Flexible pressure sensor and method of making the same

Abstract

The application relates to the technical field of sensors, and discloses a flexible pressure sensor and a preparation method thereof. The disclosed flexible pressure sensor comprises a flexible substrate, liquid metal and a first flexible tensile-resistant film. The flexible substrate is internally provided with a closed metal runner, the liquid metal is arranged in the metal runner, the flexible substrate has a pressure sensing area, the pressure sensing area has a first pressure sensing surface, and the first flexible tensile-resistant film is stacked and fixed on the first pressure sensing surface. The flexible pressure sensor provided by the application can solve the problem that, in the related art, the resistance change of the liquid metal caused by the tensile deformation of the flexible pressure sensor during pressure measurement has interference on the pressure measurement, thereby causing low pressure measurement accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a flexible pressure sensor and a preparation method thereof. BACKGROUND

[0002] The flexible pressure sensor is a device for converting a pressure signal into an electric signal, and is widely used in wearable devices, human-computer interaction and electronic skin and the like.

[0003] Liquid metal can maintain good electrical properties under large deformation, and is therefore widely used in flexible pressure sensors. When a flexible pressure sensor is used to measure pressure, external pressure acts on the flexible pressure sensor to cause deformation, and the deformation causes the resistance of the liquid metal to change. The change in the resistance of the liquid metal is used to obtain the change in the external pressure, thereby completing the measurement of the pressure.

[0004] However, stretching can also cause the flexible pressure sensor to deform, and the tensile deformation can also cause the resistance of the liquid metal to change, thereby interfering with the measurement of the pressure and leading to inaccurate pressure measurement. SUMMARY

[0005] The present application provides a flexible pressure sensor and a preparation method thereof, to solve the problem of low accuracy of pressure measurement caused by the change in the resistance of the liquid metal due to the tensile deformation of the flexible pressure sensor during pressure measurement in the related art.

[0006] The present application provides a flexible pressure sensor, comprising a flexible substrate, liquid metal and a first flexible tensile-resistant film, wherein the flexible substrate is provided with a closed metal flow channel, the liquid metal is arranged in the metal flow channel, the flexible substrate has a pressure sensing area, the area where the metal flow channel is located forms the pressure sensing area, the pressure sensing area has a first pressure sensing surface, and the first flexible tensile-resistant film is stacked and fixed on the first pressure sensing surface.

[0007] The flexible pressure sensor provided by the present application further comprises a second flexible tensile-resistant film, the second flexible tensile-resistant film is stacked and fixed on a second pressure sensing surface of the pressure sensing area, and the second pressure sensing surface and the first pressure sensing surface are arranged opposite to each other.

[0008] The first flexible tensile-resistant film is connected to the first pressure sensing surface by bonding, and the second flexible tensile-resistant film is connected to the second pressure sensing surface by bonding; or,

[0009] The first flexible tensile-resistant film is connected to the first pressure sensing surface by bonding, and the second flexible tensile-resistant film is connected to the second pressure sensing surface by bonding.

[0010] The flexible pressure sensor provided by the application further comprises an extension area connected to the outer periphery of the pressure sensing area.

[0011] The flexible pressure sensor provided by the application is provided with a liquid filling hole which is communicated with the metal flow channel, and the flexible pressure sensor further comprises a wire, one end of which is inserted into the metal flow channel through the liquid filling hole and contacted with the liquid metal, and the other end of which is located outside the flexible substrate, and the wire is fixedly connected with the first flexible tensile-resistant film.

[0012] The application further provides a preparation method of the flexible pressure sensor, which comprises the following steps:

[0013] Preparation of the first flexible base with a groove structure;

[0014] Stacking and fixing the first flexible tensile-resistant film on the first surface of the first flexible base, and the first flexible tensile-resistant film is opposite to the area where the groove structure is located;

[0015] Stacking and fixing the second flexible base on the second surface of the first flexible base to connect the first flexible base and the second flexible base to form a flexible substrate, the second surface is opposite to the first surface, and the second flexible base blocks the slot of the groove structure to form a metal flow channel;

[0016] Filling the liquid metal into the metal flow channel;

[0017] Inserting the first end of the wire into the liquid metal, and the second end of the wire is located outside the flexible substrate;

[0018] Fixing and connecting the wire to the first flexible tensile-resistant film.

[0019] According to the preparation method provided by the application, after the first flexible tensile-resistant film is stacked and fixed on the first surface of the first flexible base, before the second flexible base is stacked and fixed on the second surface of the first flexible base, the preparation method further comprises the following steps:

[0020] Opening a liquid filling hole on the first flexible tensile-resistant film and the first flexible base, and the liquid filling hole passes through the groove structure.

