CN113802119B

CN113802119B - Preparation process of universal PDMS flexible sensor high-precision metal microelectrode

Info

Publication number: CN113802119B
Application number: CN202111014485.6A
Authority: CN
Inventors: 李中南; 王洪磊; 王海军
Original assignee: General Coal Research Institute Co Ltd
Current assignee: General Coal Research Institute Co Ltd
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2022-08-30
Anticipated expiration: 2041-08-31
Also published as: CN113802119A

Abstract

The application provides a general high-precision metal microelectrode preparation process for a PDMS flexible sensor, which is characterized in that a micrometer scale electrode array is prepared from an existing metal film in a photoetching mode, and high conductivity and toughness of a metal electrode can be kept while better elasticity and biocompatibility of a device can be kept after PDMS packaging. The PDMS flexible device prepared by the process can be used for biological implantation equipment, such as a nerve stimulator, a cardiac pacemaker, an artificial cochlea and the like.

Description

Preparation process of universal PDMS flexible sensor high-precision metal microelectrode

Technical Field

The application relates to the technical field of electrode processing, in particular to a general high-precision metal microelectrode preparation process of a PDMS flexible sensor.

Background

In working environments such as coal mines and the like, the space is narrow, the activity range of workers is large, and the flexible wearable sensor needs to have better strength. The electrode material is required to have higher bending performance and toughness. Polydimethylsiloxane (PDMS) provides a suitable substrate for flexible sensors due to good elastic and tensile properties. While the metal electrode has sufficient strength and excellent conductivity.

However, it is difficult to secure strength, ductility and sufficient thickness of the electrode by a conventional method of manufacturing a micro-electrode such as a physicochemical deposition method, and the electrode may be broken during the bending of PDMS to cause damage to the device. The bonding force between the metal and PDMS is also poor.

The existing methods for preparing metal electrodes on PDMS are as follows:

1) physical chemical deposition: directly preparing the electrode shape on a PDMS substrate through a physical mask plate in a physical and chemical deposition mode.

2) Mixing metal particles into PDMS to prepare a flexible electrode: metal particles or fibers are mixed with PDMS to form a flexible conductive material.

3) The metal particles or fibers are mixed with a specific solvent and then injected into the micro-channels of PDMS to form electrodes.

The prior art has the following disadvantages:

1) physical chemical deposition:

the physicochemical deposition method has high requirement on the affinity between the substrate and the metal ions, and usually requires the surface chemical or physical modification of PDMS. The bonding force between the modified PDMS and the metal is difficult to maintain to satisfy the degree of free bending without falling off. Electrodes deposited by physical chemistry are generally relatively poor in compactness and ductility, and are prepared for too long time, the electrodes with the thickness of more than 1 micron generally need several hours, and finished products are very easy to break in the bending process.

2) Preparing a flexible electrode by mixing metal particles into PDMS:

the metal nanoparticles and the PDMS are mixed and then cured with the PDMS substrate, so that good connectivity and toughness can be realized, but the mixing of the metal particles and the PDMS can obviously reduce the conductivity of the electrode. Similar approaches also have mixed metal nanowires with PDMS, which has the same problems.

3) There is also a problem of poor conductivity. Meanwhile, the channel design of the injection electrode has great limitation, and only simple electrode shapes can be prepared.

Disclosure of Invention

The present application is directed to solving, at least to some extent, one of the technical problems in the related art.

Therefore, the application aims to provide a general high-precision metal microelectrode preparation process for the PDMS flexible sensor, which is to prepare a micron-scale electrode array from the existing metal foil in a photoetching mode, and keep the high conductivity and toughness of the metal electrode while keeping the good elasticity and biocompatibility of the device after PDMS packaging.

