Pressure and temperature multifunctional sensor for energy collection and manufacturing method thereof

Abstract

The invention relates to a pressure and temperature multifunctional sensor for energy collection and a manufacturing method thereof, the pressure and temperature multifunctional sensor adopts a double-layer composite structure: an upper wire coil layer is composed of a liquid metal coil embedded in a PDMS substrate, silver paint and a wire connected with the silver paint, and a lower magnetic fiber network layer is formed by weaving magnetic liquid crystal elastomer LCE composite fibers; the two are structurally integrated through a bonding layer; a coil conductive loop in the upper wire coil layer is formed on the surface of the PDMS substrate through a direct-writing printing technology, and packaging protection is completed through secondary pouring of PDMS; the LCE composite fiber takes an LCE hollow fiber tube as an external carrier, magnetorheological fluid is filled in the LCE composite fiber to serve as a magnetic medium, and two ends of the LCE composite fiber are sealed and packaged by adopting a compound of neodymium iron boron magnetic particles and PDMS (Polydimethylsiloxane). The sensor provided by the invention not only can realize pressure and temperature sensing, but also can be used as an energy collection device, provides a new solution for sustainable development of wearable equipment and sensors, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible multifunctional sensors, and in particular to a pressure-temperature multifunctional sensor for energy harvesting and a manufacturing method thereof. Background Art

[0002] With the rapid development of technology in the field of sensors, the demand for flexible multifunctional sensors in the fields of medical health monitoring, industrial automation, environmental monitoring, smart wearables, etc. is increasing day by day. Although traditional rigid sensors have made significant progress in terms of accuracy and stability, they are still inferior to flexible sensors in terms of flexibility, wearability, and biocompatibility. These advantages enable flexible multifunctional sensors to have better application prospects in the fields of medical health monitoring, smart wearables, complex environment monitoring, etc.

[0003] However, most of the flexible temperature sensors currently on the market rely on external power supplies or batteries for power supply, which undoubtedly limits their wide application in fields such as wearable devices. In the past, flexible temperature sensors mostly used the thermoresistance effect, the Seebeck effect, the pyroelectric effect, etc. The multi-layer structure and micro-structure design (such as the micro-structure of the interlocked pressure-sensitive layer) have increased the complexity and cost of the manufacturing process. In addition, in the previous research on preparing self-powered sensors using flexible magnetic sensing materials, for the combination method of magnetic materials and flexible materials, the scheme of doping magnetic particles in polymers is mostly adopted. This approach often makes it difficult to balance the magnetic field strength and flexibility, resulting in problems such as weak electrical signals due to weak magnetic field strength or failure of the flexible structure due to excessive doping of magnetic particles in actual use. These various problems are difficult to meet the increasingly diverse and complex application requirements. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a pressure-temperature multifunctional sensor for energy harvesting and a manufacturing method thereof.

[0005] The technical solution adopted by the present invention to solve the above technical problem is:

[0006] In a first aspect, the present invention provides a pressure-temperature multifunctional sensor for energy harvesting. The sensor is a double-layer composite structure, namely the upper wire coil layer and the lower magnetic fiber network layer. The upper layer and the lower layer are adhesively fixed and assembled together through an adhesive layer to form a complete whole;

[0007] The wire coil layer includes a flexible substrate, a coil conductive circuit, and a packaging layer. The coil conductive circuit is fixed on the flexible substrate, and the packaging layer is arranged on the coil conductive circuit;

[0008] The magnetic fiber network layer is a fiber network woven from multiple LCE composite fibers. Each LCE composite fiber has magnetism and includes an external LCE hollow fiber tube, a magnetorheological fluid filled inside the LCE hollow fiber tube, and encapsulants containing magnetic particles for providing a magnetic field at both ends of the magnetorheological fluid inside the LCE hollow fiber tube. The LCE hollow fiber tube is encapsulated by the encapsulants containing magnetic particles to form a single LCE composite fiber.

[0009] Further, the coil conductive loop adopts an Archimedean spiral shape. Both ends of the coil conductive loop are respectively fixedly connected to metal wires by conductive silver paint. Two metal wires are led out of the flexible substrate, and the encapsulation layer encapsulates the coil conductive loop, the conductive silver paint, and part of the metal wires.

[0010] Further, in a single LCE composite fiber, the length of the encapsulant is 25 - 35% of the total length, and the lengths of the encapsulants at both ends of the single LCE composite fiber are the same.

[0011] Further, the flexible substrate 12, the encapsulation layer 13, and the adhesive layer 3 are made of a flexible polymer material that is flexible and can be well combined with the coil. The flexible polymer material is PDMS or Ecoflex; the thickness of the adhesive layer is 1 - 3 mm.

