Flexible pressure sensor with stalactite-like array microstructure and manufacturing method thereof

Abstract

The invention discloses a flexible pressure sensor with a stalactite-like array microstructure and a manufacturing method thereof.The manufacturing method comprises the steps that firstly, a needed mold is manufactured through a laser ablation method, then a carbon nano tube is scraped on the mold, then a PDMS mixture is poured, then vacuumizing treatment and standing are conducted on the mold so that the mold can be cured and formed, and after mold overturning treatment, the flexible pressure sensor with the stalactite-like array microstructure can be manufactured. And assembling the PDMS simulated stalactite-shaped array structure and an interdigital electrode in a face-to-face manner, and connecting the two ends of the electrode with wires, thereby obtaining the flexible pressure sensor with the simulated stalactite-shaped array microstructure. The stalactite-like microstructure of the sensor can enable the sensor to show excellent deformation response in different pressure environments, the sensor shows high sensitivity of 0.71 kPa <-1 > in a range of 0.18-120 kPa, and the sensitivity of the sensor is 0.25 kPa <-1 > in a range of 208-355kPa; in addition, the wide detection range of 0.18 kPa to 355 kPa is achieved, and accurate response can be achieved from soft touch to strong pressure impact.

Description

Technical Field

[0001] The invention belongs to the technical field of flexible pressure sensors, and in particular relates to a flexible pressure sensor with a stalactite-shaped array microstructure and a manufacturing method thereof. Background Art

[0002] With the continuous development of science and technology, flexible pressure sensors are increasingly used in biomedicine, sports training, human-computer interaction and other fields. However, existing flexible pressure sensors still have many deficiencies in sensitivity, force range and stability. To this end, the present invention proposes a new flexible pressure sensor and a preparation method thereof, aiming to significantly improve the performance of the sensor by imitating natural structure and optimizing the manufacturing process.

[0003] In nature, stalactites are known for their unique structures. Inspired by the structure of stalactites, the present invention incorporates the morphological characteristics of stalactites into the design of flexible pressure sensors to form a unique stalactite-like structure. Compared with previous bionic structures, such as wheat ear structures and rose structures, the stalactite-like structure can produce a more uniform stress distribution when subjected to force, thereby significantly improving the sensitivity of the sensor. At the same time, the structure also has a wider force range, which can more accurately capture and respond to pressure stimuli from different directions and intensities.

[0004] In summary, the present invention significantly improves the sensitivity, force range and stability of the flexible pressure sensor by imitating the natural structure design, optimizing the manufacturing process and introducing the protruding structure. These innovations make the sensor have broad application prospects in the fields of biomedical monitoring, training and rehabilitation assessment, and human-computer interaction. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a flexible pressure sensor with a stalactite-shaped array microstructure and a manufacturing method thereof. The stalactite-shaped microstructure of the sensor can show a good deformation response under different pressure environments, so that the sensor has better sensitivity performance and a larger pressure detection range.

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

[0007] A flexible pressure sensor with a stalactite-shaped array microstructure and a manufacturing method thereof, characterized in that circular irregular holes are generated on a stainless steel surface by laser ablation as a mold, a stalactite-like structure is prepared by first scraping a carbon nanotube solution into the holes, and then using the characteristic of PDMS that the microstructure can be replicated; a flexible pressure sensor is prepared by combining interdigital electrodes manufactured by dry etching and scraping processes with the stalactite-like microstructure.

[0008] Furthermore, the mold manufacturing method is: on the stainless steel sheet, use a laser with a power of 45W and a speed of 500mm / s to ablate the stainless steel sheet to form different irregular holes, and the hole sizes include but are not limited to 0.3mm, 0.8mm, etc.

[0009] Furthermore, the carbon nanotube solution, as a kind of conductive ink, will form a conductive layer on the surface of the stalactite-like microstructure during the curing process of the PDMS mixture, thereby achieving conduction of the sensor circuit. The carbon nanotube solution includes but is not limited to PEDOT:PSS, graphene oxide aqueous solution, and silver nanowire aqueous solution.