[0021] According to the preparation method provided by the application, after the second flexible base is stacked and fixed on the second surface of the first flexible base, before the liquid metal is filled into the metal flow channel, the preparation method further comprises the following steps:

[0022] A second flexible tensile-resistant film is fixedly stacked on a surface of the second flexible base facing away from the first flexible base, and the second flexible tensile-resistant film is opposite to the area where the metal runner is located.

[0023] According to the preparation method provided by the application, the first flexible tensile-resistant film is fixedly stacked on the first surface of the first flexible base, which comprises:

[0024] The first flexible tensile-resistant film and the first surface of the first flexible base are subjected to plasma treatment, and the first flexible tensile-resistant film is attached to the first surface, so that the first flexible tensile-resistant film and the first flexible base are bonded and connected;

[0025] The second flexible base is fixedly stacked on the second surface of the first flexible base, which comprises:

[0026] The second flexible base and the second surface of the first flexible base are subjected to plasma treatment, and the second flexible base is attached to the second surface, so that the second flexible base and the first flexible base are bonded and connected;

[0027] The second flexible tensile-resistant film is fixedly stacked on a surface of the second flexible base facing away from the first flexible base, which comprises:

[0028] The surface of the second flexible base facing away from the first flexible base and the second flexible tensile-resistant film are subjected to plasma treatment, and the second flexible tensile-resistant film is attached to the surface of the second flexible base facing away from the first flexible base, so that the second flexible tensile-resistant film and the second flexible base are bonded and connected.

[0029] According to the preparation method provided by the application, the first flexible base with a groove structure comprises:

[0030] A photoresist is coated on a silicon wafer;

[0031] A mask is covered on the photoresist;

[0032] The photoresist covered with the mask is exposed to ultraviolet light;

[0033] The mask is removed;

[0034] The photoresist is washed with a developing agent, so that a photoetching structure is formed on the silicon wafer;

[0035] A flexible base prepolymer is poured on the silicon wafer with the photoetching structure, and the flexible base prepolymer is baked, so that the flexible base prepolymer forms a first flexible base;

[0036] peeling the first flexible base from the silicon wafer.

[0037] According to the preparation method provided by the application, the flexible base comprises a pressure sensing area and an extension area, the extension area is connected to the outer periphery of the pressure sensing area, and the area where the metal flow channel is located forms the pressure sensing area.

[0038] In the embodiment of the application, the first flexible tensile-resistant film limits the tensile deformation of the pressure sensing area connected thereto, that is, the pressure sensing area is not prone to tensile deformation, so that the flexible pressure sensor in the application has good resistance to tensile interference, alleviates the problem that the resistance of the liquid metal changes due to the tensile deformation of the flexible pressure sensor, thereby interfering with the pressure measurement, and improves the pressure measurement accuracy of the flexible pressure sensor. Therefore, the flexible pressure sensor of the application can solve the problem in the related art that the resistance of the liquid metal changes due to the tensile deformation of the flexible pressure sensor during pressure measurement, which interferes with the pressure measurement and results in low pressure measurement accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0040] Figure 1 is a structural schematic diagram of the flexible pressure sensor provided by the application;

[0041] Figure 2 is a structural schematic diagram of the flexible pressure sensor in a stretched state provided by the application Figure 2 the arrow direction in indicates the direction in which the flexible sensor is stretched, Figure 2 the dashed box in indicates the position of the flexible base when not stretched;

[0042] Figure 3 is a structural schematic diagram of the metal flow channel provided by the application;

[0043] Figure 4 is a structural schematic diagram of the silicon wafer coated with photoresist provided by the application;

[0044] Figure 5 is a structural schematic diagram of the photoresist covered with a mask exposed to ultraviolet light provided by the application;

[0045] Figure 6 is a structural schematic diagram of the silicon wafer with a photoetching structure provided by the application;

[0046] Figure 7 is a schematic diagram of the cooperation structure of the first flexible base, the photoetching structure and the silicon wafer provided by the present application;

[0047] Figure 8 is a schematic diagram of the first flexible base with a groove structure provided by the present application;

[0048] Figure 9 is a schematic diagram of the first flexible base and the first flexible tensile-resistant film being subjected to plasma treatment provided by the present application;

[0049] Figure 10 is a schematic diagram of the first flexible tensile-resistant film and the first flexible base being stacked and connected provided by the present application;

[0050] Figure 11 is a schematic diagram of the first flexible tensile-resistant film and the first flexible base being stacked and connected and the liquid filling hole being formed provided by the present application; Figure 11 the arrow direction in the figure indicates the direction of forming the liquid filling hole;

[0051] Figure 12 is a schematic diagram of the first flexible base and the second flexible base being subjected to plasma treatment provided by the present application;

[0052] Figure 13 is a schematic diagram of the cooperation structure of the first flexible tensile-resistant film and the flexible base provided by the present application;

[0053] Figure 14 is a schematic diagram of the second flexible tensile-resistant film and the second flexible base being subjected to plasma treatment provided by the present application;

[0054] Figure 15 is a schematic diagram of the cooperation structure of the first flexible tensile-resistant film, the second flexible tensile-resistant film and the flexible base provided by the present application;

[0055] Figure 16 is a schematic diagram of the cooperation structure of the first flexible tensile-resistant film, the second flexible tensile-resistant film, the flexible base and the liquid metal provided by the present application after the liquid metal is filled;

[0056] Figure 17 is a flow chart of the preparation of the flexible pressure sensor provided by the present application;

[0057] Figure 18 is a flow chart of the preparation of the first flexible base with a groove structure provided by the present application.

