Flexible pressure sensor and preparation method and use method thereof

Abstract

The invention provides a flexible pressure sensor as well as a preparation method and a use method thereof. The flexible pressure sensor comprises two electrodes, and a separation layer and a dielectric layer which are arranged between the two electrodes, wherein each of the two electrodes comprises a flexible substrate and a conductive material arranged on the flexible substrate; the dielectric layer is prepared on the basis of a thermoplastic polymer and an ionic liquid, and the thermoplastic polymer and the ionic liquid are soluble. According to the flexible pressure sensor and the preparation method and the use method thereof, the problem that an existing flexible pressure sensor does not have high sensitivity and air and moisture permeability at the same time can be solved.

Description

Technical Field

[0001] The present invention relates to the field of pressure detection technology, and more specifically, to a flexible pressure sensor and a preparation method and a use method thereof. Background Art

[0002] The core of digital health care is the sensing technology of various information such as human motion / physiological parameters and environment. Flexibility, especially flexible sensors, are light, thin, flexible and elastic. They can be directly integrated with objects or the human body to achieve real-time collection, wireless transmission and accurate identification of physiological information. They are strong candidates for the development of digital health care sensing technology. Among the many flexible sensors, electrical pressure sensors such as flexible resistors / capacitors / inductors have the characteristics of comfortable wearing and large pressure detection range. They can detect human health information such as pulse, heart rate, breathing, posture, etc. Therefore, the development of flexible pressure sensors is the key to the digitalization of medical health and one of the important ways to help the human body obtain health information.

[0003] In order to fully detect the movement and physiological conditions of the human body, it is crucial that flexible pressure sensors have high resolution within a wide sensing range. The pressure sensors currently studied are usually composed of a composite of solid conductive materials and an elastic matrix. The use of interface microstructures such as microcracks, pyramids, and micropores to construct a large conductive network can effectively improve the sensitivity and obtain a lower detection limit, but it is difficult to achieve air permeability and moisture permeability. The choice of a fabric matrix can achieve the air permeability and moisture permeability of the sensor, but at the same time the sensitivity is low. Therefore, it is still a challenge to achieve high sensitivity and air permeability and moisture permeability at the same time.

[0004] Based on the above technical problems, there is an urgent need for a flexible pressure sensor that achieves both high sensitivity and air and moisture permeability. Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a flexible pressure sensor and a preparation method and a use method thereof, so as to solve the problem that the existing flexible pressure sensors do not have both high sensitivity and air and moisture permeability.

[0006] The flexible pressure sensor provided by the present invention comprises two electrodes and a separation layer and a dielectric layer arranged between the two electrodes; wherein,

[0007] The two electrodes each comprise a flexible substrate and a conductive material arranged on the flexible substrate; the dielectric layer is made based on a thermoplastic polymer and an ionic liquid, and the thermoplastic polymer and the ionic liquid are miscible.

[0008] In addition, a preferred solution is that the thermoplastic polymer includes at least one of polyvinylidene fluoride-hexafluoropropylene, thermoplastic polyurethane, polyvinyl alcohol, polyvinyl chloride, polytetrafluoroethylene, and polyethylene terephthalate;

[0009] The ionic liquid includes cations and anions; wherein the cations include at least one of imidazoline, pyridine, pyrrolidine salt and quaternary ammonium salt; and the anions include at least one of diimine, methane sulfonate, tricyanomethane and hexafluorophosphate.

[0010] In addition, a preferred solution is that the thickness of the dielectric layer includes 50 μm, 100 μm, 150 μm, 200 μm, and 250 μm.

[0011] In addition, a preferred solution is that the material of the flexible substrate includes polyvinylidene fluoride-hexafluoropropylene and NN dimethylformamide;

[0012] The conductive material includes at least one of carbon black, graphene nanosheets, carbon nanotubes and silver nanowires.

[0013] In addition, a preferred solution is that the conductive material is fixed to the flexible substrate via an adhesive;

[0014] The adhesive is made based on acrylic pressure-sensitive adhesive, isopropyl alcohol and ethyl acetate.

[0015] In addition, a preferred solution is that the separation layer is a hole-type structure.

[0016] In addition, a preferred solution is that the thickness of the separation layer is 50-200 μm; and the diameter of the holes on the separation layer is 0.5-5 mm.

[0017] On the other hand, the present invention also provides a method for preparing the flexible pressure sensor as described above, the method comprising:

[0018] preparing a separation layer, a dielectric layer and two flexible substrates respectively;

[0019] Combining conductive materials on the two flexible substrates to obtain two electrodes;

[0020] The separation layer, the dielectric layer and the two electrodes are combined to obtain the flexible pressure sensor.

