Capacitive pressure sensor and its fabrication method

Abstract

This invention relates to the field of pressure sensors, specifically to a capacitive pressure sensor and its fabrication method, which significantly improves the sensitivity of capacitive pressure sensors. The capacitive pressure sensor of this invention includes a porous liquid metal electrode, an ion-gel dielectric layer, a first electrode, and a second electrode. The first electrode covers the upper surface of the porous liquid metal electrode, and the lower surface of the porous liquid metal electrode is connected to the upper surface of the ion-gel dielectric layer. The lower surface of the ion-gel dielectric layer covers the second electrode. When subjected to external force, the porous liquid metal electrode deforms, and simultaneously the charge density on the upper surface of the ion-gel dielectric layer increases. When the external force is removed, the deformation recovers, and the charge density on the upper surface of the ion-gel dielectric layer returns to its original state. This invention is applicable to pressure sensors.

Description

Technical Field

[0001] This invention relates to the field of pressure sensors, and more specifically to a capacitive pressure sensor and its fabrication method. Background Technology

[0002] In recent years, the development of the microelectronics field has begun to focus on flexible electronics. Flexible electronic devices have enormous application prospects in areas such as wireless health monitoring, sensor networks, novel human-computer interactions, and smart wearables. To enable pressure sensors to be used in fields such as smart wearables, it is necessary to improve the flexibility of the pressure sensors.

[0003] Current pressure sensors, such as the "Pressure Sensor with Porous Graphene Foam Structure and its Preparation Method" disclosed in CN107101754A, include electrodes, a porous graphene foam structure, and silver paste as a connection between the porous graphene foam structure and the electrodes to increase conductivity. The electrodes are made of aluminum strips, silver wires, or copper sheets, and are bonded to the upper and lower surfaces of the porous graphene foam structure using silver paste. This method mainly utilizes the lightweight, thinness, high strength, and good flexibility of graphene to improve the measurement application range of the sensor, but its sensitivity is relatively low. Summary of the Invention

[0004] The purpose of this invention is to provide a capacitive pressure sensor and its manufacturing method, which greatly improves the sensitivity of the capacitive pressure sensor while possessing high flexibility.

[0005] The present invention adopts the following technical solution to achieve the above objective: a capacitive pressure sensor, including a porous liquid metal electrode, an ion gel dielectric layer, a first electrode and a second electrode, wherein the first electrode covers the upper surface of the porous liquid metal electrode, the lower surface of the porous liquid metal electrode is connected to the upper surface of the ion gel dielectric layer, and the lower surface of the ion gel dielectric layer is covered by the second electrode.

[0006] The porous liquid metal electrode deforms when subjected to external force, and the charge density on the upper surface of the ion gel dielectric layer increases. When the external force is removed, the deformation will recover, and the charge density on the upper surface of the ion gel dielectric layer will return to its original state.

[0007] Furthermore, the gel material of the ionogel dielectric layer is polyvinyl alcohol, polyacrylamide, cellulose, or chitosan.

[0008] Furthermore, the ion donors of the ion gel dielectric layer are phosphate molecules and / or sodium chloride and / or potassium chloride and / or lithium chloride.

[0009] Furthermore, the thickness of the ionogel dielectric layer is 0.1–1 mm.

[0010] Furthermore, the porous liquid metal electrode is a gallium indium tin liquid alloy with different compositions and a thickness of 50–500 μm.

[0011] Furthermore, the first electrode and the second electrode are made of Ti, Pt, Au, or indium tin oxide, and their thickness is 0.01 to 0.1 mm.

[0012] A method for fabricating a capacitive pressure sensor, applied to the fabrication of the aforementioned capacitive pressure sensor, includes:

[0013] Step 1: Inject the liquid metal alloy into the PVA (polyvinyl alcohol) template and cure it at room temperature for a set time. After the liquid metal alloy has cured in the PVA template, dissolve the PVA template with hot water to obtain a porous liquid metal electrode.

[0014] Step 2: Mix deionized water, NaCl and polysaccharide monomers to prepare gel precursor solutions with different weight ratios. After the gel precursor solutions are fully mixed, inject them into a silicone template and heat them at a preset temperature. Before the gel is formed, place a liquid metal porous electrode on the unformed gel and connect it. After heating for a predetermined time, the formed gel is obtained.

[0015] Step 3: Use two collectors to sandwich the molded gel in the middle, and then use PDMS (polydimethylsiloxane) to encapsulate the whole thing, thus obtaining a capacitive pressure sensor.

[0016] When subjected to external force, the porous liquid metal electrode of this invention undergoes compressive deformation. During this deformation, the surface charge density of the porous liquid metal electrode increases, and the charge density on the upper surface of the ion gel dielectric layer also increases, resulting in a capacitance effect. Due to charge conservation, induced charges of opposite polarity and equal charge appear on the lower surface of the ion gel dielectric layer, thus generating an additional capacitance effect. This results in a double-layer capacitance effect. The synergistic superposition of the double-layer capacitance effect and the changes in the structural parameters of the capacitive pressure sensor greatly improves the sensitivity of the capacitive pressure sensor of this invention. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the capacitive pressure sensor of the present invention.

