Magnetic film-hydrogel dual-mode tactile sensor for finger monitoring

Abstract

The invention relates to a magnetic film-hydrogel dual-mode tactile sensor for finger monitoring. In the sensor, a first X-axis TMR element and a second X-axis TMR element are distributed in the longitudinal center of a flexible printed circuit board at an interval, a DN polyol organic hydrogel film wraps the first X-axis TMR element and covers the left part of the flexible printed circuit board, and an organic silicon elastic substrate wraps the second X-axis TMR element and covers the right part of the flexible printed circuit board; the DN polyol organic hydrogel film and the organic silicon elastic substrate have the same thickness; the upper surfaces of the DN polyol organic hydrogel film and the organic silicon elastic substrate are covered with neodymium iron boron-organic silicon elastomer films; the touch sensor provided by the invention has the advantages of high sensitivity, high resolution, bimodal measurement and the like, and can realize accurate measurement of bending angle, static force, dynamic force and temperature change perception.

Description

Technical Field

[0001] The present invention is based on acrylamide / carrageenan double network (DN) hydrogel, neodymium iron boron magnetic particles (Nd2Fe 14 A magnetic film-hydrogel dual-modal tactile sensor for finger monitoring was designed and fabricated using a silicon elastomer (B1) and a silicone elastomer (Ecoflex 00-30). This sensor utilizes the tunnel magnetoresistance effect, the magnetoconductance effect, and the thermal response of ion-activated conductive hydrogel to detect pressure and temperature, enabling human finger monitoring. It can accurately detect the bending angle generated at the angle measurement position, the static force applied at the force measurement position, and the temperature change of the grasped object. It can be worn on the finger as a smart wearable device for finger monitoring. Background Art

[0002] Touch is an indispensable part of the human body, and tactile sensors are the core sensors for human-computer interaction. They have broad application prospects worldwide. Their multimodal detection capabilities are the key to breaking through the robot's adaptation to the environment. Most research institutes are also conducting related sensor research. The development of multimodal tactile sensors is of great significance for the future of robotic arms to achieve human-computer interaction, intelligent perception, exploration and disaster relief, and other fields.

[0003] To date, traditional piezoelectric and piezoresistive sensors are limited to a single physical quantity detection mode, making it difficult to simultaneously acquire multi-dimensional information such as stress and temperature. Flexible tactile sensors are mostly used to test external strain and bending, detecting pressure in a single way, but research on dual-modal tactile sensors for pressure and temperature is relatively limited. Compared with traditional piezoelectric and piezoresistive sensors, magnetic sensors offer advantages such as high sensitivity, high physical robustness, and low hysteresis. Compared with traditional rigid temperature sensors, conductive hydrogels as temperature sensors offer advantages such as high sensitivity, good dynamic stability, good biocompatibility, and stretchability.

[0004] Patent (application number 202311645225.8) A flexible tactile sensor for force and tilt recognition based on the tunnel magnetoresistance effect and the magnetic permeability effect of NdFeB magnetic particles using Nd2Fe 14A flexible tactile sensor with force and tilt recognition capabilities was fabricated using a fabricated NdFeB magnetic film and a TMR tunnel magnetoresistive (TMR) element. The sensor utilizes the magnetic permeability effect of the NdFeB magnetic particles and the tunnel magnetoresistive (TMR) element. Specifically, when a force is applied to the magnetic film or a bending deformation is generated, the film elastically deforms, causing changes in the internal magnetic domains. The organic silicone elastic substrate deforms, causing the distance between the magnetic film and the TMR to change, thereby changing the magnetic field intensity around the force-applied location. The TMR converts the detected magnetic field changes into changes in internal magnetoresistive resistance, enabling accurate detection of the bending angle generated at the angle measurement location and the static and dynamic forces applied at the force measurement location. However, due to the single sensing material and the temperature insensitivity of the NdFeB material, the invention is limited to stress and bending testing and cannot achieve temperature detection. Furthermore, the sensor has a single response to external signals and lacks the ability to respond to other environmental stimuli. Therefore, it cannot be applied to wearable devices to monitor multiple finger stimuli. Summary of the Invention

