Bionic adjustable range strain sensor and preparation method and measurement method thereof

Abstract

The application discloses a bionic adjustable-range strain sensor and a preparation method and a measuring method thereof. The bionic adjustable-range strain sensor comprises an actuator base structure, a heating layer and a material layer with different thermal expansion coefficients arranged on the actuator base structure, and can convert received voltage into Joule heat to generate thermal expansion and deformation; a conductive sensitive layer sensing structure arranged on the lower side of the actuator base structure and used for measuring resistance value; and a micro bionic joint structure comprising a joint group formed by groove arrangement, which is formed by multiple rows of recesses from the conductive sensitive layer sensing structure to the actuator base structure, and the joint group formed by groove arrangement can change along with the deformation of the actuator base structure. The bionic adjustable-range strain sensor is prepared based on the tuning mechanism of a scorpion joint receptor, and the grooves of the joint group are prepared based on the structure of the scorpion joint receptor. The application improves the range of the sensor and realizes the adjustable-range effect.

Description

Technical Field

[0001] This invention relates to the field of strain detection sensing technology, and in particular to a biomimetic adjustable-range strain sensor and its preparation and measurement methods. Background Technology

[0002] Existing flexible strain sensors, due to their fixed measurement range, still struggle to balance high sensitivity and a wide sensing range. A wide measurement range often results in low sensitivity, while pursuing high sensitivity frequently reduces the sensor's detectable range. In many scenarios, such as the biomedical field, human vital signs often span a wide range of pressures, from heart rate and pulse (small signals) to muscle contractions and respiration (relatively large signals). Therefore, it is crucial to develop a sensor whose performance can be dynamically adjusted based on the target signal.

[0003] Therefore, existing technologies still need further improvement and development. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a biomimetic adjustable range strain sensor and its preparation and measurement methods. This invention provides a biomimetic adjustable range strain sensor, which achieves adjustable sensitivity and detection range by adjusting the voltage, providing a good solution for monitoring strain and pressure of various scales.

[0005] The technical solution of the present invention is as follows:

[0006] A biomimetic adjustable-range strain sensor, comprising:

[0007] The actuator base structure has a heating layer and a material layer with different coefficients of thermal expansion, which can convert the received voltage into Joule heat, causing thermal expansion and deformation.

[0008] A conductive sensing layer is disposed on the underside of the actuator substrate structure and is used to measure resistance values.

[0009] The micro-bionic slit structure includes a slit group formed by an arrangement of grooves, which is formed by multiple rows of recesses in the actuator substrate structure through the conductive sensitive layer sensing structure. The slit group formed by the arrangement of grooves can change according to the deformation of the actuator substrate structure.

[0010] The biomimetic adjustable strain sensor is biomimeticly fabricated based on the tuning mechanism of a scorpion slit sensor, and the groove of the slit assembly is biomimeticly fabricated based on the structure of a scorpion slit sensor. When a voltage is applied to the actuator substrate, electrical energy is converted into Joule heat and transferred to the entire strain sensor, causing bending based on the actuator substrate structure, and the width of the slit assembly changes accordingly due to the actuator micro-biomimetic slit structure.

[0011] The biomimetic adjustable-range strain sensor, wherein the actuator substrate structure includes: a heating layer, and a double-layer material layer with significantly different coefficients of thermal expansion connected to the heating layer.

[0012] The biomimetic adjustable strain sensor, wherein the heating layer is a multi-walled carbon nanotube heating layer, and the bilayer material layer with significantly different coefficients of thermal expansion is a cellulose paper layer and a PDMS film layer; wherein the heating layer, the cellulose paper layer, and the PDMS film layer are arranged sequentially.

[0013] The biomimetic adjustable-range strain sensor, wherein the conductive sensing layer sensing structure includes: a conductive layer and a metal electrode connected to the conductive layer.

[0014] The biomimetic adjustable range strain sensor, wherein the micro-biomimetic slit structure includes: a slit group formed by grooves arranged in an array, the slit group formed by the grooves arranged in an array disposed on the conductive layer.

[0015] The biomimetic adjustable range strain sensor wherein the groove of the slit assembly is etched on the bottom of the PDMS film layer and is parallel to the short side of the entire biomimetic adjustable range strain sensor.

[0016] The conductive layer is selected from one of nano-platinum, gold, silver, copper, and aluminum;

[0017] The adjustable range is achieved by adjusting the voltage value to regulate the temperature of the biomimetic adjustable range strain sensor, thereby adjusting the curvature of the actuator base structure and changing the width of the groove on the actuator base structure, thus adjusting the range.

