A flexible strain sensor and method of manufacture

Abstract

The application discloses a flexible strain sensor and a preparation method, and is applied to the technical field of flexible electronics, and comprises a first flexible shell, the first flexible shell has a first cavity extending along a first direction in the first flexible shell; the first flexible shell has a first end portion and a second end portion opposite to each other along the first direction; a conductive liquid is filled in the first cavity; a first electrode and a second electrode, the first electrode extends from the outside of the first end portion into the first cavity, and the first electrode is fixedly connected with the first end portion; the second electrode extends from the outside of the second end portion into the first cavity, and the second electrode is fixedly connected with the second end portion; and the initial distance between the first electrode and the second electrode is at most one tenth of the length of the first cavity along the first direction. The flexible strain sensor reduces the size of the interference signal when bending and twisting occur, and further reduces the proportion of the interference signal in the output signal, so that the resistance effect of the interference signal generated by bending and twisting is better.

Description

Technical Field

[0001] This invention relates to the field of flexible electronics technology, and in particular to a flexible strain sensor and its fabrication method. Background Technology

[0002] Flexible strain sensors have broad application prospects in fields such as human body monitoring, human-computer interaction, and soft robotics. When used in these applications, flexible strain sensors need to undergo stretching, bending, torsion, and compression deformation along with human skin, fabric, or soft robots. Stretching deformation generates a normal signal from the flexible strain sensor, while bending, torsion, and compression deformation generate interference signals. The superposition of these signals forms the output signal, which is then output as a single signal. Interference signals reduce the sensor's resolution and measurement accuracy, thus hindering its practical application in medical, everyday, and industrial scenarios. Furthermore, interference signals generated by bending and torsion significantly impact the output signal of the flexible strain sensor, resulting in poor resistance to such interference.

[0003] Therefore, it is necessary to provide a flexible strain sensor to solve the technical problem that current flexible strain sensors are not effective in resisting interference signals generated by bending and torsion. Summary of the Invention

[0004] The purpose of this invention is to provide a flexible strain sensor and its fabrication method to solve the technical problem that current flexible strain sensors do not resist interference signals generated by bending and torsion.

[0005] To address the aforementioned technical problems, this invention provides a flexible strain sensor, comprising: A first flexible shell, the first flexible shell having a first cavity extending along a first direction; the first flexible shell having opposing first ends and second ends along the first direction; A conductive liquid, wherein the conductive liquid fills the first cavity; A first electrode and a second electrode, wherein the first electrode extends from the outside of the first end into the first cavity and is fixedly connected to the first end; the second electrode extends from the outside of the second end into the first cavity and is fixedly connected to the second end; the initial distance between the first electrode and the second electrode is at most one-tenth of the length of the first cavity along the first direction.

[0006] Optionally, it also includes a second flexible shell, in which the first flexible shell is nested, and there is a gap between the first flexible shell and the second flexible shell, the gap being filled with a liquid medium.

[0007] Optionally, the gap extends circumferentially along the first flexible shell and surrounds the second flexible shell.

[0008] Optionally, the structure of the first flexible shell is axially symmetric about the first direction; The structures of the first electrode and the second electrode are symmetrical about the first direction. Both the flexible shell material and the conductive liquid are isotropic.

[0009] Optionally, the first electrode and the second electrode are connected to an AC voltage source; The AC voltage source has a first voltage terminal and a second voltage terminal; the first electrode is connected to the first voltage terminal; and the second electrode is connected to the second voltage terminal.

[0010] Optionally, the conductive liquid is an ionic liquid or a mixture of ionic liquids.

[0011] Optionally, flexible encapsulation may also be included; The first end has a first port, the first electrode extends from the outside of the first port into the first cavity, and the flexible package seals the first port and is fixedly connected to the first electrode. The second end has a second port, and the second electrode extends from the outside of the second port into the first cavity. The flexible package seals the second port and is fixedly connected to the second electrode.

[0012] This invention also provides a method for fabricating a flexible strain sensor, comprising: A first flexible housing is provided having a first cavity extending along a first direction, the first flexible housing having opposing first ends and second ends along the first direction; Injecting conductive liquid into the interior of the first cavity of the first flexible housing; The first electrode is inserted into the first cavity from the first end, and the second electrode is inserted into the first cavity from the second end. The initial distance between the first electrode and the second electrode is at most one-tenth of the length of the first cavity along the first direction.

[0013] Optionally, injecting the conductive liquid into the interior of the first cavity of the first flexible housing further includes: Provide a second flexible housing; The first flexible shell is inserted into the second flexible shell along the first direction, and there is a gap between the first flexible shell and the second flexible shell; The conductive liquid is injected into the interior of the first cavity of the first flexible housing; The liquid medium is injected into the gap.

[0014] Optionally, the first end and the second end of the first flexible housing may be sealed with a flexible encapsulation body; Two flexible packaging molds with internal cavities are respectively fitted onto the first end and the second end of the first flexible shell, and the internal cavities of the flexible packaging molds are adapted to the first end and the second end of the flexible shell; The prepolymer, which is a mixture of polydimethylsiloxane main agent and curing agent at a mass ratio of 10:1, is poured into the flexible packaging mold and heated in an oven to complete the sealing of the first end and the second end of the first flexible shell by the flexible package.

[0015] The flexible strain sensor provided by the present invention includes: a first flexible housing having a first cavity extending along a first direction; the first flexible housing having a first end and a second end opposite to each other along the first direction; a conductive liquid filling the first cavity; a first electrode and a second electrode, the first electrode extending from the outside of the first end into the first cavity and being fixedly connected to the first end; the second electrode extending from the outside of the second end into the first cavity and being fixedly connected to the second end; the initial distance between the first electrode and the second electrode is at most one-tenth of the length of the first cavity along the first direction.

