the trap may be sized to trap a single cell.Docket No. 206030-0340-00WG

[0026] The laser may emit the laser beam using nanosecond to femtosecond pulse durations. These short pulse durations may minimize heat diffusion into the membrane 104. As such, the structural integrity of the membrane 104 is preserved while enabling the precise cavity formation in the base layer 102 without damaging the membrane 104. In an example, the NIR pulsed laser irradiates the PDMS-coated graphite, rapidly heating the graphite layer. Oxygen permeates the PDMS membrane, interacting with the graphite to create a localized chemical reaction, such as a combustion reaction or other physical phase state transition that can turn the base layer into a gas. The localized chemical reaction forms a gas, such as a carbon dioxide gas, as a byproduct. The process creates an air cavity at a desired location with the PDMS membrane above the air cavity. The pulse duration and energy can be finely controlled, allowing the formation of each cavity in sub nanoseconds without significant heat diffusion into the PDMS membrane.

[0027] As the device 100 may be mounted on a motorized stage and / or incorporated into a scanning mirror system, complex patterns of air cavities may be rapidly generated across the membrane 104 with precise control over the location and density of the patterns. The pulsing of the laser may be adjusted in real time to create arbitrary shapes and arrangements of cavities facilitating large-area CMAP device production suitable for single-cell trapping applications. Further, the processes described herein are scalable for industrial production. For instance, although the membrane 104 is described in an example as being deposited on the base layer 102 via spin coating, it should be understood that this method may be adapted to create composite PDMS-graphite sheets on a roll, thereby making the sheets suitable for high-throughput, cost- effective manufacturing.

[0028] The fabrication process 200 allows for the formation of arbitrarily shaped, localized pressure fields in aqueous environments close to the surface of the device 100, thereby offering a level of spatial control that conventional methods cannot achieve. The fabrication process 200 addresses several critical limitations of existing CMAP devices. For instance, the controlled air cavity formation enabled by laser processing provides precise patterning, overcoming the random distribution associated with bead-based methods. This allows for higher-density trap arrays without aggregation issues. Moreover, graphite-coated substrates are inexpensive, and process 200 eliminates the need for cleanroom-based fabrication, making it accessible and cost- effective for large-scale production. Additionally, the ability to achieve large-area single-cell trapping with precise spatial control has significant implications for fields requiring image-basedDocket No. 206030-0340-00WG single-cell sorting, a capability not possible with flow cytometry. This technology is expected to advance applications in personalized medicine, diagnostics, and cell-based research in which high-throughput single-cell analysis is essential.

[0029] The various embodiments described above are provided by way of illustration only and should not be construed to limit the claims attached hereto. Those skilled in the art will readily recognize various modifications and changes that may be made without following the example embodiments and applications illustrated and described herein, and without departing from the spirit and scope of the following claims.

Claims

Docket No. 206030-0340-00WGCLAIMSWhat is claimed is:

1. A method of fabricating an acoustic trapping device, comprising: depositing a gas permeable membrane on a coated substrate; transmitting a pulsed laser beam through the gas permeable membrane and into the coated substrate, wherein the gas permeable membrane is optically transparent to the laser beam; and forming at least one trap positioned within the coated substrate and beneath the gas permeable membrane by creating a localized chemical or physical phase change reaction beneath the gas permeable membrane.

2. The method of claim 1, wherein the gas permeable membrane comprises polydimethylsiloxane.

3. The method of claim 1, wherein the coated substrate comprises a graphite-coated substrate.

4. The method of claim 1, wherein the gas permeable membrane is deposited on the coated substrate via spin-coating.

5. The method of claim 1, wherein the pulsed laser beam is transmitted at a wavelength of about 1030nm.

6. The method of claim 1, wherein the at least one trap is sized to trap beads that have a dimension of about 10pm.Docket No. 206030-0340-00WG7. The method of claim 1, wherein the at least one trap comprises an air cavity sized to trap a single cell.

8. The method of claim 1, wherein the laser beam is transmitted using a nearinfrared laser.

9. The method of claim 1, wherein transmitting the pulsed laser beam comprises transmitting the laser beam using nanosecond to femtosecond pulse durations.

10. The method of claim 1, wherein the chemical reaction comprises a localized combustion reaction that occurs beneath the gas permeable membrane

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