A method for manufacturing a solenoid type flexible gap and stress relaxation sensor probe

Abstract

The application relates to a preparation method of a spiral flexible gap and stress relaxation sensor probe, and belongs to the technical field of sensors.The spiral flexible probe has a sandwich structure, the upper and lower layers are made of polymer materials, the middle layer comprises a spiral conductive composite material coil, an isolation layer and a lead wire, the probe measures the gap by using the eddy current effect of the spiral coil, measures the loading stress by using the piezoresistance characteristic of the conductive composite material, and measures the relaxation stress by using the impedance relaxation of the composite material.The method can improve the preparation stability, the prepared spiral flexible probe has good softness, the thickness can be accurately controlled, and only one demolding is needed in the preparation process, so that the probe signal-to-noise ratio and stability are improved.The spiral flexible probe has the functions of measuring the gap, the loading stress and the relaxation stress, can be used for long-term monitoring of the gap and the pressure between narrow curved surfaces in large industrial equipment, and can be used in the fields of robot tactile perception and the like.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, and specifically relates to the fabrication of flexible sensors and non-contact gap measurement, as well as the measurement of applied stress and relaxed stress. Background Technology

[0002] With the development of technology, many engineering applications require the use of flexible and thin sensors. For example, in artificial electronic skin or robotic tactile sensing, it is necessary to sense the distance to a target or obstacle and detect the pressure exerted upon contact with the object. Similarly, in some industrial equipment with narrow, curved interlayer structures, it is necessary to monitor the gaps or applied pressure between components during movement to ensure that the components operate within an effective range and guarantee system safety. Furthermore, if components are under pressure and maintain a single posture for an extended period, stress relaxation may occur, so it is necessary to monitor the magnitude of stress relaxation to ensure that the pressure between components remains within an effective range. However, traditional rigid sensors cannot adhere well to narrow curved surfaces and cannot meet application requirements. Some research institutions have developed flexible displacement sensors or flexible pressure sensors, but these have limited functionality and cannot simultaneously measure gaps and pressure, let alone stress relaxation. Previous studies have used extrusion and spin coating methods to develop flexible sensors that can measure both gaps and pressure. However, stress relaxation measurement functionality has not been developed. In addition, the extrusion method requires the transfer and cutting of the polymer film after extrusion molding, which makes the transfer process difficult. Moreover, multiple transfers are required in a single preparation process, resulting in high probe noise and unstable performance. The spin coating method cannot precisely control the thickness of the polymer film, and the specifications of each probe are inconsistent, resulting in large differences in probe performance and making probe calibration difficult. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a method for fabricating a helical flexible gap and stress relaxation sensor probe. Compared with traditional metal eddy current coils, novel flexible displacement sensors, and novel flexible pressure sensors, the flexible helical probe of this invention is composed only of soft polymer materials and conductive fillers. The fabrication process is simple, low-cost, and the thickness can be precisely controlled, improving the probe's signal-to-noise ratio and fabrication stability, enhancing sensing performance. Furthermore, it combines non-contact gap measurement, applied stress measurement, and relaxation stress measurement, enabling long-term monitoring of gap and stress states. This makes it suitable for applications such as artificial electronic skin development, non-contact gap measurement and pressure measurement in narrow curved surfaces, and other fields.

[0004] The method for fabricating a spiral-shaped flexible gap and stress relaxation sensor probe proposed in this invention includes the following steps:

[0005] (1) Mix polymer materials and conductive fillers in a certain proportion, add an appropriate amount of organic solvent, disperse by ultrasonication, heat in a water bath and stir mechanically, evaporate the solvent, add catalyst and crosslinking agent and mix thoroughly to form a composite conductive material, fill the composite conductive material evenly into a mold with spiral grooves, remove the excess composite material above the mold, and connect copper foil in the end groove as an external electrode, and wait for the composite material to fully vulcanize;

[0006] (2) Place a mold of a certain thickness and a rectangular opening in the middle on the side of the spiral groove mold without the lead wire, so that the opening only covers a small part of the central circle. Then, evenly spread the polymer material with crosslinking agent and catalyst into the mold of the isolation layer, remove the excess polymer material above the mold, and form a layer of isolation film of a certain thickness after vulcanization.