[0021] In addition, a preferred solution is that the separation layer, the medium layer and the two flexible substrates are all prepared by electrospinning; wherein,

[0022] The preparation process of the medium layer includes: mixing a thermoplastic polymer and an ionic liquid according to a preset mass ratio to obtain a mixed liquid; and preparing an ion fiber film as the medium layer by an electrostatic spinning method from the mixed liquid.

[0023] On the other hand, the present invention further provides a method for using the flexible pressure sensor as described above, the method comprising:

[0024] Applying a preset strain pressure to the flexible pressure sensor to test an initial capacitance value of the flexible pressure sensor;

[0025] The magnitude, application times and frequency of the strain pressure are changed to obtain a series of reference capacitance values ​​under different strain pressure values.

[0026] Compared with the prior art, the flexible pressure sensor according to the present invention and the preparation method and use method thereof have the following beneficial effects:

[0027] When the flexible pressure sensor provided by the present invention is under compression during operation, the contact area between the dielectric layer and the electrode changes with the change of pressure. The change in the contact area is sensed by the electrostatic effect of the electrode and the double electric layer effect produced by the ionic material, and its electrical output changes, thereby realizing the detection of tiny pressures. In addition, the flexible pressure sensor provided by the present invention can significantly improve the sensitivity by making the dielectric layer with thermoplastic polymers and ionic liquids, and the conductive, breathable and moisture-permeable effects of the electrode can be realized by preparing the electrode with composite conductive materials on a flexible substrate.

[0028] In order to achieve the above and related purposes, one or more aspects of the present invention include features that will be described in detail later and are particularly pointed out in the claims. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] By referring to the following description and claims in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easier to understand. In the accompanying drawings:

[0030] Figure 1 Schematic diagram of the structure of the flexible pressure sensor provided by an embodiment of the present invention.

[0031] Figure 2 It is a curve showing the relationship between capacitance and pressure in the flexible pressure sensor provided by an embodiment of the present invention.

[0032] Reference numerals: electrode 1 , separation layer 2 , dielectric layer 3 .

[0033] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0034] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0035] Figure 1 The structure of the flexible pressure sensor provided by an embodiment of the present invention is shown.

[0036] Depend on Figure 1 It can be seen that the flexible pressure sensor provided by the present invention includes two electrodes 1 on both sides and a separation layer 2 and a dielectric layer 3 arranged between the two electrodes 1; wherein, when the flexible pressure sensor is in a compressed state, the contact area between the dielectric layer 3 and the electrode 1 adjacent thereto changes with the change of pressure, and the change of the contact area is sensed by the double electric layer effect generated by the electrostatic action of the electrode 1 and the ionic material in the dielectric layer 3, and its electrical output changes, thereby realizing the corresponding sensing effect of the pressure sensor, and the separation layer 2 is used to separate the dielectric layer 3 from the electrode 1 on the other side.

[0037] Specifically, the two electrodes 1 are characterized by being conductive, breathable, moisture-permeable and waterproof. To achieve the conductive, breathable and moisture-permeable effects of the two electrodes 1, the two electrodes 1 include a flexible substrate and a conductive material disposed on the flexible substrate. The flexible substrate is used to achieve the breathable and moisture-permeable effects of the electrode 1, and the conductive material is used to achieve the conductive effect of the electrode 1. In addition, in order to improve the sensitivity of the entire flexible pressure sensor, the dielectric layer 3 is made based on a thermoplastic polymer and an ionic liquid, and the thermoplastic polymer and the ionic liquid are miscible. In the actual production process, a thermoplastic (polar) polymer with high miscibility and an ionic liquid are mixed in a certain mass ratio, and the mixed liquid is prepared into an ionic fiber film by an electrospinning process. The ionic fiber film is used as the dielectric layer 3 to improve the sensitivity of the flexible pressure sensor.

[0038] More specifically, for the thermoplastic polymer, the thermoplastic polymer may include one or more of polyvinylidene fluoride-hexafluoropropylene, thermoplastic polyurethane (TPU), polyvinyl alcohol, polyvinyl chloride, polytetrafluoroethylene, polyethylene terephthalate, and thermoplastic polymers; preferably, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) with high tensile properties and hydrophobicity is selected.

