Flexible liquid metal electronic patch for detecting electric signals of human body and preparation method of flexible liquid metal electronic patch

Abstract

The invention relates to a preparation method of a flexible liquid metal electronic patch for detecting an electric signal of a human body, which comprises the following steps of: mixing liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay to prepare composite ink, printing the composite ink on a high-viscosity double-sided polyethylene substrate to obtain a liquid metal-based circuit, and packaging the circuit by adopting PDMS or epoxy resin. The prepared composite ink has excellent fluidity, the dispersion uniformity of the liquid metal in the ink is excellent, the composite ink does not need to be used as a photomask plate, circuit patterns do not need to be engraved virtually through the photomask plate, the period is short, and the cost is low. The liquid metal electronic circuit is directly subjected to 3D printing on the nano double-sided polyethylene substrate, the minimum height of the obtained circuit can be 26 microns, and the prepared liquid metal microelectronic patch is excellent in conductivity, low in space occupancy, high in response sensitivity and excellent in electrical signal stability.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible electronic products, and in particular to a flexible liquid metal electronic patch for detecting human body electrical signals and a preparation method thereof. Background Art

[0002] Monitoring of human electrical signals can provide individual physiological conditions and key clinical parameters, such as severe arrhythmias and heart failure associated with high-risk heart diseases. Long-term monitoring of human electrical signals and real-time early warning of heart rate disorders in the elderly are of great significance for saving lives. At present, most ordinary hospital medical systems in China generally use electrodes, wires, signal conditioning, sampling, and recording storage modules to form a measurement system when collecting human electrical signals such as electrocardiograms; the measurement equipment is large, expensive, and the monitoring time is short. Highly adhesive, breathable, and flexible electronic patches can be maintained on human skin for a long time and stably, and can non-invasively and continuously monitor human electrical signals, playing an important role in health monitoring and disease treatment. Flexible circuits are usually based on metal nanoparticles, such as nanowires and graphene. With the rapid development of flexible electronic technology, the unique physical properties of liquid metal have gradually attracted the attention of various industries and have begun to be applied to flexible electronics. Due to the high conductivity, good fluidity and low toxicity of liquid metal, it is expected to achieve highly foldable and stable flexible circuits and realize circuit recycling. The liquid metal used in flexible electronics is just a liquid metal alloy with a low melting point, which is usually liquid at room temperature.

[0003] Traditional liquid metal electronic circuit manufacturing generally uses the template method to print liquid metal circuits. To achieve continuous and reliable printing of liquid metal, a template needs to be prepared. The printed pattern is cut or hollowed out to form a template through laser, chemical etching or motor etching. This method first requires designing a pattern to make a photomask template, and then applying photoresist on the silicon wafer. The laser shines through the photomask to the photoresist to form a pattern. The cycle is long, the cost is high, and the manufactured template has a limited number of uses. At present, there are few reports on the manufacture of ultra-fine liquid metal flexible electronic devices through 3D printers, and even fewer reports on their use for human electrical signal monitoring. Summary of the invention Based on the above technical problems, the purpose of the present invention is to provide a 3D printed ultra-precision liquid metal microelectronic patch.

[0004] Another object of the present invention is to provide a method for preparing the flexible liquid metal electronic patch for detecting human body electrical signals. The preparation method is simple and low in cost.

[0005] The purpose of the present invention is achieved through the following technical solutions: An ultra-precision liquid metal microelectronic patch, characterized in that: a composite ink is prepared by mixing liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay, the composite ink is printed on a high-viscosity double-sided polyethylene substrate to obtain a liquid metal-based circuit, and the circuit is encapsulated using PDMS or epoxy resin, wherein the liquid metal in the composite ink is prepared by uniformly mixing Ga and In metals according to a mass configuration ratio of 7:3 to 7.5:2.5 to obtain gallium-indium alloy liquid metal.

[0006] Furthermore, the mass ratio of liquid metal, medical conductive gel, PVA and clay in the composite ink is 1:0.5~1:1:0.2~0.3.

[0007] Further preferably, the mass ratio of liquid metal, medical conductive gel, PVA and clay in the composite ink is 1:0.6:1:0.25.

[0008] Furthermore, the printing pulse frequency is 200-300K, and the printing pressure is 4-6kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 800~1000 mm / s 2 , the reset speed is 20~50 mm / s.

[0009] A method for preparing a flexible liquid metal electronic patch for detecting human electrical signals is characterized in that: liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay are mixed to prepare a composite ink, the composite ink is printed on a high-viscosity double-sided polyethylene substrate to obtain a liquid metal-based circuit, and the circuit is encapsulated using PDMS or epoxy resin.

[0010] Furthermore, the liquid metal in the composite ink is prepared by uniformly mixing Ga and In metals in a mass ratio of 7:3 to 7.5:2.5 to obtain gallium-indium alloy liquid metal.