In order to achieve the above purpose, the embodiment of the present application provides a general PDMS flexible sensor high-precision metal microelectrode preparation process, which includes the following steps:

step A, placing a metal foil on a spin coating platform and fixing the metal foil in a position, and spin-coating a PDMS film on the metal foil;

step B, heating until the PDMS is solidified, turning over the metal foil and fixing the metal foil on a spin-coating platform, and spin-coating a layer of photoresist on the metal foil;

step C, placing the metal foil on a photoetching machine to be photoetched to form a designed electrode pattern, and developing the photoresist by using a matched developing solution to expose the electrode to be corroded;

d, performing wet etching on the metal foil by using an etching agent to form a required electrode shape;

step E, removing the photoresist by using a matched photoresist remover;

and F, spin-coating a layer of PDMS film on the surface of the electrode, and curing to form a packaged device.

In some embodiments, in step B, a heating plate is used for heating, and the metal foil is placed on the heating plate for heating.

In some embodiments, the heating temperature in step B is 40-120 ℃.

In some embodiments, the metal foil is a copper foil. The ready-made copper foil is used as an electrode material, so that the bending performance and the toughness of the electrode are ensured.

In some embodiments, the copper foil has a thickness of 10-50 um.

In some embodiments, the thickness of the spin-coated photoresist in step B is 5 μm.

In some embodiments, the photoresist is selected to be a positive photoresist with a matched photoresist remover.

In some embodiments, the positive glue is a positive glue of AZ series.

In some embodiments, the etchant is a copper etchant, and the copper etchant is prepared from the following substances in parts by mass: 5% of copper chloride, 10% of concentrated hydrochloric acid, 25% of hydrogen peroxide and 60% of water.

In some embodiments, a photosensitive oil film and a common 365nm ultraviolet lamp in the PCB preparation process are used instead of the photoresist and the photoresist machine.

The method provided by the embodiment of the application can be used for preparing the electrode in any two-dimensional shape, the size precision is high, and the minimum line width can be smaller than 10 micrometers. The preparation process is simple and reliable, has little dependence on manual technology, and is easy to form a standard preparation process. The electrode has good strength and bending life, and is suitable for preparing electrodes made of different metal materials in a PDMS substrate.

Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.

Drawings

The above and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments taken in conjunction with the accompanying drawings,

FIGS. 1-7 are process flow diagrams of the preparation process in the examples of this application;

wherein:

fig. 1 is a schematic view of a copper foil provided in an embodiment of the present application;

FIG. 2 is a schematic view of PDMS spin-coated on copper foil in step A;

FIG. 3 is a schematic view of spin-on resist in step B;

FIG. 4 is a schematic diagram of the exposure and development in step C to expose the locations to be etched;

FIG. 5 is a schematic view of wet etching the copper foil in step D;

FIG. 6 is a schematic diagram of the removal of the photoresist in step E;

FIG. 7 is a schematic view of spin coating PDMS on the electrode surface in step F;

reference numerals:

1-copper foil; 2-PDMS film; 3-photoresist.

Detailed Description

Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application.

The following describes a general process for preparing a high-precision metal microelectrode of a PDMS flexible sensor according to an embodiment of the present application with reference to the accompanying FIGS. 1 to 7.

The embodiment of the application provides a preparation process of a universal PDMS flexible sensor high-precision metal microelectrode, which comprises the following steps:

and step A, placing a copper foil 1 with a proper size and a thickness of 10-50 um on a spin coating platform, fixing the position of the copper foil 1, dropwise adding PDMS prepolymer on the copper foil 1, and spin-coating a PDMS film 2 with a specific thickness at a controlled rotating speed omega for a controlled time t. Generally, the film thickness h is formed in an exponential relationship with the rotation speed for the same spin coating time.

Step B, heating the substrate on a heating plate at the temperature of 40-120 ℃ until PDMS is solidified, turning over the copper foil 1 and fixing the copper foil on a spin-coating platform, and spin-coating the photoresist 3 with the thickness of 5 microns at controlled rotating speed and time;

step C, the copper foil 1 is put on a photoetching machine to be photoetched to form a designed electrode pattern, and the photoresist 3 is developed by using a matched developing solution to expose the electrode to be corroded;

d, performing wet etching on the copper foil 1 by using a copper etching agent to form a required electrode shape;

step E, removing the photoresist 3 by using a matched photoresist degumming agent;

and F, spin-coating the PDMS film 2 with a certain thickness on the surface of the electrode, and curing to form a packaged device.

