A method for manufacturing a wearable flexible porous sensor based on silica gel

Abstract

The application discloses a kind of silica gel-based wearable flexible porous sensor manufacturing method, including cutting and obtaining porous polydimethylsiloxane matrix;Select glass sheet, and polyimide adhesive tape is evenly adhered on glass sheet, recess of same size with target is made on polyimide adhesive tape, and conductive glue mixture is injected in recess;The porous polydimethylsiloxane matrix of target size is placed on the conductive glue mixture in recess;After heating, after natural cooling forming, obtain half sensor body, then stripping;New recess is made again, and conductive glue is injected into new recess;The other side surface of half sensor body is placed in new recess, and porous sensor body in sandwich structure is obtained after heating and cooling again;Conductive glue is adhered on the upper surface and lower surface of porous sensor, and the production of porous sensor is completed.The electrode material of the application considers bonding strength and conductivity, is green and environment-friendly, and is friendly to biology.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor technology, and specifically to a method for fabricating a silicone-based wearable flexible porous sensor. Background Technology

[0002] Flexible porous sensors are widely used in the field of human health monitoring. They are typically made from low-stiffness polymer materials.

[0003] Since the application scenario is generally the surface of human skin, sensors have strict requirements for the biocompatibility of polymer raw materials. Polydimethylsiloxane (PDMS) is a polymer material with good biocompatibility and low stiffness, with a solid Young's modulus of approximately 1.5 MPa. Compared to the mechanical properties of human skin, its modulus is relatively high. Introducing porous structures into solid polymers is an effective method to reduce material stiffness. Methods for introducing porous structures are generally divided into chemical foaming and template methods. Compared to the template method, the foaming method is more direct. However, because PDMS is a non-polar material with a very smooth surface, conventional conductive resins and conductive tapes are difficult to adhere firmly to the sensor surface. Fabricating reliable and durable surface electrodes has become a key issue restricting the long-term service life of PDMS-based sensors.

[0004] Since the sensor is used on the surface of human skin, there are certain safety requirements for the chemicals introduced by the chemical foaming method.

[0005] In summary, existing methods for fabricating porous sensors result in products that lack both durability and skin-friendliness under long-term service conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a method for manufacturing a silicone-based wearable flexible porous sensor, in order to solve the technical problem that products prepared by existing porous sensor manufacturing methods lack both durability and skin-friendliness under long-term service conditions.

[0007] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0008] A method for fabricating a silicone-based wearable flexible porous sensor includes the following specific steps:

[0009] Step 100: Cut the porous polydimethylsiloxane sample according to the set target size to obtain a porous polydimethylsiloxane body;

[0010] Step 200: Select a glass sheet, and smoothly adhere the polyimide tape to the glass sheet. Make a groove with the same size as the target size on the polyimide tape, and inject the conductive adhesive mixture into the groove.

[0011] Step 300: Place the porous polydimethylsiloxane body of the target size flat on the conductive adhesive mixture in the groove, so that the lower surface of the porous polydimethylsiloxane body is completely immersed in the conductive adhesive mixture;

[0012] Step 400: The porous polydimethylsiloxane body and conductive adhesive mixture in the groove are heated to 80 degrees Celsius for 1 hour by a hot plate. After natural cooling and molding, a semi-sensor body is obtained. Then, the molded semi-sensor body is peeled off from the glass sheet by a blade.

[0013] Step 500: Prepare a new groove on the glass slide and inject a conductive adhesive mixture into the groove, so that the upper surface of the porous polydimethylsiloxane body of the semi-sensor body obtained in step 400 is completely immersed in the conductive adhesive mixture of the new groove.

[0014] Then, step 400 is performed again to obtain a porous sensor body with a sandwich structure.

[0015] Step 600: Use conductive adhesive to attach wires to both the upper and lower surfaces of the porous sensor to complete the fabrication of the porous sensor.

[0016] In a preferred embodiment of the present invention, in step 200, the thickness of the polyimide tape is 0.2 mm.

[0017] In a preferred embodiment of the present invention, in step 200, the conductive adhesive comprises two parts: a modified organosilicon base agent and a curing agent.

[0018] The modified organosilicon agent contains flake silver powder.

[0019] The modified organosilicon base agent and curing agent are mixed in a mass ratio of 10:1.