[0012] Further, the coil conductive loop 11 is formed on the surface of the flexible substrate by liquid metal direct writing printing technology. Conductive silver paint is used to electrically connect the two ends of the copper wire and the liquid metal LM. The encapsulation protection is completed by secondary casting of PDMS to cover the LM conductive loop and the silver paint; the coil conductive loop 11 is formed by the direct writing 3D printing platform using a 17G, 16G, or 18G needle to print the liquid metal in multiple circles according to the set path and solidify it.

[0013] Further, the LCE hollow fiber tube 211 can be woven by textile weaving methods, such as plain weave, twill weave, or other weaving methods, to obtain a magnetic fiber network.

[0014] Further, the magnetic particles in the encapsulants containing magnetic particles are made of neodymium iron boron particles or ferromagnetic particles. The encapsulant is made of the same flexible polymer material as the flexible substrate, and the mass ratio of the flexible polymer material to the magnetic particles is 1:1 to 1:4.

[0015] Further, the LCE composite fibers are woven into a whole and magnetized to form a magnetic fiber network, which has a controllable magnetic field environment, and the magnetic induction lines are perpendicular to the magnetic fiber network. During application, the liquid crystal elastomer LCE itself will deform with temperature changes. When the external environmental temperature changes and causes the LCE composite fibers to deform, the magnetic fiber network will deform, thereby causing a change in the magnetic induction line density inside the coil conductive loop 11 to generate an induced current, completing the multi-stage signal conversion of temperature-induced deformation - magnetic field regulation - electromagnetic induction, and realizing temperature sensing by detecting the current.

[0016] At the same time, when the sensor deforms under pressure, it will also cause the magnetic network composed of LCE composite fibers to deform, and the magnetic flux density inside the coil conductive loop will also change simultaneously, thereby inducing a current in the coil conductive loop. By precisely detecting the change in the induced current, the sensing of pressure is realized.

[0017] In a second aspect, the present invention provides a method for manufacturing a pressure-temperature multi-functional sensor for energy harvesting, and the manufacturing method includes the following steps:

[0018] The first step: Prepare the PDMS prepolymer with a PDMS: curing agent mass ratio of 10:1 and stir it evenly with a magnetic stirrer. Then place the PDMS prepolymer in a vacuum oven and evacuate it to remove air bubbles.

[0019] Spray the PDMS release agent on the glass slide. After it dries, spin-coat the PDMS prepolymer on the glass slide. After the spin-coating is completed, place it in an oven and heat-cure it to obtain the flexible substrate 12.

[0020] The second step: Use a direct writing 3D printing platform to print liquid metal LM on the flexible substrate 12 prepared in the first step to form the coil conductive loop 11, and use conductive silver paint 14 to connect and fix the two ends of the coil conductive loop 11 to the metal wire 15.

[0021] The third step: Use a direct writing 3D printing platform to evenly print the PDMS prepolymer on the coil conductive loop 11 prepared in the second step to maintain the coil conductive loop 11 and heat it to make the encapsulation layer 13 to obtain the upper composite structure of the sensor.

[0022] The fourth step: Use an ultrasonic oscillator to ultrasonically treat the ethyl acetate added with neodymium iron boron powder to disperse it evenly. Then, add the PDMS monomer to the neodymium iron boron / ethyl acetate mixture with a PDMS: neodymium iron boron mass ratio of 1:4 and perform magnetic stirring on the mixture until the ethyl acetate solvent evaporates completely. Then, add the PDMS curing agent to the neodymium iron boron / PDMS monomer mixture with a PDMS: curing agent mass ratio of 10:1 and stir it evenly with a magnetic stirrer to obtain the neodymium iron boron / PDMS mixture.

[0023] Step 5: Dissolve RM257, PETMP, DODT, DPA, and photoinitiator 651 in ethyl acetate and stir magnetically until evenly mixed to obtain a mixed solution. Inject the mixed solution into a silica gel tube, seal both ends, and place it in a vacuum oven. Evacuate to induce the permeation evaporation of the solvent ethyl acetate to obtain the LCE prepolymer. Then, place the LCE prepolymer in the silica gel tube in an oven and heat it at 55 - 65 °C for 9 - 12 h. Finally, perform pre-stretching and ultraviolet curing on the silica gel tube for 10 - 20 min to extract the LCE hollow fiber tube 211;