[0010] Furthermore, the PDMS mixture is a high molecular weight flexible polymer that will produce obvious deformation under the action of external force and can better detect pressure changes, including but not limited to Ecoflex and hydrogel.

[0011] Furthermore, the channel electrode is an embedded channel with an interdigitated electrode pattern. The carbon nanotubes are dripped onto the surface and then evenly filled into the channel by scraping with a scraper. After it is completely dried, the surface can be wiped with a dust-free cloth soaked in ethanol to remove excess carbon nanotubes on the surface, and the carbon nanotubes in the channel are retained.

[0012] Furthermore, the NOA UV-curing glue, whose main component is a photocurable polymer, has a certain viscosity and can be quickly cured under ultraviolet light, includes but is not limited to photosensitive resin, UV resin glue, and polyurethane acrylate.

[0013] Furthermore, the working principle of the flexible pressure sensor is: when pressure acts on the sensor, the stalactite-shaped microstructure will contact the interdigitated electrodes to form a conductive path. As the pressure increases, the contact area with the electrode gradually increases, forming more conductive paths, and the resistance decreases. The pressure is detected by observing the changes in electrical signals.

[0014] The present invention has the following advantages:

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

[0016] (2) The channel electrode is made of a flexible photocurable polymer, which has the advantages of being foldable, bendable, and able to fully fit the human body. In addition, the carbon nanotubes filled in the channel cannot fit with the protruding structure when no pressure is applied, ensuring the stability of the initial resistance. When pressure is applied, the flexible stalactite-like structure is squeezed into the channel, and the surface of the structure and the carbon nanotubes in the channel fit together to form a conductive path.

[0017] (3) The irregular stalactite-like array microstructure of the sensor enables it to exhibit good deformation response under different pressure environments, making the sensor more sensitive, showing 0.71 kPa in the range of 0.18-120 kPa. -1 High sensitivity, the sensitivity is 0.25kPa in the range of 208-355kPa -1 ; It can respond accurately from gentle touch to strong pressure shock. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a physical picture of the interdigital electrodes of the flexible pressure sensor prepared by the present invention.

[0019] Figure 2 This is a physical picture of the flexible pressure sensor prepared by the present invention.

[0020] Figure 3 This is an electron microscope image of the stalactite-like structure of the flexible pressure sensor prepared in the present invention.

[0021] Figure 4 A diagram showing relative changes in current when forces of different magnitudes are applied to the flexible pressure sensor prepared by the present invention.

[0022] Figure 5 The response-recovery time of the flexible pressure sensor prepared by the present invention under pressure.

[0023] Figure 6 The volt-ampere curves of the flexible pressure sensor prepared in the present invention under different pressures.

[0024] Figure 7 This is the sensitivity fitting diagram of the flexible pressure sensor prepared by the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0026] likeFigures 1-6 As shown, the present invention proposes a flexible pressure sensor with a stalactite-shaped array microstructure and a manufacturing method thereof. The flexible pressure strain sensor prepared by the present invention includes a strain sensor for sensing insoles and bicycle seat cushions.

[0027] The flexible pressure sensor with a stalactite-shaped array microstructure proposed in the present invention has a higher sensitivity (0.71 kPa in the range of 0.18-120 kPa). -1 High sensitivity, the sensitivity is 0.25kPa in the range of 208-355kPa -1 ); and also has better stability (stress-strain detection range of 0.18-355kPa), and can accurately respond to everything from gentle touch to strong pressure shock.

[0028] 1. Preparation of PDMS casting mold

[0029] On the stainless steel sheet, the laser ablation of the stainless steel sheet with a power of 45W and a speed of 500mm / s, the high energy of the laser causes the stainless steel to heat up and melt locally, forming plasma and generating high-pressure shock waves to cause the material to peel off, and after cooling, an irregular circular hole structure is formed. There are irregular holes distributed inside, and the hole sizes include but are not limited to 0.3mm, 0.8mm, etc.

