Embedded liquid metal microstructure electrode, flexible pressure sensor array and preparation method

Abstract

The invention discloses an embedded liquid metal microstructure electrode, a flexible pressure sensor array and a preparation method. The technical problems that an existing flexible pressure sensor array is low in sensitivity, large in crosstalk and the like are solved. Wherein the embedded liquid metal microstructure electrode comprises a first flexible substrate, a first liquid metal layer and a first packaging layer; the lower surface of the first flexible substrate is a plane, and a plurality of micro-cone structures arranged in an array are uniformly distributed on the upper surface of the first flexible substrate; the cone part of each micro-cone structure faces upwards and is flush with the upper surface of the first flexible substrate; the first liquid metal layer covers the upper surface of the first flexible substrate and all the micro-cone structures; the first packaging layer covers one surface, far away from the upper surface of the first flexible substrate, of the first liquid metal layer; meanwhile, the invention further provides a preparation method of the microstructure electrode, a flexible pressure sensor array based on the microstructure electrode and a preparation method of the flexible pressure sensor array, and the flexible pressure sensor array is high in sensitivity and low in crosstalk.

Description

Technical Field

[0001] The present invention relates to flexible electronic technology, and in particular to an embedded liquid metal microstructure electrode, a flexible pressure sensor array and a preparation method thereof. Background Art

[0002] With the development of electronic technology, flexible wearable devices have become the main direction of future electronic device development. Among them, flexible pressure sensors or flexible tactile electronic skins have great potential in robot tactile perception, wearable electronic devices and smart medical care. Flexible pressure sensors or flexible tactile electronic skins can convert external physical stimuli into electrical signals, simulating the mechanical pressure stimulation of the external environment perceived by human skin, thereby maintaining the same flexibility and stretchability as natural human skin. Taking flexible pressure sensors as an example, they are composed of flexible substrates and flexible electrode materials, with good ductility and the ability to maintain good conductivity when subjected to repeated deformation. In recent years, researchers have used a liquid metal material, gallium-based alloys, as flexible electrode materials. Taking gallium-indium alloys as an example, the melting point of this liquid metal is lower than 30°C, it is in a liquid state at room temperature, and has good electrical and thermal conductivity; in addition, gallium-indium alloys are non-toxic and harmless to the human body, so they can be used to make flexible pressure sensors.

[0003] Among the many flexible pressure sensors, capacitive pressure sensors are widely praised for their simple design, excellent stability, low power consumption and temperature independence. In addition, since the preparation of microstructured electrodes can significantly improve the pressure sensitivity of the electrodes, liquid metal-based microstructured electrodes (introducing microstructures onto flexible substrates and then covering liquid metal on the microstructures to form liquid metal microstructured electrodes) can effectively improve the sensitivity of flexible pressure sensors. However, since liquid metal is an amorphous liquid phase and is wrapped by external gallium oxide, it is difficult to print liquid metal on rough structures with micrometer or nanometer scales. Most studies use metal-philic rigid metals such as copper or gold as an intermediate layer to improve the affinity between liquid metal and substrate, but since rigid metals affect the inherent tensile properties of liquid metals, this method greatly limits the ductility of flexible pressure sensors.

[0004] In addition, in order to meet more complex application scenarios, flexible pressure sensors must not only have high pressure sensitivity, but also have the stability of the sensor's signal output under various deformation conditions. Existing flexible pressure sensors (or electronic skins) usually adopt a multi-layer stacked structure. However, during bending, torsion, and stretching, insufficient adhesion strength between interfaces will affect signal stability, making it easy for the interface layers to separate, resulting in relative displacement of pixels and subsequent signal distortion. Therefore, devices corresponding to this type of electronic skin face the challenge of working effectively under complex mechanical deformations, such as the operation of robots recognizing curved patterns (which requires the sensor to deform to make conformal contact on the surface).

[0005] In addition, arrayed pressure sensors also need to minimize crosstalk between pixels to ensure accurate measurement. Typically, signal crosstalk occurs between sensing units due to stress dispersion caused by their shared plane. When a pixel is subjected to external pressure, its deformation inevitably propagates to the surrounding area, causing responses from neighboring pixels. Although system calibration is often used to mitigate unwanted signals, it also requires complex circuits and additional energy consumption.

[0006] In summary, the existing flexible pressure sensor arrays have problems such as low sensitivity, instability under mechanical deformation, and large crosstalk. Summary of the invention

[0007] The purpose of the present invention is to solve the technical problems of low sensitivity, instability under mechanical deformation, large crosstalk and the like of the existing flexible pressure sensor array, and to provide an embedded liquid metal microstructure electrode, a flexible pressure sensor array and a preparation method.