[0024] Step 6: Fill the magnetic rheological fluid 212 into the hollow structure of the LCE hollow fiber tube 211, heat-seal the hollow structures at both ends of the LCE hollow fiber tube 211 using a neodymium iron boron / PDMS mixture, and then perform a magnetization treatment on the fiber using an electric motor magnetizer to obtain the magnetic LCE composite fiber 21;

[0025] Step 7: Weave multiple LCE composite fibers 21 into a magnetic fiber network to obtain the lower-layer composite structure of the sensor. Then, apply a PDMS prepolymer between the upper part and the lower part and perform a hot pressing treatment to obtain the pressure-temperature multi-functional sensor for energy harvesting.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] First: It has the functions of self-power supply and energy harvesting. Through a unique structural design, the sensor of the present invention uses the deformation of the magnetic LCE composite fiber to drive the liquid metal LM coil to cut the magnetic induction lines, generates an electric current based on the electromagnetic induction principle, and directly powers the sensor, realizing the self-power supply function and effectively reducing the dependence on external power sources. At the same time, the sensor can also convert mechanical energy and environmental thermal energy into electrical energy for energy harvesting, improving the practicability and economy of the sensor.

[0028] Second: It has an innovative sensing method. When the sensor is deformed under pressure or the external environmental temperature changes, causing the magnetic network composed of LCE composite fibers in its lower part to deform, the magnetic flux density inside the LM coil also changes simultaneously. As a result, an electric current is induced in the LM coil in the upper part. By precisely detecting the change in the induced current, the sensing of pressure or environmental temperature can be achieved. This pressure-temperature sensing method based on a multi-stage signal conversion mechanism of mechanical pressure / thermally induced deformation - magnetic field regulation - electromagnetic induction has unique innovation and provides a new technical path for pressure-temperature sensing.

[0029] Point 3: It has high-performance magnetic composite fibers. The magnetic LCE composite fibers in the lower part are encapsulated by an external LCE hollow fiber tube, internally filled magnetorheological fluid, and neodymium iron boron / PDMS mixture at both ends for providing magnetic fields. This core-shell structure not only endows the fibers with magnetism, effectively avoids the problem of increased Young's modulus caused by doping with traditional magnetic particles by utilizing the flexible characteristics of the magnetorheological fluid, but also through the regulation of the encapsulant, coordinates and optimizes the magnetic field strength and material flexibility, significantly enhancing the sensitivity and long-term stability of the sensor.

[0030] Point 4: The upper and lower parts are adhesively assembled through PDMS to form a complete structure, which not only ensures the integrity of the sensor, but also further enhances the flexibility and recovery ability of the sensor through the elastic characteristics of PDMS, enabling it to maintain stable performance during dynamic cycling.

[0031] Point 5: It realizes multifunctional integration and application expansion. The sensor of the present invention can not only achieve pressure and temperature sensing, but also serve as an energy harvesting device to convert mechanical energy and ambient thermal energy into electrical energy, providing a new solution for the sustainable development of wearable devices and sensors, and having broad application prospects.

[0032] Point 6: In the manufacturing method of the present invention, neodymium iron boron powder is added to ethyl acetate, after ultrasonic treatment, PDMS monomer is added and stirred until the solvent evaporates, then a curing agent is added and stirred to obtain the neodymium iron boron / PDMS mixture. RM257, PETMP, DODT, DPA, and a photoinitiator are dissolved in ethyl acetate, injected into a silica gel tube, and the solvent is evaporated under vacuum, and then heated to obtain the LCE prepolymer. After pre-stretching and ultraviolet curing, the LCE hollow fiber is extracted. The magnetorheological fluid is injected into the LCE hollow fiber, and both ends are encapsulated with the neodymium iron boron / PDMS mixture and woven into a network structure. The addition and evaporation process of the solvent ethyl acetate enables the neodymium iron boron particles to be evenly dispersed, avoiding the agglomeration phenomenon during the direct addition to PDMS; the combination of soft and hard is achieved by injecting the magnetorheological fluid into the LCE hollow fiber to prepare the LCE composite fiber, reconciling the contradiction between the magnetic field strength and flexibility. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a schematic structural diagram of the multifunctional pressure and temperature sensor for energy harvesting provided by the embodiment of the present invention.

[0035] Figure 2 Schematic diagram of the wire coil layer structure of the pressure-temperature multifunctional sensor for energy harvesting.

[0036] Figure 3 Schematic diagram of the unencapsulated state structure of the wire coil layer of the pressure-temperature multifunctional sensor for energy harvesting.

[0037] Figure 4 Schematic diagram of the LM conductive coil and its flexible substrate.

