Shape memory flexible sensor, preparation method and application

Abstract

The present invention relates to a shape memory flexible sensor, a preparation method and an application, and relates to the technical field of shape memory sensors. The shape memory flexible sensor comprises: a shape memory substrate and an electrode arranged on the shape memory substrate, wherein the shape memory substrate is made of a shape memory material by 4D printing, and the shape memory substrate has a negative Poisson's ratio structure, and the electrode comprises a shape memory film and a conductive layer, wherein the conductive layer is arranged on the surface of the shape memory film, and the shape memory film comprises a shape memory film with a first deformation structure on the surface. Compared with the prior art, the present invention has a simple structure, high reliability, and low cost, and can undergo in-plane reconstruction under the action of external stimulation and in-plane axial load, and can undergo out-of-plane reconstruction under the action of external stimulation and out-of-plane axial load, so as to adjust the mechanical properties and electrical properties of the flexible sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of shape memory sensors, and in particular to a shape memory flexible sensor, a preparation method and an application thereof. Background Art

[0002] Shape memory polymer refers to a polymer material that can restore its original shape after the initial conditions of a product are changed and fixed under certain conditions, and then it can be stimulated by external conditions (such as heat, electricity, light, chemical induction, etc.).

[0003] As the intelligent structure technology based on shape memory polymer materials becomes increasingly mature, its application in the field of health monitoring has been widely recognized and recognized. In the field of health monitoring, the pressure signals generated by the physical contact of human skin and internal tissues and organs can carry key physiological information about health status, and transmitting this information is one of the main means to achieve perceptual tactile interaction. Therefore, the development of flexible pressure sensors that can convert mechanical signals into electrical signals is of great significance to the field of wearable health monitoring. However, since health monitoring sensors are mostly used in areas where a large amount of deformation and movement occurs, traditional health monitoring sensors cannot meet the requirements of fit and stability with the measured parts, and have complex structures, low reliability, and high costs. Their mechanical and electrochemical properties cannot be adjusted according to changes in detection requirements after manufacturing. Summary of the invention

[0004] The problem solved by the present invention is that conventional health monitoring sensors have at least one of the following aspects: complex structure, low reliability, high cost, and poor adaptability to detection requirements.

[0005] To solve the above problems, in a first aspect, the present invention provides a shape memory flexible sensor, comprising: a shape memory substrate and an electrode arranged above the shape memory substrate, wherein the shape memory substrate is prepared by a shape memory material using a 4D printing method, and the shape memory substrate has a negative Poisson's ratio structure, the electrode comprises a shape memory film and a conductive layer, the conductive layer is arranged on the surface of the shape memory film, and the shape memory film comprises a shape memory film with a first deformation structure on the surface.

[0006] Optionally, the electrode includes a first conductive film and a second conductive film that are arranged opposite to each other, the first conductive film is arranged above the second conductive film, and the first conductive film includes a shape memory film with a first deformation structure on the surface and a first conductive layer, the second conductive film includes a planar shape memory film and a second conductive layer, and the first conductive layer and the second conductive layer are arranged opposite to each other.

[0007] Optionally, the shape memory flexible sensor further includes a waterproof layer disposed above the electrode, the waterproof layer is a shape memory film with a second deformation structure on the surface, and the waterproof layer is disposed in the back direction of the first conductive film.

[0008] Optionally, the shape memory flexible sensor further includes a sealing layer disposed below the electrode, and the material of the sealing layer is polydimethylsiloxane.

[0009] Optionally, the shape memory matrix in the shape memory flexible sensor is suitable for deforming under the action of external thermal stimulation and in-plane axial load, so that the shape memory flexible sensor changes from an initial state to a first temporary state, and is fixed in the first temporary state after cooling to room temperature; the electrode in the shape memory flexible sensor is suitable for deforming under the action of external thermal stimulation and out-of-plane axial load, so that the shape memory flexible sensor changes from the initial state to a second temporary state, and is fixed in the second temporary state after cooling to room temperature.

[0010] Optionally, the material of the shape memory matrix and the shape memory film is selected from one or more of shape memory polyurethane resin, epoxy thermoplastic shape memory polymer, epoxy thermosetting shape memory polymer, styrene shape memory polymer, cyanate shape memory polymer, bismaleimide shape memory polymer, polyimide shape memory polymer, polycaprolactone shape memory polymer, polyurethane shape memory polymer or polylactic acid shape memory polymer.