[0016] As can be seen, the flexible strain sensor includes a first flexible shell, within which a first cavity extends along a first direction. The first cavity is filled with a conductive liquid. A first electrode, a second electrode, the first cavity, and the conductive liquid constitute a sliding sensing structure. The initial distance between the first electrode and the second electrode is at most one-tenth of the length of the first cavity along the first direction, such that the conductive liquid within the remaining nine-tenths of the length of the first cavity along the first direction is short-circuited by the first and second electrodes. Furthermore, the output signal of the flexible strain sensor is generated between the first and second electrodes, i.e., the output signal is generated within one-tenth of the length of the first cavity along the first direction. This makes it difficult to generate interference signals when the remaining nine-tenths of the length of the first cavity along the first direction bends or twists, reducing the magnitude of interference signals when the flexible strain sensor bends or twists, and thus reducing the proportion of interference signals in the output signal. Meanwhile, this flexible strain sensor uses a conductive liquid as the sensing material. Based on the physical property that the static shear modulus of the conductive liquid is zero, when the portion between the first and second electrodes in the first cavity undergoes bending and torsion, the internal conductive liquid only undergoes flow redistribution adapted to the geometric boundaries, without producing localized stress concentration phenomena similar to those experienced by solid materials during bending and torsion. This reduces the magnitude of interference signals generated by stress concentration, thereby reducing the proportion of interference signals in the output signal. Therefore, this flexible strain sensor exhibits good resistance to interference signals generated by bending and torsion.

[0017] The present invention also provides a method for preparing a flexible strain sensor, which has the same beneficial effects as the flexible strain sensor described above, and will not be described in detail here. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the appearance of a flexible strain sensor provided in an embodiment of the present invention; Figure 2 A front view of a flexible strain sensor provided in an embodiment of the present invention; Figure 3 A cross-sectional view along the AA section line of a flexible strain sensor provided in an embodiment of the present invention; Figure 4 A cross-sectional view along the BB section line of a flexible strain sensor provided in an embodiment of the present invention; Figure 5A cross-sectional view along the AA section line of a flexible strain sensor after stretching, provided in an embodiment of the present invention. Figure 6 A cross-sectional view along the AA section line of another flexible strain sensor provided in an embodiment of the present invention; Figure 7 A cross-sectional view along the BB section line of another flexible strain sensor provided in an embodiment of the present invention; Figure 8 A cross-sectional view along the AA section line of another flexible strain sensor after stretching, provided in an embodiment of the present invention. Figure 9 A schematic flowchart illustrating a method for fabricating a flexible strain sensor according to an embodiment of the present invention; Figure 10 The strain signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention, after being stretched 30 times with a strain step of 0.1% and then retracted 30 times; Figure 11 The strain signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention, after being stretched 30 times with a strain step of 1% and then retracted 30 times; Figure 12 The strain signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention after being stretched 7 times with a step size of 10%; Figure 13 Linearity test diagram of strain signal response of the flexible strain sensor provided in Embodiment 1 of the present invention in the strain range of 0-30%; Figure 14 The bending signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention after being manually bent 180° and then manually bent 360°, and finally recovered. Figure 15 The torsional signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention after being manually twisted 180° and then manually twisted 360°, and finally recovered. Figure 16 The signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention when compressed by 50% in a third direction; Figure 17 The strain signal response diagram of the flexible strain sensor provided in Embodiment 2 of the present invention, after being stretched 30 times with a strain step of 1% and then retracted 30 times; Figure 18 The strain signal response diagram of the flexible strain sensor provided in Embodiment 3 of the present invention, after being stretched 30 times with a strain step size of 1% and then retracted 30 times; In the figure: 1. First flexible shell, 11. First cavity, 12. First port, 13. Second port, 2. Conductive liquid, 3. First electrode, 4. Second electrode, 5. Second flexible shell, 6. Gap, 7. Liquid medium, 8. Flexible package. Detailed Implementation

[0020] The core of this invention is to provide a flexible strain sensor. When used in the aforementioned applications, flexible strain sensors need to undergo stretching, bending, torsion, and compression deformations along with human skin, fabric, or soft robots. Stretching deformation generates a normal signal from the flexible strain sensor, while bending, torsion, and compression deformation generate interference signals. The normal and interference signals are superimposed to form an output signal, which is then output as a single signal. The interference signal reduces the sensor's resolution and measurement accuracy, thus hindering its practical application in medical, everyday, and industrial scenarios. Furthermore, the interference signals generated by bending and torsion significantly impact the output signal of the flexible strain sensor, resulting in poor resistance to these interference signals.

[0021] The flexible strain sensor provided by this invention includes a first flexible shell with a first cavity extending along a first direction. The first cavity is filled with a conductive liquid. A first electrode, a second electrode, the first cavity, and the conductive liquid constitute a sliding sensing structure. The initial distance between the first and second electrodes is at most one-tenth of the length of the first cavity along the first direction, such that the conductive liquid within the remaining nine-tenths of the length of the first cavity along the first direction is short-circuited by the first and second electrodes. The output signal of this flexible strain sensor is generated between the first and second electrodes. This makes it difficult to generate interference signals when the remaining nine-tenths of the length of the first cavity along the first direction undergoes bending and torsion, reducing the magnitude of interference signals during bending and torsion, and thus reducing the proportion of interference signals in the output signal. Simultaneously, this flexible strain sensor uses a conductive liquid as the sensing material. Based on the physical property that the static shear modulus of conductive liquid is zero, when the portion between the first and second electrodes in the first cavity undergoes bending and torsion, the internal conductive liquid only undergoes flow redistribution adapted to the geometric boundaries, without generating local stress concentration phenomena similar to those of solid materials during bending and torsion. This reduces the magnitude of interference signals generated by stress concentration, and thus reduces the proportion of interference signals in the output signal. Therefore, this flexible strain sensor has good resistance to interference signals generated by bending and torsion.

[0022] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please refer to Figures 1 to 5 , Figure 1 This is a schematic diagram of the appearance of a flexible strain sensor provided in an embodiment of the present invention; Figure 2 A front view of a flexible strain sensor provided in an embodiment of the present invention; Figure 3 A cross-sectional view along the AA section line of a flexible strain sensor provided in an embodiment of the present invention; Figure 4 A cross-sectional view along the BB section line of a flexible strain sensor provided in an embodiment of the present invention; Figure 5 This is a cross-sectional view along the AA section line of a flexible strain sensor after stretching, provided in an embodiment of the present invention.