[0039] For the ionic liquid, the ionic liquid further includes cations and anions; wherein the cations include imidazoline, pyridine, pyrrolidine salt and quaternary ammonium salt, including at least one of them; the anions include different combinations of bis(trifluoromethylsulfonyl)imide, methanesulfonate, tricyanomethane and hexafluorophosphate, at least one; preferably, the combination of cations and anions is preferably 1-ethyl-3-methylimidazoline, bis(trifluoromethylsulfonyl)imide [EMIM] [TFSI], and the reference ratio is 1:1-1:5.

[0040] It should be noted that the dielectric layer 3 needs to have a certain thickness design, and preferred thickness sizes of the dielectric layer 3 include 50 μm, 100 μm, 150 μm, 200 μm, and 250 μm.

[0041] In addition, in order to improve the sensitivity of the flexible pressure sensor by using a flexible substrate, the material of the flexible substrate may include polyvinylidene fluoride-hexafluoropropylene and NN dimethylformamide, and the flexible substrate is prepared by mixing polyvinylidene fluoride-hexafluoropropylene and NN dimethylformamide and then electrospinning. The ratio of polyvinylidene fluoride-hexafluoropropylene to NN dimethylformamide is 9:31.

[0042] In addition, to achieve the conductive performance of the conductive material, the conductive material may include at least one of carbon black, graphene nanosheets, carbon nanotubes and silver nanowires. Preferably, the conductive material is silver nanowires.

[0043] Specifically, after the conductive material and the flexible substrate are prepared, the conductive material is fixed to the flexible substrate through an adhesive; wherein the adhesive is prepared based on a mixture of medical acrylate pressure-sensitive adhesive (MA) with isopropyl alcohol and ethyl acetate, and the ratio of medical acrylate pressure-sensitive adhesive (MA) to isopropyl alcohol and ethyl acetate is 4:1:1.

[0044] In a preferred embodiment of the present invention, the structure of the separation layer 2 is preferably a hole-type structure.

[0045] In addition, the thickness of the separation layer 2 is set to 50-200 μm, and the diameter of the hole on the separation layer 2 is set to 0.5-5 mm, so as to achieve the separation of the dielectric layer 3 and the other side electrode 1 by the separation layer 2. It should be noted that by setting a hole structure for the separation layer 2, the electrical performance of the entire flexible pressure sensor can be further improved, thereby improving the sensitivity.

[0046] To further illustrate the implementation method of the high sensitivity and air and moisture permeability effects of the flexible pressure sensor provided by the present invention, the present invention also provides a method for preparing the flexible pressure sensor, the preparation method comprising:

[0047] Prepare a separation layer 2, a dielectric layer 3 and two flexible substrates respectively;

[0048] Combining conductive materials on the two flexible substrates to obtain two electrodes 1;

[0049] The separation layer 2, the dielectric layer 3 and the two electrodes 1 are combined by a sealing machine to obtain the flexible pressure sensor.

[0050] Specifically, the separation layer 2, the medium layer 3 and the two flexible substrates are all prepared by electrospinning, and the relevant parameters of the electrospinning method (process) include: voltage, injection speed, spinning distance, receiving roller speed, temperature, humidity, etc. The voltage reference range is 10-25kV; the injection speed reference range is 0.075-0.75ml / h; the spinning distance reference range is 5-13cm; the receiving roller speed reference range is 50-300r / min; the temperature reference range is 25-50℃; the humidity reference range is 35%-60%.

[0051] More specifically, the process of combining conductive materials on the two flexible substrates to obtain two electrodes 1 may include: compounding medical acrylate pressure-sensitive adhesive (MA) on the two flexible substrates by electrospinning, and combining silver nanowires on the flexible substrates by vacuum filtration to form two electrodes 1.

[0052] In addition, the preparation process of the dielectric layer 3 may include: mixing a thermoplastic polymer and an ionic liquid according to a preset mass ratio to obtain a mixed liquid; and preparing an ionic fiber film as the dielectric layer 3 by electrospinning the mixed liquid.

[0053] On the other hand, to further illustrate the working principle of the flexible pressure sensor provided by the present invention, FIG. Figure 2 The relationship curve between the capacitance and pressure in the flexible pressure sensor provided by the embodiment of the present invention is shown. Figure 1 and Figure 2 As shown, the present invention also provides a method for using the flexible pressure sensor, the method comprising:

[0054] Applying a preset strain pressure to the flexible pressure sensor to test an initial capacitance value of the flexible pressure sensor;

[0055] The magnitude, application times and frequency of the strain pressure are changed to obtain a series of reference capacitance values ​​under different strain pressure values.

[0056] The preparation method of the flexible pressure sensor provided by the present invention is further described below by way of specific examples.