[0038] Figure 5 Schematic diagram of the magnetic fiber network layer of the pressure-temperature multifunctional sensor for energy harvesting.

[0039] Figure 6 is Figure 5 Top view.

[0040] Figure 7 Schematic diagram of the cross-sectional structure of the LCE composite fiber.

[0041] In the figure, wire coil layer 1, flexible substrate 12, coil conductive loop 11, encapsulation layer 13, conductive silver paint 14, metal wire 15;

[0042] Magnetic fiber network layer 2, LCE composite fiber 21, LCE hollow fiber tube 211, magnetorheological fluid 212, encapsulated material containing magnetic particles 213;

[0043] Adhesive layer 3. Detailed implementation mode

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] Figure 1 Schematic diagram of the overall structure of the pressure-temperature multifunctional sensor for energy harvesting provided by the embodiment of the present invention. The pressure-temperature multifunctional sensor for energy harvesting of the present invention is a double-layer composite structure, namely the upper wire coil layer 1 and the lower magnetic fiber network layer 2. The upper layer and the lower layer are adhesively fixed and assembled together through the adhesive layer 3 to form a complete whole. The material used for the adhesive layer 3 is the same as that of the flexible substrate 12.

[0046] The thickness of the adhesive layer 3 is approximately 1 - 3 mm. If the adhesive layer 3 is too large, it will reduce the magnetic induction line density inside the coil. If the adhesive layer 3 is too small, it will cause synchronous deformation between the network and the coil, and there will be no change in the magnetic induction line density during deformation.

[0047] The wire coil layer 1 (see Figures 2-4 ) includes a flexible substrate 12, a coil conductive circuit 11, and a packaging layer 13. The coil conductive circuit 11 is fixed on the flexible substrate 12. The coil conductive circuit 11 adopts an Archimedes spiral shape. The two ends of the coil conductive circuit are respectively cured and connected to the metal wires 15 by conductive silver paint 14. The two metal wires 15 extend out of the flexible substrate 12. A packaging layer 13 is arranged on the coil conductive circuit 11 to encapsulate the coil conductive circuit 11, the conductive silver paint, and part of the metal wires 15 to form an upper composite structure.

[0048] The magnetic fiber network layer 2 (see Figure 5 and Figure 6 ) is a fiber network woven from multiple LCE composite fibers 21. Each LCE composite fiber 21 has magnetism and includes an external LCE hollow fiber tube 211 (see Figure 7 ), a magnetorheological fluid 212 filled inside the LCE hollow fiber tube 211, and encapsulants 213 containing magnetic particles for providing a magnetic field and fixed at both ends of the magnetorheological fluid 212 inside the LCE hollow fiber tube 211. The LCE hollow fiber tube 211 is encapsulated by the encapsulants 213 containing magnetic particles to form a single LCE composite fiber 21.

[0049] In the embodiment of the present invention, the coil conductive circuit 11 is formed on the surface of the flexible substrate 12 by using a liquid metal direct writing printing technology. The conductive silver paint 14 is used to realize the electrical connection between the metal wires 15 and the two ends of the coil conductive circuit 11, and the encapsulation protection is completed by secondary casting of PDMS to cover the coil conductive circuit 11 and the conductive silver paint 14. The thickness of the packaging layer is appropriate, which needs to cover the surface of the coil and does not affect the conductivity.

[0050] The coil conductive circuit 11 is formed by curing the liquid metal printed in multiple circles by a direct writing 3D printing platform using a 17G needle according to a set path. The coil printing needle size of 17G can also be changed to 16G, 18G, etc.

[0051] The present invention can be printed in the form of an Archimedes spiral or in the form of multiple concentric rectangles, etc.

[0052] The metal wires 15 can all adopt commercial conductive copper wires. The material size of this kind of conductive copper wire is uniform and the performance is stable, which is beneficial to improving the stability of the performance of this sensor and also beneficial to ensuring the measurement accuracy of this sensor. In addition, the conductive silver paint 14 is used to connect the coil conductive circuit 11 and the metal wires 15, which has good adhesion and ensures the stability of the connection.

[0053] The flexible substrate 12, the encapsulation layer 13, and the adhesive layer 3 can be made of flexible polymer materials such as PDMS and Ecoflex, which are flexible and can be well combined with the coil, and are not easily damaged and separated when subjected to external force pulling and kneading.

[0054] In the present invention, the LCE hollow fiber tube 211 can be woven by textile weaving methods, and the textile weaving methods can adopt plain weaving, twill weaving or other weaving methods to obtain the magnetic fiber network layer 2.