[0005] Addressing the current lack of research on pressure-temperature dual-modal tactile sensors, the present invention provides a magnetic film-hydrogel dual-modal tactile sensor for finger monitoring, which can be used to measure changes in stress, angle, and temperature. The sensor uses a mixture of NdFeB magnetic particles and an organic elastomer prepolymer to produce a magnetic film, which serves as the stress and angle sensing component of the flexible tactile sensor. A PAM / carrageenan DN hydrogel precursor is synthesized using a one-pot method using acrylamide (AM), carrageenan, N,N-methylenebisacrylamide (MBA), and potassium chloride (KCl). The hydrogel is then cured with 365nm UV light to produce a DN polyol organic hydrogel. The hydrogel is then immersed in a small molecule polyol solution (GLY) for 2 hours to produce the DN polyol organic hydrogel. Finally, the hydrogel is encapsulated in plastic paraffin film to prevent water evaporation from the hydrogel. Copper electrodes and copper wires serve as electrodes and conductors on either side of the hydrogel to measure changes in its conductivity after sensing temperature changes, which serves as the temperature sensing component of the flexible dual-modal tactile sensor. The DN polyol organohydrogel, a temperature-sensing component, is encapsulated by an elastomer, a plastic paraffin film. Changes in its electrical conductivity are measured in response to external temperature fluctuations. The hydrogel's temperature sensing is also unaffected by stress and angle. The tactile sensor of this invention boasts high sensitivity, high resolution, and dual-modal measurement capabilities, enabling precise measurement of bending angle, static and dynamic forces, and temperature sensing.

[0006] The technical solution of the present invention is:

[0007] A magnetic film-hydrogel dual-modal tactile sensor for finger monitoring, the sensor comprising a NdFeB-organic silicon elastomer film, a first X-axis TMR element, a DN polyol organic hydrogel film, an organic silicon elastic substrate, a flexible printed circuit board, and a second X-axis TMR element;

[0008] The first X-axis TMR element and the second X-axis TMR element are spaced apart and distributed on the longitudinal centerline of the flexible printed circuit board. The DN polyol organic hydrogel film covers the first X-axis TMR element and covers the left portion of the flexible printed circuit board. The organic silicone elastic substrate covers the second X-axis TMR element and covers the right portion of the flexible printed circuit board. The DN polyol organic hydrogel film and the organic silicone elastic substrate have the same thickness. The upper surfaces of the DN polyol organic hydrogel film and the organic silicone elastic substrate are covered with a NdFeB-organic silicone elastomer film.

[0009] The method for preparing the NdFeB-organic silicon elastomer film comprises the following steps:

[0010] The magnetic film preparation method includes: mixing NdFeB magnetic particles and silicone elastomer prepolymer in a ratio of 3:1, placing the mixture in a blender and stirring for 120 minutes to obtain a NdFeB-silicone elastomer prepolymer; pouring the prepolymer into a 3D-printed rectangular parallelepiped mold; covering the top layer with a plastic film; and curing the mixture at room temperature for 2 hours to obtain a NdFeB-silicone elastomer flexible film;

[0011] The obtained NdFeB-organic silicon elastomer flexible film is folded and fixed, and then placed in a magnetizer for magnetization to obtain a NdFeB-organic silicon elastomer magnetic film;

[0012] The silicone elastomer prepolymer is a mixture of Smooth-On's Ecoflex 00-30 series A and B, with a mass ratio of 1:1. The diameter of the NdFeB particles is 100 to 200 μm.

[0013] The thickness of the NdFeB-silicone elastomer flexible film is 1 mm;

[0014] The thickness of the organic elastic substrate is 3 mm; the length ratio of the DN polyol organic hydrogel film to the organic silicone elastic substrate is 1:2;

[0015] The preparation method of the conductive ion hydrogel comprises the following steps:

[0016] In the first step, acrylamide (AM), carrageenan, N,N-methylenebisacrylamide (MBA) and potassium chloride (KCL) are added to deionized water, and after magnetic stirring at 90-100°C for 1-3 hours, the solution is poured into a container and allowed to stand at 2-10°C for 0.5-2 hours to obtain a colloid with an ion-crosslinked carrageenan network structure;

[0017] In the second step, the film having an ion-crosslinked carrageenan network structure is irradiated with ultraviolet light at a wavelength of 365 nm for 0.5 to 2.0 hours to obtain a DN hydrogel film;

[0018] In the third step, the DN hydrogel is peeled from the container and cut into thin slices, which are then immersed in glycine (GLY) for 1.5 to 3 hours to introduce small molecule polyols. Finally, it is encapsulated with plastic paraffin film to obtain the final DN polyol organohydrogel, i.e., the conductive ion hydrogel.

[0019] The mass ratio is: acrylamide: carrageenan: UV initiator: MBA: KCl: H2O = 13-15: 2.8-3.3: 0.70-0.75: 0.005-0.008: 0.85-0.95: 78-83;

[0020] The purity of glycine (GLY) is 98% to 100%.