[0007] (3) Place a lead mold with a certain thickness and an opening in the middle on the above-mentioned isolation film, and arrange the narrow opening end on the center circle, with the opening part extending beyond the isolation film. Fill the mold with the composite material prepared in (1) above, remove the excess composite material above the mold, and connect copper foil at the end as an external electrode. Wait for the composite material to fully vulcanize.

[0008] (4) Place a packaging mold of a certain thickness on a spiral groove mold, then evenly spread a polymer material with added crosslinking agent and catalyst in the packaging mold, remove excess polymer material above the mold, and after vulcanization, form an upper surface packaging layer of a certain thickness. Demold the coil with the upper surface packaging layer from the mold, flip it over and place it in a packaging mold with a certain thickness on a horizontal plane, and spread a polymer material with added crosslinking agent and catalyst, remove excess polymer material above the mold, and after vulcanization, form a lower surface packaging layer of a certain thickness. Trim the excess polymer material at the edges to obtain a spiral flexible sensor probe.

[0009] The main principles of the spiral flexible sensor probe prepared in this invention for measuring gap, applied stress, and relaxed stress are as follows:

[0010] Composite materials prepared using polymers and conductive fillers exhibit electrical conductivity. When an alternating current is applied, the helical composite material generates eddy currents within a metallic target. These eddy currents can be used to measure the gap between the probe and the metallic target. When pressure is applied to the probe by the metallic target, the composite material deforms under pressure, altering the internal conductive network and changing the probe's impedance. Therefore, the magnitude of the applied stress can be measured based on the change in probe impedance. When the metallic target applies pressure to the probe while maintaining its displacement, stress relaxation occurs, and the probe's internal impedance also relaxes. The magnitude of this impedance relaxation can be used to measure the magnitude of stress relaxation. The rate of change of impedance of the composite material under applied stress and relaxation stress differs significantly; the magnitude of this rate of change can be used to distinguish between applied stress and relaxation stress.

[0011] Features and effects of the present invention:

[0012] 1. The spiral flexible sensor probe prepared by this invention has the functions of non-contact gap measurement, applied stress measurement and relaxed stress measurement.

[0013] 2. The spiral flexible sensor probe prepared by this invention contains only polymer materials and conductive fillers, without any metal materials. It has good flexibility, can meet higher requirements for curved surface adhesion, and the preparation process is simple, requiring only one demolding, avoiding the inconvenience caused by multiple film transfers, and improving the signal-to-noise ratio and preparation stability of the sensor probe.

[0014] 3. Each step of the preparation process of this invention uses a mold, and the thickness of each layer can be precisely controlled. Therefore, the thickness of the final probe can be precisely controlled, and sensor probes of various required thicknesses can be prepared, which improves the consistency and stability of probe preparation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a mold with spiral grooves.

[0016] Figure 2 This is a schematic diagram of the isolation layer mold.

[0017] Figure 3 This is a schematic diagram of the lead wire mold.

[0018] Figure 4 This is a schematic diagram of the upper and lower surface encapsulation molds, with different thicknesses for the upper and lower surface encapsulation molds.

[0019] Figure 5 A cross-sectional schematic diagram of a spiral-shaped flexible sensor probe.

[0020] Figure 6 This is a top view of a spiral-shaped flexible sensor probe.

[0021] Explanation of reference numerals in the figure: a represents the composite material lead on one side, b represents the polymer material isolation layer, c represents the upper surface encapsulation layer of the polymer material, d represents the electrode used to connect to the external circuit, e represents the composite material lead on the other side, f represents the spiral composite material coil, and g represents the lower surface encapsulation layer of the polymer material. Detailed Implementation

[0022] (1) Mix polymer materials and conductive fillers in a certain proportion, add an appropriate amount of organic solvent, disperse by ultrasonication, heat in a water bath and stir mechanically, evaporate the solvent, add catalyst and crosslinking agent and mix thoroughly to form a composite conductive material, uniformly fill the composite conductive material into mold 1 with spiral groove, remove excess composite material above mold 1 to form a spiral composite coil f, and connect copper foil in the end groove as an external electrode d, and wait for the composite material to be fully vulcanized;

[0023] (2) Place the isolation layer mold 2 on the side of the spiral groove mold 1 without the lead wire, so that the opening only covers a small part of the central circle. Then, evenly spread the polymer material with added crosslinking agent and catalyst in the isolation layer mold 2, remove the excess polymer material above the mold 2, and form an isolation film b after vulcanization.

