A flexible pressure sensor with a clock-milky stone-shaped array microstructure and a manufacturing method thereof

Abstract

The application discloses a flexible pressure sensor with a clock-milk-stone-shaped array microstructure and a manufacturing method thereof. First, a required mold is manufactured by using a laser ablation method, then carbon nanotubes are scraped on the mold, and then a PDMS mixture is poured, vacuumized and left to solidify. After the mold turning treatment, the PDMS clock-milk-stone-shaped array structure is assembled face to face with the interdigital electrode, and the electrode is connected with wires, so that the flexible pressure sensor with the clock-milk-stone-shaped array microstructure is manufactured. The clock-milk-stone-shaped microstructure of the sensor can make it exhibit excellent deformation response under different pressure environments, and the sensor exhibits a high sensitivity of 0.71 kPa ‑1 in the range of 0.18-120 kPa, and a sensitivity of 0.25 kPa ‑1 in the range of 208-355 kPa; and also has a wide detection range of 0.18-355 kPa, and can accurately respond to light touch to strong pressure impact.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flexible pressure sensors, and specifically relates to a flexible pressure sensor with a simulated stalactite-shaped array microstructure and a manufacturing method thereof. BACKGROUND

[0002] With the continuous development of technology, flexible pressure sensors are increasingly widely used in the fields of biomedical, sports training, human-computer interaction, etc. However, the existing flexible pressure sensors still have many shortcomings in terms of sensitivity, stress range and stability. Therefore, the present application proposes a brand-new flexible pressure sensor and its manufacturing method, aiming to significantly improve the performance of the sensor through the simulation of natural structure and optimized manufacturing process.

[0003] In nature, stalactites are known for their unique structure. Inspired by the structure of stalactites, the present application integrates the morphological characteristics of stalactites into the design of the flexible pressure sensor, forming a unique simulated stalactite structure. Compared with previous biomimetic structures such as wheat structure and rose structure, the simulated stalactite structure can produce more uniform stress distribution when stressed, thereby significantly improving the sensitivity of the sensor. At the same time, this structure also has a wider stress range, which can more accurately capture and respond to pressure stimuli from different directions and intensities.

[0004] In summary, the present application significantly improves the sensitivity, stress range and stability of the flexible pressure sensor through the design of natural structure simulation, optimized manufacturing process and the introduction of convex structure. These innovations make the sensor have a wide application prospect in the fields of biomedical monitoring, training and rehabilitation evaluation, and human-computer interaction. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a flexible pressure sensor with a simulated stalactite-shaped array microstructure and a manufacturing method thereof. The simulated stalactite-shaped microstructure of the sensor can exhibit good deformation response under different pressure environments, thereby making the sensor have good sensitivity performance and a larger pressure detection range.

[0006] The technical solution of the present application is as follows:

[0007] A flexible pressure sensor with a simulated stalactite-shaped array microstructure and a manufacturing method thereof, characterized in that: a circular irregular hole is generated on the surface of stainless steel by laser ablation as a mold, a carbon nanotube solution is first coated into the hole, and then PDMS is used to reproduce the microstructure to prepare a simulated stalactite structure; a flexible pressure sensor is prepared by combining the interdigital electrode made by dry etching and coating process with the simulated stalactite microstructure.

[0008] Further, the manufacturing method of the mold is as follows: laser ablation of the stainless steel sheet is carried out on the stainless steel sheet by using a laser with a power of 45 W and a speed of 500 mm / s to form different irregular holes, and the hole diameters include but are not limited to 0.3 mm and 0.8 mm.

[0009] Further, the carbon nanotube solution, as a kind of conductive ink, forms a conductive layer on the stalactite-shaped microstructure surface during the curing process of the PDMS mixture, and then realizes the conduction of the sensor circuit, and the carbon nanotube solution includes but is not limited to PEDOT:PSS, graphene oxide aqueous solution and silver nanowire aqueous solution.

[0010] Further, the PDMS mixture is a high-molecular-weight flexible polymer, which can be deformed obviously under external force, and can better detect pressure changes, and includes but is not limited to Ecoflex and hydrogel.