[0024] See Figures 1 to 5 (The first and second ends are not shown in the figure, and the first cavity and conductive liquid are not distinguished. This embodiment takes the case where the conductive liquid completely fills the first cavity.) In this embodiment, the flexible strain sensor includes: a first flexible housing 1, the first flexible housing 1 having a first cavity 11 extending along a first direction; the first flexible housing 1 having a first end and a second end opposite to each other along the first direction; conductive liquid 2, the conductive liquid 2 filling the first cavity 11; a first electrode 3 and a second electrode 4, the first electrode 3 extending from the outside of the first end into the first cavity 11, and the first electrode 3 being fixedly connected to the first end; the second electrode 4 extending from the outside of the second end into the first cavity 11, and the second electrode 4 being fixedly connected to the second end; the initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction.

[0025] The aforementioned flexible strain sensor includes a first flexible housing 1, a first electrode 3, a second electrode 4, and a conductive liquid 2. The first flexible housing 1 has a first cavity 11 extending along a first direction. The first electrode 3 extends from the outer side of the first end of the first flexible housing 1 into the first cavity 11, and the second electrode 4 extends from the outer side of the second end of the first housing into the first cavity 11. The conductive liquid 2 fills the first cavity 11. The first cavity 11, the first electrode 3, the second electrode 4, and the conductive liquid 2 constitute a sliding sensing structure, wherein the first direction is the X-axis direction.

[0026] In use, the conductive liquid 2 is in electrical contact with the first electrode 3 and the second electrode 4. When the flexible strain sensor is subjected to tension or normal compression along the first direction, the first flexible housing 1 undergoes elastic deformation, causing a change in the geometry of the first cavity 11. This results in a change in the effective conductive path length and effective conductive cross-sectional area of ​​the conductive liquid 2 between the first electrode 3 and the second electrode 4, thereby causing a corresponding change in the impedance amplitude between the first electrode 3 and the second electrode 4. By detecting this impedance amplitude, the magnitude of the strain experienced by the flexible strain sensor in the first direction can be obtained. Similarly, when the flexible strain sensor is bent or torn, the same principle applies, which will not be elaborated further here.

[0027] This embodiment does not limit the shape of the first flexible shell 1. Figures 1 to 5 (This is merely an example illustrating the shape of the first flexible housing 1.) It can be symmetrical about the first direction, or not symmetrical about the first direction, or in other feasible ways, as long as the first flexible housing 1 has a first cavity 11 extending along the first direction, forming a sliding sensing structure with the first electrode 3, the second electrode 4, and the conductive liquid 2. Similarly, this embodiment does not limit the material of the flexible housing; relevant technologies can be consulted, and will not be elaborated further here. For example, in this embodiment, the first flexible housing 1 is a silicone tube.

[0028] This embodiment does not limit the relative positions of the first electrode 3 and the second electrode 4. Figures 1 to 5 (This example only illustrates the relative positions of the first electrode 3 and the second electrode 4.) The first electrode 3 and the second electrode 4 can be arranged opposite each other along the first direction, or staggered along the first direction, or in other feasible ways, as long as the initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction. The following embodiment uses the arrangement of the first electrode 3 and the second electrode 4 opposite each other along the first direction as an example. Similarly, this embodiment does not limit the shape and material of the first electrode 3 and the second electrode 4, as long as they do not exhibit irregular expansion and contraction when the flexible strain sensor is stretched. Specifically, the shape of the first electrode 3 and the second electrode 4 can be a rod-shaped structure with any cross-section; the material of the first electrode 3 and the second electrode 4 is selected from any one or any combination of the following materials: copper wire, silver wire, gold wire, platinum wire, silver-plated copper wire, gold-plated copper wire, platinum-plated copper wire, gold-plated silver wire, or platinum-plated silver wire. For example, in this embodiment, the first electrode 3 and the second electrode 4 are both cylindrical pure silver electrodes, and the first electrode 3 and the second electrode 4 can be arranged opposite each other along the first direction.

[0029] In this embodiment, the initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction, so that the conductive liquid in the remaining nine-tenths of the length of the first cavity along the first direction is short-circuited by the first electrode 3 and the second electrode 4, and the output signal of the flexible strain sensor is generated between the first electrode 3 and the second electrode 4, that is, the output signal is generated in one-tenth of the length of the first cavity 11 along the first direction, so that when the remaining nine-tenths of the length of the first cavity 11 along the first direction is bent and twisted, it is difficult to generate interference signals, thereby reducing the magnitude of the interference signal when the flexible strain sensor is bent and twisted, and thus reducing the proportion of interference signals in the output signal.

[0030] Meanwhile, since the output signal is composed of the normal signal generated by stretching and the interference signal generated by interference, the sensitivity can be understood as the ability of the flexible strain sensor to convert a unit tensile strain into a normal signal change. Initially, the upper limit of the interference signal generated by bending, torsion, and compression deformation of the flexible strain sensor is fixed. The higher the sensitivity, the faster the normal signal generated when the sensor is stretched, and the lower the proportion of the interference signal in the output signal. Furthermore, the sensitivity of the flexible strain sensor is proportional to the length of the first cavity along the first direction and the distance between the first electrode 3 and the second electrode 4. In this embodiment, the initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction. The sensitivity of the flexible strain sensor increases as the ratio of the initial distance between the first electrode 3 and the second electrode 4 to the length of the first cavity 11 along the first direction decreases. This makes the flexible strain sensor highly sensitive to tensile deformation, increasing the magnitude of the normal signal when the sensor undergoes tensile deformation, thereby reducing the proportion of signal interference in the output signal. Simultaneously, the design of the initial distance between the first electrode 3 and the second electrode 4 being at most one-tenth of the length of the first cavity 11 along the first direction in this application has the effect of reducing the noise of the high aspect ratio flexible strain sensor. Specifically, to achieve better anti-interference (bending and torsion) effects, in this embodiment, the initial positions of the first electrode 3 and the second electrode 4 are axially symmetrical about the plane containing the center position of the first cavity 11 in the first direction. During stretching, the first electrode 3 of the flexible strain sensor does not move relative to the first end, and the second electrode 4 does not move relative to the second end. The first electrode 3 and the second electrode 4 move relative to the first flexible housing 1 and the conductive liquid 2. In this embodiment, the distance between the two electrodes after the movement is at most seven-tenths of the length of the first cavity 11 along the first direction.

