WO2020206646A1 - 一种基于银粉和pdms的柔性导电薄膜及其制备方法 - Google Patents

一种基于银粉和pdms的柔性导电薄膜及其制备方法 Download PDF

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WO2020206646A1
WO2020206646A1 PCT/CN2019/082154 CN2019082154W WO2020206646A1 WO 2020206646 A1 WO2020206646 A1 WO 2020206646A1 CN 2019082154 W CN2019082154 W CN 2019082154W WO 2020206646 A1 WO2020206646 A1 WO 2020206646A1
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silver powder
pdms
flexible conductive
conductive film
film
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French (fr)
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李晖
张劲杰
王磊
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Shenzhen Institute of Advanced Technology of CAS
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Shenzhen Institute of Advanced Technology of CAS
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Priority to US17/413,292 priority Critical patent/US20220076858A1/en
Priority to PCT/CN2019/082154 priority patent/WO2020206646A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/40—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials
    • H10P14/46—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials using a liquid

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  • the invention belongs to the technical field of flexible conductive films, and in particular relates to a flexible conductive film based on silver powder and PDMS and a preparation method thereof.
  • the current preparation methods of stretchable flexible conductive films based on silver powder and PDMS mainly include the following:
  • the PDMS prepolymer and curing agent were mixed, and then the prepared core-shell PS@Ag filler was added, and mixed at a speed of 2000 rpm for 5 minutes. Then the mixture is degassed under vacuum for 10 minutes, and then the viscous mixture is poured into a mold and scraped to prepare a conductive film, or directly printed on the substrate by manual screen printing to obtain various conductive patterns, and then 80 Heat at °C for 4 hours to cure.
  • the unexposed areas are fully crosslinked, while the exposed areas remain uncured.
  • the uncured PDMS was placed in toluene for 5 seconds to remove. Rinse with 2-propanol after development and blow dry with nitrogen flow.
  • the pattern prepared on the flexible substrate is laminated or oxygen plasma bonded to form a multilayer device. Finally, a thermal compression step is used to mold the micromachined device into the desired shape for biomedical applications.
  • the surface of the pre-strained PDMS substrate was then exposed to ultraviolet light ozone (UVO) for 30 minutes.
  • UVO ultraviolet light ozone
  • the pre-strained PDMS substrate was released at a rate of 1 mm/sec to form a wavy pattern on the PDMS substrate.
  • the PDMS substrate was fixed on the substrate holder with a constant pre-strain of 20%, and the UV-ozone treatment time was increased by 40 to 60 minutes.
  • Direct current reactive magnetron sputtering DC sputtering
  • a DC sputtering system was used to deposit translucent Ag films of various thicknesses (10, 15, 20 nm) on the wavy pattern and flat PDMS substrate.
  • the PDMS substrate was constantly rotated at a speed of 20 rpm at room temperature.
  • the translucent Ag film was grown under a constant DC reaction power of 100W, a working pressure of 2 mtorr, and an argon (Ar) flow rate of 20 sccm (standard milliliters/minute).
  • the preparation process is complicated, and complicated pretreatment is required for the conductive material-silver powder to modify the surface of the silver powder;
  • the preparation process involves chemical reagents harmful to the human body such as styrene, divinylbenzene, azobisisobutyronitrile and benzophenone;
  • the flexible conductive film prepared by the above scheme is weak in conductivity and stretchability.
  • the present invention aims to solve at least one of the above technical problems. It provides a flexible conductive film based on silver powder and PDMS and a preparation method thereof.
  • the preparation process is simple, does not involve harmful chemical reagents, and has low requirements on equipment. The stretchability is better.
  • the technical solution of the present invention is: a method for preparing a flexible conductive film based on silver powder and PDMS, including the following steps: preparing silver powder, PDMS prepolymer and PDMS curing agent, and the diameter of the silver powder is less than 12 microns;