[0011] Further, the channel electrode is an embedded channel with an interdigital electrode pattern, the carbon nanotubes are filled in the channel by means of drop coating and scraping coating, and after complete drying, the surface can be wiped with ethanol-dipped dust-free cloth to remove the excess carbon nanotubes on the surface, and the carbon nanotubes in the channel are retained.

[0012] Further, the NOA ultraviolet curing glue mainly comprises a photocurable polymer, has certain viscosity, and can be rapidly cured under irradiation of ultraviolet light, and includes but is not limited to photosensitive resin, UV resin glue and polyurethane acrylate.

[0013] Further, the working principle of the flexible pressure sensor is as follows: when pressure acts on the sensor, the stalactite-shaped microstructure contacts the interdigital electrode to form a conductive path, with the increase of the pressure, the contact area with the electrode gradually increases, more conductive paths are formed, the resistance is reduced, and the pressure can be detected by observing the change of the electric signal.

[0014] The present application has the following advantages:

[0015] (1) By means of scraping the carbon nanotubes first and then pouring the PDMS mixture on the template, part of the carbon nanotubes can be embedded in the PDMS surface during the curing process of the PDMS, so as to improve the adhesion of the carbon nanotubes, and then improve the stability of the sensor, so that the sensor has better performance in the subsequent use process.

[0016] (2) The channel electrode adopts flexible photocured polymer, which has the advantages of foldable, bendable and fully conformable to the human body. In addition, the carbon nanotubes filled in the channel cannot conform to the convex structure when no pressure is loaded, which ensures the stability of the initial resistance. When pressure is loaded, the flexible stalactite-like structure is squeezed into the channel, and the structure surface and the carbon nanotubes in the channel conform to each other to form a conductive path.

[0017] (3) The irregular stalactite-like array microstructure of the sensor can make it exhibit better deformation response under different pressure environments, so that the sensor has higher sensitivity. In the range of 0.18-120kPa, it exhibits a high sensitivity of 0.71kPa -1 , and in the range of 208-355kPa, the sensitivity is 0.25kPa -1 ; it can accurately respond from gentle touch to strong pressure impact. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The interdigital electrode of the flexible pressure sensor prepared by the present application is shown in the figure.

[0019] Figure 2 The flexible pressure sensor prepared by the present application is shown in the figure.

[0020] Figure 3 The electron microscope image of the stalactite-like structure of the flexible pressure sensor prepared by the present application is shown in the figure.

[0021] Figure 4 The relative change of current of the flexible pressure sensor prepared by the present application when different sizes of force are applied is shown in the figure.

[0022] Figure 5 The response-recovery time of the flexible pressure sensor prepared by the present application under pressure is shown in the figure.

[0023] Figure 6 The volt-ampere curve of the flexible pressure sensor prepared by the present application under different pressures is shown in the figure.

[0024] Figure 7 The sensitivity fitting graph of the flexible pressure sensor prepared by the present application is shown in the figure. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described in detail below in combination with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0026] AsFigures 1-6 The application provides a flexible pressure sensor with a clock-milkstone-shaped array microstructure and a manufacturing method thereof.

[0027] The flexible pressure sensor with the clock-milkstone-shaped array microstructure has higher sensitivity (0.71 kPa -1 of high sensitivity in the range of 208-355 kPa, and 0.25 kPa -1 of sensitivity); and also has better stability (a stress-strain detection range of 0.18-355 kPa), and can accurately respond to light touch to strong pressure impact.

[0028] I. Preparation of a PDMS pouring mold

[0029] The stainless steel sheet is ablated by a laser with a power of 45 W and a speed of 500 mm / s, high energy of the laser makes the stainless steel locally heat and melt, forms a plasma and generates a high pressure shock wave to cause material spalling, and forms an irregular circular hole structure after cooling. The inner part is distributed with irregular holes, and the hole diameters include but are not limited to 0.3 mm, 0.8 mm and the like.