[0021] The first X-axis TMR element and the second X-axis TMR element are both TMR2003 type, with X-axis magnetic sensitivity direction; the package form is SOT23-5, and the element size is 3mm×3mm×1.45mm; the first X-axis TMR element measures normal force, and the second X-axis TMR element measures bending angle;

[0022] The flexible tactile sensor has an overall length of 58 to 62 mm, a width of 18 to 22 mm, and a height of 3 to 5 mm.

[0023] The essential features of the present invention are:

[0024] Currently, magnetic thin film sensors mainly realize sensing functions based on the internal uniform magnetic field after ignoring the edge effect, and there is little research on dual-modal tactile perception of pressure and temperature;

[0025] This flexible tactile dual-modal sensor consists of NdFeB-silicone elastomer magnetic film, DN polyol organic hydrogel film, silicone elastic substrate, TMR2003 and flexible printed circuit board. It can be worn tightly on the finger to perform stress recognition, accurate identification of different bending angles, and precise perception of object temperature.

[0026] The thermosensitivity of ion-conductive hydrogels stems from the thermally activated migration of ions. The increase in temperature not only promotes the migration of ions, but also causes the decomposition of ions, thereby increasing the concentration of ion carriers. Therefore, when the DN hydrogel film is worn on the finger as a sensor and senses the change in external temperature, it is connected to an impedance analyzer through copper electrodes and copper wires on both sides to measure the change in its conductivity and output it, using the change in conductivity to reflect the change in temperature.

[0027] When the NdFeB-silicone elastomer magnetic film is subjected to force, causing the flexible tactile sensor to sag or bend, the organic elastic substrate is deformed, causing the relative position between the magnetic film and the TMR element to change. At the same time, the relative position of the NdFeB magnetic particles in the magnetic film changes. Both changes cause the magnetic field intensity detected by the TMR element to change. The change in the magnetic field will cause the change in the internal magnetic resistance of the TMR element. Then, the change in internal magnetic resistance is converted into a voltage change through a bridge circuit and output.

[0028] The beneficial effects of the present invention are:

[0029] The DN polyol organic hydrogel film, which is the temperature sensing part of the flexible bimodal tactile sensor, has good sensitivity to temperature changes, fast response time, wide detection range, good stretchability and biocompatibility. Designing the temperature sensing material as a hydrogel microstructure (film) can accelerate the heat transfer between the device and the environment, and is expected to solve the problems of slow response and recovery time and inconsistent contact interface of existing hydrogel-based temperature sensors. And because the microstructured hydrogel faces the problem of water evaporation, the present invention introduces small molecule polyols (GLY) into the DN hydrogel film, and then encapsulates it in a plastic paraffin film to effectively improve the environmental tolerance and water retention of the hydrogel, so that it has good environmental stability and can be installed on a mechanical finger to sense the temperature range of the object from 20-70°C. When measuring temperature, the output conductivity value reaches 150μs at 20°C, and the output conductivity value reaches 800.5μs at 70°C, with an average sensitivity of 12.5μs per 1°C. As Figure 4 As shown, the temperature measurement sensitivity within 20℃-40℃ is 7.5μs per 1℃. As the temperature increases, the sensitivity increases to 15μs per 1℃ within 40℃-70℃. Compared with the existing magnetic tactile sensor, the temperature measurement function is added, the temperature measurement function is good and the environmental stability is good.

[0030] The NdFeB-silicone elastomer magnetic film, which is the part of the flexible tactile dual-modal sensor that senses stress and angle changes, combines the high magnetic properties of NdFeB magnetic particles and the strong flexibility of silicone elastomer. The tunnel magnetoresistive element of the detection part has the advantage of high sensitivity. The two form part of the flexible tactile sensor, realizing the measurement of bending angle and normal force. Figure 6It can be seen that the relationship between the static normal force F applied to the flexible tactile sensor and the TMR1 output voltage U1 is that the force measurement sensitivity is maximum in the static force range of 0-1N, with a sensitivity of 60mV / N, and the force measurement sensitivity decreases with the increase of the applied static force; when the static force is 10N, the output voltage reaches a maximum value of 251mV, and the force measurement sensitivity within 1-10N is 35mV / N, which is significantly improved compared to the force measurement sensitivity of existing magnetic tactile sensors. Figure 5 It can be seen that the relationship between the bending angle θ of the flexible tactile sensor and the TMR2 output voltage U2 is that the angular measurement sensitivity of the flexible tactile sensor first increases and then decreases with the increase of the bending angle. When bent to 30°, the angular measurement sensitivity is the largest, with a sensitivity of 20mV per 5 degrees; when the bending angle is 75°, the output voltage reaches a maximum value of 160mV, and the angular measurement sensitivity within 0-75° is 15mV per 5 degrees, which is significantly improved compared with the angular measurement sensitivity of existing magnetic tactile sensors.