[0030] 2. Preparation of PDMS mixture

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

[0032] Step S2: drying the mold coated with the carbon nanotube solution in a vacuum dryer at 80° C. for 30 minutes to ensure that the water in the solution is completely evaporated;

[0033] Step S3: PDMS (polydimethylsiloxane) body and curing agent are mixed evenly in a ratio of 10:1, and then placed in a vacuum dryer for vacuum degassing pretreatment. This step is to remove bubbles generated when the curing agent and body are mixed, to ensure that PDMS can stably enter the circular hole;

[0034] Step S4: pouring the vacuum-treated PDMS mixture onto the mold with the carbon nanotubes, and placing it in a vacuum dryer for another vacuum treatment for 30-50 minutes, which can stably remove the air inside the circular hole to ensure that the PDMS mixture completely enters the circular hole, and then taking it out and letting it stand for 10-12 hours to allow the PDMS to self-level and fully cross-link;

[0035] Step S5: After the PDMS mixture is completely solidified and formed, it is peeled off from the mold and trimmed, leaving only the part containing the stalactite-shaped structure protrusions to obtain the sensor sensitive layer.

[0036] 3. Fabrication of interdigitated electrodes

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

[0038] Step S2: pouring a certain amount of PDMS body and curing agent ratio (10:1) on the patterned silicon wafer surface, vacuum degassing for 40-60 minutes, to obtain a PDMS surface convex template of the electrode pattern, and PDMS can completely replicate the microstructure inside the channel;

[0039] Step S3: Use NOA UV-curable glue to drop on the surface of PET (polyethylene terephthalate) film, and then press the raised part of the PDMS template surface onto the surface of UV-curable glue. Use UV light to irradiate for 5-10 minutes, and the UV-curable glue will cure quickly, not only obtaining the interdigital electrode pattern channel consistent with the silicon wafer template, but also having the flexibility of the material, ensuring the stability during assembly;

[0040] Step S4: Use a scraper to scrape the carbon nanotube aqueous solution into the channels of the interdigitated electrodes, and put them into an oven to dry for 10-15 minutes to obtain the channel electrodes.

[0041] 4. Combined Flexible Pressure Sensor

[0042] The PDMS stalactite-like structure and the interdigital electrode are assembled face to face, and the two ends of the electrode are connected to the wires respectively, so as to prepare a flexible pressure sensor with a stalactite-like array microstructure.

[0043] Embodiment 1

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

[0045] S1: On a stainless steel sheet, a laser ablation of the stainless steel sheet was performed at a power of 45 W and a speed of 500 mm / s. The surface of the mold had a plurality of irregular circular hole structures arranged in a matrix, and irregular holes were distributed inside;

[0046] S2: drying the mold coated with the carbon nanotube solution in a vacuum dryer at 80°C for 30 minutes;

[0047] S3: Mix the PDMS (polydimethylsiloxane) body and the curing agent evenly, and then put them into a vacuum dryer for vacuum degassing treatment;

[0048] S4: pouring the vacuum-treated PDMS mixture onto the mold with carbon nanotubes, and placing it in a vacuum dryer for vacuum treatment for 30 minutes, then taking it out and letting it stand for 12 hours;

[0049] S5: After the PDMS mixture is completely cured and formed, it is peeled off from the mold and trimmed, leaving only the part with the stalactite-shaped structure protrusion to obtain the sensor sensitive layer;

[0050] S6: Place the side of the PDMS sample containing the stalactite-shaped structure opposite to the prepared interdigital electrode surface, and connect the two ends of the electrode to the wires respectively, so as to obtain a flexible pressure sensor with a stalactite-shaped array microstructure.