[0020] As a preferred embodiment of the present invention, a method for preparing a porous polydimethylsiloxane sample is also included, specifically comprising the following steps:

[0021] Step 101: Mix the polydimethylsiloxane precursor and crosslinking agent at a ratio of 10:1 to form a polydimethylsiloxane prepolymer;

[0022] Step 102: Sodium bicarbonate and acetic acid are successively mixed into the polydimethylsiloxane prepolymer and stirred until a mixture is formed;

[0023] Step 103: Place the mixture in an open mold, place the open mold on a leveling hot plate, and heat the mold with the hot plate.

[0024] The reaction between sodium bicarbonate and acetic acid in the mixture generates carbon dioxide gas, which expands the mixture. The thermosetting properties of polydimethylsiloxane fix the shape of the mixture expanded by the carbon dioxide gas, thus obtaining the final sample.

[0025] Step 104: Place the final sample in deionized water for ultrasonic cleaning to remove residual impurities and obtain porous polydimethylsiloxane sample.

[0026] As a preferred embodiment of the present invention, in step 102, sodium bicarbonate is first added to the polydimethylsiloxane prepolymer at a set mass ratio and stirred for 10 minutes, and then acetic acid is added and stirred for 5 minutes.

[0027] The mass ratio of sodium bicarbonate to polydimethylsiloxane prepolymer must be set to ensure that the molar ratio of sodium bicarbonate to acetic acid is 1:1.

[0028] As a preferred embodiment of the present invention, in step 103, the mold is covered with a metal cover to isolate the mold from the external environment.

[0029] As a preferred embodiment of the present invention, it further includes a method for controlling the surface shape of the porous sensor body, comprising:

[0030] Equally spaced grooves are set on the inner bottom wall of the open mold, with the length of the grooves being the same as the width of the open mold. Salt granules are injected into the grooves and pressed against the inner bottom wall of the open mold by a pressure plate with equally spaced arc-shaped grooves on its surface. The mold is then heated to solidify the salt granules, forming salt strips with an arc-shaped longitudinal section on the grooves. The mixture is then injected into the open mold, and subsequently, steps 103 and 104 are performed to dissolve the salt strips in deionized water, forming equally spaced arc-shaped grooves on the bottom surface of the obtained porous polydimethylsiloxane sample.

[0031] As a preferred embodiment of the present invention, the surface of the arc-shaped groove is sprayed with a water film, and the arc-shaped groove and the groove correspond one-to-one.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] Compared to conventional electrode materials, the electrode material selected in this invention solves the stability problem of polydimethylsiloxane materials during deformation, while balancing adhesive strength and conductivity. The foaming agents used in the porous material fabrication method are all readily available in daily life, making them green, environmentally friendly, and biocompatible. Attached Figure Description

[0034] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the chemical foaming method for preparing porous polydimethylsiloxane according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the process for fabricating the porous polydimethylsiloxane electrode according to an embodiment of the present invention;

[0037] Figure 3 Scanning electron microscope image of cross-section of porous polydimethylsiloxane prepared in the embodiments of the present invention, trend of porosity with foaming agent ratio X, and schematic diagram of finished sensor product;

[0038] Figure 4 This is a schematic diagram of the sensor prepared for the embodiment of the present invention, including cyclic load loading, flexural electrical signal response, and cyclic bending signal of a human finger. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] like Figures 1 to 4 As shown, this invention provides a method for fabricating a silicone-based wearable flexible porous sensor, including the following specific steps:

[0041] Step 100: Cut the porous polydimethylsiloxane sample according to the set target size to obtain a porous polydimethylsiloxane body;

[0042] Step 200: Select a glass sheet, and smoothly adhere the polyimide tape to the glass sheet. Make a groove with the same size as the target size on the polyimide tape, and inject the conductive adhesive mixture into the groove.

[0043] Step 300: Place the porous polydimethylsiloxane body of the target size flat on the conductive adhesive mixture in the groove, so that the lower surface of the porous polydimethylsiloxane body is completely immersed in the conductive adhesive mixture;

[0044] Step 400: The porous polydimethylsiloxane body and conductive adhesive mixture in the groove are heated to 80 degrees Celsius for 1 hour by a hot plate. After natural cooling and molding, a semi-sensor body is obtained. Then, the molded semi-sensor body is peeled off from the glass sheet by a blade.