[0011] Optionally, the material of the conductive layer is selected from one of flexible conductive silver paste, flexible nano-gold or poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) solution.

[0012] The advantages of the present invention over the prior art are:

[0013] On the one hand, the shape memory matrix of the shape memory flexible sensor of the present invention is a shape memory material with a negative Poisson's ratio structure, and its tensile expansion performance and bionic "J-shaped" σ-λ curve can improve the compliance when adhering to the skin surface and enhance the sensitivity to signal feedback. In addition, the present invention can undergo in-plane reconstruction under the action of external stimulation and in-plane axial load, and the present invention can adjust the mechanical properties of the flexible sensor according to the shape memory characteristics of the shape memory matrix to adapt to the different mechanical properties of the part to be detected;

[0014] On the other hand, the electrode of the shape memory flexible sensor of the present invention includes a shape memory film with a first deformation structure on the surface, which can undergo out-of-plane reconstruction under the action of external stimulation and out-of-plane axial load, and the present invention can adjust the electrical properties of the flexible sensor according to the shape memory characteristics of the shape memory film with a first deformation structure on the surface to adapt to the different electrical properties of the part to be detected; and compared with flat electrodes, its signal-to-noise ratio and sensitivity are significantly improved.

[0015] In a second aspect, the present invention provides a method for preparing the shape memory flexible sensor, comprising the following steps:

[0016] Step S1, preparing a shape memory matrix by 4D printing;

[0017] Step S2, dissolving shape memory material particles in a carbon tetrachloride solution to obtain a mixed solution, spin-coating the mixed solution on a silicon wafer mold, and volatilizing at room temperature to obtain a planar shape memory film and a shape memory film having a first deformation structure on the surface;

[0018] Step S3, spin-coating a conductive layer material on the surface of the shape memory film having a first deformation structure on the surface to obtain a first conductive film having a first conductive layer; spin-coating the conductive layer material on the surface of the planar shape memory film to obtain a second conductive film having a second conductive layer, and arranging the first conductive layer of the first conductive film and the second conductive layer of the second conductive film in a positive direction opposite to each other to obtain an electrode;

[0019] Step S4, connecting the electrode to the shape memory matrix.

[0020] Optionally, in step S2, the silicon wafer mold used to prepare the shape memory film having the first deformation structure on the surface is provided with a preset structure suitable for forming the first deformation structure, and the silicon wafer mold used to prepare the planar shape memory film is a planar silicon wafer mold.

[0021] The preparation method of the shape memory flexible sensor of the present invention is simple, and the preparation method of the shape memory flexible sensor of the present invention has the same advantages as the shape memory flexible sensor over the prior art, which will not be described in detail here.

[0022] In a third aspect, the present invention provides an application of a shape memory flexible sensor, which is mainly manifested in that the shape memory flexible sensor is suitable for collecting health status information to achieve health monitoring.

[0023] The application of the shape memory flexible sensor of the present invention is the same as the advantages of the shape memory flexible sensor over the prior art, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the structure of a shape memory flexible sensor according to an embodiment of the present invention;

[0025] Figure 2 It is a schematic structural diagram of a shape memory flexible sensor in an initial state according to an embodiment of the present invention;

[0026] Figure 3 It is a schematic structural diagram of the shape memory flexible sensor according to an embodiment of the present invention in a first temporary state;

[0027] Figure 4 It is a schematic structural diagram of the shape memory flexible sensor of an embodiment of the present invention in a second temporary state;

[0028] Figure 5 A schematic structural diagram of a shape memory substrate of a shape memory flexible sensor according to an embodiment of the present invention;

[0029] Figure 6 σ-λ curve diagram of shape memory substrates with different geometric parameters in the 0° direction according to an embodiment of the present invention;

[0030] Figure 7 A schematic diagram of a deformation state of a shape memory matrix according to an embodiment of the present invention;

[0031] Figure 8 A schematic diagram of radial artery pulse and capacitance response wave of a shape memory flexible sensor using electrodes with different deformation structures on the surface according to an embodiment of the present invention;

[0032] Fig. 9 Schematic diagram of the deformation state of the shape memory flexible sensor according to an embodiment of the present invention.