[0031] 1. A flexible printed circuit board (FPC) with soldered TMR elements is placed beneath a silicone elastic substrate and hydrogel film. Due to the excellent flexibility of the DN polyol organohydrogel film, a magnetic film is bonded to the combined hydrogel film and silicone elastic substrate, protecting the underlying TMR elements and enhancing the overall flexibility of the tactile sensor. The sensor can be mounted on the inside of a robotic arm and flex with it from 0-75°. It can also adhere closely to human skin to detect the bending angle of knuckles or elbows. It can also be mounted on a robotic finger to sense temperatures ranging from 20-70°C.

[0032] 2. The silicone elastic substrate of the present invention is made by curing a silicone elastomer prepolymer cast onto a flexible printed circuit board. Together with the hydrogel film, it forms an integral elastic substrate that can be used to maintain the distance between the NdFeB-silicone elastomer magnetic film and the TMR, leaving sufficient space for deformation of the magnetic film while allowing the TMR to operate in the linear range.

[0033] 3. The present invention has excellent temperature perception test performance, dynamic force and static force test performance, and has faster response time and recovery time.

[0034] 4. Compared with the existing technology, the present invention combines soft magnetic film and hydrogel film and applies them to the field of dual-modal tactile detection, providing a new method for dual-modal tactile sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a disassembled diagram of the various components of the magnetic film-hydrogel dual-modal flexible tactile sensor for finger monitoring;

[0036] Among them, 1-NdFeB-organic silicon elastomer magnetic film, 2-TMR2003(1), 3-DN polyol organic hydrogel film, 4-organic silicon elastic substrate, 5-flexible printed circuit board, 6-TMR2003(2);

[0037] Figure 2 This is the overall structural assembly diagram of the magnetic film-hydrogel dual-modal flexible tactile sensor for finger monitoring;

[0038] Figure 3 This is a circuit diagram of a flexible printed circuit board for a magnetic film-hydrogel dual-modal flexible tactile sensor for finger monitoring.

[0039] Figure 4 is the output conductance diagram of the tactile sensor at different temperatures;

[0040] Figure 5 is the output voltage diagram of the tactile sensor at different bending angles;

[0041] Figure 6 is the output voltage diagram of the tactile sensor under different static pressures; DETAILED DESCRIPTION

[0042] The magnetic film-hydrogel dual-modal flexible tactile sensor designed for finger monitoring is composed of a NdFeB-organic silicon elastomer magnetic film, a DN polyol organic hydrogel, an organic silicon elastic substrate, a tunnel magnetoresistive element, and a flexible printed circuit board. It can sense static and dynamic forces, as well as temperature, and accurately identify different bending angles. The DN polyol organic hydrogel film serves as the temperature sensing component of the tactile sensor, providing a stable ion channel and sensing temperature changes of the contacted object. When the hydrogel film senses temperature changes, the ion-conductive hydrogel's thermal sensitivity stems from the thermally activated migration of ions. Rising temperature not only promotes ion migration but also causes ion decomposition, increasing the concentration of ion carriers, ultimately manifesting as an increase in the hydrogel's ionic conductivity. The ion-conductive hydrogel's conductivity is then measured to indirectly reflect temperature changes. The conductivity signal, output by copper electrodes and copper wires on both sides, is then transmitted to a computer via an impedance analyzer and converted into a visual conductivity curve image.

[0043] The magnetized NdFeB-silicone elastomer flexible film serves as the pressure and angle sensing element of the tactile sensor, providing a stable magnetic field and sensing external tactile information. When force is applied to the magnetic film, it undergoes elastic deformation, causing changes in the internal magnetic domains. This deformation of the entire elastic substrate changes the distance between the magnetic film and the TMR, which in turn changes the magnetic field strength around the force-applied location. The TMR detects this magnetic field change as a change in internal magnetic resistance. This change in internal magnetic resistance is then converted to a voltage change through a bridge circuit and output. The TMR output voltage signal is fed to a computer via an acquisition card and converted into a visual voltage curve. The magnetic film is bonded to a DN polyol organic hydrogel film and a silicone elastomer. The hydrogel is then bonded to a circuit board with an adhesive. A silicone elastomer is cast over TMR2 as a substrate, and a hydrogel film over TMR1 as a substrate.