[0058] Reference signs:

[0059] 100, flexible substrate; 110, pressure sensing area; 120, extension area; 130, metal flow channel; 140, first flexible base; 141, groove structure; 150, second flexible base;

[0060] 200, liquid metal;

[0061] 310, first flexible tensile-resistant film; 320, second flexible tensile-resistant film;

[0062] 400, liquid filling hole;

[0063] 610, silicon wafer; 620, photoresist; 630, mask; 631, light-transmitting area; 632, light-blocking area; 640, ultraviolet light. DETAILED DESCRIPTION

[0064] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0065] Please refer to Figures 1 to 3 The present application discloses a flexible pressure sensor, which comprises a flexible substrate 100, a liquid metal 200 and a first flexible tensile-resistant film 310.

[0066] The flexible substrate 100 is provided with a closed metal flow channel 130, and the liquid metal 200 is encapsulated in the metal flow channel 130. When the flexible substrate 100 is deformed under pressure, the liquid metal 200 will also be deformed under pressure, so that the liquid metal 200 generates resistance change, thereby responding to the pressure on the area in the form of pressure deformation leading to resistance change. The flexible substrate 100 has a pressure sensing area 110, and the area where the metal flow channel 130 is located forms the pressure sensing area 110. The pressure sensing area 110 has a first pressure sensing surface, and the first flexible tensile-resistant film 310 is stacked and fixed on the first pressure sensing surface.

[0067] The first flexible tensile-resistant film 310 is not stretchable, thereby limiting the tensile deformation of the pressure sensing area 110 fixedly connected with the first flexible tensile-resistant film 310, so that the pressure sensing area 110 has the effect of resisting tensile deformation. Therefore, the liquid metal 200 located in the pressure sensing area 110 is not easy to generate resistance change when subjected to tensile action, and the first flexible tensile-resistant film 310 does not affect the pressure deformation of the pressure sensing area 110, nor does it affect the pressure measurement of the flexible pressure sensor. Thus, the flexible pressure sensor in the present application can resist the influence of tensile action on pressure measurement, thereby improving the accuracy of pressure measurement.

[0068] Optionally, the material of the flexible substrate 100 can be PDMS (polydimethylsiloxane), the material of the flexible substrate 100 can also be Ecoflex (aliphatic aromatic random copolyester), of course, the flexible substrate 100 can also be made of other flexible and elastic materials, which are not limited in the present application. The first flexible anti-stretching film 310 can be a PI (Polyimide) film, which is not stretchable, the first flexible anti-stretching film 310 can also be a PET (polyethylene glycol terephthalate) film, of course, the first flexible anti-stretching film 310 can also be other non-stretchable films.

[0069] In the embodiment of the present application, the first flexible anti-stretching film 310 limits the tensile deformation of the pressure sensing area 110 connected thereto, that is, the pressure sensing area 110 is not prone to tensile deformation, so that the flexible pressure sensor in the present application has good resistance to tensile interference, alleviates the problem that the tensile deformation of the flexible pressure sensor causes the resistance of the liquid metal 200 to change, thereby interfering with the pressure measurement, improves the pressure measurement accuracy of the flexible pressure sensor, and the flexible pressure sensor with such structure is simple and reliable in structure and high in working stability. As can be seen, the flexible pressure sensor of the present application can solve the problem of related art that the tensile deformation of the flexible pressure sensor interferes with the pressure measurement, resulting in low pressure measurement accuracy of the flexible pressure sensor.

[0070] In a further technical solution, the flexible pressure sensor can further include a second flexible anti-stretching film 320, the second flexible anti-stretching film 320 can be fixed on the second pressure sensing surface of the pressure sensing area 110 in a superimposed manner, and the second pressure sensing surface and the first pressure sensing surface are arranged opposite to each other. In this case, the tensile deformation of the two opposite surfaces of the pressure sensing area 110 is limited, which can further improve the limitation of the tensile deformation of the pressure sensing area 110, thereby further alleviating the problem that the tensile deformation of the flexible pressure sensor causes the resistance of the liquid metal 200 to change, thereby interfering with the pressure measurement, and further improving the pressure measurement accuracy of the flexible pressure sensor.