  • the liquid flexible conductive film is evenly coated to a set thickness and cured to obtain a flexible conductive film.
  • the cleaning step includes:
  • the ethanol above the silver powder is sucked and the remaining ethanol is evaporated.
  • the diameter of the silver powder is 2 micrometers to 3.5 micrometers.
  • the weight ratio of the silver powder to the PDMS film substrate is between 150 wt.% and 200 wt.%.
  • the weight ratio between the PDMS prepolymer and the PDMS curing agent is 10:1.
  • the curing of the liquid flexible conductive film includes the following steps:
  • the liquid flexible conductive film obtained by mixing is poured on a silicon wafer, and then spin-coated on a homogenizer to form a film to be cured.
  • the spin coating speed of the homogenizer is 400-1000 rpm, and the spin coating time is 15- 25s;
  • the film to be cured on the heating plate together with the silicon wafer, and heat for 15-30 minutes in an environment of 60-100°C.
  • the film to be cured forms a cured flexible conductive film.
  • the flexible conductive film is peeled from the silicon wafer.
  • the embodiment of the present invention also provides a flexible conductive film based on silver powder and PDMS, including silver powder and a PDMS film substrate, the silver powder is evenly dispersed in the PDMS film substrate, and the diameter of the silver powder is less than 12 microns.
  • the diameter of the silver powder is 2 micrometers to 3.5 micrometers.
  • the weight ratio of the silver powder to the PDMS film substrate is between 150 wt.% and 200 wt.%.
  • the present invention provides a flexible conductive film based on silver powder and PDMS.
  • the flexible conductive film can change its shape arbitrarily, such as stretching, bending, and twisting, which can be used in conjunction with any curved surface.
  • the PDMS film matrix also has biological characteristics. It has the characteristics of compatibility and non-toxicity, and has good adherence to the skin, can be widely used in wearable devices, and has high sensitivity and good use effect.
  • the preparation process is simpler and faster, and does not require any dangerous chemical reagents such as strong acids and alkalis and high-precision, high-tech equipment during the preparation process.
  • experiments have also verified that the sensitivity coefficient of the flexible conductive film prepared by the present invention can reach 939, which is much higher than the current similar products.
  • FIG. 1 is a schematic diagram of a reference flow chart of a method for preparing a flexible conductive film based on silver powder and PDMS provided by an embodiment of the present invention
  • FIG. 2 is the GF value at each stage in the stretching process of a flexible conductive film based on silver powder and PDMS provided by an embodiment of the present invention.
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • the embodiment of the present invention provides a method for preparing a flexible conductive film based on silver powder and PDMS, which includes the following steps: preparing silver powder, PDMS (polydimethylsiloxane) prepolymer and PDMS curing agent, and The diameter of silver powder is less than 12 microns to ensure sensitivity;
  • the silver powder is ground, cleaned, and dried, it is added to the PDMS prepolymer and mixed, and then the PDMS curing agent is added and mixed to obtain a liquid flexible conductive film, that is, the PDMS is mixed evenly by mixing twice The effect is better, the distribution of silver powder is more uniform, and the sensing accuracy of the prepared flexible conductive film is higher;
  • the liquid flexible conductive film is evenly coated to a set thickness and cured to obtain a flexible conductive film.
  • the preparation method is simple and rapid. The preparation process does not require any dangerous chemical reagents such as strong acids or alkalis and high-precision, high-tech equipment. The preparation cost is low and the finished product effect is good.
  • the cleaning step includes:
  • the ethanol above the silver powder is sucked and the remaining ethanol is evaporated.
  • the diameter of the silver powder is 1.5 ⁇ m to 5 ⁇ m, and in this embodiment, the diameter of the silver powder is 2 ⁇ m to 3.5 ⁇ m.
  • the weight ratio of the silver powder to the PDMS film substrate is between 150 wt.% and 200 wt.%.
  • the weight ratio between the PDMS prepolymer and the PDMS curing agent is 10:1.