[0044] The flexible tactile sensor in this embodiment has a NdFeB-silicone elastomer magnetic film component measuring 60 mm long, 20 mm wide, and 1 mm high. The silicone elastomer base is 40 mm long, 20 mm wide, and 3 mm high. The hydrogel film is 20 mm long, 20 mm wide, and 3 mm high. Both TMR1 and TMR2 are oriented along the X-axis. Both are packaged in a SOT23-5 package measuring 3 mm long, 3 mm wide, and 1.45 mm high. The TMR element and NdFeB-silicone elastomer magnetic film are placed parallel to the flexible printed circuit board. TMR1 is 25 mm from the top edge of the sensor, while TMR2 is 13 mm from the bottom edge. The two TMR elements are 32 mm apart. When a force is applied to the magnetic film, the magnetic film undergoes elastic deformation and causes the internal magnetic domains to change. The silicone elastic substrate and the hydrogel film deform, causing the distance between the magnetic film and the TMR to change, thereby causing the magnetic field strength around the force to change. The TMR will detect the change in the magnetic field and convert it into a change in internal magnetic resistance. The change in internal magnetic resistance is then converted into a change in voltage through a bridge circuit and output, thereby accurately detecting the size of the normal force or bending angle. The normal force is detected directly above TMR1, and the bending angle is detected 2 mm in front of TMR2. When performing static pressure measurement, the experimental results show that the force measurement sensitivity decreases with the increase of the applied static force. The static force measurement sensitivity is maximum in the range of 0-1N, with a sensitivity of 60mV / N. When the static force is 10N, the output voltage reaches a maximum value of 251mV, and the force measurement sensitivity within 1-10N is 32mV / N; when performing bending measurement, the experimental results show that the angular measurement sensitivity of the flexible tactile sensor first increases and then decreases with the increase of the bending angle. The angular measurement sensitivity is maximum when bent to 30 degrees, with a sensitivity of 20mV per 5 degrees; when the bending angle is 75 degrees, the output voltage reaches a maximum value of 160mV, and the angular measurement sensitivity within 0-75 degrees is 15mV per 5 degrees; when performing temperature measurement, the output conductivity value reaches 150μs at 20℃, and the output conductivity value reaches 800.5μs at 70℃, with a sensitivity of 12.5μs per 1℃. Compared with existing magnetic tactile sensors, this flexible tactile sensor has significantly improved force and angle measurement sensitivity, and has invented a temperature measurement function. It can be worn on human fingers to provide accurate tactile information.

[0045] The disassembly diagram of the various parts of the flexible dual-mode tactile sensor of the present invention is as follows: Figure 1 As shown, it consists of a NdFeB-silicone elastomer film 1, a first X-axis TMR element 2, a DN polyol organic hydrogel film 3, a silicone elastic substrate 4, a flexible printed circuit board 5, and a second X-axis TMR element 6;

[0046] The overall structure of the flexible dual-modal tactile sensor is as follows: Figure 2As shown, the first X-axis TMR element 2 and the second X-axis TMR element 6 are spaced apart and distributed in the longitudinal center of the flexible printed circuit board 5. The DN polyol organic hydrogel film 3 covers the first X-axis TMR element 2 and covers the left part of the flexible printed circuit board. The organic silicone elastic substrate 4 covers the second X-axis TMR element 6 and covers the right part of the flexible printed circuit board 5. The DN polyol organic hydrogel film 3 and the organic silicone elastic substrate 4 have the same thickness. The upper surfaces of the DN polyol organic hydrogel film 3 and the organic silicone elastic substrate 4 are covered with the NdFeB-organic silicone elastomer film 1.

[0047] The first X-axis TMR element 2 is located at the center of the lower part of the DN polyol organic hydrogel film 3 ; the second X-axis TMR element 6 is located at the center of the lower part of the organic silicone elastic substrate 4 .

[0048] The present invention is further described in detail below. This embodiment is only a specific description of the invention and is not to be regarded as limiting the scope of protection.

[0049] Example 1

[0050] Preparation of DN polyol organohydrogel film: DN hydrogels were prepared using a one-pot polymerization method in aqueous solutions of acrylamide and carrageenan. The PAM / carrageenan DN hydrogels were composed of acrylamide (AM) and carrageenan, N,N-methylenebisacrylamide (MBA), potassium chloride (KCl), and deionized water. The total weight percentage of each chemical was: acrylamide / carrageenan / UV initiator / MBA / KCl / H2O = 14.7:3:0.73:0.006:0.89:80.7;