[0071] In the application of the flexible pressure sensor to wearable devices and other fields, the flexible pressure sensor can need to be bent and deformed, and for this purpose, in the embodiment of the present application, the flexible substrate 100 can further comprise an extensible region 120, which can be connected to the outer periphery of the pressure sensing region 110, and the extensible region 120 of the flexible substrate 100 is not connected to the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320, so that the extensible region 120 of the flexible substrate 100 can be tensilely deformed. The pressure sensing region 110 and the extensible region 120 can be of an integrated structure. When the flexible pressure sensor is not subjected to tensile action, the pressure sensing region 110 and the extensible region 120 can be coplanar.

[0072] In this case, the extensible region 120 of the flexible substrate 100 can be tensilely deformed, so that the flexible pressure sensor can be bent and deformed, thereby making the flexible pressure sensor applicable to occasions or devices that need to be bent and deformed.

[0073] In the embodiment of the present application, the extensible region 120 enables the flexible pressure sensor to be tensilely deformed, so that the flexible pressure sensor can be applied to occasions that need to be bent and deformed, and the pressure sensing region 110 of the flexible pressure sensor is resistant to tensile deformation, thereby relieving the influence of tensile deformation on the resistance of the liquid metal 200, so that the flexible pressure sensor still has high pressure measurement accuracy under greater tensile deformation.

[0074] In the above scheme, the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320 are both connected to the pressure sensing region 110, and there are various ways to achieve the fixed connection of the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320 to the pressure sensing region 110.

[0075] In an alternative embodiment, the first flexible tensile-resistant film 310 can be connected to the first pressure sensing surface by plasma bonding, and the first flexible tensile-resistant film 310 can be bonded and connected to the first pressure sensing surface of the pressure sensing region 110 by the method of plasma bonding. The second flexible tensile-resistant film 320 can be connected to the second pressure sensing surface by plasma bonding, and the second flexible tensile-resistant film 320 can be bonded and connected to the second pressure sensing surface of the pressure sensing region 110 by the method of plasma bonding.

[0076] In this case, the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320 are bonded to the pressure sensing region 110 by the method of plasma bonding, which can achieve the close connection of the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320 to the pressure sensing region 110.

[0077] In another optional embodiment, the first flexible anti-stretching film 310 may be bonded to the first pressure sensing surface by glue, and the second flexible anti-stretching film 320 may be bonded to the second pressure sensing surface by glue.

[0078] In another optional embodiment, when the pressure sensing area 110 is in a semi-solid state, the first flexible anti-stretching film 310 can be attached to the first pressure sensing surface to achieve a fixed connection between the first pressure sensing surface and the first flexible anti-stretching film 310. When the pressure sensing area 110 is in a semi-solid state, the second flexible anti-stretching film 320 can be attached to the second pressure sensing surface to achieve a fixed connection between the second pressure sensing surface and the second flexible anti-stretching film 320.

[0079] To output the resistance change of the liquid metal 200, the flexible substrate 100 can be provided with a liquid filling hole 400, which can be connected to the metal flow channel 130. The flexible pressure sensor can also include a wire, one end of which can extend into the metal flow channel 130 through the liquid filling hole 400 and contact the liquid metal 200. The other end of the wire can be located outside the flexible substrate 100, and the wire can be connected to the first flexible stretch-resistant film 310 using an adhesive or other connection method. In this case, the connection between the wire and the liquid metal 200 can be stable, preventing the wire from being displaced relative to the flexible substrate 100 and causing it to separate from the liquid metal 200.

[0080] Optionally, the conductive wire may be a copper wire, and the conductive wire may be connected to the first flexible stretch-resistant film 310 via an adhesive, and the adhesive may be 705 silicone.

[0081] To seal the filling hole 400, in an optional embodiment, the outer surface of the wire can be in sealing contact with the wall of the filling hole 400, thereby sealing the filling hole 400 and preventing leakage of the liquid metal 200. In an optional embodiment, a sealing ring can be provided between the wire and the wall of the filling hole 400 to prevent leakage of the liquid metal 200.

[0082] In another optional embodiment, the adhesive used to connect the wire and the first flexible stretch-resistant film 310 can penetrate into the portion of the first flexible stretch-resistant film 310 corresponding to the liquid filling hole 400, thereby sealing the liquid filling hole 400 and preventing leakage of the liquid metal 200. However, the adhesive does not penetrate into the portion of the flexible substrate 100 corresponding to the liquid filling hole 400, thereby avoiding affecting the performance of the liquid metal 200.

[0083] In the process of bonding the conductive wire and the first flexible tensile-resistant film 310, the adhesive can be coated on the first flexible tensile-resistant film 310 and around the conductive wire, so that the conductive wire is bonded and fixed with the first flexible tensile-resistant film 310. Since the gap between the conductive wire and the liquid injection hole 400 is small, the viscosity of the adhesive is large, and the amount of the adhesive is controlled, so that the adhesive can penetrate into the part of the first flexible tensile-resistant film 310 corresponding to the liquid injection hole 400, but will not penetrate into the part of the flexible substrate 100 corresponding to the liquid injection hole 400.