[0018] The aforementioned biomimetic adjustable range strain sensor, wherein the heating layer is manufactured by brushing a conductive solution in a U-shape onto the actuator substrate structure to form a conductive path;

[0019] The conductive solution brushed onto the heating layer is one or a mixture of multi-walled carbon nanotubes, conductive graphite, conductive carbon black, carbon fiber, and graphene.

[0020] The biomimetic adjustable range strain sensor is wherein the thickness of the heating layer is less than the thickness of the cellulose paper layer and the PDMS film layer, the thickness of the cellulose paper layer is less than the thickness of the PDMS film layer, and the cellulose paper layer and the PDMS film layer are bonded together by an ultra-thin silicone layer.

[0021] A measurement method for a biomimetic adjustable-range strain sensor as described in any of the preceding claims, wherein when the voltage applied to the heating layer is adjusted, its electrical charge is converted into Joule heat, and the actuator base structure of the biomimetic adjustable-range strain sensor bends to varying degrees, causing the groove group of the slot assembly to deform until it is adjusted to a specified performance threshold for the sensor to detect strain. At this time, strain is applied to the strain sensor, causing the groove to deform and thus changing the resistance value of the conductive layer. The resistance difference before and after the strain is applied is recorded, and finally the magnitude of the strain value to be measured is detected.

[0022] A method for fabricating a biomimetic adjustable-range strain sensor as described in any of the preceding claims, comprising the steps of:

[0023] A bilayer material with different coefficients of thermal expansion is prepared, and a conductive solution is directly printed and deposited on the bilayer material through a repeated brushing process to form a conductive layer, thus completing the step of preparing the actuator substrate structure.

[0024] On the lower surface of the actuator substrate structure, a groove group is formed by casting a groove group onto a PDMS film using a casting printing process, thereby completing the preparation of the groove arrangement of the micro-bionic slit structure.

[0025] A thin layer of gold is then sputtered onto the groove surface of the slit assembly to form a conductive layer. Two metal wires are then led out from both ends of the conductive layer to serve as metal electrodes connected to the conductive layer, thus completing the fabrication of the biomimetic adjustable strain sensor.

[0026] This invention provides a novel biomimetic adjustable-range strain sensor and its fabrication and measurement methods. The sensor comprises an actuator base, a conductive sensitive layer sensing portion, and a micro-biomimetic slit structure. The actuator base includes a heating layer and a double-layer material with significantly different coefficients of thermal expansion. The conductive sensitive layer sensing portion includes a conductive layer and a metal electrode. The micro-biomimetic slit structure comprises a slit array formed by arranged grooves. The manufacturing theory of the biomimetic slit array originates from the slit sensory organ of a scorpion. Scorpions change their leg posture according to the external environment, thereby changing the width of the compressed slit. The slit sensory organ is adjusted to the optimal dynamic pressure detection range according to the environment, significantly improving the dynamic range and sensitivity to signal pressure, thus detecting various vibrations from prey and predators to high and low levels. Specifically, strip-shaped grooves are machined into the bottom material of the actuator structure, and a thin layer of gold is sputtered onto the surface of the grooves to form a conductive sensitive layer. The resistance value of the conductive sensitive layer is measured to achieve pressure detection. A voltage is applied to the heating layer of the actuator substrate, converting electrical energy into Joule heat which is then transferred to the entire sensor. Due to the thermal expansion mismatch between the two layers of the actuator, the actuator bends, causing the width of the slot structure to change accordingly. If the slot width increases, greater pressure is required to close the slot, thus increasing the sensor's range. In other words, by adjusting the voltage, the sensor's pressure detection range is increased, achieving an adjustable range. This invention can be applied in biomedicine to detect mechanical signals at different pressure ranges, and to detect vital signs such as neck vibration, heart rate, and muscle contraction, fulfilling pressure detection needs in various scenarios. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the biomimetic adjustable range strain sensor according to an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the bottom structure of the biomimetic adjustable range strain sensor according to an embodiment of the present invention.

[0029] Figure 3 This is a front view of a biomimetic adjustable range strain sensor according to an embodiment of the present invention.

[0030] Figure 4 This is a side view of a biomimetic adjustable range strain sensor according to an embodiment of the present invention.

[0031] Figure 5 This is a top view of the biomimetic adjustable range strain sensor according to an embodiment of the present invention.

[0032] Figure 6 This is a schematic diagram of the bending of a biomimetic adjustable range strain sensor under a 15V voltage according to an embodiment of the present invention.

[0033] Figure 7This is a schematic diagram of the bending of a biomimetic adjustable range strain sensor under a 10V voltage according to an embodiment of the present invention.

[0034] Figure 8 This is a schematic diagram of the bending of a biomimetic adjustable range strain sensor under a 20V voltage according to an embodiment of the present invention.

[0035] Figure 9 This is a front view of the biomimetic adjustable range strain sensor under no applied voltage according to an embodiment of the present invention.