[0033] Description of reference numerals:

[0034] 1- shape memory matrix; 2- electrode; 21- first conductive film; 22- second conductive film; 3- packaging layer; 4- first deformation structure; 5- external wire, 6- waterproof layer. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] In the description of the embodiments of the present application, the description of the term "some embodiments" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0037] In the description of the embodiments of the present application, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, without requiring or implying any actual relationship or order between these entities or operations. Moreover, the term "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also other elements not explicitly listed. Each embodiment is described in a progressive manner herein, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. For the structures, products, etc. disclosed in the embodiments, since they correspond to the parts disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0038] like Figure 1 As shown, the present invention provides a shape memory flexible sensor, comprising: a shape memory substrate 1 and an electrode 2 arranged above the shape memory substrate 1, wherein the shape memory substrate 1 is made of shape memory material by 4D printing, and the shape memory substrate 1 has a negative Poisson's ratio structure, the electrode 2 comprises a shape memory film and a conductive layer, the conductive layer is arranged on the surface of the shape memory film, and the shape memory film comprises a shape memory film with a first deformation structure 4 on the surface.

[0039] The shape memory flexible sensor in this embodiment includes a shape memory substrate 1 with a negative Poisson's ratio structure and a shape memory film with a first deformation structure 4 on the surface as an electrode 2. On the one hand, the 4D printed shape memory substrate 1 has the characteristics of reconfigurable mechanical properties, bionic "J-shaped" mechanical curve and large strain range, which broadens the working range of the flexible shape memory sensor, enhances its adaptability and compliance to human skin, and improves the sensitivity and signal-to-noise ratio of the shape memory flexible sensor.

[0040] In this embodiment, the shape memory matrix 1 is made of shape memory material by 4D printing, and its negative Poisson's ratio structure is designed by fractal geometry. One unit cell is subdivided into multiple small unit cells, which are repeated in a geometric shape similar to the whole structure, and a multi-order auxiliary structure is designed. The first-order filaments are composed of two centrally symmetrical arcs with the same geometric parameters, which not only meets the requirements of the grid being assembled into an overall structure in topology, but also meets the requirements of being split into multi-order microstructures according to the principles of fractal geometry.

[0041] Figure 5Schematic diagram of the structure of the shape memory matrix 1 designed by fractal geometry method, where R is the radius, θ is the center angle, and Figure (A) is the control geometric parameters of the first-order and second-order fractal geometry shape memory matrix 1; Figure (B) is a schematic diagram of the structure of the first-order fractal geometry shape memory matrix 1 with different center angles; Figures (C)-(E) are schematic diagrams of the structure of the multi-order fractal geometry shape memory matrix 1, N=1 in Figure (C), N=2 in Figure (D), and N=3 in Figure (E), where N is the order; Figure (F) is a unit cell combination form of the first-order shape memory matrix 1 (N=1); Figures (G)-(I) are skeletons of unit cell assembly of the second-order shape memory matrix 1, n=2 in Figure (G), n=4 in Figure (H), and n=6 in Figure (I), where n represents the number of microstructures.

[0042] In this embodiment, there is no restriction on the shape of the first deformable structure 4, as long as the structure can achieve the height change of the electrode 2 through structural deformation, such as compression, stretching, etc., the height change range is 5μm-500μm. In some specific embodiments, the first deformable structure 4 is a column array structure with uniform diameter and height, and the structure is neat.

[0043] In some embodiments, the electrode 2 is a capacitive electrode 2, and the electrode 2 includes a first conductive film 21 and a second conductive film 22 that are relatively arranged, the first conductive film 21 is arranged above the second conductive film 22, and the first conductive film 21 includes a shape memory film with a first deformation structure 4 on the surface and a first conductive layer, the second conductive film 22 includes a planar shape memory film and a second conductive layer, and the first conductive layer and the second conductive layer are arranged relatively.

[0044] In some embodiments, the conductive layer, i.e., the first conductive layer and the second conductive layer, is made of a material selected from a flexible conductive silver paste, a flexible nano-gold, or a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) solution. In some preferred embodiments, the mass fraction of the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) solution is 1.5-30%, thereby ensuring the conductive effect.