[0018] In the attached figure, 1-1 is the first electrode, 1-2 is the second electrode, 2 is the porous liquid metal electrode, and 3 is the ion gel dielectric layer. Detailed Implementation

[0019] The present invention provides a capacitive pressure sensor comprising a porous liquid metal electrode, an ion gel dielectric layer, a first electrode, and a second electrode. The first electrode covers the upper surface of the porous liquid metal electrode, the lower surface of the porous liquid metal electrode is connected to the upper surface of the ion gel dielectric layer, and the lower surface of the ion gel dielectric layer is covered by the second electrode.

[0020] When a porous liquid metal electrode is subjected to external force, it will deform, and at the same time, the charge density on the upper surface of the ion gel dielectric layer will increase. When the external force is removed, the deformation will be restored, and the charge density on the upper surface of the ion gel dielectric layer will return to its original state.

[0021] The gel material of the ionogel dielectric layer is polyvinyl alcohol, polyacrylamide, cellulose, or chitosan.

[0022] The ion donors for the ion gel dielectric layer are phosphate molecules and / or sodium chloride and / or potassium chloride and / or lithium chloride.

[0023] The thickness of the ionogel dielectric layer is 0.1–1 mm.

[0024] The porous liquid metal electrode is a gallium indium tin liquid alloy with different compositions and a thickness of 50–500 μm.

[0025] The first and second electrodes are made of Ti (titanium metal), Pt (platinum metal), Au (gold), or indium tin oxide, with a thickness of 0.01–0.1 mm.

[0026] A method for fabricating a capacitive pressure sensor, applied to the fabrication of the aforementioned capacitive pressure sensor, includes:

[0027] Step 1: Inject the liquid metal alloy into the PVA (polyvinyl alcohol) template and cure it at room temperature for a set time. After the liquid metal alloy has cured in the PVA template, dissolve the PVA template with hot water to obtain a porous liquid metal electrode.

[0028] Step 2: Mix deionized water, NaCl and polysaccharide monomers to prepare gel precursor solutions with different weight ratios. After the gel precursor solutions are fully mixed, inject them into a silicone template and heat them at a preset temperature. Before the gel is formed, place a liquid metal porous electrode on the unformed gel and connect it. After heating for a predetermined time, the formed gel is obtained.

[0029] Step 3: Use two collectors to sandwich the molded gel in the middle, and then use PDMS (polydimethylsiloxane) to encapsulate the whole thing, thus obtaining a capacitive pressure sensor.

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the structure of the capacitive pressure sensor of the present invention, including a porous liquid metal electrode 2, an ion gel dielectric layer 3, a first electrode 1-1 and a second electrode 1-2. The first electrode 1-1 covers the upper surface of the porous liquid metal electrode 2, the lower surface of the porous liquid metal electrode 2 is connected to the upper surface of the ion gel dielectric layer 3, and the lower surface of the ion gel dielectric layer 3 is covered by the second electrode 1-2.

[0032] The porous liquid metal electrode 2 is fabricated by a template method. By changing the porosity and thickness of the template, the pore size and thickness of the porous electrode can be adjusted.

[0033] The ionogel dielectric layer 3 is polymerized from a precursor monomer dispersion via a Sol-Gel process. During gel formation, a porous liquid metal electrode is directly placed on the gel surface, and after gelation, it bonds with the porous electrode. The Sol-Gel method is a novel wet chemical method for material preparation. It involves the gradual gelation and post-treatment of organometallic compounds, inorganic metal compounds, or mixtures thereof through hydrolysis and polycondensation to obtain oxides or other compounds.

[0034] An embodiment of the method for fabricating the capacitive pressure sensor of the present invention is as follows:

[0035] Example 1

[0036] The first step is to inject 1g of liquid gallium indium tin alloy into a PVA template and cure it at room temperature for 8 hours. After curing, the PVA template is dissolved in hot water to obtain a porous electrode.

[0037] The second step involves preparing a 5ml dispersion of deionized water, NaCl, and polysaccharide monomers in a weight ratio of 4:0.1:3, and heating it at 75°C for 4 hours to obtain a gel. It is important to note that the liquid metal porous electrode should be placed on top of the partially gelled state to ensure they are connected.

[0038] The third step involves sandwiching the gel and porous electrode between two Ti current collector plates and encapsulating them together using PDMS.

[0039] Example 2

[0040] The preparation method is basically the same as in Example 1, except that a dispersion with a ratio of 4:0.5:3 is used, and the resulting sensor structure is similar to... Figure 1 .