[0036] Figure 10a This is a top view of the parameter annotation of the biomimetic adjustable range strain sensor under no applied voltage according to an embodiment of the present invention.

[0037] Figure 10b This is a front view parameter annotation diagram of the biomimetic adjustable range strain sensor under no applied voltage according to an embodiment of the present invention.

[0038] Figure 10c This is a right-view parameter annotation diagram of the biomimetic adjustable range strain sensor under no applied voltage according to an embodiment of the present invention. Detailed Implementation

[0039] This invention provides a biomimetic adjustable-range strain sensor and its fabrication and measurement methods. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0041] The inventors discovered that the micro-vibration receptors at the ends of the metatarsal joints of a scorpion's lobe consist of 12 slit units. These slits penetrate the exoskeleton and extend to the subcutaneous tissue. Under different amplitude vibrations, the scorpion adjusts its leg posture, controlling the compression or release of these slits to stimulate the dendrites of neurons, generating different nerve impulses to sense external vibrations. Small prey and large predators produce vibrations of different magnitudes. The scorpion amplifies the sensitivity of its sensory organs across different vibration ranges by adjusting its leg posture to move the threshold, thus adjusting the vibration information to be identified to the optimal performance threshold that the slits can recognize. For example, when hunting small prey, the scorpion bends its legs, compressing the slits. This reduces the depth ratio of the slit group, adjusting the detection range and high sensitivity to the low-magnitude vibration region. When escaping a large predator, the scorpion extends its legs, opening the slits. This increases the depth ratio of the slit group (the ratio of the width to the depth of the slit unit), adjusting the detection range and high sensitivity to the high-magnitude vibration region. Therefore, the slit is of survival significance for scorpions to identify these vibrational information, enabling them to distinguish strains of different scales.

[0042] Therefore, the present invention provides a biomimetic adjustable range strain sensor. By drawing on the sensing mechanism and structural characteristics of scorpion vibration receptors, the present invention provides a biomimetic adjustable range strain sensor. The sensitivity and detection range are adjustable by adjusting the voltage, providing a good solution for monitoring strain and pressure of various scales.

[0043] Please also refer to Figure 1-Figure 1 0( Figure 10a -c) This invention provides some embodiments of a biomimetic adjustable-range strain sensor.

[0044] The study investigated the geometry and tuning mechanism of scorpion micro-vibration receptors. Scorpions adjust their leg posture to alter the width of the compressed slit, thereby shifting the threshold and amplifying the sensitivity of the sensory organ across different vibration ranges. By adjusting the slit sensory organ to the optimal dynamic pressure detection range based on external vibration information, the sensitivity to signal pressure states is significantly improved, enabling the detection of vibrations from predators to various levels, from high to low. Based on the slit's tuning mechanism and sensing principle, the biomimetic strain sensor of this application adjusts the voltage value to change the system temperature, thereby controlling the sensor's bending state, compressing and releasing nanoscale cracks, achieving adjustable strain detection range and sensitivity, and thus detecting strain and pressure of various scales.

[0045] like Figures 1 to 10c As shown in the figure, an embodiment of the present invention provides a biomimetic adjustable range strain sensor, comprising:

[0046] The actuator includes an actuator substrate structure 100, a conductive sensitive layer sensing structure 200, and a micro-bionic slit structure 300. The actuator substrate structure has material layers with different coefficients of thermal expansion, which convert the received voltage into Joule heat, causing thermal expansion and deformation. The conductive sensitive layer sensing structure 200 is located below the actuator substrate structure 100; the micro-bionic slit structure 300 is located above the conductive sensitive layer sensing structure 200. The conductive sensitive layer sensing structure 200 is used to measure resistance values. The micro-bionic slit structure 300 includes a group of slits formed by grooves arranged in multiple rows through the conductive sensitive layer sensing structure towards the actuator substrate structure. The slits formed by the grooves can change according to the deformation of the actuator substrate structure. The micro-bionic slit structure 300, compared to a seamless structure, improves sensitivity and makes resistance changes more noticeable.

[0047] Among them, such as Figure 2 As shown, the actuator substrate structure 100 includes: a heating layer 1, and a bilayer material layer with significantly different coefficients of thermal expansion connected to the heating layer; in this embodiment, the heating layer 1 is preferably a multi-walled carbon nanotube heating layer, and the heating layer 1 is used to convert voltage into Joule heat when applied. The bilayer material layer with significantly different coefficients of thermal expansion is preferably: a cellulose paper layer 2 and a PDMS film layer 3; wherein the heating layer 1, the cellulose paper layer 2, and the PDMS film layer 3 are arranged sequentially.