[0031] In this embodiment, the flexible strain sensor uses conductive liquid 2 as the sensing material. Based on the physical property that the static shear modulus of conductive liquid is zero, when the portion between the first and second electrodes in the first cavity undergoes bending and torsion, the internal conductive liquid only undergoes flow redistribution adapted to the geometric boundaries, without producing local stress concentration phenomena similar to those of solid materials during bending and torsion. This eliminates the interference signal introduced by the Poisson's ratio effect and bending strain gradient of solid conductive materials (while bending and torsion of the silicone tube still causes changes in the cross-sectional area and length of the silicone tube, generating interference signals that cannot be completely eliminated), reducing the magnitude of the interference signal and thus reducing its proportion in the output signal. Therefore, this flexible strain sensor has good resistance to interference signals generated by bending and torsion. Since ionic liquids have low viscosity, extremely low volatility, and a wide electrochemical window, the conductive liquid 2 used in this embodiment is an ionic liquid or a mixture of ionic liquids. When mixing ionic liquids, the conditions for mixing hydrophilic ionic liquids and hydrophobic ionic liquids must be met. Specifically, ionic liquids include, but are not limited to, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-ethyl-3-methylimidazolium acetate, and 1-butyl-3-methylimidazolium chloride salt.

[0032] The flexible strain sensor provided by the present invention includes a first flexible housing 1, a first cavity 11 extending along a first direction, and a conductive liquid 2 filling the first cavity 11. A first electrode 3, a second electrode 4, the first cavity 11, and the conductive liquid 2 constitute a sliding sensing structure. The initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction, such that the conductive liquid within the remaining nine-tenths of the length of the first cavity along the first direction is short-circuited by the first and second electrodes. The output signal of the flexible strain sensor is generated between the first electrode 3 and the second electrode 4, that is, the output signal is generated within one-tenth of the length of the first cavity 11 along the first direction. This makes it difficult to generate interference signals when the remaining nine-tenths of the length of the first cavity 11 along the first direction bends or twists, thereby reducing the magnitude of interference signals when the flexible strain sensor bends or twists, and thus reducing the proportion of interference signals in the output signal. Meanwhile, this flexible strain sensor uses a conductive liquid 2 as the sensing material. Based on the physical property that the static shear modulus of the conductive liquid is zero, when the portion between the first and second electrodes in the first cavity undergoes bending and torsion, the internal conductive liquid only undergoes flow redistribution adapted to the geometric boundaries, without producing local stress concentration phenomena similar to those of solid materials during bending and torsion. This reduces the magnitude of interference signals generated by stress concentration, thereby reducing the proportion of interference signals in the output signal. Therefore, this flexible strain sensor has good resistance to interference signals generated by bending and torsion, and also has high sensitivity.

[0033] The specific structure of another flexible strain sensor provided by the present invention will be described in detail in the following embodiments.

[0034] Please refer to Figures 6 to 8 , Figure 6 A cross-sectional view along the AA section line of another flexible strain sensor provided in an embodiment of the present invention; Figure 7 A cross-sectional view along the BB section line of another flexible strain sensor provided in an embodiment of the present invention; Figure 8 A cross-sectional view along the AA section line of another flexible strain sensor after stretching, provided in an embodiment of the present invention.

[0035] See Figures 6 to 8(The third and fourth ends are not shown in the figure, and the gap and liquid medium are not distinguished; this embodiment takes the example of the gap being completely filled with liquid medium.) Based on the above embodiment, the flexible strain sensor also includes a second flexible shell 5, inside which a first flexible shell 1 is fitted. There is a gap between the first flexible shell 1 and the second flexible shell 5, and the gap is filled with liquid medium 7. This liquid medium is chemically compatible with the first flexible shell 1 and the second flexible shell 5. Under an ambient temperature of 25°C and normal pressure, the liquid medium will not cause chemical degradation of the first flexible shell 1 and the second flexible shell 5.

[0036] Specifically, the size of the second flexible shell 5 is larger than that of the first flexible shell 1, and there is a gap between the first flexible shell 1 and the second flexible shell 5. The second flexible shell 5 has a third end and a fourth end opposite to each other along the first direction. The first electrode 3 extends from the outside of the third end of the second flexible shell 5, passes through the gap and the first end of the first flexible shell 1 to the first cavity 11. The second electrode 4 extends from the outside of the fourth end of the second flexible shell 5, passes through the gap and the second end of the first flexible shell 1 to the first cavity 11.

[0037] In this embodiment, the gap 6 between the first flexible shell 1 and the second flexible shell 5 is filled with liquid medium 7. The liquid medium 7 can fill the gap 6 completely or partially. This embodiment does not impose specific limitations and can be adjusted according to the actual situation. This embodiment takes the example of filling the gap 6 between the first flexible shell 1 and the second flexible shell 5 with liquid medium 7.

[0038] In this embodiment, the first cavity 11, the gap 6 (equivalent to the presence of a cavity), and the conductive liquid 2 within the first cavity 11 and the liquid medium 7 within the gap 6 constitute a dual-cavity structure. When the flexible strain sensor is subjected to compressive deformation (e.g., radial compression or localized contact) perpendicular to the axial direction (i.e., the first direction) of the second flexible housing 5, the second flexible housing 5 first undergoes localized deformation, transmitting the external force that causes this deformation to the gap 6 located between the first flexible housing 1 and the second flexible housing 5. The gap cavity 6 is a closed cavity filled with the liquid medium 7. Due to the uniform pressure transmission of the liquid medium 7 within the gap cavity 6, the locally applied concentrated compressive force is rapidly converted into a uniformly distributed normal stress within the gap 6, acting on the entire outer surface of the first flexible housing 1.