[0084] Please refer to Figures 4 to 18 The application further discloses a preparation method of the flexible pressure sensor, and the preparation method comprises the following steps:

[0085] Step S101: preparing a first flexible base 140 with a groove structure 141.

[0086] The shape of the groove structure 141 is consistent with the shape of the metal flow channel 130 required by the flexible pressure sensor, and the shape of the groove structure 141 is not limited herein.

[0087] Step S102: stacking and fixing the first flexible tensile-resistant film 310 on the first surface of the first flexible base 140, and the first flexible tensile-resistant film 310 is opposite to the area where the groove structure 141 is located.

[0088] That is, the first flexible tensile-resistant film 310 is stacked and fixed on the area where the groove structure 141 of the first flexible base 140 is located. It should be noted that the first surface is the surface of the first flexible base 140 away from the slot of the groove structure 141.

[0089] Step S103: stacking and fixing the second flexible base 150 on the second surface of the first flexible base 140, so that the first flexible base 140 and the second flexible base 150 are connected to form the flexible substrate 100, the second surface is opposite to the first surface, and the second flexible base 150 blocks the slot of the groove structure 141 to form the metal flow channel 130.

[0090] It should be noted that the second surface is the surface where the slot of the groove structure 141 is located.

[0091] Step S104: injecting the liquid metal 200 into the metal flow channel 130.

[0092] The resistance of the liquid metal 200 changes when pressure is applied to the area where the metal flow channel 130 is located, so that the measurement of the pressure is realized.

[0093] Step S105: inserting the first end of the conductive wire into the liquid metal 200, and the second end of the conductive wire is located outside the flexible substrate 100.

[0094] Optionally, the outer surface of the wire can be sealed and matched with the inner wall of the liquid filling hole 400, so as to block the liquid filling hole 400 and prevent the liquid metal 200 from leaking. Of course, a sealing ring can also be installed between the wire and the hole wall of the liquid filling hole 400, so as to prevent the liquid metal 200 from leaking.

[0095] Step S106: The wire is fixedly connected to the first flexible tensile-resistant film 310.

[0096] Optionally, the wire can be a copper wire, and the wire can be connected to the first flexible tensile-resistant film 310 through an adhesive. The adhesive can be 705 silicone glue, and the adhesive can penetrate into the liquid filling hole 400 of the first flexible tensile-resistant film 310, thereby also playing a role in blocking the liquid filling hole 400 and preventing the liquid metal 200 from leaking.

[0097] When the wire and the first flexible tensile-resistant film 310 are bonded, the adhesive can be coated on the first flexible tensile-resistant film 310 and around the wire, so that the wire is bonded and fixed to the first flexible tensile-resistant film 310. In the case that there is a gap between the wire and the liquid filling hole 400, the adhesive can penetrate into the liquid filling hole 400 of the first flexible tensile-resistant film 310, thereby achieving the blocking of the liquid filling hole 400 and preventing the liquid metal 200 from leaking. Since the adhesive has high viscosity, the amount of the adhesive can be controlled so that the adhesive cannot penetrate into the liquid filling hole 400 of the flexible substrate 100.

[0098] In the embodiment of the present application, the first flexible tensile-resistant film 310 is fixedly stacked on the surface of the flexible substrate 100 prepared by the above preparation method. The first flexible tensile-resistant film 310 has non-stretchability, so that the tensile deformation of the part of the flexible substrate 100 fixedly connected with the first flexible tensile-resistant film 310 is limited. Since the first flexible tensile-resistant film 310 is opposite to the metal runner 130, the area where the metal runner 130 is located is not easy to produce tensile deformation, and the liquid metal 200 in the metal runner 130 is not easy to change the resistance due to tensile deformation. The problem that the change of the resistance of the liquid metal 200 due to the tensile deformation of the flexible pressure sensor interferes with the pressure measurement is alleviated, and the pressure measurement accuracy of the flexible pressure sensor is improved.

[0099] In the above scheme, the liquid metal 200 needs to be injected into the metal runner 130. Since the second flexible base 150 blocks the slot of the slot structure 141, the metal runner 130 is a closed metal runner 130. In order to be able to inject the liquid metal 200 into the metal runner 130, in an optional embodiment, a liquid filling hole 400 can be formed on the flexible substrate 100, and the liquid metal 200 is injected into the metal runner 130 through the liquid filling hole 400. However, the liquid filling hole 400 formed on the flexible substrate 100 is easy to penetrate the flexible substrate 100, which brings difficulty to block the liquid filling hole 400 later.