[0048] The conductive sensing layer sensing structure 200 includes: a conductive layer 4 and a metal electrode 6 connected to the conductive layer 4;

[0049] The micro-biomimetic slit structure 300 includes: a slit group 5 formed by an arrangement of grooves, the slit group 5 being disposed on the conductive layer 4. Wherein, for example... Figure 2 As shown, the groove arrangement forming the slot group 5 is formed by the following method: multiple strip-shaped grooves are etched on the actuator substrate structure 100, and a thin layer of gold is sputtered on the surface of the grooves to form a conductive layer 4. Two metal wires are led out at both ends of the conductive layer 4 as metal electrodes 6 connected to the conductive layer 4, which are used to measure the resistance value of the conductive sensitive layer under different strains, so as to realize the detection of pressure.

[0050] In this embodiment of the invention, the adjustable range is achieved by adjusting the voltage value to regulate the temperature of the biomimetic adjustable range strain sensor, thereby adjusting the curvature of the actuator base structure 100 and changing the width of the groove on the actuator base structure, thus realizing the adjustment of the sensor's dynamic range. In scenarios involving large strain detection, the voltage value is increased to expand the detection range. In scenarios involving small strain detection, the voltage value is decreased to achieve more sensitive detection within a smaller range.

[0051] In this embodiment of the invention, applying progressively increasing voltage values ​​to the heating layer 1 leads to an increase in current and thus power. This results in more energy being converted into Joule heat, manifesting as an overall temperature rise in the sensor. Since cellulose paper and PDMS film have significantly different coefficients of thermal expansion, they expand at significantly different rates as the temperature rises. This means the sensor structure bends more when the temperature increases, i.e., it is stretched more, thus widening the grooves attached to it. The advantage is that the measurement range can be quantitatively changed directly by adjusting the voltage, making it easier to detect wide strain conditions. It eliminates the need for multiple sensors with different ranges as in traditional methods; simply adjusting the voltage conveniently meets the measurement requirements for different strains.

[0052] In scenarios involving relatively large strain, such as muscle contraction causing relatively large displacement deformation of the skin, the voltage value is increased to expand the detection range. In scenarios involving small strain, such as pulse beats causing relatively small displacement deformation of the skin, the voltage value is decreased to achieve more sensitive detection within a smaller range. In this embodiment, the voltage applied to the heating layer 1 is preferably in the range of 0 to 30V.

[0053] In this embodiment, preferably, the actuator base structure 100 is selected as an electrothermal soft actuator as the base part, that is, it is controlled by an electrothermal driving mechanism. By applying voltage, the temperature of the material is changed, and the material's sensitivity to temperature is used to generate different deformations, thereby causing the actuator base structure to bend.

[0054] In this embodiment of the invention, the actuator substrate structure 100 is composed of two layers of materials with significantly different coefficients of thermal expansion. When the temperature of the actuator substrate changes, the thermal expansion mismatch between the two layers will cause the actuator substrate structure 100 to bend. The ratio of the thermal expansion coefficients of the two layers of materials is selected to be more than 10 times to ensure good actuation effect.

[0055] In this embodiment of the invention, preferably, the temperature change of the actuator substrate structure 100 originates from the heating layer 1, which can be made of resistance heating metal wire and disposed in a double-layer material layer. Alternatively, a conductive solution can be brushed onto the surface of the actuator substrate structure 100, and after drying, a voltage is applied to form a conductive path, converting Joule heating into heat energy. The heating layer has both electrical and heat transfer functions.

[0056] In the embodiments of the present invention, preferably, as follows: Figure 1 As shown, the heating layer 1 is manufactured by brushing a conductive solution in a U-shape onto the actuator substrate structure 100 to form a conductive path. Figure 1The voltage-applying circuit V on the right applies voltage to the U-shaped loop, which generates current. Electrical energy is converted into Joule heat energy, providing temperature change.

[0057] In the embodiments of the present invention, preferably, as follows: Figure 1 As shown, the thickness of the heating layer 1 is much smaller than the thickness of the double-layer material with significantly different coefficients of thermal expansion, that is, smaller than the thickness of the cellulose paper layer 2 and the PDMS film layer 3. The thickness of the upper layer material of the double-layer material is smaller than the thickness of the lower layer material, that is, the thickness of the cellulose paper layer 2 is smaller than the thickness of the PDMS film layer 3. Furthermore, the double-layer material of the cellulose paper layer 2 and the PDMS film layer 3 is bonded together by an ultra-thin silicone layer, which can ensure that the actuator has a good bending effect.

[0058] In the embodiments of the present invention, preferably, as follows: Figure 1 and Figure 2 As shown, the groove is etched on the bottom of the lower actuator material, that is, on the bottom of the PDMS film layer 3, and is parallel to the short side of the entire biomimetic adjustable strain sensor, which facilitates processing and manufacturing.