[0030] II. Preparation of a PDMS mixture

[0031] Step S1: Take the carbon nanotube solution and drop it on the surface of the mold and evenly scrape it with a scraper, to ensure that the solution completely covers the mold;

[0032] Step S2: Place the mold coated with the carbon nanotube solution in a 80℃ vacuum drying machine and dry for 30 minutes, to ensure that the water in the solution is completely evaporated;

[0033] Step S3: Mix the PDMS (polydimethylsiloxane) body and the curing agent in a ratio of 10:1, and then put them into a vacuum drying machine for vacuum degassing pretreatment, to remove the bubbles generated when the curing agent and the body are mixed, and to ensure that the PDMS can stably enter the circular hole;

[0034] Step S4: Pour the PDMS mixture treated by vacuum into the mold with carbon nanotubes, and put it into a vacuum drying machine again for vacuum treatment for 30-50 minutes, to stably remove the air in the circular hole, so as to ensure that the PDMS mixture completely enters the circular hole, and then take it out and stand for 10-12 hours, to make the PDMS self-leveling and fully crosslinking;

[0035] Step S5: After the PDMS mixture is completely cured and formed, it is removed from the mold and trimmed to only retain the portion with the stalactite-shaped structure protrusions, thereby obtaining a sensor sensitive layer.

[0036] III. Fabrication of interdigital electrodes

[0037] Step S1: a channel with an interdigital electrode pattern is etched on the surface of a silicon wafer using a dry etching method;

[0038] Step S2: a certain amount of PDMS body and curing agent (10:1) is cast on the patterned silicon wafer surface, and vacuum degassing treatment is performed for 40-60 minutes, thereby obtaining a PDMS surface protrusion template of the electrode pattern, and the PDMS can completely reproduce the microstructure inside the channel;

[0039] Step S3: NOA ultraviolet curing glue is dropped on the surface of a PET (polyethylene terephthalate) film, and then the protruding part of the PDMS template surface is pressed on the surface of the ultraviolet curing glue. Ultraviolet light is irradiated for 5-10 minutes, and the ultraviolet curing glue is quickly cured, thereby obtaining not only the interdigital electrode pattern channel consistent with the silicon wafer template, but also the flexibility of the material, which ensures the stability during assembly;

[0040] Step S4: the carbon nanotube aqueous solution is scraped and coated in the interdigital electrode channel by using a scraper, and is placed in an oven for drying for 10-15 minutes, thereby obtaining a channel electrode.

[0041] IV. Combined flexible pressure sensor

[0042] The PDMS stalactite-shaped structure is assembled face to face with the interdigital electrode, and the two ends of the electrode are connected with wires, thereby obtaining a flexible pressure sensor with a stalactite-shaped array microstructure.

[0043] Example 1

[0044] The manufacturing method of the strain sensor with a stalactite array microstructure according to the embodiment of the present application comprises the following steps:

[0045] S1: laser ablation is performed on a stainless steel sheet at a power of 45W and a speed of 500mm / s, and the mold surface has a plurality of irregular circular hole structures arranged in a matrix, and irregular holes are distributed inside the structures;

[0046] S2: the mold coated with the carbon nanotube solution is placed in a vacuum drying machine at 80℃ for drying for 30 minutes;

[0047] S3: the PDMS (polydimethylsiloxane) body and the curing agent are uniformly mixed, and then are placed in a vacuum drying machine for vacuum degassing treatment;

[0048] S4: The vacuum treated PDMS mixture is poured on the mold with carbon nanotubes, and is placed into a vacuum drying machine for vacuum treatment for 30 minutes, and then is taken out and left for 12 hours;

[0049] S5: After the PDMS mixture is completely cured and formed, it is removed from the mold and trimmed, only the part containing the imitation stalactite-shaped structure protrusion is reserved, to obtain a sensor sensitive layer;

[0050] S6: The side of the PDMS sample containing the imitation stalactite-shaped structure is opposite to the surface of the prepared interdigital electrode, and the two ends of the electrode are connected with wires respectively, so that a flexible pressure sensor with an imitation stalactite-shaped array microstructure is prepared.