[0045] In some embodiments, the shape memory flexible sensor further includes a waterproof layer 6 disposed above the electrode 2 , wherein the waterproof layer 6 is a shape memory film having a second deformation structure on its surface, and the waterproof layer 6 is disposed opposite to the first conductive film 21 .

[0046] Specifically, the waterproof layer 6 includes a second film layer and a second deformation structure arranged on the surface of the second film layer, and the shape memory film with the first deformation structure 4 on the surface includes a first film layer and the first deformation structure 4 arranged on the surface of the first film layer, and the positions of the waterproof layer 6 and the shape memory film with the first deformation structure 4 on the surface are from top to bottom: second deformation structure, second film layer, first film layer, first deformation structure 4.

[0047] In some preferred embodiments, the structure of the waterproof layer 6 is the same as the shape of the shape memory film with the first deformation structure 4 on the surface, wherein the second deformation structure is also a column array structure with a uniform diameter and height. Therefore, the waterproof layer 6 is set as the outermost layer of the shape memory flexible sensor, that is, the second deformation structure is on the outermost side, so that the shape memory flexible sensor as a whole has waterproof and anti-fouling properties, thereby improving the stability of the flexible sensor and extending its service life.

[0048] In some embodiments, the shape memory flexible sensor further comprises a sealing layer disposed below the electrode 2, and the sealing layer is made of polydimethylsiloxane, thereby ensuring the integrity of the structure.

[0049] In this embodiment, the shape memory matrix 1 in the shape memory flexible sensor is suitable for deforming under the action of external thermal stimulation and in-plane axial load, so that the shape memory flexible sensor changes from an initial state to a first temporary state, and is fixed in the first temporary state after cooling to room temperature; the electrode 2 in the shape memory flexible sensor is suitable for deforming under the action of external thermal stimulation and out-of-plane axial load, so that the shape memory flexible sensor changes from the initial state to a second temporary state, and is fixed in the second temporary state after cooling to room temperature.

[0050] Therefore, the flexible sensor of the shape memory matrix 1 in the first temporary state can have different mechanical properties from those in the initial state, and the flexible sensor in the second temporary state can have different electrical properties from those in the initial state, so as to meet different detection requirements.

[0051] In some specific embodiments, the materials of the shape memory matrix 1 and the shape memory film are selected from one or more of shape memory polyurethane resin, epoxy thermoplastic shape memory polymer, epoxy thermosetting shape memory polymer, styrene shape memory polymer, cyanate shape memory polymer, bismaleimide shape memory polymer, polyimide shape memory polymer, polycaprolactone shape memory polymer, polyurethane shape memory polymer or polylactic acid shape memory polymer.

[0052] Therefore, on the one hand, the shape memory substrate 1 of the shape memory flexible sensor in the present embodiment is a shape memory material having a negative Poisson's ratio structure, and its tensile expansion performance and bionic "J-shaped" σ-λ curve can improve the compliance when adhering to the skin surface and enhance the sensitivity to signal feedback. In addition, the present embodiment can undergo in-plane reconstruction under the action of external stimulation and in-plane axial load, and the present embodiment can adjust the mechanical properties of the flexible sensor according to the shape memory characteristics of the shape memory substrate 1 to adapt to the different mechanical properties of the part to be detected;

[0053] On the other hand, the electrode 2 of the shape memory flexible sensor in this embodiment includes a shape memory film with a first deformation structure 4 on the surface, which can undergo out-of-plane reconstruction under the action of external stimulation and out-of-plane axial load, and this embodiment can adjust the electrical properties of the flexible sensor according to the shape memory characteristics of the shape memory film with the first deformation structure 4 on the surface to adapt to the different electrical properties of the part to be detected; and compared with the flat electrode 2, its signal-to-noise ratio and sensitivity are significantly improved.

[0054] Another embodiment of the present invention provides a method for preparing a shape memory flexible sensor, comprising the following steps:

[0055] Step S1, preparing a shape memory matrix 1 by 4D printing;

[0056] Step S2, dissolving shape memory material particles in a carbon tetrachloride solution to obtain a mixed solution, spin-coating the mixed solution on a silicon wafer mold, and volatilizing at room temperature to obtain a planar shape memory film and a shape memory film having a first deformation structure 4 on the surface;

[0057] Step S3, spin-coating a conductive layer material on the surface of the shape memory film having the first deformation structure 4 on the surface to obtain a first conductive film 21 having a first conductive layer; spin-coating the conductive layer material on the surface of the planar shape memory film to obtain a second conductive film 22 having a second conductive layer, and arranging the first conductive layer of the first conductive film 21 and the second conductive layer of the second conductive film 22 opposite to each other in a positive direction to obtain an electrode 2;

[0058] Step S4, connecting the electrode 2 to the shape memory matrix 1.