[0059] In this embodiment of the invention, preferably, the ratio of the width to the depth of the grooves in the groove group 5 formed by the arrangement of grooves is greater than 2, and they are evenly distributed. This ensures a slightly larger measuring range, enabling the detection of greater strain, expanding application scenarios, and facilitating processing.

[0060] In the embodiments of the present invention, preferably, as follows: Figure 1 and Figure 2 As shown, the conductive layer 4 can be selected from various conductive metals such as nano-platinum, gold, silver, copper, and aluminum, or it can be formed by brushing a conductive solution onto one side of the groove in the actuator substrate structure 100. The conductive layer covers the entire surface of the groove side, including the groove wall.

[0061] Optionally, in specific embodiments of the present invention, such as Figure 1 As shown, the heating layer 1 is a multi-walled carbon nanotube heating layer; the bilayer material with significantly different coefficients of thermal expansion includes: a cellulose paper layer 2 and a PDMS (polydimethylsiloxane) layer 3; the heating layer 1, the cellulose paper layer 2, and the PDMS (polydimethylsiloxane) layer 3 are sequentially stacked; the bottom surface of the PDMS layer 3 is provided with a grooved slit group 5; in this embodiment, the conductive layer 4 is a nano-gold layer laid on the grooved slit group 5; a metal electrode 6 is disposed on the nano-gold layer. In this embodiment, the PDMS layer is a high-molecular elastic polymer film prepared from polydimethylsiloxane.

[0062] In this specific embodiment, the biomimetic adjustable-range strain sensor is biomimeticly fabricated based on the tuning mechanism of a scorpion slit receptor, and the grooves of the slit group 5 are biomimeticly fabricated based on the structure of a scorpion slit receptor. Adjusting the voltage applied to the heating layer 1 converts electrical energy into Joule heat. Due to the different thermal expansion rates of the cellulose paper layer 2 and the PDMS layer 3, the actuator base structure of the biomimetic adjustable-range strain sensor will bend to varying degrees, causing deformation of the groove group of the slit group 5 formed by the groove arrangement. This deformation continues until the optimal performance threshold for the biomimetic adjustable-range strain sensor to detect the strain is reached. At this point, strain is applied to the sensor, causing the grooves to deform and thus changing the resistance value of the conductive layer. Recording the resistance difference before and after applying the strain allows for the final detection of the strain value. For example, when the parameters of the biomimetic adjustable-range strain sensor set in this embodiment are as follows... Figure 10a , Figure 10b , Figure 10c When the initial groove 51 width is 100μm and a voltage of 15V is applied, the average temperature of the heating layer 1 is 85.69℃ and the bending curvature is 3.7524, according to finite element simulation analysis. At this time, the average width of the groove group is 106.48μm. When a pressure of 0.001MPa is applied, the groove is completely closed, that is, the maximum strain value that can be detected at this time is 0.001MPa.

[0063] The actuator base structure 100 can be controlled by one of the driving mechanisms such as heat, light, humidity, electricity, magnetism, fluid, etc. In this embodiment of the invention, the electrothermal driving mechanism is preferably selected to drive the actuator base structure 100.

[0064] In this embodiment of the invention, the actuator substrate structure 100 includes: a heating layer 1 and a bilayer material with significantly different coefficients of thermal expansion. The upper layer of the bilayer material with significantly different coefficients of thermal expansion can be a material with a low coefficient of thermal expansion, such as a cellulose paper layer, a liquid crystal elastomer, a composite film material made of multi-walled CNTs and polymers; the lower layer is a material with a high coefficient of thermal expansion, such as a PP film, a PI film, or a PDMS film layer. Preferably, the upper layer material selected in this invention is a cellulose paper layer 2 with a coefficient of thermal expansion of 8.0 × 10⁻⁶. -6 K -1 The lower layer is PDMS layer 3, with a thermal expansion coefficient of 320 × 10⁻⁶. -6 K -1 The thermal expansion rates of the two differ by 40 times. Therefore, when a voltage is applied, the high temperature generated by the multi-walled carbon nanotube heating layer 1 will cause a significant mismatch in the thermal expansion of the two structural layers, thereby causing the actuator base structure 100 to bend. The actuator base structure 100 is prepared based on the tuning mechanism principle of scorpions adjusting their leg posture, and has a large actuation effect and a fast actuation response.

[0065] like Figure 10c As shown, preferably, the thickness of the heating layer 1 is 30 μm, the thickness of the cellulose paper layer is 270 μm, and the thickness of the PDMS (polydimethylsiloxane) layer 3 is 200 μm. The PDMS layer is a high molecular elastic polymer film.