[0051] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the skilled person in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0052] The above embodiments are only exemplary embodiments of the present application, and are not used to limit the present application, the protection scope of the present application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements to the present application within the spirit and protection scope of the present application, and such modifications or equivalent replacements are also regarded as falling within the protection scope of the present application.

Claims

1. A method for fabricating a flexible pressure sensor with a stalactite-like array microstructure, characterized in that, It includes the following steps: Step S1: First, a mold is made, with an array of holes on the surface generated by laser ablation; Step S2: Drop the carbon nanotube solution onto the surface of the mold and spread it evenly with a scraper to ensure that the solution completely covers the mold; Step S3: Place the mold coated with carbon nanotube solution in an 80°C vacuum dryer and dry for 30 minutes; Step S4: Mix the PDMS polydimethylsiloxane bulk and curing agent evenly at a ratio of 10:1, and then put them into a vacuum dryer for vacuum degassing treatment; Step S5: Pour the vacuum-treated PDMS mixture onto a mold with carbon nanotubes, and place it in a vacuum dryer for another 30 minutes of vacuum treatment. Then remove it and let it stand for 10-12 hours to allow it to fully adhere to the mold. Step S6: After the PDMS mixture has completely solidified and formed, peel it off the mold and trim it, keeping only the part with the stalactite-shaped array structure protrusions to obtain the sensor sensitive layer; Step S7: Use dry etching to etch channels with interdigitated electrode patterns on the silicon wafer surface; Step S8: Cast a certain amount of PDMS body and curing agent in a ratio of 10:1 on the patterned silicon wafer surface, and perform vacuum degassing treatment for 40-50 minutes to obtain the PDMS surface raised template with electrode pattern. Step S9: Apply NOA UV-curable adhesive droplets to the surface of the PET film, then press the raised part of the PDMS template surface onto the UV-curable adhesive surface, and irradiate with a UV lamp for 5-10 minutes to obtain interdigitated electrode channels; Step S10: Use a scraper to coat the carbon nanotube aqueous solution into the interdigital electrode channel, and dry it in an oven for 10-20 minutes to obtain the channel electrode; Step S11: Assemble the PDMS stalactite-shaped array structure face-to-face with the interdigitated electrodes, and connect the two ends of the electrodes to wires respectively, thereby obtaining a flexible pressure sensor with a stalactite-shaped array microstructure.

2. The method for fabricating a flexible pressure sensor with a stalactite-shaped array microstructure according to claim 1, characterized in that: The method for manufacturing the mold is as follows: ablation of a stainless steel sheet using a laser with a power of 45W and a speed of 500mm / s, with a hole size ranging from 0.3 to 0.8mm.

3. The method for fabricating a flexible pressure sensor with a stalactite-shaped array microstructure according to claim 1, characterized in that: By casting a PDMS mixture onto the surface of a mold, different stalactite-shaped array microstructures are formed after molding.

4. The method for fabricating a flexible pressure sensor with a stalactite-shaped array microstructure according to claim 1, characterized in that: The carbon nanotube solution can be replaced with other conductive inks, including PEDOT:PSS, graphene aqueous solution, or silver nanowires.

5. The method for fabricating a flexible pressure sensor with a stalactite-shaped array microstructure according to claim 1, characterized in that: The PDMS mixture may be replaced with other flexible polymers, including Ecoflex, hydrogel, or thermoplastic polyurethane.

6. The method for fabricating a flexible pressure sensor with a stalactite-shaped array microstructure according to claim 1, characterized in that: The aforementioned channel electrode is an embedded channel with an interdigitated electrode pattern. Carbon nanotubes are filled into the channel by drop-coating the surface and then scraping it evenly with a scraper. After it is completely dry, the surface can be wiped with an ethanol-soaked lint-free cloth to remove excess carbon nanotubes, while the carbon nanotubes in the channel are retained.

7. The method for fabricating a flexible pressure sensor with a stalactite-shaped array microstructure according to claim 1, characterized in that: The NOA UV-curable adhesive in step S9 is replaced with other photocurable polymers, including photosensitive resins, UV resin adhesives, or polyurethane acrylates.

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