[0008] To achieve the above invention objectives, the technical solutions provided by the present invention are as follows:

[0009] The present invention provides an embedded liquid metal microstructure electrode, which is special in that:

[0010] It includes a first flexible substrate, a first liquid metal layer and a first packaging layer;

[0011] The lower surface of the first flexible substrate is a plane, and the upper surface is in a groove shape, and the groove is provided with a plurality of micro-cone structures arranged in an array; the cone portion of each micro-cone structure faces upward and is flush with the upper surface of the first flexible substrate;

[0012] The first liquid metal layer is located on the upper surface of the first flexible substrate and covers all micro-cone structures;

[0013] The first packaging layer covers the surface of the first liquid metal layer.

[0014] Furthermore, the height of the micro-cone structure area is

[0015] The material of the first flexible substrate is PDMS or silicone material;

[0016] The material of the first liquid metal layer is gallium-based alloy.

[0017] The present invention also provides a method for preparing the above-mentioned embedded liquid metal microstructure electrode, comprising the following steps:

[0018] Step [1] processing a metal mask with a hollow electrode pattern;

[0019] Step [2] preparing a first flexible substrate and attaching a sacrificial layer to the upper surface of the first flexible substrate;

[0020] Step [3] Processing the embedded micro-cone structure on the first flexible substrate

[0021] 3.1) placing the first flexible substrate on the two-dimensional platform of the femtosecond laser lens system;

[0022] 3.2) placing the metal mask obtained in step 1] on the first flexible substrate attached with the sacrificial layer, and focusing the femtosecond laser on the sacrificial layer through a lens;

[0023] 3.3) Set up the bow-shaped scanning program for the two-dimensional platform;

[0024] 3.4) Based on the scanning program set in step 3.3), the two-dimensional platform is controlled to move, and the femtosecond laser ablates a plurality of patterned embedded micro-cone structures extending to the upper surface of the first flexible substrate on the sacrificial layer through the hollow electrode pattern on the metal mask;

[0025] Step [4] Preparation of embedded liquid metal microstructure electrodes

[0026] 4.1) performing oxygen plasma surface hydrophilic modification treatment on the first flexible substrate processed in step 3.4);

[0027] 4.2) Wetting the upper surface of the first flexible substrate after the hydrophilic modification with deionized water so that the deionized water covers each micro-cone structure;

[0028] 4.3) dripping liquid metal so that it covers the upper surface of deionized water;

[0029] 4.4) dripping the hydrogel solution on the upper surface of the liquid metal so that the hydrogel solution completely covers the liquid metal;

[0030] 4.5) drying the first flexible substrate on which the hydrogel solution and the liquid metal are drop-coated, so that the hydrogel solution solidifies, the deionized water evaporates, and the liquid metal covers all the micro-cone structures to form a first liquid metal layer;

[0031] 4.6) sequentially tearing off the solidified hydrogel, absorbing the excess liquid metal on the surface of the first flexible substrate, tearing off the sacrificial layer, and then encapsulating to obtain a patterned embedded liquid metal microstructure electrode.

[0032] Furthermore, step [1] is specifically as follows:

[0033] 1.1) Prepare a metal film and place it on the processing platform of the femtosecond laser galvanometer system;

[0034] 1.2) Adjust the height of the processing platform so that the femtosecond laser is focused on the metal film through the galvanometer;

[0035] 1.3) Draw the electrode pattern to be processed in the background program of the femtosecond laser galvanometer system, and set the processing program corresponding to the electrode pattern; the scanning speed of the femtosecond laser galvanometer system is 0.1-10 mm / s;

[0036] 1.4) Based on the processing program set in step 1.3), a femtosecond laser is controlled to cut an electrode pattern on the metal film to form a metal mask with a hollow electrode pattern; the central wavelength of the femtosecond laser is 325nm to 1200nm, the pulse width is 30fs to 150fs, the repetition frequency is 10Hz to 100KHz, and the laser power is 100mW to 1000mW.

[0037] Furthermore, in step [2], the material of the first flexible substrate is PDMS or silicone material; the sacrificial layer is polyethylene terephthalate tape, and its thickness is 10 μm to 50 μm;

[0038] In step 3.4), the moving speed of the two-dimensional platform is 0.1-10 mm / s; the central wavelength of the femtosecond laser is 325 nm-1200 nm, the pulse width is 30 fs-150 fs, the repetition frequency is 10 Hz-100 KHz, and the laser power is 100 mW-1000 mW;

[0039] In step 4.3), the liquid metal is a gallium-based alloy, and the thickness of the drop coating is 2 to 5 mm;

[0040] In step 4.4), the hydrogel solution is a polyvinyl alcohol solution with a mass ratio of 5 to 20%, and the thickness of the drop coating is 0.5 to 2 mm.