[0066] Based on the biomimetic adjustable range strain sensor described in the above embodiments, this invention also provides a measurement method for the biomimetic adjustable range strain sensor as described in any of the preceding claims, comprising the following steps:

[0067] When the voltage applied to the heating layer is adjusted, its electrical charge is converted into Joule heat. The actuator base structure of the biomimetic adjustable strain sensor bends to varying degrees, causing the slot group, i.e. the groove group, to deform until it is adjusted to the specified performance threshold for the sensor to detect strain. At this time, strain is applied to the strain sensor, causing the groove to deform and the resistance value of the conductive layer to change. The resistance difference before and after the strain is applied is recorded, and finally the magnitude of the strain value to be measured is detected.

[0068] Based on the above embodiments, the present invention also provides a method for fabricating a biomimetic adjustable-range strain sensor as described in any of the preceding claims, comprising the steps of:

[0069] S100. Prepare a double-layer material with different coefficients of thermal expansion, and directly print and deposit a conductive solution onto the double-layer material through a repeated brushing process to form a conductive layer, thus completing the step of preparing the actuator substrate structure.

[0070] S200: On the lower surface of the actuator substrate structure, a groove group is formed by reverse printing on a PDMS film using a reverse printing process, thereby completing the preparation of the groove arrangement of the micro-bionic slit structure.

[0071] S300, a thin layer of gold is sputtered onto the groove surface of the slit assembly to form a conductive layer, and two metal wires are led out from both ends of the conductive layer as metal electrodes connected to the conductive layer, thus completing the fabrication of the biomimetic adjustable strain sensor.

[0072] In this embodiment of the invention, optionally, the heating layer 1 is directly printed and deposited on the front side of the cellulose paper layer 2 by a repeated brush coating process, such as... Figure 1 As shown, the heating layer 1 is preferably U-shaped to form a conductive path and locally control the temperature of the actuator, preferably as follows: Figure 10aAs shown, the overall length of the U-shaped heating layer is 30mm, the overall width is 10mm, the width of the U-shaped part is 2mm, and the width of the bottom wall of the U-shaped part is 7mm. The conductive solution brushed onto the heating layer 1 of the actuator substrate structure 100 can be one of the following: multi-walled carbon nanotubes, conductive graphite, conductive carbon black, carbon fiber, graphene, or any solution of the former mixed with other substances to form a high conductivity solution.

[0073] Optionally, the PDMS layer 3 can be generated by mixing PDMS prepolymer and curing agent in a ratio of 10:1, and the flexible PDMS is spin-coated onto the master plate and removed after curing.

[0074] Optionally, the grooves of the micro-biomimetic slit structure 300, arranged to form the slit group 5, can be fabricated by first photolithographically etching the slit dimensions onto a silicon wafer, and then using a casting printing process to cast the slit group onto a PDMS film, thus completing the slit fabrication. Then, ultra-thin silicone is used to bond the cellulose paper and the fabricated PDMS together. Figure 3 , Figure 4 , Figure 5 and Figure 10b As shown, the overall length of the biomimetic adjustable range strain sensor in this embodiment is marked as L, for example, 30mm, and the height is H. The groove group 5 structure is formed by the arrangement of grooves. The initial width of the groove w is 100um, the distance I between two grooves is 150um, and the distance between the two ends of the conductive layer 4 and the end of the actuator substrate structure 100 is 2000um.

[0075] In this embodiment of the invention, the conductive layer is made of nano-gold and prepared using a metal growth method. Au is deposited onto the seam surface and inner walls of the PDMS layer at the bottom using methods such as evaporation and sputtering to form a thin film structure. Evaporation offers the advantages of simplicity and the high purity and density of the resulting Au film.

[0076] Optionally, the metal electrode 6 can be led out at both ends of the short side of the conductive layer 4 by sputtering metal Au wires.

[0077] The inventors discovered that the ratio of the width to the depth of a scorpion's suture units is called the depth ratio. Sutures with a low depth ratio are more sensitive to vibrations, capable of detecting minute vibrations for hunting small prey, but their sensing range is small. When external vibration stimuli exceed their sensing range, their sensitivity decreases, making it difficult to detect vibrations from large predators. Suture units with a high depth ratio have a larger vibration sensing range, but their sensitivity to minute vibrations is poor, while they still have good sensitivity to stronger vibrations, allowing them to evade predators. Scorpions change the depth ratio of their suture units by shifting their leg postures, thus satisfying their sensitivity to minute vibrations while also expanding their sensing range.