[0100] In the embodiment of the present application, after the step of stacking and fixing the first flexible tensile-resistant film 310 on the first surface of the first flexible base 140, before the step of stacking and fixing the second flexible base 150 on the second surface of the first flexible base 140, the preparation method can further comprise:

[0101] Step A1: drilling liquid-filling holes 400 on the first flexible tensile-resistant film 310 and the first flexible base 140, the liquid-filling holes 400 penetrating the groove structure 141.

[0102] In this case, before the first flexible base 140 and the second flexible base 150 are connected to form the flexible substrate 100, the first flexible tensile-resistant film 310 and the first flexible base 140 are drilled, which can avoid the problem that the liquid-filling holes 400 penetrate the entire flexible substrate 100 during the drilling process, and facilitate the subsequent plugging of the liquid-filling holes 400.

[0103] In order to better alleviate the problem that the tensile deformation of the flexible substrate 100 causes the resistance change of the liquid metal 200, thereby interfering with the pressure measurement results, after the step of stacking and fixing the second flexible base 150 on the second surface of the first flexible base 140, before the step of pouring the liquid metal 200 into the metal flow channel 130, the preparation method can further comprise:

[0104] Step B1: stacking and fixing a second flexible tensile-resistant film 320 on the surface of the second flexible base 150 away from the first flexible base 140, the second flexible tensile-resistant film 320 being opposite to the area where the metal flow channel 130 is located.

[0105] In this case, the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320 are respectively stacked and fixed on the opposite surfaces of the flexible substrate 100, and the first flexible tensile-resistant film 310 and the second tensile-resistant film are both opposite to the metal flow channel 130, so that the tensile deformation of the two surfaces of the area of the flexible substrate 100 opposite to the metal flow channel 130 is limited, which can further improve the limitation of the tensile deformation of the area of the flexible substrate 100 opposite to the metal flow channel 130, thereby further reducing the interference of the tensile deformation of the flexible pressure sensor with the pressure measurement.

[0106] In the embodiment of the present application, the method of stacking and fixing the first flexible tensile-resistant film 310 on the first surface of the first flexible base 140 in the above-mentioned step has multiple forms.

[0107] In an alternative embodiment, the surface of the first flexible base 140 to which the first flexible tensile-resistant film 310 is to be attached and the first surface of the first flexible base 140 can be subjected to plasma treatment, i.e. an activated group is formed on the surface of the first flexible base 140 to which the first flexible tensile-resistant film 310 is to be attached and the first surface of the first flexible base 140, and then the first flexible tensile-resistant film 310 subjected to plasma treatment is attached to the first surface, so that the first flexible tensile-resistant film 310 and the first flexible base 140 are bonded and connected.

[0108] In another alternative embodiment, the first flexible tensile-resistant film 310 can be attached and fixed to the first surface of the first flexible base 140 using an adhesive, so as to realize the superimposed fixation of the two.

[0109] In another alternative embodiment, the first flexible tensile-resistant film 310 can be attached to the first surface of the first flexible base 140 when the first flexible base 140 is in a semi-cured state, so as to realize the superimposed fixation of the two.

[0110] In the embodiments of the present application, there are multiple methods for superimposed fixation of the second flexible base 150 to the second surface of the first flexible base 140 in the above-mentioned step.

[0111] In an alternative embodiment, the surface of the first flexible base 140 to which the first flexible tensile-resistant film 310 is to be attached and the first surface of the first flexible base 140 can be subjected to plasma treatment, i.e. an activated group is formed on the surface of the first flexible base 140 to which the first flexible tensile-resistant film 310 is to be attached and the first surface of the first flexible base 140, and then the first flexible tensile-resistant film 310 subjected to plasma treatment is attached to the first surface, so that the first flexible tensile-resistant film 310 and the first flexible base 140 are bonded and connected.

[0112] In another alternative embodiment, the first flexible tensile-resistant film 310 can be attached and fixed to the first surface of the first flexible base 140 using an adhesive, so as to realize the superimposed fixation of the two.

[0113] In another alternative embodiment, the first flexible tensile-resistant film 310 can be attached to the first surface of the first flexible base 140 when the first flexible base 140 is in a semi-cured state, so as to realize the superimposed fixation of the two.

[0114] In the embodiments of the present application, there are multiple methods for superimposed fixation of the second flexible base 150 to the second surface of the first flexible base 140 in the above-mentioned step.

[0115] In an alternative embodiment, the surface of the second flexible base 150 facing away from the first flexible base 140 and the second flexible anti-stretching film 320 can be subjected to plasma treatment, that is, a layer of activated groups is formed on the surface of the second flexible base 150 facing away from the first flexible base 140 and the surface of the second flexible anti-stretching film 320, and then the surface of the second flexible anti-stretching film 320 subjected to plasma treatment is attached to the surface of the second flexible base 150 facing away from the first flexible base 140, so as to bond the second flexible anti-stretching film 320 to the second flexible base 150.