[0051] The first step is to pour the above-mentioned test samples into deionized water according to the proportions. The present invention adds chemicals including 7.5g acrylamide (AM), 1.5g carrageenan, 0.005g N, N-methylenebisacrylamide (MBA) and 0.09g potassium chloride (KCL) to 41.0g deionized water. After magnetically stirring the mixture at 95°C for 2 hours, the solution is poured into a plastic container and the system is allowed to stand at 5°C for one hour to form an ion-crosslinked carrageenan network. Then, the system is placed under ultraviolet light with a wavelength of 365nm for one hour (the irradiation distance is 9cm and the light intensity is 8mW / cm 2 ) for cross-linking the secondary PAM network. The DN hydrogel was then peeled from the plastic container and cut into thin slices. The DN hydrogel was then soaked in glycine (GLY) (98% to 100% purity) for 2 hours to introduce a small molecule polyol. Finally, the hydrogel was wrapped in plastic paraffin film to prevent water evaporation from the hydrogel and improve its moisture resistance, resulting in the final DN polyol organohydrogel.

[0052] To ensure sufficient adhesion between the prepared hydrogel film and the silicone elastic base, cut the hydrogel into thin sheets of the same thickness as the silicone mold and the designed sensor length, then place them into the silicone mold. When preparing the silicone elastic base, pour the silicone prepolymer into the mold containing the hydrogel sheet, ensuring that the hydrogel and silicone positions match the sensor design. Leave the mold at room temperature for 2 hours to ensure a stable, integrated hydrogel film and silicone base.

[0053] The magnetic film preparation method includes: mixing NdFeB magnetic particles and silicone elastomer prepolymer in a ratio of 3:1, placing the mixture in a blender and stirring for 120 minutes to obtain a NdFeB-silicone elastomer prepolymer; pouring the prepolymer into a 3D-printed rectangular parallelepiped mold; covering the top layer with a plastic film; and curing the mixture at room temperature for 2 hours to obtain a NdFeB-silicone elastomer flexible film;

[0054] The obtained NdFeB-organic silicon elastomer flexible film is folded and fixed, and then placed in a magnetizer for magnetization, with the magnetization direction being along the height direction of the film, to obtain a NdFeB-organic silicon elastomer magnetic film;

[0055] The method for preparing the flexible dual-modal tactile sensor comprises the following steps:

[0056] A flexible printed circuit board (FPCB) with two TMR2003s welded to it was laid flat on the bottom surface of a 3D-printed mold. A hydrogel film was placed on TMR1 of the FPCB. A silicone elastomer prepolymer was poured on TMR2 of the FPCB. The prepolymer was cured at room temperature for two hours to obtain a silicone elastic substrate that was closely connected to the FPCB. The hydrogel film and the silicone elastic substrate together formed a complete elastic substrate. A magnetic film was attached to the hydrogel film and the silicone elastic substrate. Sil-Poxy from Smooth-On was used to bond the DN polyol organohydrogel film and the silicone elastic substrate together to form a complete flexible substrate, resulting in a complete flexible tactile sensor.

[0057] When measuring normal force, the flexible tactile sensor applies force directly above TMR1. The DN polyol organohydrogel film is located directly above TMR1, serving as its flexible substrate. When measuring bending angle, the sensor's bending position is 2 mm in front of TMR2.

[0058] The relationship between temperature changes and output conductance when the temperature detection portion of the flexible dual-modal tactile sensor detects temperature changes was tested. The flexible dual-modal tactile sensor was placed on a heating platform and the temperature was gradually increased to detect changes in conductance. The main purpose of this example was to study the input-output relationship of the flexible dual-modal tactile sensor and its sensitivity to temperature detection.

[0059] Implementation platform construction: The flexible dual-modal tactile sensor is fixed on the experimental platform, which includes a heating platform, an impedance analyzer, a 1V AC power supply, a copper electrode, and a copper wire;

[0060] Experimental process and results: The hydrogel film in the flexible dual-modal tactile sensor is connected to the impedance analyzer using copper electrodes and copper wires as the output end. The sensor is placed on a heating platform. Based on the thermal activation effect of ion-conductive hydrogels, the increase in temperature not only promotes the migration of ions inside the hydrogel, but also causes the decomposition of ions, thereby increasing the concentration of ion carriers and increasing the detected conductivity. The conductivity change is then displayed on the impedance analyzer and recorded. The flexible dual-modal tactile sensor senses the temperature increase every 5°C within the range of 20-70°C, and the output conductivity diagram is as follows: Figure 4 As shown, the output conductance is 150μs at 20°C, the sensitivity is 12.5μs / °C, and the maximum output conductance at 80°C is 800.5μs. The temperature measurement sensitivity within the range of 20°C to 40°C is 7.5μs per 1°C. The sensitivity increases with temperature, reaching 15μs per 1°C within the range of 40°C to 70°C. This adds a temperature measurement function compared to existing magnetic tactile sensors, providing excellent temperature measurement capabilities and good environmental stability. After cooling, the sensor's conductance decreases and essentially returns to its initial level, demonstrating that this flexible dual-modal tactile sensor has good temperature measurement stability and significantly surpasses currently known magnetic tactile sensors.