[0039] Meanwhile, the conductive liquid filling the first cavity 11 is incompressible, providing uniform static pressure support to the inner wall of the first flexible shell 1. Under the combined action of external uniform normal stress and internal static pressure, the tube wall of the first flexible shell 1 is in a state of radial force equilibrium, thus preventing radial concavity, ellipticization of the cross-section, or other changes in cross-sectional shape perpendicular to the axial direction. The geometric configuration of the conductive liquid remains stable, and its signal value hardly changes with external compression disturbances. Therefore, this flexible strain sensor reduces the magnitude of the generated interference signal (interference signal generated by compression deformation), thereby reducing the proportion of the interference signal in the output signal.

[0040] This embodiment does not limit the shape of the second flexible shell 5. Figures 6 to 8 (This is merely an illustrative example showing the shape of the first flexible shell 1. It can be symmetrical about the first direction, or not symmetrical about the first direction, or in other feasible ways, as long as a gap 6 is formed between the first flexible shell 1 and the second flexible shell 5. In this embodiment, the first flexible shell 1 and the second flexible shell 5 have similar shapes, but the size of the second flexible shell 5 is larger than the size of the first flexible shell 1. Similarly, this embodiment does not limit the material of the flexible shell; relevant technologies can be consulted, and will not be elaborated further here. For example, in this embodiment, the second flexible shell 5 is a silicone tube.)

[0041] This embodiment does not impose specific limitations on the shape of the gap formed between the first flexible shell 1 and the second flexible shell 5, and can be designed according to actual needs. This embodiment does not limit the type of liquid medium 7; it can be any liquid that will not damage the first flexible shell 1, meaning that the liquid medium is chemically compatible with both the first and second flexible shells 5, and will not cause chemical degradation of the first and second flexible shells 1 and 5 at an ambient temperature of 25°C and normal pressure. Specifically, in this embodiment, the liquid medium 7 is glycerol, water, an ionic liquid, or hydraulic oil.

[0042] The flexible strain sensor provided in this embodiment has a dual-cavity structure consisting of a first cavity 11, a gap 6 (equivalent to a cavity), and a conductive liquid 2 within the first cavity 11 and a liquid medium 7 within the gap 6. In addition to the effects mentioned above, it also reduces the proportion of interference signals caused by compression deformation in the output signal. Therefore, this flexible strain sensor has good resistance to interference signals generated by bending, torsion, and compression deformation, and also has high sensitivity.

[0043] Based on the above embodiments, in order to further improve the resistance of the flexible strain sensor to interference signals generated by bending, torsion, and compression deformation, the gap extends circumferentially along the first flexible housing 1 and surrounds the second flexible housing 5. At this time, the gap and the second flexible housing 5 completely cover the first flexible housing 1.

[0044] Based on the above embodiments, to further improve the resistance of the flexible strain sensor to interference signals generated by bending, torsion, and compression deformation, the structure of the first flexible housing 1 is axially symmetrical about the first direction; the structures of the first electrode 3 and the second electrode 4 are axially symmetrical about the first direction; the materials of the flexible housing and the conductive liquid 2 are isotropic. For even better results, the structure of the second flexible housing 5 is axially symmetrical about the first direction, and the material of the second flexible housing 5 is isotropic. At this point, all structures of the flexible strain sensor are axially symmetrical about the first direction, and all materials (the materials of the first flexible housing 1 and the second flexible housing 5, and the conductive liquid 2) are isotropic. This flexible strain sensor resists interference signals caused by bending and compression deformation parallel to the second direction and a third direction (i.e., parallels between the second and third directions). The first direction is the X-axis, the second direction is the Y-axis, and the third direction is the Z-axis.

[0045] Based on the above embodiments, in order to improve the signal response speed of the flexible strain sensor and reduce signal drift, the first electrode 3 and the second electrode 4 are connected to an AC voltage source; the AC voltage source has a first voltage terminal and a second voltage terminal, the first electrode 3 is electrically connected to the first voltage terminal, and the second electrode 4 is electrically connected to the second voltage terminal.

[0046] If a DC voltage is applied between the first electrode 3 and the second electrode 4, when the length of the first cavity 11 changes along the first direction due to stretching or compression of the sensor, the ions in the conductive liquid (ionic liquid) filled in the first cavity 11 need to undergo a relatively slow diffusion and migration process to redistribute under the new electrode spacing and reach a steady state. This ion rearrangement relaxation process introduces a large electrical response time constant, resulting in a slow sensor signal response.

[0047] When an AC voltage is applied between the first electrode 3 and the second electrode 4, due to the high-frequency alternating characteristics of the AC electric field, ions only need to undergo short-range high-frequency oscillations near the electrode interface. They do not need to complete a full long-distance migration from one electrode to the other, thus transmitting impedance information corresponding to changes in the cavity's geometric dimensions in real time. This significantly shortens the sensor's response time and greatly improves its response speed. Simultaneously, the AC excitation method effectively suppresses Faraday currents and electrolytic side reactions that may occur under DC bias. In particular, it avoids the continuous electrolysis of residual impurities in the ionic liquid (such as water molecules) to produce gaseous products, reducing signal drift caused by electrolysis and fundamentally ensuring the stability and signal fidelity of the sensor during long-term operation.

[0048] Specifically, the first electrode 3 and the second electrode 4 of the flexible strain sensor are connected to a constant voltage AC source, wherein the constant voltage is 0-10V and the frequency of the constant voltage is 100Hz-100MHz. The constant voltage AC source has a first voltage terminal and a second voltage terminal, and the flexible strain sensor also has a first terminal and a second terminal. When the flexible strain sensor is connected to the constant voltage AC source, the first terminal of the flexible strain sensor is connected to the first voltage terminal, and the second terminal of the flexible strain sensor is connected to the second voltage terminal. That is, the first electrode 3 of the flexible strain sensor is connected to the first voltage terminal through the connection of the first terminal of the flexible strain sensor, and the second electrode 4 of the flexible strain sensor is connected to the second voltage terminal through the connection of the second terminal of the flexible strain sensor. During the positive half-cycle of the AC voltage, the first voltage terminal is positive and the second voltage terminal is negative. Anions in the conductive liquid 2 in the first cavity 11 migrate towards the first electrode 3 under the drive of the electric field, while cations migrate towards the second electrode 4. During the negative half-cycle, the voltage polarity is reversed, and the migration directions of anions and cations are reversed accordingly. Because the frequency of the applied alternating voltage is much higher than the characteristic frequency required for ions to complete long-range migration between electrodes, the anions and cations only oscillate at short ranges in a local region between the first electrode 3 and the second electrode 4 in each cycle, rather than forming a complete redistribution from one electrode to the other.