[0057] The structure of the flexible ionization pressure sensor is as follows Figure 1As shown, it is composed of an electrode 1, a separator 2 and a dielectric layer 3. Among them, the electrode 1 is specifically made of polyvinylidene fluoride-hexafluoropropylene, NN dimethylformamide, medical acrylate pressure-sensitive adhesive (MA), isopropyl alcohol, ethyl acetate and silver nanowires; the separator 2 is specifically made of polyvinylidene fluoride-hexafluoropropylene and NN dimethylformamide; the dielectric layer 3 is specifically made of a mixture of polyvinylidene fluoride-hexafluoropropylene, NN dimethylformamide and 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide.

[0058] Furthermore, the preparation method of the flexible ionization pressure sensor comprises the following steps:

[0059] An electrode flexible substrate is prepared by an electrospinning method, and a medical acrylate pressure-sensitive adhesive is composited on the flexible substrate by electrospinning to provide adhesion, and silver nanowires are filtered by vacuum extraction; a mixture of polyvinylidene fluoride-hexafluoropropylene, NN dimethylformamide and 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide is spun by electrospinning to obtain a dielectric layer; a film prepared by electrospinning is collected by a template method to obtain a separation layer with a microstructure, and a flexible ionization pressure sensor is obtained by hot pressing the electrode, the separation layer and the dielectric layer with a sealing machine.

[0060] As above Figure 1 and Figure 2 The flexible pressure sensor and its preparation method and use method according to the present invention are described in an exemplary manner. However, those skilled in the art should understand that various improvements can be made to the flexible pressure sensor and its preparation method and use method proposed in the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A flexible pressure sensor, characterized in that: It comprises two electrodes and a separation layer and a dielectric layer arranged between the two electrodes; wherein, The two electrodes each include a flexible substrate and a conductive material disposed on the flexible substrate; the dielectric layer is made based on a thermoplastic polymer and an ionic liquid, and the thermoplastic polymer and the ionic liquid are miscible.

2. The flexible pressure sensor according to claim 1, characterized in that: The thermoplastic polymer includes at least one of polyvinylidene fluoride-hexafluoropropylene, thermoplastic polyurethane, polyvinyl alcohol, polyvinyl chloride, polytetrafluoroethylene, and polyethylene terephthalate; The ionic liquid includes cations and anions; wherein the cations include at least one of imidazoline, pyridine, pyrrolidine salt and quaternary ammonium salt; and the anions include at least one of diimine, methane sulfonate, tricyanomethane and hexafluorophosphate.

3. The flexible pressure sensor according to claim 2, characterized in that: The thickness of the dielectric layer includes 50 μm, 100 μm, 150 μm, 200 μm and 250 μm.

4. The flexible pressure sensor according to claim 1, characterized in that: The flexible substrate is made of materials including polyvinylidene fluoride-hexafluoropropylene and NN dimethylformamide; The conductive material includes at least one of carbon black, graphene nanosheets, carbon nanotubes and silver nanowires.

5. The flexible pressure sensor according to claim 4, characterized in that: The conductive material is fixed to the flexible substrate via an adhesive; The adhesive is made based on acrylic pressure-sensitive adhesive, isopropyl alcohol and ethyl acetate.

6. The flexible pressure sensor according to any one of claims 1 to 5, characterized in that: The separation layer is a hole structure.

7. The flexible pressure sensor according to claim 6, characterized in that: The thickness of the separation layer is 50-200 μm; The diameter of the holes on the separation layer is 0.5-5 mm.

8. A method for preparing a flexible pressure sensor according to any one of claims 1 to 7, characterized in that: The preparation method comprises: preparing a separation layer, a dielectric layer and two flexible substrates respectively; Combining conductive materials on the two flexible substrates to obtain two electrodes; The separation layer, the dielectric layer and the two electrodes are combined to obtain the flexible pressure sensor.

9. The method for preparing a flexible pressure sensor according to claim 8, characterized in that: The separation layer, the medium layer and the two flexible substrates are all prepared by electrospinning; wherein, The preparation process of the medium layer includes: mixing a thermoplastic polymer and an ionic liquid according to a preset mass ratio to obtain a mixed liquid; and preparing an ion fiber film as the medium layer by an electrostatic spinning method from the mixed liquid.

10. A method for using the flexible pressure sensor according to any one of claims 1 to 7, characterized in that: The method of use includes: Applying a preset strain pressure to the flexible pressure sensor to test an initial capacitance value of the flexible pressure sensor; The magnitude, application times and frequency of the strain pressure are changed to obtain a series of reference capacitance values ​​under different strain pressure values.

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