[0116] In another alternative embodiment, an adhesive can be used to attach and fix the second flexible anti-stretching film 320 to the surface of the second flexible base 150 facing away from the first flexible base 140, so as to realize the stacking and fixing of the two.

[0117] In another alternative embodiment, the second flexible anti-stretching film 320 can be attached to the surface of the second flexible base 150 facing away from the first flexible base 140 when the second flexible base 150 is in a semi-cured state, so as to realize the stacking and fixing of the two.

[0118] The method for preparing the first flexible base 140 with the groove structure 141 in the above steps can include:

[0119] Step S201: coating a photoresist 620 on a silicon wafer 610.

[0120] The photoresist 620 can be an SU-8 photoresist. After coating the photoresist 620 on the silicon wafer 610, the photoresist 620 can be subjected to a first baking to improve the connection strength of the photoresist 620 and the silicon wafer 610.

[0121] Step S202: covering a mask 630 on the photoresist 620.

[0122] The mask 630 includes a light-transmitting region 631 and a light-blocking region 632. The shape of the light-transmitting region 631 is consistent with the shape of the metal runner 130 required.

[0123] Step S203: exposing the photoresist 620 covered with the mask 630 to ultraviolet light 640.

[0124] The ultraviolet light 640 can penetrate the light-transmitting region 631 to irradiate the photoresist 620 and make the irradiated photoresist 620 cured, while the ultraviolet light 640 cannot penetrate the light-blocking region 632 of the mask 630, so that the photoresist 620 opposite to the light-blocking region 632 cannot be cured.

[0125] Step S204: removing the mask 630.

[0126] After the mask 630 is removed from the photoresist 620, the photoresist 620 can be baked again to further promote the photocuring reaction of the photoresist 620.

[0127] Step S205: The photoresist 620 is washed with a developer to form a photoetching structure on the silicon wafer 610.

[0128] The developer can dissolve the uncured photoresist 620, while the cured photoresist 620 cannot be dissolved by the developer and remains on the silicon wafer 610, forming a photoetching structure.

[0129] After the above steps S201, S202, S203, S204 and S205, the photoetching structure with a specific shape is made on the silicon wafer 610 through the soft lithography process.

[0130] Step S206: Pouring a flexible substrate prepolymer on the silicon wafer 610 with the photoetching structure and baking the flexible substrate prepolymer to form a first flexible base 140.

[0131] The flexible substrate prepolymer can be mixed by the base agent and the curing agent of PDMS at a ratio of 10:1. After baking the flexible substrate prepolymer, the flexible substrate prepolymer is cured to form the first flexible base 140, and the area of the silicon wafer 610 with the photoetching structure forms a groove structure 141.

[0132] Step S207: Peeling the first flexible base 140 from the surface of the silicon wafer 610.

[0133] The first flexible base 140 is peeled from the silicon wafer 610 to obtain the first flexible substrate 100 with the groove structure 141, and the shape of the groove structure 141 is the same as that of the photoetching structure. Steps S206 and S207 can also be called the process of flexible substrate inverse molding (PDMS inverse molding). In this way, the first flexible base 140 with the groove structure 141 is obtained by the method of soft lithography and flexible substrate inverse molding (PDMS inverse molding).

[0134] The flexible base can include a pressure sensing area 110 and an extensible area 120, the extensible area 120 can be connected to the outer periphery of the pressure sensing area 110, the area where the metal runner 130 is located forms the pressure sensing area 110, and the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320 are respectively laminated and fixed on the opposite surfaces of the pressure sensing area 110. In this case, the extensible area 120 is not provided with the first flexible tensile-resistant film 310 and the second flexible tensile-resistant film 320, so that the extensible area 120 can be stretched and deformed, so that the flexible pressure sensor can be bent and deformed, and the flexible pressure sensor can be applied to occasions requiring bending and deformation.

[0135] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features therein can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A flexible pressure sensor, characterized in that: The invention comprises a flexible substrate (100), liquid metal (200) and a first flexible anti-stretching film (310), wherein a closed metal flow channel (130) is provided in the flexible substrate (100), the liquid metal (200) is provided in the metal flow channel (130), the flexible substrate (100) has a pressure sensing area (110), the area where the metal flow channel (130) is located forms the pressure sensing area (110), the pressure sensing area (110) has a first pressure sensing surface, and the first flexible anti-stretching film (310) is superimposed and fixed on the first pressure sensing surface.

2. The flexible pressure sensor according to claim 1, characterized in that The flexible pressure sensor further comprises a second flexible anti-stretching film (320), the second flexible anti-stretching film (320) being superimposed and fixed on a second pressure sensing surface of the pressure sensing area (110), the second pressure sensing surface being arranged opposite to the first pressure sensing surface.