[0041] At the same time, the present invention also provides a flexible pressure sensor array, which is special in that it includes a liquid metal flat plate electrode and the aforementioned embedded liquid metal microstructure electrode;

[0042] The liquid metal flat plate electrode comprises a second flexible substrate, a second liquid metal layer and a second packaging layer;

[0043] The second flexible substrate has the same size as the first flexible substrate, and a plurality of protrusions are evenly distributed on the upper surface of the second flexible substrate;

[0044] The second liquid metal layer includes a plurality of liquid metal regions, which are arranged in an array and disposed on the lower surface of the second flexible substrate; positions of the plurality of liquid metal regions correspond one-to-one to positions of the plurality of micro-cone structures;

[0045] The second encapsulation layer covers the second liquid metal layer and the lower surface of the second flexible substrate;

[0046] The first encapsulation layer and the second encapsulation layer are assembled by plasma bonding.

[0047] Furthermore, anti-adhesion particles are sprayed between the first encapsulation layer and the second encapsulation layer and are located between each liquid metal area and the corresponding micro-cone structure.

[0048] At the same time, the present invention also provides a method for preparing the above-mentioned flexible pressure sensor array, comprising the following steps:

[0049] Step 1: Preparation of embedded liquid metal microstructure electrodes

[0050] The corresponding embedded liquid metal microstructure electrode is prepared according to the aforementioned method for preparing the embedded liquid metal microstructure electrode;

[0051] Step 2: Preparation of liquid metal flat electrode

[0052] 2.1) preparing a second flexible substrate and placing it on the processing platform of the femtosecond laser galvanometer system;

[0053] 2.2) adjusting the height of the processing platform so that the femtosecond laser is focused on the upper surface of the second flexible substrate through the galvanometer;

[0054] 2.3) Draw a convex pattern in the background program of the femtosecond laser galvanometer system, and set the processing program corresponding to the convex pattern;

[0055] 2.4) controlling the movement of the processing platform according to the processing program set in step 2.3), so that the femtosecond laser processes a convex structure on the upper surface of the flexible substrate;

[0056] 2.5) using the same metal mask as that used to prepare the embedded liquid metal microstructure electrode, applying the liquid metal to the lower surface of the second flexible substrate by template printing, thereby forming a second liquid metal layer;

[0057] 2.6) encapsulating the lower surface of the second flexible substrate having the second liquid metal layer, thereby obtaining a liquid metal flat plate electrode;

[0058] Step 3: Assemble the embedded liquid metal microstructure electrode prepared in step 1 and the liquid metal flat electrode obtained in step 2.6) to obtain a flexible pressure sensor array.

[0059] Furthermore, step three is specifically as follows:

[0060] 3.1) performing oxygen plasma surface modification treatment on the embedded liquid metal microstructure electrode prepared in step 1 and the liquid metal flat plate electrode obtained in step 2.6);

[0061] 3.2) Bringing the first encapsulation layer and the second encapsulation layer close to each other and spraying anti-adhesion particles between the two; the anti-adhesion particles are located between each liquid metal area and the corresponding micro-cone structure;

[0062] 3.3) The first packaging layer and the second packaging layer are laminated together so as to obtain a flexible pressure sensor array with embedded liquid metal microstructures.

[0063] Furthermore, in step 3.2), the anti-adhesion particles are SiO2 nanoparticles, and the diameter of a single particle is 10nm to 100nm.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] 1. The present invention introduces a micro-cone structure and a first liquid metal layer on a first flexible substrate to obtain an embedded liquid metal microstructure electrode. Compared with using copper and gold with affinity for liquid metal as an intermediate layer to improve the surface affinity between the liquid metal and the substrate, the present application introduces the micro-cone structure, so that the flexibility of the electrode is not affected by the rigid metal material, and the mechanical stability and pressure sensitivity are significantly improved.

[0066] 2. The flexible pressure sensor of the present invention is based on an embedded liquid metal microstructure electrode. Due to the introduction of the microstructure electrode, the sensitivity of the flexible pressure sensor is greatly improved.

[0067] 3. The pressure sensor array prepared by the present invention has strong interface adhesion and can work stably under deformation such as bending, stretching, and torsion without problems such as delamination and pixel misalignment.

[0068] 4. The pressure sensor array prepared by the present invention has low signal crosstalk and does not require additional complex circuit algorithms to process and filter signals, thereby saving system costs and improving response speed.

[0069] 5. The present invention addresses the shortcomings of the current flexible sensor array in terms of flexibility and stability, which is limited to the recognition of planar patterns. The high-performance pressure sensor array prepared by the present invention can realize the accurate recognition of curved surface patterns. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic structural diagram of an embodiment of an embedded liquid metal microstructure electrode of the present invention.