[0078] Therefore, in the embodiments of the present invention, such as Figure 1 As shown, the fixed end is the right side. A pressure p is applied to the surface on the left side of the vertical sensor to detect the range of strain that the sensor can detect under different voltages, i.e., different temperatures. The pressure at which the groove of the slit assembly 5 just closes and reaches the deformation limit (i.e., the groove width is just 0) is defined as the critical closing pressure of the groove, i.e., the maximum strain value that can be detected. Similar to the slit unit of the scorpion slit sensor, after the groove reaches the deformation limit, no matter how much pressure is applied, the resistance value of the nano-gold layer attached to the surface and inner wall of the groove no longer changes.

[0079] When a voltage is applied, the conductive path of the heating layer 1 generates a current, which is then converted into Joule heat, ultimately manifesting as a temperature change in the sensor. Because the cellulose paper layer 2 and the PDMS layer 3 have significantly different coefficients of thermal expansion, a large mismatch in thermal expansion occurs between the two structural layers as the temperature rises, causing the biomimetic adjustable-range strain sensor of this embodiment to bend. Figure 6 As shown.

[0080] like Figure 9 The image shows a front view of a biomimetic adjustable strain sensor with 100 micrometer-wide slits, each 100 μm wide, without an applied voltage; while Figure 7 This is a schematic diagram showing the state when a voltage of 10V is applied, compared to the state when no voltage is applied. Figure 9 In comparison, the width and curvature of the groove (i.e., the slot group) are increased. According to finite element simulation analysis, the average width of the groove is 102.4μm. Figure 8 This is the state when a voltage of 20V is applied. According to finite element simulation analysis, the average width of the groove is 113.85μm.

[0081] When the sensor is subjected to force, the boundary condition for the groove to be completely closed is:

[0082] p>wEH / 3h L 2 (w+l)

[0083] Where h is the groove depth, w is the groove width, l is the groove spacing, p is the pressure on the flexible sensor, E is the elastic modulus of the sensor, H is the sensor thickness, and L is the sensor length.

[0084] As can be seen from the formula, the wider the groove, the larger the range of strain detection, so applying voltage can achieve the purpose of controllable range.

[0085] Due to the different applied voltages Figure 7 The degree of bending is less than Figure 8 The groove attached to it is narrower than the latter, thus requiring less strain. Figure 7Narrower grooves will slowly close completely, meaning the Au on both sides of the groove will conduct sequentially, and the resistance value will gradually stop changing. Detecting the resistance difference before and after applying strain achieves the purpose of strain detection. Reaching the strain limit, where a relatively small force allows the sensor to reach its detection range, also makes it more sensitive to changes in critical closing pressure and higher to small strains, but the strain range is smaller. At this point, the optimal performance threshold for strain detection by the sensor is adjusted within the small strain range, thus enabling better detection of smaller forces.

[0086] Figure 8 The degree of curvature is greater than Figure 7 The groove on the first sensor is wider than the former, making it less likely to reach the deformation limit. This means a greater force is required to completely close the groove, at which point the resistance of Au stops changing, indicating a larger strain range and the ability to detect larger strains. Compared to the first sensor, the sensitivity for detecting small strains is slightly reduced, but due to the slit structure, it can still detect large strains with good sensitivity. Furthermore, the increased groove width and depth ratio conform to the scorpion's sensitivity tuning mechanism, meaning the optimal performance threshold for strain detection is adjusted within a large strain range, thus enabling better detection of larger forces. In summary, based on the above analysis, the sensor can achieve high sensitivity to strains of different magnitudes by adjusting the voltage value, thus giving the sensor high sensitivity and a large range.

[0087] In summary, this invention provides a biomimetic adjustable-range strain sensor, comprising an actuator base, a conductive sensitive layer sensing portion, and a micro-biomimetic slit structure portion. The actuator base includes a heating layer and a double-layer material with significantly different coefficients of thermal expansion; the conductive sensitive layer sensing portion includes a conductive layer and metal electrodes; the micro-biomimetic slit structure portion includes a slit assembly formed by arranged grooves. The manufacturing theory of the biomimetic slit assembly originates from the slit sensory organ of a scorpion. Scorpions change their leg posture according to the external environment, thereby changing the width of the compressed slit. By adjusting the slit sensory organ to the optimal dynamic pressure detection range according to the environment, the dynamic range and sensitivity to signal pressure are significantly improved, thus detecting various vibrations from prey and predators to high to low levels. Specifically, strip-shaped grooves are machined into the bottom material of the actuator structure, and a thin layer of gold is sputtered onto the surface of the grooves to form a conductive sensitive layer. The resistance value of the conductive sensitive layer is measured to achieve pressure detection. A voltage is applied to the heating layer of the actuator substrate, converting electrical energy into Joule heat which is then transferred to the entire sensor. Due to the thermal expansion mismatch between the two layers of the actuator, the actuator bends, causing the width of the slot structure to change accordingly. If the slot width increases, greater pressure is required to close the slot, thus increasing the sensor's range. In other words, by adjusting the voltage, the sensor's pressure detection range is increased, achieving an adjustable range. This invention can be applied in biomedicine to detect mechanical signals at different pressure ranges, and to detect vital signs such as neck vibration, heart rate, and muscle contraction, fulfilling pressure detection needs in various scenarios.