In some embodiments, the electrode material is not limited to the copper foil 1, and the process can be applied to any commercially available metal foil, and a matching etchant is selected for different metal materials in the wet etching process.

In some embodiments, the photoresist 3 is a positive photoresist with a matched photoresist remover, such as AZ 4620.

In some embodiments, the positive glue is a positive glue of AZ series. The photoresist 3 is not limited to AZ series positive photoresist, and other brands of positive photoresist can be used, and the matched photoresist remover is required to be used for removing the photoresist 3.

In some embodiments, the copper etchant is formulated in the following parts by mass: 5% of copper chloride, 10% of concentrated hydrochloric acid, 25% of hydrogen peroxide and 60% of water.

In some embodiments, a photosensitive oil film and a common 365nm ultraviolet lamp in the PCB preparation process are used instead of the photoresist and the photoresist machine. The process cost can be significantly reduced with a concomitant reduction in precision, but still an electrode with a minimum line width of 50 μm can be prepared, and the electrode shape is likewise not limited.

The process of the embodiment can realize the preparation of the electrode shape of any two-dimensional pattern, and the minimum line width can reach below 10 mu m. By utilizing the process, the high-strength metal electrode can be prepared in the PDMS substrate and forms stable combination with the PDMS. The PDMS flexible device prepared by the process can be used for biological implantation equipment, such as a nerve stimulator, a cardiac pacemaker, an artificial cochlea and the like.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; may be mechanically coupled, may be electrically coupled or may be in communication with each other; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. The preparation process of the universal PDMS flexible sensor high-precision metal microelectrode is characterized by comprising the following steps:

a, placing a copper foil on a spin-coating platform and fixing the copper foil at a fixed position, wherein the thickness of the copper foil is 10-50 um, and spin-coating a PDMS film on the copper foil;

step B, heating until PDMS is solidified, turning over the copper foil and fixing the copper foil on a spin-coating platform, and spin-coating a layer of photoresist on the copper foil, wherein the thickness of the spin-coated photoresist is 5 micrometers;

step C, placing the copper foil on a photoetching machine to be photoetched to form a designed electrode pattern, and developing the photoresist by using a matched developing solution to expose the electrode to be corroded;

d, performing wet etching on the copper foil by using an etching agent to form a required electrode shape;

step E, removing the photoresist by using a matched photoresist remover;

2. The process for preparing the universal high-precision metal microelectrode of the PDMS flexible sensor as claimed in claim 1, wherein in the step B, a heating plate is used for heating, and a copper foil is placed on the heating plate for heating.

3. The preparation process of the universal PDMS flexible sensor high-precision metal microelectrode according to claim 2, wherein in the step B, the heating temperature is 40-120 ℃.

4. The process for preparing a universal PDMS flexible sensor high-precision metal microelectrode according to any one of claims 1 to 3, wherein the photoresist is a positive photoresist with a matched photoresist remover.

5. The preparation process of the universal PDMS flexible sensor high-precision metal microelectrode according to claim 4, wherein the positive glue is AZ series positive glue.

6. The process for preparing the universal high-precision metal microelectrode of the PDMS flexible sensor as claimed in claim 1, wherein the etching agent is copper etching agent, and the formula of the copper etching agent comprises the following substances by mass: 5% of copper chloride, 10% of concentrated hydrochloric acid, 25% of hydrogen peroxide and 60% of water.

7. The process for preparing a universal PDMS flexible sensor high-precision metal microelectrode according to claim 1, wherein a photosensitive oil film and a common 365nm ultraviolet lamp in a PCB preparation process are adopted to replace a photoresist and a photoetching machine.