[0059] In some preferred embodiments, in step S2, the silicon wafer mold used to prepare the shape memory film having the first deformation structure 4 on the surface is provided with a preset structure suitable for forming the first deformation structure 4, and the silicon wafer mold used to prepare the planar shape memory film is a planar silicon wafer mold.

[0060] In some preferred embodiments, the silicon wafer mold used to prepare the shape memory film having the first deformation structure 4 on the surface is made by photolithography, and the silicon wafer mold can ensure that the preset structure on the silicon wafer surface is completely transferred to the shape memory film surface after demolding, and when the first deformation structure 4 is a micro-column array structure, the prepared single columnar structure is a regular circular structure with a smooth surface, and there is no damage or lodging. In addition, in this embodiment, the spacing and geometric dimensions of the micro-column structure can be used as parameters for adjusting the electrical properties of the electrode 2.

[0061] The preparation method of the shape memory flexible sensor described in this embodiment is simple, and the preparation method of the shape memory flexible sensor described in this embodiment has the same advantages as the shape memory flexible sensor over the prior art, which will not be repeated here.

[0062] Yet another embodiment of the present invention provides an application of a shape memory flexible sensor, which is mainly manifested in that the shape memory flexible sensor is suitable for collecting health status information to achieve health monitoring.

[0063] The shape memory flexible sensor in this embodiment has the characteristics of high sensitivity, high signal-to-noise ratio, light weight and high flexibility. It broadens the application of shape memory polymer materials in flexible electronics, human-computer interaction and other fields, and provides ideas for the domestic application of shape memory polymer materials in health monitoring and other fields. It not only expands the application field of shape memory polymer materials, but also accelerates the progress of smart wearable electronic technology, which has a far-reaching impact on the development of domestic flexible electronics and science and technology.

[0064] The application of the shape memory flexible sensor of the present invention is the same as the advantages of the shape memory flexible sensor over the prior art, which will not be repeated here.

[0065] Example 1

[0066] like Figure 1 As shown, this embodiment provides a shape memory flexible sensor, including a waterproof layer 6, an electrode 2, a shape memory matrix 1 and a sealing layer arranged in sequence from top to bottom, and also includes an external wire 5 connected to the electrode 2. Among them, the shape memory matrix 1 is made of shape memory material by 4D printing, and the shape memory matrix 1 has a negative Poisson's ratio structure, and the electrode 2 includes a shape memory film and a conductive layer, and the conductive layer is arranged on the surface of the shape memory film.

[0067] Specifically, the electrode 2 includes a first conductive film 21 and a second conductive film 22 that are arranged opposite to each other, the first conductive film 21 is arranged above the second conductive film 22, and the first conductive film 21 includes a shape memory film with a first deformation structure 4 on the surface and a first conductive layer, the second conductive film 22 includes a planar shape memory film and a second conductive layer, and the first conductive layer and the second conductive layer are arranged opposite to each other.

[0068] In this embodiment, the waterproof layer 6 is a shape memory film with a second deformation structure on the surface, and the first deformation structure 4 and the second deformation structure are both column array structures with uniform diameter and height.

[0069] In this embodiment, the shape memory materials of the shape memory matrix 1, the shape memory film and the waterproof layer 6 are all selected from racemic polylactic acid (PDLLA) material; the conductive layer material is a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) solution (PEDOT:PSS) with a mass fraction of 10%.

[0070] The material of the sealing layer is polydimethylsiloxane.

[0071] It should be noted that in biointegration applications, the geometric parameters of the cellular substrate microstructure can be adjusted to match the mechanical properties of tissue or skin, thereby improving biocompatibility and compliance. The network design can achieve a precise match of the J-shaped stress-strain curve of human skin in different regions (e.g., the back and abdominal regions). In this network design, the geometry or lattice topology of the horseshoe-shaped microstructure of the epoxy polymer can be used to produce the desired nonlinear mechanical response. Therefore, the "J-shaped" stress-strain behavior can be controlled by inverse design of the geometric parameters to accurately match the parameters of human skin or other biological tissues.