[0055] In actual operation, the liquid metal (LM) is especially the gallium-indium alloy, and other liquid metals can also be used, such as gallium-indium-tin alloy, etc.

[0056] The magnetic particles in the encapsulation containing magnetic particles can be made of neodymium iron boron particles, ferromagnetic particles, etc. The encapsulation can be made of the same material as the flexible substrate, such as PDMS for curing encapsulation. The mass ratio of PDMS to neodymium iron boron is 1:1 to 1:4. The appropriate amount of neodymium iron boron can not only induce the magnetorheological fluid to exhibit magnetism, but also occupy part of the volume as the encapsulation to ensure the overall flexibility and magnetic requirements.

[0057] In the embodiment of the present invention, the LCE hollow fiber tube 211 is used as the external carrier, the magnetorheological fluid 212 is filled inside as the magnetic medium, and the two ends are hermetically encapsulated with the encapsulation 213 containing magnetic particles. After being woven and magnetized as a whole, a controllable magnetic field environment is formed, and the magnetic induction lines are perpendicular to the magnetic fiber network. When in use, the liquid crystal elastomer LCE itself will deform with the change of pressure or temperature. When the external pressure or ambient temperature changes and causes the LCE composite fiber to deform, the magnetic fiber network deforms, and then the magnetic induction line density inside the coil conductive loop 11 changes to generate an induced current, completing the multi-stage signal conversion of mechanical pressure / temperature-induced deformation - magnetic field regulation - electromagnetic induction, and realizing pressure and temperature sensing by detecting the current.

[0058] Embodiment 1

[0059] The manufacturing method of the pressure and temperature multi-functional sensor for energy harvesting in this embodiment includes the following steps:

[0060] The first step: Prepare the PDMS prepolymer with a PDMS:curing agent mass ratio of 10:1 and perform magnetic stirring for 10 min. Then place the PDMS prepolymer in a vacuum oven and evacuate to remove air bubbles. In this embodiment, the PDMS prepolymer is subjected to a 10-min vacuum treatment;

[0061] Spray the PDMS release agent on the glass slide. After it dries, spin-coat the PDMS prepolymer on the glass slide. After the spin-coating is completed, place it in an oven and heat-cure it at 100 °C for 30 min to prepare the flexible substrate 12.

[0062] Step 2: Use a direct-write 3D printing platform to print liquid metal LM on the flexible substrate 12 prepared in the first step to form a coil conductive circuit 11, and use conductive silver paint 14 to connect and fix both ends of the coil conductive circuit 11 to the metal wire 15.

[0063] Step 3: Use a direct-write 3D printing platform to uniformly print the PDMS prepolymer on the coil conductive circuit 11 prepared in the second step to maintain the coil conductive circuit 11 and heat it to fabricate the encapsulation layer 13 to obtain the upper composite structure of the sensor.

[0064] Step 4: Use an ultrasonic oscillator to ultrasonically treat ethyl acetate added with neodymium iron boron powder for 1 h. Ethyl acetate, as a solvent, can effectively prevent the aggregation of neodymium iron boron particles. Then, add PDMS monomer to the neodymium iron boron / ethyl acetate mixture at a PDMS:neodymium iron boron mass ratio of 1:4 and perform magnetic stirring on the mixture until the ethyl acetate solvent has completely evaporated. Then, add PDMS curing agent to the neodymium iron boron / PDMS monomer mixture at a PDMS:curing agent mass ratio of 10:1 and perform magnetic stirring for 10 min to obtain a neodymium iron boron / PDMS mixture.

[0065] Step 5: Dissolve 0.8 g of RM257 and 0.022 g of photoinitiator 651 in 2 mL of ethyl acetate. Additionally, add 67 μL of crosslinking agent PETMP, 142 μL of chain extender DODT, and 29 μL of catalyst DPA to this ethyl acetate. Magnetically stir this solution for 10 min to obtain a mixture. Inject the mixture into a silica gel tube, seal both ends, and place it in a vacuum oven. Evacuate for 1.5 - 2 h to induce the permeation and evaporation of the solvent ethyl acetate. The small-molecule solvent of ethyl acetate will permeate through the silica gel tube and evaporate, obtaining an LCE prepolymer. Then, place the LCE prepolymer in the silica gel tube in an oven and heat it at 60 °C for 10 h. Finally, perform pre-stretching and ultraviolet curing on the silica gel tube for 10 - 20 min, and extract to obtain the LCE hollow fiber tube 211. During the evaporation process, the solvent decreases, the overall liquid part decreases, and the remaining solute adheres to the silica gel tube wall to form a hollow fiber tube. After stretching and ultraviolet curing, it is extracted from the silica gel tube to form a hollow fiber tube.