[0011] Furthermore, the mass ratio of liquid metal, medical conductive gel, PVA and clay in the composite ink is 1:0.5~1:1:0.2~0.3.

[0012] Adding conductive gel to liquid metal can improve the conductivity of the circuit. However, after the conductive gel is added, it is found that when the circuit is directly printed on a polyethylene substrate, the adhesion performance of the circuit on the substrate surface decreases and the uniformity of the prepared circuit is poor.

[0013] In the present invention, the adhesion, emulsification and fluidity of the liquid metal are adjusted by adding polyvinyl alcohol (PVA) and a small amount of clay, the adhesion performance of the prepared composite ink on the surface of the polyethylene substrate is significantly improved, and the uniformity of the printed circuit lines is significantly improved.

[0014] Further preferably, the mass ratio of liquid metal, medical conductive gel, PVA and clay in the composite ink is 1:0.6:1:0.25.

[0015] Furthermore, the printing pulse frequency is 200-300K, and the printing pressure is about 4-6kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 800~1000 mm / s 2 , the reset speed is 20~50 mm / s.

[0016] Furthermore, the encapsulation is to coat the prepared encapsulation solution on a high-viscosity double-sided polyethylene substrate printed with a liquid metal circuit, spray a small amount of water mist to soften the PVA film, and then slowly dry it at room temperature. The encapsulation solution is prepared by mixing glycerol, the encapsulation main material and deionized water in a mass ratio of 1:5:50 and stirring for 1 hour at a temperature of 70°C to 80°C. The encapsulation main material is PDMS or epoxy resin.

[0017] Furthermore, the printed electronic patch was attached to the human body, and the prepared sensor was changed by the changes in the throat when the human body speaks and the acceleration of the ECG signal after running, and the change in resistance was measured at the same time. The experimental results show that the resistance of the sensor circuit shows a curve trend of first increasing and then decreasing during the swallowing process. During the swallowing process, the sensor is compressed, resulting in a decrease in resistance, and then the resistance recovers after the pressure is released.

[0018] When using the patch to test the ECG signal, the ECG signal causes subtle changes in the surface morphology of the human body. The 3D printed patch measures the human heartbeat resistance change rate to be between 0.65% and 1.3%. Most specifically, a method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals is characterized by comprising the following steps: S1. After mixing Ga and In in a mixing ratio of 7:3~7.5:2.5, the mixture is continuously stirred at a temperature of 55°C~65°C for 25min~35min to obtain a pure functional gallium-indium alloy (EGaIn) liquid metal, and the liquid metal, medical conductive gel, polyvinyl alcohol PVA and clay are mixed in a mass ratio of 1:0.5~1:1:0.2~0.3, and a composite ink is formed by ultrasonic treatment; S2. According to the designed circuit diagram, the composite ink is printed on the high-viscosity double-sided polyethylene substrate by 3D printing to produce the required liquid metal circuit. The pulse frequency of 3D printing is 200K and the printing pressure is 4~6kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 1000 mm / s 2 , the reset speed is 20~50 mm / s; S3. The prepared encapsulation solution is coated on a high-viscosity double-sided polyethylene substrate printed with a liquid metal circuit, a small amount of water mist is sprayed to soften the PVA film, and then slowly dried at room temperature. The encapsulation solution is prepared by mixing glycerol, encapsulation main material and deionized water in a mass ratio of 1:5:50 and stirring at a temperature of 70°C to 80°C for 1 hour. The encapsulation main material is PDMS or epoxy resin.

[0019] The present invention has the following technical effects: The composite ink prepared by the present invention has excellent fluidity, and the liquid metal has excellent uniformity of dispersion in the ink. The composite ink does not require a photomask plate, and does not require virtual engraving of circuit patterns through a photomask plate, so the cycle is short and the cost is low. The liquid metal electronic circuit is directly 3D printed on a nano double-sided polyethylene substrate, and the minimum height of the obtained circuit can be 26 μm. The prepared liquid metal microelectronic patch has excellent conductivity, low space occupancy, high response sensitivity, and excellent electrical signal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : Scanning electron microscope (SEM) image of the composite ink prepared by the present invention.

[0021] Figure 2 : Ultra-precision liquid metal microelectronic circuit printed by the composite ink prepared by the present invention.

[0022] Figure 3 : The composite ink prepared by the present invention has the effect of printing circuits on different substrate surfaces.

[0023] Figure 4 : The ultra-precision liquid metal microelectronic patches prepared in Example 1 (purple) and Comparative Example 1 (green) are used for the corresponding electrical signal monitoring curves of the human throat.

[0024] Figure 5 : The change in the resistance value R of the ultra-precision liquid metal microelectronic patch prepared in Example 1 under different pressures, and the resistance change value △R / R curve. DETAILED DESCRIPTION

[0025] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.