  • the curing of the liquid flexible conductive film includes the following steps:
  • the liquid flexible conductive film obtained by mixing is poured on a silicon wafer, and then spin-coated on a homogenizer to form a film to be cured.
  • the spin coating speed of the homogenizer is 400-1000 rpm, and the spin coating time is 15- 25s; Release agent can be sprayed on the silicon wafer in advance.
  • the film to be cured on the heating plate together with the silicon wafer, and heat for 15-30 minutes in an environment of 60-100°C.
  • the film to be cured forms a cured flexible conductive film.
  • the flexible conductive film is peeled from the silicon wafer.
  • the Ag/PDMS film is made of highly flexible PDMS as a base material, mixed with silver powder with relatively uniform particles, and cured by ultrasound, stirring, spin coating and heating And so on. By controlling the weight ratio of the silver powder to the PDMS substrate and the spin coating speed and time, flexible conductive films with different characteristics can be obtained.
  • the flexible conductive film method of PDMS does not require any dangerous chemical reagents such as strong acids and alkalis and high-precision, high-tech equipment in the preparation process.
  • the flexible conductive film controls the conductivity and thickness of the film by controlling the weight ratio of silver powder and PDMS and the spin coating speed and time.
  • the prepared film can meet the needs of different applications.
  • the flexible conductive film has a larger weight ratio and spin coating speed. It can be applied to flexible sensors with lower sensitivity but larger measuring range. On the contrary, a flexible conductive film with a smaller weight ratio and spin coating speed can be used for flexible sensors that require high sensitivity but a small measurement range
  • the thickness of the film can be controlled by controlling the spin coating speed and time.
  • the spin coating speed is 400-1000 rpm, and the spin coating time is 15-25 s.
  • the flexible conductive film can be stretched experiment, that is, by measuring the initial resistance value and initial size of the flexible conductive film, and measuring the stretched size and the resistance value of the corresponding size.
  • wires can be connected to both ends of the flexible conductive film, and the wires can be connected to a resistance measuring device (such as an SMU source meter). Clamp the two ends of the flexible conductive film by the clamp of the stretching device, and start to stretch the flexible conductive film step by step through the stretching device, and record the resistance value under the corresponding stretch size until the flexible conductive film breaks and fails.
  • 2 is the GF value of the flexible conductive film at each stage in the stretching process, and the overall GF value is 939.
  • the embodiment of the present invention proves that the flexible conductive film has good conductivity and stretchability through stretching experiments on the above-mentioned flexible conductive film, the maximum stretch rate is 48%, and the maximum sensitivity (GF) can reach 939.
  • GF gauge factor
  • R 0 and R represent the initial resistance of the flexible conductive film and the resistance value after stretching, respectively;
  • L 0 and L represent the initial length and the length of the flexible conductive film after being stretched, respectively.
  • the embodiment of the present invention provides a flexible conductive film based on silver powder and PDMS and a preparation method thereof.
  • the preparation process is simpler and faster, and does not require any dangerous chemical reagents such as strong acids and alkalis, high precision and high technology in the preparation process. device of.
  • experiments have also verified that the sensitivity coefficient of the silver powder/PDMS film (flexible conductive film) prepared by the present invention can reach 939, which is much higher than the current similar products.
  • the embodiment of the present invention provides a flexible conductive film based on silver powder and PDMS, which can be prepared by the preparation method of the first embodiment and can be used for sensors of wearable devices, including silver powder and PDMS film substrate (PDMS film substrate), PDMS is polydimethylsiloxane, It is odorless, highly transparent, has high stretchability, heat resistance, cold resistance, and the viscosity changes little with temperature.