[0071] Figure 2 It is a schematic diagram of the process of an embodiment of the method for preparing an embedded liquid metal microstructure electrode of the present invention.

[0072] Figure 3 The figures are electron microscope images and actual objects of each layer structure in the embodiment of the embedded liquid metal microstructure electrode of the present invention, wherein: (a) is an electron microscope image of PDMS, (b) is an actual image of PDMS; (c) is an electron microscope image of PDMS with liquid metal added, (d) is an actual image of PDMS with liquid metal added; (e) is an electron microscope image of PDMS after encapsulation, and (f) is an actual image of PDMS after encapsulation.

[0073] Figure 4 These are physical pictures of the embedded liquid metal microstructure electrode of the present invention, wherein (a) is a physical picture of the embedded PDMS microcone structure, and (b) is a physical picture of the embedded liquid metal microstructure electrode.

[0074] Figure 5 It is a schematic structural diagram of an embodiment of a flexible pressure sensor array of the present invention.

[0075] Figure 6 It is a schematic diagram of the process of an embodiment of a method for preparing a flexible pressure sensor array of the present invention.

[0076] Figure 7 Schematic diagram of the layered structure of the flexible pressure sensor array embodiment of the present invention.

[0077] Figure 8 These are actual pictures of the flexible pressure sensor array of the present invention under different deformations, wherein (a) is a picture of the flattened state, (b) is a picture of the stretched state, and (c) is a picture of the bent state.

[0078] Fig. 9 It is a comparison diagram of the anti-crosstalk capability of the flexible pressure sensor array of the present invention and the traditional sensor array, wherein (a) is a schematic diagram of the anti-crosstalk capability of the traditional sensor array, and (b) is a schematic diagram of the anti-crosstalk capability of the flexible pressure sensor array of the present invention.

[0079] Fig.10 It is a pressure signal mapping diagram of the flexible pressure sensor array of the present invention to the 3D printed spherical model; wherein, (a) is a 3D printed spherical model diagram with the curved letter "SOFT", and (b) is a dynamic process diagram of the pressure signal mapping of the flexible pressure sensor array of the present invention to the curved letter "S".

[0080] Fig.11 This is a capacitance signal mapping diagram of the curved letter “SOFT” by the flexible pressure sensor array of the present invention.

[0081] The reference numerals are as follows:

[0082] 1-first flexible substrate, 2-first liquid metal layer, 3-first encapsulation layer, 4-micro-cone structure, 5-second flexible substrate, 6-second liquid metal layer, 7-second encapsulation layer, 8-protrusion. DETAILED DESCRIPTION

[0083] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0084] Reference Figure 1 This embodiment provides an embedded liquid metal microstructure electrode, including a first flexible substrate 1, a first liquid metal layer 2 and a first packaging layer 3.

[0085] The first flexible substrate 1 is a polymer material with high ductility, such as PDMS (polydimethylsiloxane) or a silicone film-like flexible polymer. The lower surface of the first flexible substrate 1 is flat, and the upper surface is in a groove shape. A plurality of micro-cone structures 4 arranged in an array are arranged in the groove. The cone of each micro-cone structure 4 faces upward and is flush with the upper surface of the first flexible substrate 1. Generally, the height of the micro-cone structure 4 is 1 / 2 of the thickness of the first flexible substrate 1. The height of the micro-cone structure 4 can be determined according to actual needs, and the position and number of the micro-cone structure 4 can be set.

[0086] The first liquid metal layer 2 is a metal material that is liquid at room temperature (melting point is lower than 30° C.), which covers the upper surface of the first flexible substrate 1 and all micro-cone structures 4. The first liquid metal layer 2 of this embodiment is a gallium-based alloy, such as gallium-indium alloy, gallium-indium-tin alloy, etc.

[0087] The first encapsulation layer 3 covers the surface of the first liquid metal layer 2 and is used to protect the first liquid metal layer 2 .

[0088] Reference Figure 2 , Figure 3 , the preparation method of the above embedded liquid metal microstructure electrode is as follows:

[0089] Step [1] Processing a metal mask with a hollow electrode pattern

[0090] 1.1) Prepare a metal film and place it on the processing platform of the femtosecond laser galvanometer system.

[0091] 1.2) Adjust the height of the processing platform so that the femtosecond laser can be focused onto the metal film through the galvanometer.

[0092] 1.3) Draw the electrode pattern to be processed in the background program of the femtosecond laser galvanometer system, and set the processing program corresponding to the electrode pattern. The scanning speed of the femtosecond laser galvanometer system is 0.1-10 mm / s.