[0026] The medical conductive gel used in the present invention is American Weaver gel, and its main components are water, aluminum oxide, 1,2-propylene glycol, sodium polyacrylate, methyl p-carboxybenzoate and pigment.

[0027] Example 1 A method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals comprises the following steps: S1. After mixing Ga and In in a mixing ratio of 7:3, stirring was continued at 60°C for 30 minutes to obtain a pure functional gallium-indium alloy (EGaIn) liquid metal, and the liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay were mixed in a mass ratio of 1:0.6:1:0.25, and ultrasonic treatment was performed to form a composite ink; S2. According to the designed circuit diagram, the composite ink is printed on the high-viscosity double-sided polyethylene substrate by 3D printing to produce the required liquid metal circuit. The pulse frequency of 3D printing is 200K and the printing pressure is 5kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 1000 mm / s 2 , the reset speed is 30 mm / s; S3. The prepared PVA solution is coated on a high-viscosity double-sided polyethylene substrate printed with a liquid metal circuit, a small amount of water mist is sprayed to soften the PVA film, and then slowly dried at room temperature. The PVA solution is prepared by mixing glycerol, PVA and deionized water in a mass ratio of 1:5:50 and stirring at 75°C for 1 hour.

[0028] Figure 1 FIG. 1 is a scanning electron microscope image of the composite ink prepared in this embodiment. It can be seen that the liquid metal in the ink is evenly dispersed in the ink. Figure 2 As shown, the height of the circuit prepared in this embodiment is 26 μm. According to the method of Example 1, circuits are printed on different substrate surfaces as shown in FIG. Figure 3 As shown, (a) is a paper substrate, (b) is a plant leaf substrate, and (c) is a polyethylene substrate. It can be seen that the composite ink is discontinuous when printing circuits on the paper and the plant leaf surfaces, while the circuits printed on the polyethylene substrate surface have excellent continuity, that is, the composite ink prepared by the present invention has better compatibility with the polyethylene substrate.

[0029] In the process of preparing composite inks, we tried composite inks prepared by pure liquid metal, liquid metal + medical conductive gel, liquid metal + medical conductive gel + PVA, and liquid metal + medical conductive gel + clay, and printed the circuit on the surface of polyethylene substrate with a 210 μm needle. The circuit was tested with tape to check the adhesion performance of the circuit on the substrate surface and observe the circuit properties. The results are shown in Table 1.

[0030] Table 1:

[0031] And through testing, the conductivity of liquid metal + medical conductive gel + clay is significantly off the shelf, and the internal resistance of the circuit rises sharply. The circuit prepared by the composite ink of Example 1 has excellent conductivity, and the simultaneous addition of PVA and clay has no negative impact on the conductivity of the circuit. The internal resistance of the prepared circuits is liquid metal + medical conductive gel + clay > liquid metal + medical conductive gel + PVA > liquid metal + medical conductive gel > Example 1 > pure liquid metal.

[0032] Comparative Example 1 In the process of preparing the composite ink, no conductive gel was added. Only liquid metal, PVA and clay were mixed in a ratio of 1:1:0.2. The remaining steps were the same as in Example 1.

[0033] The liquid metal flexible patch prepared in Example 1 and Comparative Example 1 was attached to the throat and skin of a human body, and electrical signal detection was performed. The results are as follows: Figure 4 As shown, it can be seen that during the process of swallowing and sliding up and down in the throat of the human body, the patch test resistance prepared in Example 1 (purple) shows a regular rise and fall change, that is, the greater the stretching of the throat part of the human body, the more obvious the change of the patch test resistance. When the throat part is reset, the resistance value also decreases regularly, which shows that the liquid metal electronic patch prepared by the present invention has sensitive signal response, high accuracy and excellent signal stability. The patch resistance of Comparative Example 1 (green) changes irregularly, and as time goes on, the patch test resistance gradually increases, and does not change regularly with the movement of the throat. This shows that the addition of PVA and clay has an impact on the change law of the electrical signal detected by liquid metal, and has an adverse effect on the transmission of electrical signals. In the composite system of liquid metal and conductive gel, the addition of PVA and clay does not affect the transmission of electrical signals of the patch.

[0034] from Figure 5 It can be seen that, under the action of external pressure, the resistance value of the liquid metal electronic patch prepared in Example 1 gradually increases with the increase of pressure, and the resistance change value △R / R has excellent change stability.