[0072] Therefore, if Figure 6 and Figure 7 As shown, Figure 6 The σ-λ curves of the shape memory matrix 1 with different geometric parameters in the 0° direction are given, where: Figure 6 (a) shows the σ-λ curve of the first-order shape memory matrix 1 at 0° direction with different geometric parameters. Figure 6 (b) and 6(c) give the σ-λ curves of the second-order shape memory matrix 1 under different n; Figure 7 A schematic diagram of the deformation state of the shape memory matrix 1 is given, where Figure 7 (a)-(c) are schematic diagrams of the deformation modes of first-order metamaterials Figure 7 (d)-(i) are schematic diagrams of multi-step deformation modes of the second-order metamaterial. This embodiment illustrates the deformation process of the shape memory matrix 1 through a σ-λ curve diagram and a deformation state schematic diagram.

[0073] like Figure 6 (a), the first-order shape memory matrix 1 undergoes two-phase deformation (such as Figure 7 After (a)-(c), a "j-type" σ-λ curve is formed, and under small strain, the shape memory matrix 1 first experiences a bending-dominated phase (phase I), and the curved filamentous microstructure gradually unfolds with the increase of λ. In phase I, the σ-λ curve shows a lower stress increase rate with the increase of λ, indicating that the equivalent elastic modulus is low at this time, and an obvious rapid growth stage occurs when the curved filamentous tissue is stretched into a straight line. Subsequently, the shape memory matrix 1 enters a deformation stage dominated by stretching (phase II), and the filamentous structure is completely stretched into a straight line. At this time, the "j"-type σ-λ curve enters a linear hardening stage, and the stress of the σ-λ curve increases rapidly, showing a higher equivalent elastic modulus.

[0074] like Figure 6 (b) and 6(c), for the second-order fractal shape memory matrix 1, its deformation mode is significantly different from that of the first-order shape memory matrix 1, which can be based on Figure 7 The two critical relative strains shown in (d)-(i) divide it into three deformation stages. The first and second stages are mainly bending. In the first stage, as λ increases, the first-order morphological structure in the second-order structure gradually unfolds, accompanied by slight deformation of the second-order morphological structure until the first-order morphological structure is fully unfolded; when the deformation continues to increase, the secondary filamentous microstructure gradually flattens.

[0075] In addition, if Figure 7 It can be seen that the modulus of the second-order structure is smaller than that of the first-order structure, and the stiffness decreases with the increase of n. When θ = 90°, the arc in the unit cell is the smallest, so its effective stiffness is the largest, and as n increases, the effective stiffness first decreases and then increases.

[0076] In order to demonstrate the effect of the shape memory film with a column array structure on the performance of the electrode 2, this embodiment Figure 8The schematic diagram of radial artery pulse and capacitance response wave of shape memory flexible sensor using electrode 2 with different deformation structures on the surface is given, where (a) is a planar electrode 2 made of shape memory film with planar structure, (b) is a micro-pillar electrode 2 made of shape memory film with column array structure (micro-pillar structure III) on the surface, the spacing between each micro-pillar is 30μm, (c) is a micro-pillar electrode 2 made of shape memory film with column array structure (micro-pillar structure II) on the surface, the spacing between each micro-pillar is 20μm, and (d) is a micro-pillar electrode 2 made of shape memory film with column array structure (micro-pillar structure I) on the surface, the spacing between each micro-pillar is 10μm. The image shows the sensitivity of the four devices, where the larger the sensitivity coefficient, the higher the sensitivity. It can be seen that the sensitivity of the shape memory flexible sensor with micro-pillar electrode 2 is greater than that of the shape memory flexible sensor with planar electrode 2, and the smaller the micro-pillar spacing, the greater the sensitivity of the shape memory flexible sensor.

[0077] Therefore, the shape memory flexible sensor in this embodiment can adjust the mechanical and electrical properties of the shape memory flexible sensor through the geometric parameters and topological structure of the shape memory substrate 1, the geometric morphology of the shape memory film with the first deformation structure 4 on the surface, and the geometric parameters of the first deformation structure 4 (micro-column spacing, diameter, height), etc.