[0051] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this 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 intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A flexible pressure sensor with a stalactite-shaped array microstructure and a method for manufacturing the same, characterized in that: The following steps are involved: Step S1: firstly, a mold is prepared, and the mold surface has array-distributed holes generated by laser ablation; Step S2: drop the carbon nanotube solution on the surface of the mold and apply it evenly with a scraper to ensure that the solution completely covers the mold; Step S3: drying the mold coated with the carbon nanotube solution in a vacuum dryer at 80° C. for 30 minutes; Step S4: PDMS (polydimethylsiloxane) body and curing agent are mixed evenly in a ratio of 10:1, and then placed in a vacuum dryer for vacuum degassing treatment; Step S5: pouring the vacuum-treated PDMS mixture onto the mold with the carbon nanotubes, and placing it in a vacuum dryer for another vacuum treatment for 30 minutes, then taking it out and letting it stand for 10-12 hours to make it completely fit the mold; Step S6: After the PDMS mixture is completely cured and formed, it is peeled off from the mold and trimmed, leaving only the part containing the protrusions of the stalactite-shaped array structure to obtain the sensor sensitive layer; Step S7: etching a channel having an interdigital electrode pattern on the surface of the silicon wafer using a dry etching method; Step S8: pouring a certain amount of PDMS body and curing agent ratio (10:1) on the patterned silicon wafer surface, vacuum degassing for 40-50 minutes, and obtaining a PDMS surface convex template of the electrode pattern; Step S9: drop NOA (Norland Optical Adhesive) UV curing glue on the surface of PET (polyethylene terephthalate) film, then press the raised part of the PDMS template surface on the surface of UV curing glue, and irradiate with UV lamp for 5-10 minutes to obtain interdigitated electrode channels; Step S10: Use a scraper to scrape the carbon nanotube aqueous solution into the interdigital electrode channel, and put it into an oven to dry for 10-20 minutes to obtain a channel electrode; Step S11: assembling the PDMS stalactite-shaped array structure and the interdigital electrodes face to face, and connecting the two ends of the electrodes to the wires respectively, so as to obtain a flexible pressure sensor with a stalactite-shaped array microstructure.

2. The method for manufacturing a flexible pressure sensor having a stalactite-shaped array microstructure according to claim 1, characterized in that: The method for making the mold is to use a laser with a power of 45W and a speed of 500mm / s to ablate the stainless steel sheet, and the aperture size includes but is not limited to 0.3-0.8mm.

3. The method for manufacturing a flexible pressure sensor having a stalactite-shaped array microstructure according to claim 1, characterized in that: By pouring the PDMS mixture on the mold surface, different stalactite-shaped array microstructures are formed after remolding.

4. The method for manufacturing a flexible pressure sensor having a stalactite-shaped array microstructure according to claim 1, characterized in that: The carbon nanotube solution is a conductive ink, which includes but is not limited to PEDOT:PSS, graphene aqueous solution, and silver nanowires.

5. The method for manufacturing a flexible pressure sensor having a stalactite-shaped array microstructure according to claim 1, characterized in that: The stalactite-like microstructure is a natural-like multi-layer protrusion structure, including but not limited to wheat ears, octopus tentacles, and rose structures.

6. The method for manufacturing a flexible pressure sensor having a stalactite-shaped array microstructure according to claim 1, characterized in that: The PDMS mixture is a high molecular weight flexible polymer that will produce significant deformation under the action of external force, including but not limited to Ecoflex, hydrogel, and thermoplastic polyurethane.

7. The method for manufacturing a flexible pressure sensor having a stalactite-like microstructure according to claim 1, characterized in that: The channel electrode is an embedded channel with an interdigitated electrode pattern. The carbon nanotubes are dripped onto the surface and then evenly filled into the channel by scraping with a scraper. After complete drying, the surface can be wiped with a dust-free cloth soaked in ethanol to remove excess carbon nanotubes on the surface, while the carbon nanotubes in the channel are retained.

8. The method for manufacturing a flexible pressure sensor having a stalactite-like microstructure according to claim 1, characterized in that: The NOA UV-curing glue in step s9 is mainly composed of a photocurable polymer, has a certain viscosity, and can be quickly cured under ultraviolet light, including but not limited to photosensitive resin, UV resin glue, and polyurethane acrylate.

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