[0045] Step 500: Prepare a new groove on the glass slide and inject a conductive adhesive mixture into the groove, so that the upper surface of the porous polydimethylsiloxane body of the semi-sensor body obtained in step 400 is completely immersed in the conductive adhesive mixture of the new groove.

[0046] Then, step 400 is performed again to obtain a porous sensor body with a sandwich structure.

[0047] Step 600: Use conductive adhesive to attach wires to both the upper and lower surfaces of the porous sensor to complete the fabrication of the porous sensor.

[0048] The electrode material used in the fabrication method of the porous sensor provided by this invention has low stiffness after curing and strong adhesion to the host material (polydimethylsiloxane), resulting in high service stability. It maintains stable signal output even under more than 10,000 three-point bending cyclic displacement loads. Figure 3 As shown.

[0049] The porous sensor prepared by this invention uses a material that is undoped and lacks piezoelectricity. The signal from this porous sensor originates from the flexural effect. However, the material can be modified by doping, and its applications are not limited to the flexural effect.

[0050] In step 200, the thickness of the polyimide tape is 0.2 mm.

[0051] In step 200, the conductive adhesive comprises two parts: a modified silicone base agent and a curing agent;

[0052] The modified organosilicon agent contains flake silver powder.

[0053] The modified organosilicon base agent and curing agent are mixed in a mass ratio of 10:1.

[0054] It also includes a method for preparing a porous polydimethylsiloxane sample, specifically comprising the following steps:

[0055] Step 101: Mix the polydimethylsiloxane precursor and crosslinking agent at a ratio of 10:1 to form a polydimethylsiloxane prepolymer solution;

[0056] Step 102: Sodium bicarbonate and acetic acid are sequentially mixed into the polydimethylsiloxane prepolymer solution and stirred until homogeneous to form a mixture;

[0057] Step 103: Place the mixture in an open mold, place the open mold on a leveling hot plate, and heat the mold with the hot plate.

[0058] The reaction between sodium bicarbonate and acetic acid in the mixture generates carbon dioxide gas, which expands the mixture. The thermosetting properties of the polydimethylsiloxane prepolymer fix the shape of the mixture expanded by the carbon dioxide gas, thus obtaining the final sample.

[0059] Step 104: Place the final sample in deionized water for ultrasonic cleaning to remove residual impurities and obtain a porous polydimethylsiloxane sample. At this point, the main material required for the sensor has been formed and is biosafe.

[0060] In step 102, sodium bicarbonate is first added to the polydimethylsiloxane prepolymer at a set mass ratio and stirred for 10 minutes, and then acetic acid is added and stirred for 5 minutes.

[0061] Specifically, the mass ratio of sodium bicarbonate to polydimethylsiloxane prepolymer must ensure a molar ratio of sodium bicarbonate to acetic acid of 1:1, as detailed below. Figure 3 The middle chart shows the set mass ratio of sodium bicarbonate and polydimethylsiloxane prepolymer.

[0062] Of course, in order to obtain an ideally flat porous polydimethylsiloxane sample, the mold needs to be level when the mixture is placed in the open mold, and the hot plate also needs to be level during the heating process. Therefore, in order to avoid the influence of the external environment on the mixture in the open mold during the heating process, in step 103, the mold is covered with a metal cover to isolate the mold from the external environment.

[0063] Furthermore, in this invention, the flexible porous sensor is designed to have a longer service life, better folding and bending performance, and precise conductivity.

[0064] It also includes a method for controlling the surface shape of the porous sensor body, including:

[0065] Equally spaced grooves are set on the inner bottom wall of the open mold, with the length of the grooves being the same as the width of the open mold. Salt granules are injected into the grooves and pressed against the inner bottom wall of the open mold by a pressure plate with equally spaced arc-shaped grooves on its surface. The mold is then heated to solidify the salt granules, forming salt strips with an arc-shaped longitudinal section on the grooves. The mixture is then injected into the open mold, and subsequently, through steps 103 and 104, the salt strips are dissolved in deionized water, forming multiple equally spaced arc-shaped grooves on the bottom surface of the obtained porous polydimethylsiloxane sample.

[0066] A water film is sprayed onto the surface of the arc-shaped groove, and the arc-shaped groove and the groove correspond one-to-one.

[0067] The purpose is to give the surface of the porous polydimethylsiloxane sample multiple equally spaced arc-shaped grooves, which are then filled with conductive adhesive in the final flexible porous sensor.