[0066] Step 6: Fill the hollow structure of the LCE hollow fiber tube 211 with magnetorheological fluid 212, use the neodymium iron boron / PDMS mixture to heat-seal the two ends of the hollow structure of the LCE hollow fiber tube 211, and then use an electric motor magnetizer to magnetize the fiber to obtain a magnetic LCE composite fiber 21. In a single LCE composite fiber, the length of the encapsulant is 30% of the total length, and the lengths of the encapsulants at both ends of a single LCE composite fiber are the same.

[0067] Step 7: Weave multiple LCE composite fibers 21 into a magnetic fiber network by plain weaving to obtain the lower-layer composite structure of the sensor. Then, apply the PDMS prepolymer between the upper and lower parts and use hot pressing treatment to prepare a self-powered pressure-temperature multifunctional sensor for energy harvesting.

[0068] Example 2:

[0069] The pressure-temperature multifunctional sensor for energy harvesting in this example is a double-layer composite structure, which is respectively the wire coil layer 1 in the upper part and the magnetic fiber network layer 2 woven by the magnetic LCE composite fibers 21 in the lower part;

[0070] The wire coil layer 1 includes a flexible substrate 12, a coil conductive circuit 11, and a packaging layer 13. The coil conductive circuit 11 is fixed on the flexible substrate 12. The coil conductive circuit adopts an Archimedean spiral shape. The two ends of the coil conductive circuit are respectively cured and connected to the metal wires 15 by conductive silver paint 14. The two metal wires 15 extend out of the flexible substrate 12. A packaging layer 13 is arranged on the coil conductive circuit 11 to encapsulate the coil conductive circuit 11, the conductive silver paint, and part of the metal wires 15 to form the upper-layer composite structure; the magnetic fiber network layer 2 is a fiber network woven by multiple LCE composite fibers 21. Each LCE composite fiber 21 has magnetism and includes an external LCE hollow fiber tube 211, a magnetorheological fluid 212 filled inside the LCE hollow fiber tube 211, and encapsulants 213 containing magnetic particles for providing a magnetic field and fixed at both ends of the magnetorheological fluid inside the LCE hollow fiber tube 211. The LCE hollow fiber tube is encapsulated by the encapsulants 213 containing magnetic particles to form a single LCE composite fiber. The upper and lower parts are assembled by PDMS as the adhesive layer 3 to form a complete structure.

[0071] Example 3:

[0072] The manufacturing method of the pressure-temperature multifunctional sensor for energy harvesting in this example includes the following steps:

[0073] Step 1: Prepare the PDMS prepolymer with a PDMS:curing agent mass ratio of 10:1 and perform magnetic stirring for 10 min. Then, place the PDMS prepolymer in a vacuum oven and evacuate to remove air bubbles;

[0074] Spray the PDMS release agent on the glass slide. After it dries, spin-coat the PDMS prepolymer on the glass slide. After the spin-coating is completed, place it in an oven and heat-cure it at 100 °C for 30 min to prepare the flexible substrate 12;

[0075] Step 2: Use a direct-write 3D printing platform to print LM on the flexible substrate 12 prepared in the first step to form a coil conductive circuit 11, and use conductive silver paint 14 to connect and fix both ends of the coil conductive circuit 11 to the metal wire 15;

[0076] Step 3: Use a direct-write 3D printing platform to evenly print the PDMS prepolymer on the coil conductive circuit 11 prepared in the second step to maintain the coil conductive circuit 11 and heat it to fabricate the encapsulation layer 13 to obtain the upper composite structure of the sensor;

[0077] Step 4: Use an ultrasonic oscillator to ultrasonically treat ethyl acetate containing neodymium iron boron powder for 1 h. Then, add PDMS monomer to the neodymium iron boron / ethyl acetate mixture in a PDMS:neodymium iron boron mass ratio of 1:4 and perform magnetic stirring on the mixture until the ethyl acetate solvent evaporates completely. Then, add PDMS curing agent to the neodymium iron boron / PDMS monomer mixture in a PDMS:curing agent mass ratio of 10:1 and perform magnetic stirring for 10 min to obtain a neodymium iron boron / PDMS mixture;