[0041] Example 3

[0042] The preparation method is basically the same as in Example 1, except that a dispersion with a ratio of 4:1:3 is used, and the resulting sensor structure is similar to... Figure 1 .

[0043] Example 4

[0044] The preparation method is basically the same as in Example 1, except that a dispersion with a ratio of 4:1.5:3 is used, and the resulting sensor structure is similar to... Figure 1 .

[0045] Example 5

[0046] The preparation method is basically the same as in Example 1, except that a dispersion with a ratio of 4:2:3 is used, and the resulting sensor structure is similar to... Figure 1 .

[0047] Example 6

[0048] The preparation method is basically the same as in Example 1, except that the gel used is PAM (polyacrylamide), and the resulting sensor structure is similar to... Figure 1 .

[0049] Example 7

[0050] The preparation method is basically the same as in Example 1, except that the gel used is PVA (polyvinyl alcohol), and the resulting sensor structure is similar to... Figure 1 .

[0051] Example 8

[0052] The preparation method is basically the same as in Example 1, except that the ion donor used is H3PO4, and the resulting sensor structure is similar to... Figure 1 .

[0053] Example 9

[0054] The preparation method is basically the same as in Example 1, except that the ion donor used is LiCl, and the resulting sensor structure is similar to... Figure 1 .

[0055] This invention includes, but is not limited to, the above embodiments. The above description is only a preferred embodiment of this invention. It should be noted that, for those skilled in the art, other improvements made based on this invention should also be within the scope of protection of this invention.

[0056] Compared with the prior art, the present invention has the following advantages:

[0057] The capacitive pressure sensor described in this invention benefits from a porous liquid metal electrode and an ion-gel dielectric layer. When the liquid metal electrode is compressed, the overall thickness of the device decreases, while the charge density on the surface of the ion-gel dielectric layer increases, thereby enhancing the double-layer capacitance effect. While pressure causes changes in structural parameters leading to capacitance changes, the ion-gel dielectric layer can also provide an additional double-layer capacitance effect, synergistically enhancing the sensor's sensitivity. Therefore, the pressure sensor described in this invention can significantly improve the sensitivity of capacitive pressure sensors.

Claims

1. A capacitive pressure sensor, characterized in that, It includes a porous liquid gallium indium tin alloy electrode, an ion gel dielectric layer, a first electrode and a second electrode. The first electrode covers the upper surface of the porous liquid gallium indium tin alloy electrode, the lower surface of the porous liquid gallium indium tin alloy electrode is connected to the upper surface of the ion gel dielectric layer, and the lower surface of the ion gel dielectric layer is covered with the second electrode. The porous liquid gallium indium tin alloy electrode deforms when subjected to external force, and the charge density on the upper surface of the ion gel dielectric layer increases. When the external force is removed, the deformation will recover, and the charge density on the upper surface of the ion gel dielectric layer will return to its original state.

2. The capacitive pressure sensor according to claim 1, characterized in that, The gel material of the ionogel dielectric layer is polyvinyl alcohol, polyacrylamide, cellulose, or chitosan.

3. The capacitive pressure sensor according to claim 1 or 2, characterized in that, The ion donors of the ion gel dielectric layer are phosphate molecules and / or sodium chloride and / or potassium chloride and / or lithium chloride.

4. The capacitive pressure sensor according to claim 3, characterized in that, The thickness of the ionogel dielectric layer is 0.1–1 mm.

5. The capacitive pressure sensor according to claim 1, characterized in that, The porous liquid gallium indium tin alloy electrode is a liquid gallium indium tin alloy with different compositions.

6. The capacitive pressure sensor according to claim 5, characterized in that, The porous liquid gallium indium tin alloy electrode has a thickness of 50–500 μm.

7. The capacitive pressure sensor according to claim 1, characterized in that, The materials of the first electrode and the second electrode are Ti, Pt, Au, or indium tin oxide.

8. The capacitive pressure sensor according to claim 7, characterized in that, The thickness of the first electrode and the second electrode is 0.01 to 0.1 mm.

9. A method for manufacturing a capacitive pressure sensor, applied to the manufacture of the capacitive pressure sensor according to any one of claims 1-8, characterized in that, include: Step 1: Inject liquid gallium indium tin alloy into a PVA template and cure it at room temperature for a set time. After the liquid gallium indium tin alloy has cured in the PVA template, dissolve the PVA template with hot water to obtain a porous liquid gallium indium tin alloy electrode. Step 2: Mix deionized water, NaCl and polysaccharide monomers to prepare gel precursor solutions with different weight ratios. After the gel precursor solutions are fully mixed, inject them into a silicone template and heat them at a preset temperature. Before the gel is formed, place a liquid metal porous electrode on the unformed gel and connect it. After heating for a predetermined time, the formed gel is obtained. Step 3: Use two collectors to sandwich the molded gel in the middle, and then use PDMS to encapsulate the whole thing to obtain a capacitive pressure sensor.

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