[0068] The arc-shaped structure of the arc groove can effectively improve the matrix properties of the porous polydimethylsiloxane sample. At the same time, the flexible porous sensor prepared from the porous polydimethylsiloxane sample will compress the conductive medium formed by the conductive adhesive during the application process, thereby obtaining more sensitive conductivity.

[0069] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A method for fabricating a silicone-based wearable flexible porous sensor, characterized in that, Including specific steps: Step 100: Cut the porous polydimethylsiloxane sample according to the set target size to obtain a porous polydimethylsiloxane body; Step 200: Select a glass sheet, and smoothly adhere the polyimide tape to the glass sheet. Make a groove with the same size as the target size on the polyimide tape, and inject the conductive adhesive mixture into the groove. Step 300: Place the porous polydimethylsiloxane body of the target size flat on the conductive adhesive mixture in the groove, so that the lower surface of the porous polydimethylsiloxane body is completely immersed in the conductive adhesive mixture; Step 400: The porous polydimethylsiloxane body and conductive adhesive mixture in the groove are heated to 80 degrees Celsius for 1 hour by a hot plate. After natural cooling and molding, a semi-sensor body is obtained. Then, the molded semi-sensor body is peeled off from the glass sheet by a blade. Step 500: Prepare a new groove on the glass slide and inject a conductive adhesive mixture into the groove, so that the upper surface of the porous polydimethylsiloxane body of the semi-sensor body obtained in step 400 is completely immersed in the conductive adhesive mixture of the new groove. Then, step 400 is performed again to obtain a porous sensor body with a sandwich structure. Step 600: Use conductive adhesive to attach wires to both the upper and lower surfaces of the porous sensor to complete the fabrication of the porous sensor. In step 200, the thickness of the polyimide tape is 0.2 mm; In step 200, the conductive adhesive comprises two parts: a modified silicone base agent and a curing agent; The modified organosilicon agent contains flake silver powder. The modified organosilicon base agent and curing agent are mixed in a mass ratio of 10:1; It also includes a method for preparing a porous polydimethylsiloxane sample, specifically comprising the following steps: Step 101: Mix the polydimethylsiloxane precursor and crosslinking agent at a ratio of 10:1 to form a polydimethylsiloxane prepolymer; Step 102: Sodium bicarbonate and acetic acid are successively mixed into the polydimethylsiloxane prepolymer and stirred until a mixture is formed; Step 103: Place the mixture in an open mold, place the open mold on a leveling hot plate, and heat the mold with the hot plate. The reaction between sodium bicarbonate and acetic acid in the mixture generates carbon dioxide gas, which expands the mixture. The thermosetting properties of polydimethylsiloxane fix the shape of the mixture expanded by the carbon dioxide gas, thus obtaining the final sample. Step 104: Place the final sample in deionized water for ultrasonic cleaning to remove residual impurities and obtain porous polydimethylsiloxane sample. It also includes a method for controlling the surface shape of the porous sensor body, including: Equally spaced grooves are set on the inner bottom wall of the open mold, with the length of the grooves being the same as the width of the open mold. Salt granules are injected into the grooves and pressed against the inner bottom wall of the open mold by a pressure plate with equally spaced arc-shaped grooves on its surface. The mold is then heated to solidify the salt granules, forming salt strips with an arc-shaped longitudinal section on the grooves. The mixture is then injected into the open mold, and subsequently, steps 103 and 104 are performed to dissolve the salt strips in deionized water, forming equally spaced arc-shaped grooves on the bottom surface of the obtained porous polydimethylsiloxane sample. A water film is sprayed onto the surface of the arc-shaped groove, and the arc-shaped groove and the groove correspond one-to-one.

2. The method for fabricating a silicone-based wearable flexible porous sensor according to claim 1, characterized in that, In step 102, sodium bicarbonate is first added to the polydimethylsiloxane prepolymer at a set mass ratio and stirred for 10 minutes, and then acetic acid is added and stirred for 5 minutes. The mass ratio of sodium bicarbonate to polydimethylsiloxane prepolymer must be set to ensure that the molar ratio of sodium bicarbonate to acetic acid is 1:

1.

3. The method for fabricating a silicone-based wearable flexible porous sensor according to claim 1, characterized in that, In step 103, the mold is covered with a metal cover to isolate it from the external environment.

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