[0078] Step 5: Dissolve 0.8 g of RM257 and 0.022 g of photoinitiator 651 in 2 mL of ethyl acetate. Additionally, add 67 μL of crosslinking agent PETMP, 142 μL of chain extender DODT, and 29 μL of catalyst DPA to this ethyl acetate. Magnetically stir this solution for 10 min to obtain a mixture. Inject the mixture into a silicone tube, seal both ends, and place it in a vacuum oven. Evacuate for 1.5 - 2 h to induce the permeation and evaporation of the solvent ethyl acetate. The small-molecule ethyl acetate solvent will permeate through the silicone tube and evaporate to obtain an LCE prepolymer. Then, place the LCE prepolymer in the silicone tube in an oven and heat it at 60 °C for 10 h. Finally, perform pre-stretching and ultraviolet curing on the silicone tube for 10 - 20 min to extract the LCE hollow fiber tube 211;

[0079] Step 6: Fill the hollow structure of the LCE hollow fiber tube 211 with magnetorheological fluid 212, use the neodymium iron boron / PDMS mixture to heat-seal the two ends of the hollow structure of the LCE hollow fiber tube 211, and then use a motorized magnetic charger to magnetize the fiber to fabricate a magnetic LCE composite fiber 21;

[0080] Step 7: Weave multiple LCE composite fibers 21 into a magnetic fiber network by flat weaving to obtain the lower composite structure of the sensor. Then, apply PDMS prepolymer between the upper and lower parts and use hot pressing to fabricate a pressure-temperature multifunctional sensor for energy harvesting.

[0081] In this embodiment, the outer diameter of the LCE hollow fiber tube 211 is 1 mm, and the wall thickness is 80 - 90 μm. By changing the diameter of the silica gel tube, the diameter of the prepared LCE hollow fiber tube 211 can be controlled, and the wall thickness can also be adjusted by changing the process of the vacuum infiltration process.

[0082] Example 4:

[0083] When the external force applied to the sensor or the external environmental temperature changes, the magnetic LCE composite fiber 21 deforms, and then the entire magnetic fiber network layer 2 deforms, that is, the signal conversion of mechanical pressure / temperature-induced deformation - magnetic field regulation is completed, resulting in a change in the magnetic flux density of the wire coil layer 1. A current is generated in the upper coil conduction loop 11, that is, the signal conversion of magnetic field regulation - electromagnetic induction is completed, and the environmental temperature is sensed by detecting the current change.

[0084] Example 5:

[0085] When the sensor is in an environment with continuous temperature fluctuations, the magnetic fiber network layer 2 woven by the lower magnetic LCE composite fiber 21 undergoes reversible deformation, and a continuous current is induced in the coil conduction loop 11. This current can be used to light an LED lamp or connect to an energy storage device to store electrical energy.

[0086] Matters not described in the present invention are applicable to the prior art.

Claims

1. A pressure-temperature multi-functional sensor for energy harvesting, characterized in that: The sensor has a double-layer composite structure, namely a wire coil layer on the upper layer and a magnetic fiber network layer on the lower layer. The upper layer and the lower layer are adhesively fixed and assembled together through an adhesive layer to form a complete whole; The wire coil layer includes a flexible substrate, a coil conductive circuit, and a packaging layer. The coil conductive circuit is fixed on the flexible substrate, and the packaging layer is arranged on the coil conductive circuit; The magnetic fiber network layer is a fiber network woven by multiple LCE composite fibers. Each LCE composite fiber has magnetism and includes an external LCE hollow fiber tube, a magnetorheological fluid filled inside the LCE hollow fiber tube, and encapsulants containing magnetic particles for providing a magnetic field at both ends of the magnetorheological fluid inside the LCE hollow fiber tube. The LCE hollow fiber tube is encapsulated by the encapsulants containing magnetic particles to form a single LCE composite fiber.

2. The sensor according to claim 1, characterized in that, The coil conductive circuit adopts an Archimedean spiral shape. Both ends of the coil conductive circuit are respectively connected to metal wires by conductive silver paint curing. Two metal wires are led out from the flexible substrate, and the packaging layer encapsulates the coil conductive circuit, the conductive silver paint, and part of the metal wires.

3. The sensor according to claim 1, wherein In a single LCE composite fiber, the length of the encapsulant is 25 - 35% of the total length, and the lengths of the encapsulants at both ends of the single LCE composite fiber are the same.

4. The sensor according to claim 1, characterized in that, The flexible substrate, the packaging layer, and the adhesive layer are made of a flexible polymer material that is flexible and can be well combined with the coil. The flexible polymer material is PDMS or Ecoflex; the thickness of the adhesive layer is 1 - 3 mm.