3. The flexible pressure sensor according to claim 2, characterized in that: The first flexible anti-stretching film (310) is bonded to the first pressure sensing surface, and the second flexible anti-stretching film (320) is bonded to the second pressure sensing surface; or, The first flexible anti-stretching film (310) is bonded to the first pressure-sensing surface, and the second flexible anti-stretching film (320) is bonded to the second pressure-sensing surface.

4. The flexible pressure sensor according to claim 1, characterized in that The flexible substrate (100) further comprises an extension area (120), wherein the extension area (120) is connected to the outer periphery of the pressure sensing area (110).

5. The flexible pressure sensor according to claim 1, characterized in that The flexible substrate (100) is provided with a liquid filling hole (400), and the liquid filling hole (400) is connected to the metal flow channel (130). The flexible pressure sensor further comprises a wire, one end of which extends into the metal flow channel (130) through the liquid filling hole (400) and contacts the liquid metal (200), and the other end of the wire is located outside the flexible substrate (100), and the wire is fixedly connected to the first flexible anti-stretching film (310).

6. A method for preparing a flexible pressure sensor, characterized in that: The preparation method comprises: preparing a first flexible base (140) having a groove structure (141); A first flexible stretch-resistant film (310) is superimposed and fixed on the first surface of the first flexible base (140), with the first flexible stretch-resistant film (310) facing the area where the groove structure (141) is located; A second flexible base (150) is stacked and fixed on the second surface of the first flexible base (140), so that the first flexible base (140) and the second flexible base (150) are connected to form a flexible substrate (100), the second surface is opposite to the first surface, and the second flexible base (150) blocks the notch of the groove structure (141) to form a metal flow channel (130); pouring liquid metal (200) into the metal flow channel (130); Inserting a first end of a wire into the liquid metal (200), with a second end of the wire located outside the flexible substrate (100); The conductive wire is fixedly connected to the first flexible stretch-resistant film (310).

7. The preparation method according to claim 6, characterized in that After the first flexible stretch-resistant film (310) is stacked and fixed on the first surface of the first flexible base (140), and before the second flexible base (150) is stacked and fixed on the second surface of the first flexible base (140), the preparation method further comprises: A liquid filling hole (400) is provided on the first flexible anti-stretching film (310) and the first flexible base (140), and the liquid filling hole (400) passes through the groove structure (141).

8. The preparation method according to claim 6, characterized in that After the second flexible base (150) is stacked and fixed on the second surface of the first flexible base (140), and before the liquid metal (200) is poured into the metal flow channel (130), the preparation method further comprises: A second flexible anti-stretching film (320) is stacked and fixed on a surface of the second flexible base (150) facing away from the first flexible base (140), and the second flexible anti-stretching film (320) is opposite to the area where the metal runner (130) is located.

9. The preparation method according to claim 8, characterized in that The method of stacking and fixing the first flexible stretch-resistant film (310) on the first surface of the first flexible base (140) comprises: Plasma-treating the first flexible anti-stretching film (310) and the first surface of the first flexible base (140), and laminating the first flexible anti-stretching film (310) on the first surface, so that the first flexible anti-stretching film (310) and the first flexible base (140) are bonded and connected; The method of stacking and fixing the second flexible base (150) on the second surface of the first flexible base (140) comprises: Plasma-treating the second surface of the second flexible base (150) and the first flexible base (140), and laminating the second flexible base (150) on the second surface, so that the second flexible base (150) and the first flexible base (140) are bonded and connected; The method of stacking and fixing a second flexible stretch-resistant film (320) on a surface of the second flexible base (150) facing away from the first flexible base (140) comprises: The surface of the second flexible base (150) facing away from the first flexible base (140) and the second flexible anti-stretching film (320) are plasma treated, and the second flexible anti-stretching film (320) is attached to the surface of the second flexible base (150) facing away from the first flexible base (140) so that the second flexible anti-stretching film (320) is bonded to the second flexible base (150).

10. The preparation method according to claim 6, characterized in that The method of preparing the first flexible base (140) having the groove structure (141) comprises: Coating a photoresist (620) on a silicon wafer (610); Covering the photoresist (620) with a mask (630); exposing the photoresist (620) covered with the mask (630) to ultraviolet light (640); removing the mask (630); Using a developer to rinse the photoresist (620) to form a photolithographic structure on the silicon wafer (610); pouring a flexible base prepolymer onto the silicon wafer (610) having the photolithographic structure, and baking the flexible base prepolymer to form a first flexible base (140); The first flexible base (140) is peeled off from the silicon wafer (610).

11. The preparation method according to claim 6, characterized in that The flexible substrate (100) comprises a pressure sensing area (110) and an extension area (120), wherein the extension area (120) is connected to the outer periphery of the pressure sensing area (110), and the area where the metal flow channel (130) is located forms the pressure sensing area (110).

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