[0024] (3) Place the lead wire mold 3 on the above-mentioned isolation film b, and place the narrow opening end on the center circle of the spiral groove mold 1, with the opening part extending beyond the isolation film b. Fill the mold 3 with the composite material prepared in (1) above, remove the excess composite material above the mold 3, form the lead wire a, and connect the end with copper foil as an external electrode d, and wait for the composite material to be fully vulcanized.

[0025] (4) Place the encapsulation mold 4 on the spiral groove mold 1, and then evenly spread the polymer material with added crosslinking agent and catalyst in the encapsulation mold 4. Remove the excess polymer material above the mold 4. After vulcanization, the upper surface encapsulation layer c is formed. Demold the coil with the upper surface encapsulation layer c from the spiral groove mold 1, flip it over and place it in the encapsulation mold 4 located on the horizontal plane, and spread the polymer material with added crosslinking agent and catalyst. Remove the excess polymer material above the mold 4. After vulcanization, the lower surface encapsulation layer g is formed. Trim the excess polymer material at the edge to obtain the spiral flexible sensor probe.

[0026] Example 1

[0027] (1) Mix polymer materials and conductive fillers at a mass ratio of 100:20, add an appropriate amount of organic solvent, and after ultrasonic dispersion, water bath heating and mechanical stirring, the solvent evaporates. Then add catalyst and crosslinking agent (mass ratio of polymer materials, catalyst and crosslinking agent is 100:2.4:1.2) and mix thoroughly to form a composite conductive material. The composite conductive material is uniformly coated into an acrylic mold 1 with a spiral groove (10 turns, line width of 1 mm, line spacing of 0.5 mm, and thickness of 0.5 mm). Remove the excess composite material above the mold 1 to form a spiral composite material coil f. Connect copper foil in the end groove as an external electrode d. Wait for the composite material to fully vulcanize.

[0028] (2) Place the 0.1mm thick isolation layer mold 2 on the side of the acrylic mold 1 without the lead wire, so that the opening only covers a small part of the center circle. Then, evenly spread the polymer material with added crosslinking agent and catalyst in the isolation layer mold 2, remove the excess polymer material higher than the mold 2, and form a 0.1mm thick isolation film b after vulcanization.

[0029] (3) Place the 0.2mm thick lead mold 3 on the above-mentioned isolation film b, and place the narrow opening end on the center circle of the spiral groove mold 1, with the opening part extending beyond the isolation film b. Fill the mold 3 with the composite material prepared in (1) above, remove the excess composite material above the mold 3, form a 0.2mm thick lead a, and connect copper foil at the end as an external electrode d, and wait for the composite material to fully vulcanize.

[0030] (4) Place the 0.35mm thick (thickness slightly higher than the sum of the thickness of the isolation film and the lead wire) encapsulation mold 4 on the acrylic mold 1, and then evenly spread the polymer material with added crosslinking agent and catalyst in the encapsulation mold 4. Remove the excess polymer material above the mold 4. After vulcanization, the upper surface encapsulation layer c is formed. Demold the coil with the upper surface encapsulation layer c from the spiral groove mold 1, flip it over and place it in the 0.9mm thick (thickness slightly higher than the sum of the thickness of the upper surface encapsulation layer and the thickness of the spiral groove) encapsulation mold 4 located on the horizontal plane, and spread the polymer material with added crosslinking agent and catalyst. Remove the excess polymer material above the mold 4. After vulcanization, the lower surface encapsulation layer g is formed. Trim the excess polymer material at the edge to obtain a spiral flexible sensor probe with a mass ratio of 0.2, 10 turns, and a thickness of 0.9mm.

[0031] Example 2

[0032] (1) Mix polymer materials and conductive fillers at a mass ratio of 100:8, add an appropriate amount of organic solvent, and after ultrasonic dispersion, water bath heating and mechanical stirring, the solvent evaporates. Then add catalyst and crosslinking agent (mass ratio of polymer materials, catalyst and crosslinking agent is 100:2.4:1.2) and mix thoroughly to form a composite conductive material. The composite conductive material is uniformly coated into an acrylic mold 1 with a spiral groove (20 turns, line width of 0.5 mm, line spacing of 0.3 mm, and thickness of 0.25 mm). Remove the excess composite material above the mold 1 to form a spiral composite coil f. Connect copper foil in the end groove as an external electrode d. Wait for the composite material to fully vulcanize.