[0093] 1.4) Based on the processing program set in step 1.3), a femtosecond laser is controlled to cut an electrode pattern on the metal film to form a metal mask with a hollow electrode pattern.

[0094] In step 1.4), the central wavelength of the femtosecond laser is 325nm-1200nm, the pulse width is 30fs-150fs, the repetition frequency is 10Hz-100KHz, and the laser power is 100mW-1000mW.

[0095] Step [2]: Prepare a first flexible substrate 1 and attach a sacrificial layer to the upper surface of the first flexible substrate 1.

[0096] In this embodiment, the material of the first flexible substrate 1 is PDMS or silicone material; the sacrificial layer is PET (polyethylene terephthalate) tape, and its thickness is generally 10 μm to 50 μm.

[0097] Step [3]: Processing the embedded micro-cone structure 4 on the upper surface of the first flexible substrate 1.

[0098] 3.1) Placing the first flexible substrate 1 on the two-dimensional platform of the femtosecond laser lens system.

[0099] 3.2) The metal mask obtained in step 1.4) is placed on the first flexible substrate 1 attached with the sacrificial layer, and the femtosecond laser is focused on the sacrificial layer through a lens.

[0100] 3.3) Set up the bow-shaped scanning program for the two-dimensional platform.

[0101] 3.4) Based on the scanning program set in step 3.3), the two-dimensional platform is controlled to move, and the femtosecond laser ablates a plurality of patterned embedded micro-cone structures 4 extending to the upper surface of the first flexible substrate 1 on the sacrificial layer through the hollow electrode pattern on the metal mask.

[0102] In this embodiment, the moving speed of the two-dimensional platform is in the range of 0.1 to 10 mm / s; the central wavelength of the femtosecond laser is 325 nm to 1200 nm, the pulse width is 30 fs to 150 fs, the repetition frequency is 10 Hz to 100 KHz, and the laser power is 100 mW to 1000 mW.

[0103] This embodiment adopts the laser direct writing method, and the process is that the femtosecond laser directly scans the surface of the flexible substrate, which greatly reduces the processing time. The structure after laser direct writing is a micro-groove type, and a micro-cone structure 4 is formed after horizontal and vertical cross scanning. The moving speed of the two-dimensional platform and the laser power simultaneously affect the height of the micro-cone structure 4. By adjusting the moving speed and laser power, the height of the micro-cone can reach 50 to 500 μm.

[0104] Step [4] Prepare the embedded liquid metal microstructure electrode using water / hydrogel-assisted patterning method.

[0105] 4.1) The first flexible substrate 1 processed in step 3.4) is subjected to oxygen plasma surface hydrophilic modification treatment.

[0106] 4.2) Wetting the upper surface of the first flexible substrate 1 after the hydrophilic modification with deionized water, so that the deionized water covers each micro-cone structure 4 .

[0107] 4.3) Liquid metal is dripped to cover the upper surface of deionized water. The liquid metal is a gallium-based alloy, and the thickness of the dripping is 2 to 5 mm.

[0108] 4.4) Apply a drop of hydrogel solution on the upper surface of the liquid metal to completely cover the liquid metal.

[0109] In this embodiment, the hydrogel solution is a polyvinyl alcohol (PVA) solution with a mass ratio of 5 to 20%, and the thickness of the drop coating is 0.5 to 2 mm.

[0110] 4.5) The first flexible substrate 1 coated with the hydrogel solution and the liquid metal is placed in an oven for drying, so that the hydrogel solution solidifies, the deionized water evaporates, and the liquid metal covers all the micro-cone structures 4 to form a first liquid metal layer 2.

[0111] 4.6) Sequentially tear off the solidified hydrogel, absorb the excess liquid metal on the surface of the first flexible substrate 1, tear off the sacrificial layer, and then encapsulate to obtain a patterned embedded liquid metal microstructure electrode.

[0112] Figure 4 In the figure, (a) is a physical picture of the original embedded PDMS micro-cone substrate, and (b) is a physical picture of the embedded microstructure liquid metal electrode after covering with liquid metal. The coverage of liquid metal is relatively uniform.

[0113] The present invention induces microstructures on the surface of a flexible substrate by using a femtosecond laser. The pulse width of the femtosecond laser is extremely short (10 -15 ), extremely high peak power density (~10 15 W / cm 2 ), and the minimum spot size can reach hundreds of nanometers, with the ability of high-precision processing, so that a very high integration electrode pattern can be prepared. This method breaks through the limitation of liquid metal wettability on rough surfaces and prepares embedded microstructured liquid electrodes, which significantly improve the mechanical stability and pressure sensitivity of the electrode. After the flexible material substrate with circuit patterns is modified by surface oxygen plasma, it can be bonded and assembled to form a high-performance capacitive pressure sensor array.