[0078] This embodiment Fig. 9 Schematic diagrams of the deformation states of the shape memory flexible sensor are given, where Ⅰ) is the out-of-plane reconstruction mode, Ⅱ) is the in-plane reconstruction mode, (A) is the structural schematic diagram of the original state; (B) is the structural schematic diagram of the temporary shape; (C) is the structural schematic diagram of the original state after restoration; (D) is the SEM image of the original state; (E) is the SEM image of the second temporary shape; (F) is the SEM image of the original state after restoration.

[0079] like Figure 2-4As shown, specifically, in the initial state, the shape memory matrix 1 of the shape memory flexible sensor is in a natural state, and the column array structure is in an upright state. When the shape memory flexible sensor is heated to a glass transition temperature of 55°C or higher and subjected to uniaxial stretching, the shape memory flexible sensor enters an in-plane reconstruction mode, and the shape memory matrix 1 is deformed, so that the shape memory flexible sensor changes from the initial state to a first temporary state, and is fixed in the first temporary state after cooling to room temperature. At this time, the shape memory matrix 1 is in a stretched state, and the column array structure is still in an upright state. When heated again to a glass transition temperature of 55°C or higher, the shape memory flexible sensor enters an in-plane reconstruction mode. The shape memory flexible sensor recovers from a first temporary state to an initial state; when the shape memory flexible sensor is heated to a glass transition temperature of above 55°C and is subjected to an out-of-plane uniform load, the shape memory flexible sensor enters an out-of-plane reconstruction mode, and the electrode 2 in the shape memory flexible sensor is deformed, so that the shape memory flexible sensor changes from the initial state to a second temporary state, and is fixed in the second temporary state after cooling to room temperature. At this time, the shape memory matrix 1 is in a natural state, and the column array structure is still in a lodging state. When heated to a glass transition temperature of above 55°C again, the shape memory flexible sensor recovers from the second temporary state to the initial state.

[0080] In this embodiment, the flexible sensor of the shape memory matrix 1 in the first temporary state can have different mechanical properties from those in the initial state, and the flexible sensor in the second temporary state can have different electrical properties from those in the initial state, so as to meet different detection requirements.

[0081] Example 2

[0082] This embodiment provides a shape memory flexible sensor, which is different from the embodiment 1 in that:

[0083] In this embodiment, the shape memory substrate 1, the shape memory film and the shape memory material of the waterproof layer 6 can be replaced by one of shape memory polyurethane resin, epoxy thermoplastic shape memory polymer, epoxy thermosetting shape memory polymer, styrene shape memory polymer, cyanate shape memory polymer, bismaleimide shape memory polymer, polyimide shape memory polymer, polycaprolactone shape memory polymer and polyurethane shape memory polymer; the conductive layer material can be replaced by one of flexible conductive silver paste or flexible nano gold.

[0084] In the shape memory flexible sensor of this embodiment, in the initial state, the shape memory matrix 1 of the shape memory flexible sensor is in a natural state, and the first deformation structure 4 is in an upright state. When the shape memory flexible sensor is heated to above the glass transition temperature of the shape memory material and subjected to uniaxial stretching, the shape memory flexible sensor enters an in-plane reconstruction mode, and the shape memory matrix 1 is deformed, so that the shape memory flexible sensor changes from the initial state to a first temporary state, and is fixed in the first temporary state after cooling to room temperature. At this time, the shape memory matrix 1 is in a stretched state, and the first deformation structure 4 is still in an upright state. When heated again to above the glass transition temperature of the shape memory material, the The shape memory flexible sensor recovers from a first temporary state to an initial state; when the shape memory flexible sensor is heated to above the glass transition temperature of the shape memory material and is subjected to an out-of-plane uniform load, the shape memory flexible sensor enters an out-of-plane reconstruction mode, and the electrode 2 in the shape memory flexible sensor is deformed, so that the shape memory flexible sensor changes from the initial state to a second temporary state, and is fixed in the second temporary state after cooling to room temperature. At this time, the shape memory matrix 1 is in a natural state, and the first deformation structure 4 is still in a prostrated state. When heated again to above the glass transition temperature of the shape memory material, the shape memory flexible sensor recovers from the second temporary state to the initial state.