[0049] When the flexible strain sensor is subjected to tension or compression, causing changes in the geometry of the first cavity 11, the ionic liquid can instantly reflect the structural change as a change in impedance through real-time high-frequency oscillation of ions near the electrode interface, without undergoing a slow diffusion-controlled rearrangement process. This significantly shortens the sensor's electrical response time and reduces the slow signal response caused by ion relaxation under DC excitation, further ensuring the real-time performance and signal fidelity of dynamic strain monitoring. Simultaneously, the AC excitation method effectively suppresses Faraday current and electrolytic side reactions that may occur under DC bias. In particular, it avoids the continuous electrolysis of residual impurities in the ionic liquid (such as water molecules) to produce gaseous products, reducing signal drift caused by electrolysis and fundamentally ensuring the stability and signal fidelity of the sensor during long-term operation.

[0050] Based on the above embodiments, the flexible strain sensor further includes a flexible package 8; the first end has a first port 12, the first electrode 3 extends from the outside of the first port 12 into the first cavity 11, the flexible package 8 seals the first port 12 and is fixedly connected to the first electrode 3; the second end has a second port 13, the second electrode 4 extends from the outside of the second port 13 into the first cavity 11, the flexible package 8 seals the second port 13 and is fixedly connected to the second electrode 4.

[0051] The flexible strain sensor provided by this invention, in addition to reducing the magnitude of interference signals when the flexible strain sensor bends and twists, thereby reducing the proportion of interference signals in the output signal and having a good resistance to interference signals generated by bending and twisting, also has high sensitivity. Furthermore, the flexible strain sensor is provided with a dual-cavity structure consisting of a first cavity 11, a gap 6 (equivalent to the presence of a cavity), and a conductive liquid 2 in the first cavity 11 and a liquid medium 7 in the gap 6. In addition to the above-mentioned effects, it also reduces the proportion of interference signals caused by compression deformation in the output signal and has a good resistance to interference signals generated by compression deformation.

[0052] The method for fabricating a flexible strain sensor provided by this invention will be described in detail in the following embodiments.

[0053] Please refer to Figure 9 , Figure 9 This is a schematic flowchart illustrating a method for fabricating a flexible strain sensor according to an embodiment of the present invention.

[0054] See Figure 9 The present invention provides a method for fabricating a flexible strain sensor, used to fabricate the aforementioned flexible strain sensor, comprising: S100, a first flexible housing 1 is provided having a first cavity 11 extending along a first direction, the first flexible housing 1 having opposing first ends and second ends along the first direction.

[0055] S110, Inject the conductive liquid 2 into the interior of the first cavity 11 of the first flexible shell 1.

[0056] In this step, the conductive liquid 2 is centrifuged using a centrifuge, the length of the first flexible shell 1 in the first direction is stretched to twice its original length and held for 5 minutes, and then the first flexible shell 1 is heated in an oven; then the conductive liquid 2 is injected into the first cavity 11 of the first flexible shell 1.

[0057] In this embodiment, injecting the conductive liquid 2 into the first cavity 11 of the first flexible shell 1 further includes: providing a second flexible shell 5; inserting the first flexible shell 1 into the second flexible shell 5 along a first direction, with a gap 6 between the first flexible shell 1 and the second flexible shell 5; injecting the conductive liquid 2 into the first cavity 11 of the first flexible shell 1; and injecting a liquid medium 7 into the gap 6, wherein the liquid medium 7 is difficult to compress.

[0058] In this step, the conductive liquid 2 is centrifuged using a centrifuge, and the lengths of the first flexible shell 1 and the second flexible shell 5 in the first direction are stretched to twice their original lengths and held for 5 minutes. Then, the first flexible shell 1 and the second flexible shell 5 are heated in an oven. The first flexible shell 1 is inserted into the second flexible shell 5, and the conductive liquid 2 is injected into the first cavity 11 of the first flexible shell 1. There is a gap 6 between the first flexible shell 1 and the second flexible shell 5. Liquid medium 7 is injected into the gap 6. The step of injecting liquid medium 7 into the gap 6 can be done after the conductive liquid 2 is injected into the first cavity 11 of the first flexible shell 1, or it can be done after the following steps (extending the first electrode 3 from the first end into the first cavity 11 and extending the second electrode 4 from the second end into the first cavity 11). This embodiment does not impose specific limitations.

[0059] S120. The first electrode 3 is inserted into the first cavity 11 from the first end, and the second electrode 4 is inserted into the first cavity 11 from the second end. The initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction.

[0060] In this step, the first electrode 3 is inserted into the first cavity 11 from the first end, and the second electrode 4 is inserted into the first cavity 11 from the second end. The initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction.

[0061] In this embodiment, the method for preparing the flexible strain sensor further includes sealing the first end and the second end of the first flexible shell 1 with a flexible encapsulation body 8; placing two flexible encapsulation molds with internal cavities onto the first end and the second end of the first flexible shell 1 respectively, with the internal cavities of the flexible encapsulation molds matching the first end and the second end of the flexible shell; pouring a prepolymer of polydimethylsiloxane main agent and curing agent mixed at a mass ratio of 10:1 into the flexible encapsulation mold and heating it in an oven to complete the sealing of the first end and the second end of the first flexible shell 1 with the flexible encapsulation body 8.