[0114] Therefore, refer to Figure 5 This embodiment also provides a flexible pressure sensor array, including a liquid metal flat electrode and an embedded liquid metal microstructure electrode, wherein the liquid metal flat electrode includes a second flexible substrate 5, a second liquid metal layer 6 and a second packaging layer 7.

[0115] The material and size of the second flexible substrate 5 are the same as those of the first flexible substrate 1 , and a plurality of protrusions 8 (ie, bumps) are evenly distributed on the upper surface of the second flexible substrate 5 .

[0116] The second liquid metal layer 6 includes a plurality of liquid metal regions arranged in an array and disposed on the lower surface of the second flexible substrate 5; the positions of the plurality of liquid metal regions correspond one-to-one to the positions of the plurality of micro-cone structures 4. The material of the second liquid metal layer 6 is the same as that of the first liquid metal layer 2.

[0117] The second encapsulation layer 7 covers the lower surface of the second liquid metal layer 6 and the second flexible substrate 5 .

[0118] Anti-adhesion particles are sprayed between the first encapsulation layer 3 and the second encapsulation layer 7, which are located between each liquid metal area and the corresponding micro-cone structure 4. Afterwards, the first encapsulation layer 3 and the second encapsulation layer 7 are assembled by plasma bonding to form a flexible pressure sensor array.

[0119] The flexible pressure sensor array of this embodiment uses liquid metal as a flexible electrode material, a thin packaging layer of flexible substrate material and silicon dioxide nanoparticles as a dielectric layer to form a capacitive structure. All materials used in the sensor are extremely ductile materials, so the sensor itself has good flexibility and ductility. The upper layer of the sensor structure contains liquid metal flat electrodes, and the lower layer contains embedded liquid metal microstructure electrodes. After the upper and lower layers are bonded and assembled, the interfaces between the sensor array units are bonded together, and there is a large interface adhesion strength, so it can remain stable under various deformation conditions.

[0120] To this end, combined Figure 6 , Figure 7 This embodiment provides a method for preparing a flexible pressure sensor array, comprising the following steps:

[0121] Step 1: Preparation of embedded liquid metal microstructure electrodes

[0122] The embedded liquid metal microstructure electrode is prepared according to the aforementioned method, which will not be described in detail here.

[0123] Step 2: Preparation of liquid metal flat electrode

[0124] 2.1) Prepare a second flexible substrate 5 and place it on the processing platform of the femtosecond laser galvanometer system.

[0125] 2.2) Adjust the height of the processing platform so that the femtosecond laser is focused on the upper surface of the second flexible substrate 5 through the galvanometer.

[0126] 2.3) Draw a convex pattern in the background program of the femtosecond laser galvanometer system, and set the processing program corresponding to the convex pattern.

[0127] 2.4) According to the processing program set in step 2.3), the processing platform is controlled to move, and the femtosecond laser processes a protruding structure on the upper surface of the flexible substrate.

[0128] 2.5) Using the same metal mask as that used in step [1] to prepare the embedded liquid metal microstructure electrode, liquid metal is applied to the lower surface of the second flexible substrate 5 by template printing, thereby forming a second liquid metal layer 6.

[0129] 2.6) Encapsulating the lower surface of the second flexible substrate 5 having the second liquid metal layer 6, thereby obtaining a liquid metal flat plate electrode.

[0130] Step 3: Assemble the embedded liquid metal microstructure electrode prepared according to the above method and the liquid metal flat electrode obtained in step 2.6) to obtain a flexible pressure sensor array. Specifically:

[0131] 3.1) The embedded liquid metal microstructure electrode and the liquid metal flat plate electrode obtained in step 2.6) are respectively subjected to oxygen plasma surface modification treatment.

[0132] 3.2) The first encapsulation layer 3 and the second encapsulation layer 7 are brought close together, and anti-adhesion particles are sprayed between the two. The anti-adhesion particles are located between each liquid metal area and the corresponding micro-cone structure 4 .

[0133] In this embodiment, the anti-adhesion particles are SiO2 nanoparticles, and the diameter of a single particle is 10nm-100nm.

[0134] 3.3) The first packaging layer 3 and the second packaging layer 7 are laminated together so as to obtain a flexible pressure sensor array with embedded liquid metal microstructures.

[0135] Figure 8 Shown is the flexible pressure sensor array of this embodiment and its actual picture under stretching and bending deformation, indicating that the prepared liquid metal pressure sensor array has good flexibility and can be effectively applied to flexible electronic fields such as wearable devices, flexible electronic skin, and flexible robots.