[0035] Example 2 A method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals comprises the following steps: S1. After mixing Ga and In in a mixing ratio of 7.5:2.5, stirring was continued at 55°C for 35 minutes to obtain a pure functional gallium-indium alloy (EGaIn) liquid metal, and the liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay were mixed in a mass ratio of 1:0.5:1:0.2, and ultrasonic treatment was performed to form a composite ink; S2. According to the designed circuit diagram, the composite ink is printed on the high-viscosity double-sided polyethylene substrate by 3D printing to produce the required liquid metal circuit. The pulse frequency of 3D printing is 300K and the printing pressure is 4kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 900 mm / s 2 , the reset speed is 50 mm / s; S3. The prepared PVA solution is coated on a high-viscosity double-sided polyethylene substrate printed with a liquid metal circuit, a small amount of water mist is sprayed to soften the PVA film, and then slowly dried at room temperature. The PVA solution is prepared by mixing glycerol, PVA and deionized water in a mass ratio of 1:5:50 and stirring at 80°C for 1 hour.

[0036] The height of the circuit prepared in this embodiment is 30 μm, and the prepared ultra-precision liquid metal microelectronic patch has high precision and high test sensitivity.

[0037] Example 3 A method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals comprises the following steps: S1. After mixing Ga and In in a mixing ratio of 7:3, stirring was continued at 65°C for 25 minutes to obtain pure functional gallium-indium alloy (EGaIn) liquid metal, and the liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay were mixed in a mass ratio of 1:1:1:0.3, and ultrasonic treatment was performed to form a composite ink; S2. According to the designed circuit diagram, composite ink is printed on a high-viscosity double-sided polyethylene substrate through 3D printing to produce the required liquid metal circuit. The pulse frequency of 3D printing is 250K and the printing pressure is 6kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 800 mm / s 2 , the reset speed is 20mm / s; S3. The prepared PVA solution is coated on a high-viscosity double-sided polyethylene substrate printed with a liquid metal circuit, a small amount of water mist is sprayed to soften the PVA film, and then slowly dried at room temperature. The PVA solution is prepared by mixing glycerol, PVA and deionized water in a mass ratio of 1:5:50 and stirring at 70°C for 1 hour.

[0038] The height of the circuit prepared in this embodiment is 32 μm, and the prepared ultra-precision liquid metal microelectronic patch has high precision and high test sensitivity.

Claims

1. A method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals, characterized in that: The composite ink is prepared by mixing liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay, and the composite ink is printed on a high-viscosity double-sided polyethylene substrate to obtain a liquid metal-based circuit, which is then encapsulated using PDMS or epoxy resin.

2. The method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals as claimed in claim 1, characterized in that: The mass ratio of liquid metal, medical conductive gel, PVA and clay in the composite ink is 1:0.5~1:1:0.2~0.

3.

3. The method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals according to claim 1 or 2, characterized in that: The printing pulse frequency is 200~300K, and the printing pressure is about 4~6kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 800~1000 mm / s 2 , the reset speed is 20~50 mm / s.

4. A method for preparing a flexible liquid metal electronic patch for detecting human body electrical signals, characterized in that: The steps include: S1. After mixing Ga and In in a mixing ratio of 7:3~7.5:2.5, the mixture is continuously stirred at a temperature of 55°C~65°C for 25min~35min to obtain a pure functional gallium-indium alloy (EGaIn) liquid metal, and the liquid metal, medical conductive gel, polyvinyl alcohol PVA and clay are mixed in a mass ratio of 1:0.5~1:1:0.2~0.3, and a composite ink is formed by ultrasonic treatment; S2. According to the designed circuit diagram, composite ink is printed on a high-viscosity double-sided polyethylene substrate by 3D printing to produce the required liquid metal circuit. The pulse frequency of 3D printing is 200K and the printing pressure is 4~6kg / cm 2 , pulse equivalent is 0.0055mm, acceleration is 1000 mm / s 2 , the reset speed is 20~50 mm / s; S3. The prepared encapsulation solution is coated on a high-viscosity double-sided polyethylene substrate printed with a liquid metal circuit, a small amount of water mist is sprayed to soften the PVA film, and then slowly dried at room temperature. The encapsulation solution is prepared by mixing glycerol, encapsulation main material and deionized water in a mass ratio of 1:5:50 and stirring at a temperature of 70°C to 80°C for 1 hour. The encapsulation main material is PDMS or epoxy resin.

5. An ultra-precision liquid metal microelectronic patch, characterized in that: The invention discloses a composite ink prepared by mixing liquid metal, medical conductive gel, polyvinyl alcohol (PVA) and clay, printing the composite ink on a high-viscosity double-sided polyethylene substrate to obtain a liquid metal-based circuit, and encapsulating the circuit with PDMS or epoxy resin. The liquid metal in the composite ink is prepared by uniformly mixing Ga and In metals according to a mass configuration ratio of 7:3 to 7.5:2.5 to obtain gallium-indium alloy liquid metal.

6. The ultra-precision liquid metal microelectronic patch according to claim 5, characterized in that: The mass ratio of liquid metal, medical conductive gel, PVA and clay in the composite ink is 1:0.5~1:1:0.2~0.3.

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