[0062] The flexible strain sensor fabricated by the method provided in this embodiment of the invention includes a first flexible shell 1, a first cavity 11 extending along a first direction within the first flexible shell 1, and a conductive liquid filling the first cavity 11. A first electrode 3, a second electrode 4, the first cavity 11, and the conductive liquid 2 constitute a sliding sensing structure. The initial distance between the first electrode 3 and the second electrode 4 is at most one-tenth of the length of the first cavity 11 along the first direction, such that the conductive liquid in the remaining nine-tenths of the length of the first cavity 11 is short-circuited by the electrodes. The output signal of the flexible strain sensor is generated between the first electrode 3 and the second electrode 4, that is, the output signal is generated at one-tenth of the length of the first cavity 11 along the first direction. This makes it difficult to generate interference signals when the remaining nine-tenths of the length of the first cavity 11 along the first direction bends or twists, thereby reducing the magnitude of interference signals when the flexible strain sensor bends or twists, and thus reducing the proportion of interference signals in the output signal. Meanwhile, this flexible strain sensor uses a conductive liquid 2 as the sensing material. Based on the physical property that the static shear modulus of the conductive liquid is zero, when the part between the first and second electrodes in the first cavity undergoes bending and torsion, the internal conductive liquid only undergoes flow redistribution adapted to the geometric boundaries, without producing a local stress concentration phenomenon similar to that of solid materials during bending and torsion. This reduces the proportion of interference signals in the output signal. Therefore, this flexible strain sensor has good resistance to interference signals generated by bending and torsion.

[0063] The following examples (Example 1, Example 2, and Example 3) illustrate the fabrication method and effects of the flexible strain sensor of this application. The specific process of each example is as follows: Example 1 The specific structure of the flexible strain sensor in this embodiment can be referred to the structure of the aforementioned flexible strain sensor (see reference). Figure 6 The flexible strain sensor is axially symmetrical about the first direction, wherein the first flexible housing 1 and the second flexible housing 5 are both silicone tubes, the first electrode 3 and the second electrode 4 are both cylindrical pure silver electrodes with a diameter of 0.1 mm, and the flexible package 8 is an elastic package.

[0064] The fabrication method of the flexible strain sensor in this embodiment includes the following steps: Step 1: Centrifuge 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt at 8000 rpm for 5 minutes. Stretch the first flexible shell 1 with an inner diameter of 0.3 mm and the second flexible shell 5 with an inner diameter of 1.7 mm to 200% of their original length and hold for 5 minutes. Then place them in an 80°C oven and heat for 30 minutes.

[0065] Step 2: Insert the first flexible shell 1 with an inner diameter of 0.3 mm into the second flexible shell 5 with an inner diameter of 1.7 mm, and then inject 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt into the first cavity 11 of the first flexible shell 1 with an inner diameter of 0.3 mm.

[0066] Step 3: Insert the first electrode 3 and the second electrode 4, with a diameter of 0.1 mm, into the interior of the first cavity 11 from both ends of the first flexible shell 1 with a diameter of 0.3 mm, such that the initial distance between the first electrode 3 and the second electrode 4 is 4 mm (i.e., the initial distance between the first electrode 3 and the second electrode 4 is four percent of the length of the first cavity 11 along the first direction).

[0067] Step 4: Inject glycerol into the gap 6 between the first flexible shell 1 with an inner diameter of 0.3 mm and the second flexible shell 5 with an inner diameter of 1.7 mm. Then, fit two elastic encapsulation molds with internal cavities onto both sides of the silicone tube on which the first flexible shell 1 with an inner diameter of 1.7 mm is fitted. Pour the prepolymer, which is a mixture of polydimethylsiloxane main agent and curing agent at a mass ratio of 10:1, into the flexible encapsulation mold and place it in a 70°C oven for 4 hours.

[0068] The flexible strain sensor prepared in this embodiment was subjected to the following conditions: stretching 30 times with a strain step of 0.1% followed by 30 retractions; stretching 30 times with a strain step of 1% followed by 30 retractions; stretching 7 times with a strain step of 10%; manually bending 180° then 360° and finally returning to its original position; manually twisting 180° then 360° and finally returning to its original position; and compressing 50% along a third direction. The signal response diagrams of the flexible strain sensor were measured to verify its effectiveness. For details, please refer to... Figures 10 to 16 , Figure 10 The strain signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention, after being stretched 30 times with a strain step of 0.1% and then retracted 30 times; Figure 11 The strain signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention, after being stretched 30 times with a strain step of 1% and then retracted 30 times; Figure 12 The strain signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention after being stretched 7 times with a step size of 10%; Figure 13 Linearity test diagram of strain signal response of the flexible strain sensor provided in Embodiment 1 of the present invention in the strain range of 0-30%; Figure 14 The bending signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention after being manually bent 180° and then manually bent 360°, and finally recovered. Figure 15The torsional signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention after being manually twisted 180° and then manually twisted 360°, and finally recovered. Figure 16 The signal response diagram of the flexible strain sensor provided in Embodiment 1 of the present invention when compressed by 50% in a third direction.

[0069] In this embodiment, the signal response of the impedance amplitude type flexible strain sensor is defined as Δ|Z| / |Z0|, where |Z0| is the initial impedance amplitude of the flexible strain sensor when it is not subjected to strain, Δ|Z| =|Z|-|Z0| is the change in impedance amplitude of the flexible strain sensor after being subjected to strain, and |Z| is the impedance amplitude after being subjected to strain. Define the sensitivity (gauge factor) GF of this impedance amplitude flexible strain sensor as: GF=(Δ|Z| / |Z0|) / ε in: |Z0| is the initial impedance amplitude of the sensor when it is not subjected to strain; Δ|Z|=|Z|-|Z0|, which is the change in impedance amplitude of the sensor after being subjected to strain ε, where |Z| is the impedance amplitude after being subjected to strain; ε = ΔL / L0 is the strain applied by the sensor along the principal strain direction, which is the ratio of the length change ΔL of the sensor along the first direction to the initial length L0.

[0070] Example 2

[0071] The difference from Embodiment 1 is that the initial distance between the first electrode 3 and the second electrode 4 is adjusted to 10mm (that is, the initial distance between the first electrode 3 and the second electrode 4 is four percent of the length of the first cavity 11 along the first direction), while the other structures and materials are the same.