[0136] Fig. 9 The figure shows the anti-crosstalk capability of the pressure sensor array. Compared with the 58% crosstalk between units of the sensor array without bonding interface and surface protrusions, the crosstalk of the sensor array with bonding interface and protrusions prepared in this embodiment is reduced to 7.9%, which is a significant improvement.

[0137] Fig.10 The figure shows a 3D printed sphere model with the curved letter "SOFT" and a dynamic process of mapping the pressure signal of the curved letter "S" using the flexible pressure sensor array prepared in this embodiment. It can be seen from the figure that the flexible pressure sensor array has good flexibility and high pressure signal mapping accuracy; Fig.11 This is a signal mapping diagram of the letters "SOFT" on the curved surface, and the mapping of each part is relatively clear.

[0138] In summary, the present invention provides an embedded microstructure electrode and a flexible pressure sensor array based on the microelectrode structure. By selectively printing liquid metal on the embedded micro-cone structure, the sensor sensitivity is significantly improved, and it can work stably under deformation, while reducing crosstalk between sensor arrays.

[0139] The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit the present invention. Although the above embodiments have described the present invention in detail, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present invention.

Claims

1. An embedded liquid metal microstructure electrode, characterized in that: It comprises a first flexible substrate (1), a first liquid metal layer (2) and a first packaging layer (3); The lower surface of the first flexible substrate (1) is a plane, and the upper surface is in the shape of a groove, and a plurality of micro-cone structures (4) arranged in an array are provided in the groove; the cone portion of each micro-cone structure (4) faces upward and is flush with the upper surface of the first flexible substrate (1); The first liquid metal layer (2) is located on the upper surface of the first flexible substrate (1) and covers all the micro-cone structures (4); The first encapsulation layer (3) covers the surface of the first liquid metal layer (2).

2. The embedded liquid metal microstructure electrode according to claim 1, characterized in that: The height of the micro-cone structure (4) is equal to the thickness of the first flexible substrate (1). The material of the first flexible substrate (1) is PDMS or silicone material; The material of the first liquid metal layer (2) is a gallium-based alloy.

3. A method for preparing the embedded liquid metal microstructure electrode according to claim 1 or 2, characterized in that: The following steps are involved: Step [1] processing a metal mask with a hollow electrode pattern; Step [2] preparing a first flexible substrate (1), and attaching a sacrificial layer to the upper surface of the first flexible substrate (1); Step [3] Processing the embedded micro-cone structure (4) on the upper surface of the first flexible substrate (1); 3.1) placing the first flexible substrate (1) on a two-dimensional platform of a femtosecond laser lens system; 3.2) placing the metal mask obtained in step 1] on the first flexible substrate (1) attached with the sacrificial layer, and focusing the femtosecond laser on the sacrificial layer through a lens; 3.3) Set up the bow-shaped scanning program for the two-dimensional platform; 3.4) Based on the scanning program set in step 3.3), the two-dimensional platform is controlled to move, and a femtosecond laser ablates a plurality of patterned embedded micro-cone structures (4) extending to the upper surface of the first flexible substrate (1) on the sacrificial layer through the hollow electrode pattern on the metal mask; Step [4] preparing an embedded liquid metal microstructure electrode; 4.1) performing oxygen plasma surface hydrophilic modification treatment on the first flexible substrate (1) processed in step 3.4); 4.2) Wetting the upper surface of the first flexible substrate (1) after the hydrophilic modification with deionized water, so that the deionized water covers each micro-cone structure (4); 4.3) dripping liquid metal so that it covers the upper surface of deionized water; 4.4) dripping the hydrogel solution on the upper surface of the liquid metal so that the hydrogel solution completely covers the liquid metal; 4.5) drying the first flexible substrate (1) on which the hydrogel solution and the liquid metal are drop-coated, so that the hydrogel solution solidifies, the deionized water evaporates, and the liquid metal covers all the micro-cone structures (4) to form a first liquid metal layer (2); 4.6) sequentially tearing off the solidified hydrogel, absorbing the excess liquid metal on the surface of the first flexible substrate (1), tearing off the sacrificial layer, and then encapsulating to obtain a patterned embedded liquid metal microstructure electrode.

4. The method for preparing the embedded liquid metal microstructure electrode according to claim 3, characterized in that: Step [1] is as follows: 1.1) Prepare a metal film and place it on the processing platform of the femtosecond laser galvanometer system; 1.2) Adjust the height of the processing platform so that the femtosecond laser is focused on the metal film through the galvanometer; 1.3) Draw the electrode pattern to be processed in the background program of the femtosecond laser galvanometer system, and set the processing program corresponding to the electrode pattern; the scanning speed of the femtosecond laser galvanometer system is 0.1-10 mm / s; 1.4) Based on the processing program set in step 1.3), a femtosecond laser is controlled to cut an electrode pattern on the metal film to form a metal mask with a hollow electrode pattern; the central wavelength of the femtosecond laser is 325nm to 1200nm, the pulse width is 30fs to 150fs, the repetition frequency is 10Hz to 100KHz, and the laser power is 100mW to 1000mW.