5. The sensor according to claim 1, wherein The coil conductive circuit is formed on the surface of the flexible substrate by a liquid metal direct writing printing technique. Conductive silver paint is used to achieve electrical connection of the two ends of the copper wire and the liquid metal LM. The LM conductive circuit and the silver paint are encapsulated and protected by secondary pouring of PDMS; the coil conductive circuit is formed by multi-loop printing and curing of liquid metal using a 17G, 16G, or 18G needle by a direct writing 3D printing platform according to a set path.

6. The sensor according to claim 1, characterized in that, The LCE hollow fiber tube can be woven by textile weaving methods, such as plain weave, twill weave, or other weaving methods, to obtain a magnetic fiber network.

7. The sensor according to claim 1, characterized in that The magnetic particles in the encapsulants containing magnetic particles are neodymium iron boron particles or ferromagnetic particles. The encapsulant is made of the same flexible polymer material as the flexible substrate, and the mass ratio of the flexible polymer material to the magnetic particles is 1:1 to 1:

4.

8. The sensor according to claim 1, characterized in that, The LCE composite fibers are woven into a whole and magnetized to form a magnetic fiber network with a controllable magnetic field environment, and the magnetic induction lines are perpendicular to the magnetic fiber network; during application, the liquid crystal elastomer LCE itself will deform with temperature changes. When the external environmental temperature changes and causes the LCE composite fibers to deform, the magnetic fiber network deforms, which in turn causes a change in the magnetic induction line density inside the coil conductive circuit to generate an induced current, completing the multi-stage signal conversion of temperature-induced deformation - magnetic field regulation - electromagnetic induction, and realizing temperature sensing by detecting the current; Meanwhile, when the sensor is deformed under pressure, it will also cause the deformation of the magnetic network composed of LCE composite fibers. At the same time, the magnetic flux density inside the coil conductive loop also changes, and then an induced current is generated in the coil conductive loop. By accurately detecting the change of the induced current, the sensing of pressure is realized.

9. A manufacturing method of a pressure-temperature multi-functional sensor for energy harvesting, characterized in that, The manufacturing method includes the following steps: The first step: Prepare the PDMS prepolymer with a PDMS:curing agent mass ratio of 10:1 and stir it evenly by magnetic force. Then place the PDMS prepolymer in a vacuum oven and evacuate to remove air bubbles. Spray the PDMS release agent on the glass slide. After it dries, spin-coat the PDMS prepolymer on the glass slide. After the spin-coating is completed, place it in an oven and heat-cure to obtain a flexible substrate. The second step: Use a direct-write 3D printing platform to print liquid metal LM on the flexible substrate prepared in the first step to form a coil conductive loop, and use conductive silver paint to connect and fix the two ends of the coil conductive loop to the metal wire. The third step: Use a direct-write 3D printing platform to evenly print the PDMS prepolymer on the coil conductive loop prepared in the second step to maintain the coil conductive loop and heat to make the encapsulation layer to obtain the upper composite structure of the sensor. The fourth step: Use an ultrasonic oscillator to ultrasonically treat the ethyl acetate added with neodymium iron boron powder to make it disperse evenly. Then add the PDMS monomer to the neodymium iron boron / ethyl acetate mixture with a PDMS:neodymium iron boron mass ratio of 1:4 and magnetically stir the mixture until the ethyl acetate solvent evaporates completely. Then add the PDMS curing agent to the neodymium iron boron / PDMS monomer mixture with a PDMS:curing agent mass ratio of 10:1 and stir evenly by magnetic force to obtain the neodymium iron boron / PDMS mixture. The fifth step: Dissolve RM257, PETMP, DODT, DPA, and photoinitiator 651 in ethyl acetate and stir evenly by magnetic force to obtain a mixed solution. Inject the mixed solution into a silicone tube, seal both ends, and place it in a vacuum oven. Evacuate to induce the permeation and evaporation of the solvent ethyl acetate to obtain the LCE prepolymer. Then place the LCE prepolymer in the silicone tube in an oven, heat it at 55-65 °C for 9-12 h, and finally perform pre-stretching and ultraviolet curing on the silicone tube for 10-20 min, and extract to obtain the LCE hollow fiber tube. The sixth step: Fill the magnetic rheological fluid into the hollow structure of the LCE hollow fiber tube, heat-seal the two ends of the hollow structure of the LCE hollow fiber tube with the neodymium iron boron / PDMS mixture, and then use a motor magnetizer to magnetize the fiber to obtain a magnetic LCE composite fiber. The seventh step: Weave multiple LCE composite fibers into a magnetic fiber network to obtain the lower composite structure of the sensor. Then apply the PDMS prepolymer between the upper part and the lower part and use hot pressing to obtain the pressure-temperature multifunctional sensor for energy harvesting.

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