[0061] The software and protocols involved in the present invention are all well-known technologies.

[0062] Example 2

[0063] The relationship between the bending angle and the output voltage when a force is applied to the bending angle detection portion of the flexible dual-modal tactile sensor is tested. The flexible tactile sensor is bent upward or downward 2 mm in front of TMR2. The main purpose of this embodiment is to study the input-output correspondence of the flexible dual-modal tactile sensor and its sensitivity to bending angle detection.

[0064] Experimental platform construction: The flexible tactile sensor is fixed on the experimental platform, which includes an angle measuring instrument, a 5V DC power supply, a DH-8303 dynamic data acquisition card, and a computer. The 5V DC power supply provides a stable voltage for the TMR. The output voltage of the TMR is processed by the acquisition card and displayed intuitively on the computer.

[0065] Experimental process and results: The output end of the flexible tactile sensor is connected to the DH-8303 dynamic data acquisition card, and the output end of the data acquisition card is connected to the computer. A clamp is used to apply a bending angle to the bending angle detection position of the flexible tactile sensor, and the angle meter is used to read the real-time bending angle. Based on the magnetic permeability effect of the NdFeB magnetic particles, the magnetic field intensity around the bending position changes. TMR2 converts the detected magnetic field change into a change in internal magnetic resistance, and then the change in internal magnetic resistance is converted into a voltage change through a bridge circuit and output. The flexible tactile sensor is continuously bent at intervals of 5 degrees within the range of 0-75°, and the output voltage is shown in the figure below. Figure 6 As shown in the figure, the angular sensitivity of the flexible tactile sensor first increases and then decreases with increasing bending angle. The angular sensitivity reaches its maximum at 30°, with a sensitivity of 20mV per 5°. At a bending angle of 75°, the output voltage reaches a maximum of 160mV, and the angular sensitivity within the range of 0-75° is 15mV per 5°. After the force is removed, the flexible tactile sensor quickly returns to a horizontal state, and the output voltage drops to essentially zero, demonstrating excellent angular stability. The angular sensitivity and angular range of this flexible tactile sensor are significantly higher than those of currently known magnetic tactile sensors, demonstrating excellent angular measurement characteristics.

[0066] Magnetization is a well-known technology and can also be performed through commercial commissioning.

[0067] Example 3

[0068] The relationship between pressure and output voltage when a static force is applied to the normal force detection portion of the flexible tactile sensor is tested. A static pressure of 0-10N is applied to the magnetic film directly above TMR1. The main purpose of this example is to study the input-output correspondence and sensitivity of the flexible tactile sensor to static force.

[0069] Construction of experimental platform: Place the tactile sensor according to Figure 2 The assembly is completed as shown in the figure; the experimental platform includes a digital push-pull force gauge, a 5V DC power supply, a DH-8303 dynamic data acquisition card and a computer; the tactile sensor is fixed on the base of the digital push-pull force gauge, and the normal force detection part is placed directly below it. The rotation axis of the push-pull force gauge is rotated to apply a static force to the normal force detection part (directly above TMR1). The 5V DC power supply provides a stable voltage for the TMR. The output voltage of the TMR is processed by the acquisition card and intuitively displayed on the computer.

[0070] Experimental process and results: The output end of the flexible dual-modal tactile sensor is connected to the DH-8303 dynamic data acquisition card, and the output end of the data acquisition card is connected to the computer. A digital push-pull force gauge is used to apply a normal force of 0-10N to the normal force detection part of the flexible dual-modal tactile sensor. The push-pull force gauge transmission shaft contacts exert pressure on the magnetic film, causing the magnetic film to undergo elastic deformation and causing changes in the internal magnetic domains. The deformation of the silicone elastic substrate causes the distance between the magnetic film and the TMR to change, thereby causing the magnetic field detected by the TMR to change and output a changing voltage signal. A static force is applied to the flexible tactile sensor at intervals of 1N within the range of 0-10N, and the resulting output voltage is shown in the figure below. Figure 5 As shown in the figure, the sensor has a force measurement resolution of 0.05N, and the output voltage is 51mV at 0.05N. The force measurement sensitivity is maximum within the static force range of 0-1N, at 60mV / N, and decreases with increasing static force. The output voltage reaches a maximum of 251mV at a static force of 10N, and the force measurement sensitivity within the range of 1-10N is 35mV / N. After the static force is removed, the sensor quickly returns to its original state, with the output voltage dropping to essentially zero, indicating that the tactile sensor has excellent force measurement stability. The force measurement sensitivity and force measurement range of this flexible tactile sensor are significantly higher than those of currently known magnetic tactile sensors, demonstrating excellent force measurement characteristics.