[0072] The flexible strain sensor prepared in this embodiment was stretched 30 times and then retracted 30 times with a strain step size of 0.1% to measure its signal response, thus verifying the effectiveness of the flexible strain sensor. See details... Figure 17 , Figure 17 The strain signal response diagram of the flexible strain sensor provided in Embodiment 2 of the present invention is shown after being stretched 30 times with a strain step size of 1% and then retracted 30 times.

[0073] Example 3

[0074] The difference from Example 1 is that the conductive liquid 2 is replaced with a mixture of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt and 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt in a 1:1 ratio, while the other structures and materials are the same.

[0075] The flexible strain sensor prepared in this embodiment was stretched 30 times and then retracted 30 times with a strain step size of 0.1% to measure its signal response, thus verifying the effectiveness of the flexible strain sensor. See details... Figure 18 , Figure 18 The strain signal response diagram of the flexible strain sensor provided in Embodiment 3 of the present invention is shown after being stretched 30 times with a strain step size of 1% and then retracted 30 times.

[0076] As can be seen from the above embodiments and the corresponding test diagrams, The flexible strain sensor provided by this invention can increase the magnitude of the normal signal when the sensor undergoes tensile deformation by improving its sensitivity, thereby reducing the proportion of interference signals in the output signal. This flexible strain sensor exhibits good resistance to interference signals generated by bending, torsion, and compression deformation, while also possessing high sensitivity.

[0077] For details, please refer to Figure 10 and Figure 17 Comparing Embodiment 1 and Embodiment 2, it can be seen that increasing sensitivity reduces the proportion of interference signals. Furthermore, the sensitivity of Embodiment 1 is 20, while that of Embodiment 2 is 8. This indicates that the sensitivity of the flexible strain sensor increases as the ratio of the initial distance between the first electrode 3 and the second electrode 4 to the length of the first cavity 11 along the first direction decreases. This results in high sensitivity of the flexible strain sensor to tensile deformation, increasing the magnitude of the normal signal when the sensor undergoes tensile deformation, thereby reducing the proportion of interference signals in the output signal.

[0078] For details, please refer to Figure 10 and Figure 18 Comparing Examples 1 and 2, it can be seen that the sensitivity of Example 1 is 20, while the sensitivity of Example 3 is 21. This indicates that the sensitivity of the flexible strain sensor is related to the ratio of the initial distance between the first electrode 3 and the second electrode 4 to the length of the first cavity 11 along the first direction, and is independent of the type of conductive liquid. Furthermore, using a mixture of ionic liquids as the conductive liquid 2 can achieve the same effect as using only one type of ionic liquid as the conductive liquid 2.

[0079] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0080] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0081] The flexible strain sensor and its fabrication method provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of this invention.

Claims

1. A flexible strain sensor, characterized in that, include: A first flexible shell, wherein the first flexible shell has a first cavity extending along a first direction; The first flexible shell has a first end and a second end opposite to each other along the first direction; A conductive liquid, wherein the conductive liquid fills the first cavity; A first electrode and a second electrode, wherein the first electrode extends from the outside of the first end into the first cavity and is fixedly connected to the first end; the second electrode extends from the outside of the second end into the first cavity and is fixedly connected to the second end; the initial distance between the first electrode and the second electrode is at most one-tenth of the length of the first cavity along the first direction.

2. The flexible strain sensor according to claim 1, characterized in that, It also includes a second flexible shell, in which the first flexible shell is nested, and there is a gap between the first flexible shell and the second flexible shell, the gap being filled with a liquid medium.

3. The flexible strain sensor according to claim 2, characterized in that, The gap extends circumferentially along the first flexible shell and surrounds the second flexible shell.

4. The flexible strain sensor according to claim 1, characterized in that, The structure of the first flexible shell is axially symmetrical about the first direction; The structures of the first electrode and the second electrode are symmetrical about the first direction. Both the flexible shell material and the conductive liquid are isotropic.

5. The flexible strain sensor according to claim 1, characterized in that, The first electrode and the second electrode are connected to an AC voltage source; The AC voltage source has a first voltage terminal and a second voltage terminal; the first electrode is connected to the first voltage terminal; and the second electrode is connected to the second voltage terminal.

6. The flexible strain sensor according to claim 1, characterized in that, The conductive liquid is an ionic liquid or a mixture of ionic liquids.

7. The flexible strain sensor according to claim 1, characterized in that, It also includes flexible packaging; The first end has a first port, the first electrode extends from the outside of the first port into the first cavity, and the flexible package seals the first port and is fixedly connected to the first electrode. The second end has a second port, and the second electrode extends from the outside of the second port into the first cavity. The flexible package seals the second port and is fixedly connected to the second electrode.

8. A method for fabricating a flexible strain sensor, used to fabricate the flexible strain sensor as described in any one of claims 1 to 7, characterized in that, include: A first flexible housing is provided having a first cavity extending along a first direction, the first flexible housing having opposing first ends and second ends along the first direction; Injecting conductive liquid into the interior of the first cavity of the first flexible housing; The first electrode is inserted into the first cavity from the first end, and the second electrode is inserted into the first cavity from the second end. The initial distance between the first electrode and the second electrode is at most one-tenth of the length of the first cavity along the first direction.

9. The method for fabricating a flexible strain sensor according to claim 8, characterized in that, The step of injecting conductive liquid into the interior of the first cavity of the first flexible housing further includes: Provide a second flexible housing; The first flexible shell is inserted into the second flexible shell along the first direction, and there is a gap between the first flexible shell and the second flexible shell; The conductive liquid is injected into the interior of the first cavity of the first flexible housing; The liquid medium is injected into the gap.

10. The method for fabricating a flexible strain sensor according to claim 8, characterized in that, It also includes sealing the first end and the second end of the first flexible housing with a flexible encapsulation body; Two flexible packaging molds with internal cavities are respectively fitted onto the first end and the second end of the first flexible shell, and the internal cavities of the flexible packaging molds are adapted to the first end and the second end of the flexible shell; The prepolymer, which is a mixture of polydimethylsiloxane main agent and curing agent at a mass ratio of 10:1, is poured into the flexible packaging mold and heated in an oven to complete the sealing of the first end and the second end of the first flexible shell by the flexible package.

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