[0085] In this embodiment, the flexible sensor of the shape memory matrix 1 in the first temporary state can have different mechanical properties from those in the initial state, and the flexible sensor in the second temporary state can have different electrical properties from those in the initial state, so as to meet different detection requirements.

[0086] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A shape memory flexible sensor, characterized in that: The invention comprises a shape memory matrix (1) and an electrode (2) arranged above the shape memory matrix (1), wherein the shape memory matrix (1) is made of a shape memory material by 4D printing, and the shape memory matrix (1) has a negative Poisson's ratio structure, the electrode (2) comprises a shape memory film and a conductive layer, the conductive layer is arranged on the surface of the shape memory film, and the shape memory film comprises a shape memory film with a first deformation structure (4) on the surface, the electrode (2) comprises a first conductive film (21) and a second conductive film (22) arranged opposite to each other, the first conductive film (21) is arranged above the second conductive film (22), and the first conductive film (21) comprises the shape memory film with the first deformation structure (4) on the surface and the first conductive layer, the second conductive film (22) comprises a planar shape memory film and a second conductive layer, and the first conductive layer and the second conductive layer are arranged opposite to each other.

2. The shape memory flexible sensor according to claim 1, characterized in that: It also comprises a waterproof layer (6) arranged above the electrode (2), the waterproof layer (6) being a shape memory film with a second deformation structure on its surface, and the waterproof layer (6) and the first conductive film (21) are arranged in the opposite directions.

3. The shape memory flexible sensor according to claim 1, characterized in that: It also includes a sealing layer arranged below the electrode (2), and the material of the sealing layer is polydimethylsiloxane.

4. The shape memory flexible sensor according to claim 1, characterized in that: The shape memory substrate (1) in the shape memory flexible sensor is suitable for deforming under the action of external thermal stimulation and in-plane axial load, so that the shape memory flexible sensor changes from an initial state to a first temporary state, and is fixed in the first temporary state after cooling to room temperature; The electrode (2) in the shape memory flexible sensor is suitable for deforming under the action of external thermal stimulation and out-of-plane axial load, so that the shape memory flexible sensor changes from the initial state to a second temporary state, and is fixed in the second temporary state after cooling to room temperature.

5. The shape memory flexible sensor according to claim 1, characterized in that: The material of the shape memory matrix (1) and the shape memory film is selected from one or more of shape memory polyurethane resin, epoxy-based thermoplastic shape memory polymer, epoxy-based thermosetting shape memory polymer, styrene-based shape memory polymer, cyanate-based shape memory polymer, bismaleimide shape memory polymer, polyimide shape memory polymer, polycaprolactone-based shape memory polymer, polyurethane-based shape memory polymer or polylactic acid-based shape memory polymer.

6. The shape memory flexible sensor according to claim 1, characterized in that: The material of the conductive layer is selected from one of flexible conductive silver paste, flexible nano-gold or poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) solution.

7. A method for preparing a shape memory flexible sensor as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1, preparing a shape memory matrix (1) by 4D printing; Step S2, dissolving shape memory material particles in a carbon tetrachloride solution to obtain a mixed solution, spin-coating the mixed solution on a silicon wafer mold, and volatilizing at room temperature to obtain a planar shape memory film and a shape memory film having a first deformation structure (4) on the surface; Step S3, spin-coating a conductive layer material onto the surface of the shape memory film having the first deformation structure (4) on the surface, to obtain a first conductive film (21) having a first conductive layer; spin-coating the conductive layer material onto the surface of the planar shape memory film, to obtain a second conductive film (22) having a second conductive layer, and arranging the first conductive layer of the first conductive film (21) and the second conductive layer of the second conductive film (22) opposite to each other in a positive direction, to obtain an electrode (2); Step S4, connecting the electrode (2) to the shape memory matrix (1).

8. The method for preparing the shape memory flexible sensor according to claim 7, characterized in that: In step S2, the silicon wafer mold used to prepare the shape memory film having the first deformation structure (4) on the surface is provided with a preset structure suitable for forming the first deformation structure (4), and the silicon wafer mold used to prepare the planar shape memory film is a planar silicon wafer mold.

9. An application of the shape memory flexible sensor as claimed in any one of claims 1 to 6, characterized in that: Shape memory flexible sensors are suitable for collecting health status information to achieve health monitoring.

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