[0071] Matters not covered by the present invention are known technologies.

Claims

1. A magnetic film-hydrogel dual-modal tactile sensor for finger monitoring, characterized by: The sensor includes a NdFeB-organic silicon elastomer film, a first X-axis TMR element, a DN polyol organic hydrogel film, an organic silicon elastic substrate, a flexible printed circuit board, and a second X-axis TMR element; The first X-axis TMR element and the second X-axis TMR element are spaced apart and distributed on the longitudinal centerline of the flexible printed circuit board. The DN polyol organic hydrogel film covers the first X-axis TMR element and covers the left portion of the flexible printed circuit board. The organic silicone elastic substrate covers the second X-axis TMR element and covers the right portion of the flexible printed circuit board. The DN polyol organic hydrogel film and the organic silicone elastic substrate have the same thickness. The upper surfaces of the DN polyol organic hydrogel film and the organic silicone elastic substrate are covered with a NdFeB-organic silicone elastomer film. The method for preparing the conductive ion hydrogel comprises the following steps: In the first step, acrylamide (AM), carrageenan, N,N-methylenebisacrylamide (MBA) and potassium chloride (KCL) are added to deionized water, and after magnetic stirring at 90-100° C. for 1-3 hours, the solution is poured into a container and allowed to stand at 2-10° C. for 0.5-2 hours to obtain a colloid having an ion-crosslinked carrageenan network structure; In the second step, the film having an ion-crosslinked carrageenan network structure is irradiated with ultraviolet light at a wavelength of 365 nm for 0.5 to 2.0 hours to obtain a DN hydrogel film; In the third step, the DN hydrogel is peeled from the container and cut into thin slices, which are then immersed in glycine (GLY) for 1.5 to 3 hours to introduce small molecule polyols. Finally, it is encapsulated with plastic paraffin film to obtain the final DN polyol organohydrogel, i.e., the conductive ion hydrogel. The mass ratio is acrylamide: carrageenan: UV initiator: MBA: KCl: H2O = 13-15: 2.8-3.3: 0.70-0.75: 0.005-0.008: 0.85-0.95: 78-83.

2. The magnetic film-hydrogel dual-modal tactile sensor for finger monitoring according to claim 1, characterized in that: The method for preparing the NdFeB-silicone elastomer film comprises the following steps: The magnetic film preparation method includes: mixing NdFeB magnetic particles and silicone elastomer prepolymer in a ratio of 3:1, placing the mixture in a blender and stirring for 120 minutes to obtain a NdFeB-silicone elastomer prepolymer; pouring the prepolymer into a 3D-printed rectangular parallelepiped mold; covering the top layer with a plastic film; and curing the mixture at room temperature for 2 hours to obtain a NdFeB-silicone elastomer flexible film; The obtained NdFeB-organic silicon elastomer flexible film is folded and fixed, and then placed in a magnetizer for magnetization to obtain a NdFeB-organic silicon elastomer magnetic film; The organosilicon elastomer prepolymer is a mixture of Ecoflex 00-30 series A agent and B agent of Smooth-On Company, and their mass ratio is 1:

1.

3. The magnetic film-hydrogel dual-modal tactile sensor for finger monitoring according to claim 1, characterized in that: The diameter of the NdFeB particles is 100-200 μm; The thickness of the NdFeB-silicone elastomer flexible film is 1 mm; The thickness of the organic silicon elastic substrate is 3 mm; the length ratio of the DN polyol organic hydrogel film to the organic silicon elastic substrate is 1:

2.

4. The magnetic film-hydrogel dual-modal tactile sensor for finger monitoring according to claim 1, wherein: The purity of glycine (GLY) is 98% to 100%.

5. The magnetic film-hydrogel dual-modal tactile sensor for finger monitoring according to claim 1, characterized in that: The first X-axis TMR element and the second X-axis TMR element are both TMR2003 type, with X-axis magnetic sensitivity direction; the package form is SOT23-5, and the element size is 3mm×3mm×1.45mm.

6. The magnetic film-hydrogel dual-modal tactile sensor for finger monitoring according to claim 1, characterized in that: The flexible tactile sensor has an overall length of 58 to 62 mm, a width of 18 to 22 mm, and a height of 3 to 5 mm.

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