5. The method for preparing the embedded liquid metal microstructure electrode according to claim 3 or 4, characterized in that: In step [2], the material of the first flexible substrate (1) is PDMS or silicone material; the sacrificial layer is polyethylene terephthalate tape, and its thickness is 10 μm to 50 μm; In step 3.4), the moving speed of the two-dimensional platform is 0.1-10 mm / s; the central wavelength of the femtosecond laser is 325 nm-1200 nm, the pulse width is 30 fs-150 fs, the repetition frequency is 10 Hz-100 KHz, and the laser power is 100 mW-1000 mW; In step 4.3), the liquid metal is a gallium-based alloy, and the thickness of the drop coating is 2 to 5 mm; In step 4.4), the hydrogel solution is a polyvinyl alcohol solution with a mass ratio of 5 to 20%, and the thickness of the drop coating is 0.5 to 2 mm.

6. A flexible pressure sensor array, characterized in that: It comprises a liquid metal flat plate electrode and the embedded liquid metal microstructure electrode according to claim 1 or 2; The liquid metal flat plate electrode comprises a second flexible substrate (5), a second liquid metal layer (6) and a second packaging layer (7); The size of the second flexible substrate (5) is the same as that of the first flexible substrate (1), and a plurality of protrusions (8) are evenly distributed on the upper surface of the second flexible substrate (5); The second liquid metal layer (6) comprises a plurality of liquid metal areas, which are arranged in an array and disposed on the lower surface of the second flexible substrate (5); the positions of the plurality of liquid metal areas correspond one to one to the positions of the plurality of micro-cone structures (4); The second packaging layer (7) covers the second liquid metal layer (6) and the lower surface of the second flexible substrate (5); The first encapsulation layer (3) and the second encapsulation layer (7) are assembled by plasma bonding.

7. The flexible pressure sensor array according to claim 6, characterized in that: Anti-adhesion particles are sprayed between the first encapsulation layer (3) and the second encapsulation layer (7), and are located between each liquid metal area and the corresponding micro-cone structure (4).

8. A method for preparing a flexible pressure sensor array, characterized in that: The following steps are involved: Step 1: Prepare the embedded liquid metal microstructure electrode according to claim 1 or 2 The embedded liquid metal microstructure electrode is prepared according to the preparation method of claim 3, 4 or 5; Step 2: Preparation of liquid metal flat electrode 2.1) preparing a second flexible substrate (5) and placing it on a processing platform of a femtosecond laser galvanometer system; 2.2) adjusting the height of the processing platform so that the femtosecond laser is focused on the upper surface of the second flexible substrate (5) through the galvanometer; 2.3) Draw a convex pattern in the background program of the femtosecond laser galvanometer system, and set the processing program corresponding to the convex pattern; 2.4) controlling the movement of the processing platform according to the processing program set in step 2.3), so that the femtosecond laser processes a convex structure on the upper surface of the flexible substrate; 2.5) using the same metal mask as that used in preparing the embedded liquid metal microstructure electrode, applying the liquid metal to the lower surface of the second flexible substrate (5) by template printing, thereby forming a second liquid metal layer (6); 2.6) encapsulating the lower surface of the second flexible substrate (5) having the second liquid metal layer (6) to obtain a liquid metal flat plate electrode; Step 3: Assemble the embedded liquid metal microstructure electrode prepared in step 1 and the liquid metal flat electrode obtained in step 2.6) to obtain a flexible pressure sensor array.

9. The method for preparing the flexible pressure sensor array according to claim 8, characterized in that: Step three is as follows: 3.1) performing oxygen plasma surface modification treatment on the embedded liquid metal microstructure electrode prepared in step 1 and the liquid metal flat plate electrode obtained in step 2.6); 3.2) bringing the first encapsulation layer (3) and the second encapsulation layer (7) close to each other and spraying anti-adhesion particles between the two; the anti-adhesion particles are located between each liquid metal area and the corresponding micro-cone structure (4); 3.3) The first packaging layer (3) and the second packaging layer (7) are laminated together at their adjacent sides, thereby obtaining a flexible pressure sensor array with embedded liquid metal microstructures.

10. The method for preparing a flexible pressure sensor array according to claim 9, characterized in that: In step 3.2), the anti-adhesion particles are SiO2 nanoparticles, and the diameter of a single particle is 10nm to 100nm.

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