[0088] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A biomimetic adjustable-range strain sensor, characterized in that, include: The actuator base structure has a heating layer and a material layer with different coefficients of thermal expansion, which can convert the received voltage into Joule heat, causing thermal expansion and deformation. A conductive sensing layer is disposed on the underside of the actuator substrate structure and is used to measure resistance values. The microscopic biomimetic slit structure includes a slit group formed by an arrangement of grooves. Multiple rows of indentations are formed in the conductive sensitive layer sensing structure towards the actuator substrate structure. The slit group formed by the groove arrangement can change according to the deformation of the actuator substrate structure. The pressure at which the grooves of the slit group close to the deformation limit is the critical closure pressure of the grooves. The critical closure pressure is the maximum detectable strain value. The boundary condition for the complete closure of the grooves is: p>wEH / 3h L 2 (w+l) Where h is the groove depth, w is the groove width, l is the groove spacing, p is the pressure on the strain sensor, E is the elastic modulus of the strain sensor, H is the thickness of the strain sensor, and L is the length of the strain sensor. The biomimetic adjustable-range strain sensor is biomimeticly fabricated based on the tuning mechanism of a scorpion slit receptor, and the grooves of the slit assembly are biomimeticly fabricated based on the structure of the scorpion slit receptor. When a voltage is applied to the actuator substrate, electrical energy is converted into Joule heat and transferred to the entire strain sensor, causing bending based on the actuator substrate structure, which in turn causes the width of the slit assembly of the micro-bionic slit structure to change. The adjustable range is achieved by adjusting the voltage value to regulate the temperature of the biomimetic adjustable-range strain sensor, thereby adjusting the degree of bending of the actuator substrate structure and changing the width of the grooves on the actuator substrate structure. Specifically, when the temperature increases, the degree of bending of the actuator substrate structure increases, and the grooves attached to it are correspondingly stretched and widened.

2. The biomimetic adjustable range strain sensor according to claim 1, characterized in that, The actuator substrate structure includes: a heating layer, and a double-layer material layer with significantly different coefficients of thermal expansion connected to the heating layer.

3. The biomimetic adjustable range strain sensor according to claim 2, characterized in that, The heating layer is a multi-walled carbon nanotube heating layer, and the bilayer material layer with significantly different coefficients of thermal expansion is: a cellulose paper layer and a PDMS film layer; The heating layer, the cellulose paper layer, and the PDMS film layer are arranged sequentially.

4. The biomimetic adjustable range strain sensor according to claim 3, characterized in that, The conductive sensing layer includes a conductive layer and a metal electrode connected to the conductive layer.

5. The biomimetic adjustable range strain sensor according to claim 4, characterized in that, The micro-bionic seam structure includes a seam group formed by an arrangement of grooves, which is disposed on the conductive layer.

6. The biomimetic adjustable range strain sensor according to claim 5, characterized in that, The groove of the slit assembly is disposed on the PDMS film layer and is parallel to the short side of the entire biomimetic adjustable range strain sensor. The conductive layer is selected from one of nano-platinum, gold, silver, copper, and aluminum.

7. The biomimetic adjustable range strain sensor according to claim 2, characterized in that, The heating layer is manufactured by brushing a conductive solution in a U-shape onto the actuator substrate structure to form a conductive path; The conductive solution brushed onto the heating layer is one or a mixture of multi-walled carbon nanotubes, conductive graphite, conductive carbon black, carbon fiber, and graphene.

8. The biomimetic adjustable range strain sensor according to claim 3, characterized in that, The thickness of the heating layer is less than the thickness of the cellulose paper layer and the PDMS film layer, the thickness of the cellulose paper layer is less than the thickness of the PDMS film layer, and the cellulose paper layer and the PDMS film layer are bonded together by an ultra-thin silicone layer.

9. A measurement method for a biomimetic adjustable-range strain sensor as described in any one of claims 1-8, characterized in that, When the voltage applied to the heating layer is adjusted, its electrical charge is converted into Joule heat. The actuator base structure of the biomimetic adjustable strain sensor bends to varying degrees, causing the groove of the slot group to deform until it is adjusted to the specified performance threshold for the sensor to detect strain. At this time, strain is applied to the strain sensor, causing the groove to deform and the resistance value of the conductive layer to change. The resistance difference before and after the strain is applied is recorded, and finally the magnitude of the strain value to be measured is detected.

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