[0033] (2) Place the 0.05mm thick isolation layer mold 2 on the side of the acrylic mold 1 without the lead wire, so that the opening only covers a small part of the center circle. Then, evenly spread the polymer material with added crosslinking agent and catalyst in the isolation layer mold 2, remove the excess polymer material higher than the mold 2, and form an isolation film b after vulcanization.

[0034] (3) Place the 0.1mm thick lead mold 3 on the above-mentioned isolation film b, and place the narrow opening end on the center circle of the spiral groove mold 1, with the opening part extending beyond the isolation film b. Fill the mold 3 with the composite material prepared in (1) above, remove the excess composite material above the mold 3, form a 0.1mm thick lead a, and connect copper foil at the end as an external electrode d, and wait for the composite material to fully vulcanize.

[0035] (4) Place the 0.2mm thick (thickness slightly higher than the sum of the thickness of the isolation film and the lead wire) encapsulation mold 4 on the acrylic mold 1, and then evenly spread the polymer material with added crosslinking agent and catalyst in the encapsulation mold 4. Remove the excess polymer material above the mold 4. After vulcanization, the upper surface encapsulation layer c is formed. Demold the coil with the upper surface encapsulation layer c from the spiral groove mold 1, flip it over and place it in the 0.5mm thick (thickness slightly higher than the sum of the thickness of the upper surface encapsulation layer and the thickness of the spiral groove) encapsulation mold 4 located on the horizontal plane, and spread the polymer material with added crosslinking agent and catalyst. Remove the excess polymer material above the mold 4. After vulcanization, the lower surface encapsulation layer g is formed. Trim the excess polymer material at the edge to obtain a spiral flexible sensor probe with a mass ratio of 0.08, 20 turns, and a thickness of 0.5mm.

Claims

1. A method for fabricating a spiral-shaped flexible gap and stress relaxation sensor probe, comprising the following steps: (1) Mix polymer materials and conductive fillers in a certain proportion, add an appropriate amount of organic solvent, disperse by ultrasonication, heat in water bath and stir mechanically, evaporate the solvent, add catalyst and crosslinking agent and mix thoroughly to form conductive composite material, fill the conductive composite material evenly into a mold with spiral groove, remove excess composite material from the mold surface, and connect copper foil in the end groove as an external electrode, and wait for the composite material to fully vulcanize. (2) Place a certain thickness of the isolation layer mold with a rectangular opening in the middle on the side of the above spiral groove mold without the lead wire, so that the opening only covers a small part of the central circle. Then, evenly spread the polymer material with crosslinking agent and catalyst in the isolation layer mold, remove the excess polymer material above the mold, and form an isolation film with a certain thickness after vulcanization. (3) Place a lead mold with a certain thickness and an opening in the middle on the above-mentioned isolation film, and place the narrow opening end on the center circle so that the opening part extends beyond the isolation film. Fill the mold with the conductive composite material prepared in (1) above, remove the composite material that is higher than the mold, and connect copper foil at the end as an external electrode. Wait for the composite material to be fully vulcanized. (4) Place a certain thickness of the encapsulation mold on the spiral groove mold, then evenly spread the polymer material with added crosslinking agent and catalyst in the encapsulation mold, remove the excess polymer material above the mold, and after vulcanization, form a certain thickness of upper surface encapsulation layer. Demold the coil with the upper surface encapsulation layer from the mold, flip it over and place it in the encapsulation mold with a certain thickness on the horizontal plane, and spread the polymer material with added crosslinking agent and catalyst, remove the excess polymer material above the mold, and after vulcanization, form a certain thickness of lower surface encapsulation layer. Trim the excess polymer material at the edge to obtain the spiral flexible gap and stress relaxation sensor probe. The spiral-shaped flexible gap and stress relaxation sensor probe includes, from top to bottom, an upper surface encapsulation layer, a composite material lead layer, a polymer material isolation layer, a composite material conductive layer, and a lower surface encapsulation layer. Electrodes are installed at the ends of the composite material lead layer and the composite material conductive layer. The composite material conductive layer is spiral-shaped.

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