  • the silver powder is uniformly dispersed in the PDMS film matrix, the diameter of the silver powder can be less than 12 microns, the conductive effect of the silver powder is good, and the micron-level particle size can ensure the sensitivity of the flexible conductive film, because the silver powder is uniformly dispersed in the In the PDMS film matrix, and the PDMS film matrix can be deformed at will, when the flexible conductive film is deformed by an external force, the local spacing and local density of the silver powder will change at the deformed place, which will cause the resistance of the flexible conductive film to change, thereby causing the flow
  • the current passing through the flexible conductive film or/and the voltage change applied to the flexible conductive film has high sensitivity (super sensitivity).
  • the diameter of the silver powder may be less than 10 microns, for example, the diameter of the silver powder may be 1 to 6 microns to ensure its sensitivity.
  • the diameter of the silver powder may be 1-4.5 micrometers, preferably, the diameter of the silver powder may be 2 micrometers-3.5 micrometers.
  • the weight ratio of the silver powder to the PDMS film substrate may be between 100 wt.% and 300 wt.%.
  • the weight ratio of the silver powder to the PDMS film substrate is between 150 wt.% and 200 wt.%.
  • the weight ratio is lower than 150wt.%, the conductivity of the film is relatively poor; when the weight ratio is higher than 200wt.%, the mixture of silver powder and PDMS is relatively viscous, which is not easy for subsequent uniform spin coating, and the forming performance is poor.
  • conductive electrodes can be inserted or pasted or clamped on both sides of the PDMS film substrate.
  • the conductive electrode can be connected to a resistance measuring device.
  • a flexible protective layer can be provided on the surface of the PDMS film substrate.
  • the flexible protective layer can be a wear-resistant, tear-resistant, and corrosion-resistant protective layer, such as a silicone protective layer.
  • the PDMS film substrate can be polygonal (rectangular, triangular), circular, cylindrical, cylindrical, etc.
  • the embodiment of the present invention proves that the flexible conductive film has good conductivity and stretchability through stretching experiments on the above-mentioned flexible conductive film, the maximum stretch rate is 48%, and the maximum sensitivity (GF) can reach 939.
  • GF gauge factor
  • GF strain sensitivity factor
  • GF [(R- R 0 )/ R 0 ]/[(L- L 0 )/ L 0 ]
  • R 0 and R represent the initial resistance of the flexible conductive film and the resistance value after stretching, respectively;
  • L 0 and L represent the initial length and the length of the flexible conductive film after being stretched, respectively.
  • the embodiment of the present invention provides a flexible conductive film based on silver powder and PDMS and a preparation method thereof.
  • the preparation process is simpler and faster, and does not require any dangerous chemical reagents such as strong acids and alkalis, high precision and high technology in the preparation process. device of.
  • experiments have also verified that the sensitivity coefficient of the silver powder/PDMS film (flexible conductive film) prepared by the present invention can reach 939, which is much higher than the current similar products.
  • the thickness of the above-mentioned flexible conductive film may be 0.05 to 5 mm or other suitable thickness.
  • the thickness of the aforementioned flexible conductive film is 0.1 to 2 mm.
  • the embodiment of the present invention provides a flexible conductive film based on silver powder and PDMS.
  • the flexible conductive film can change its shape arbitrarily, such as stretching, bending, and twisting, which can be used in conjunction with any curved surface.
  • the PDMS film matrix is also It has the characteristics of biocompatibility and non-toxicity, and has good adherence to the skin, can be widely used in wearable devices, and has high sensitivity and good use effect.

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Abstract

本发明适用于柔性导电薄膜技术领域，公开了一种基于银粉和PDMS的可拉伸、超灵敏的柔性导电薄膜及其制备方法。制备方法，包括以下步骤：制备银粉、PDMS预聚物和PDMS固化剂；将所述银粉进行研磨、清洗、干燥后，加入所述PDMS预聚物中混匀再加入所述PDMS固化剂混匀得到液态柔性导电薄膜；将所述液态柔性导电薄膜涂匀至设定厚度并固化后得到柔性导电薄膜。柔性导电薄膜，包括银粉和PDMS薄膜基体，所述银粉均匀分散于所述PDMS薄膜基体内。本发明提供的一种基于银粉和PDMS的柔性导电薄膜及其制备方法，其制备工艺简单、不涉及有害化学试剂、对设备要求低，产品在导电性和拉伸性上表现较佳。

Description

一种基于银粉和PDMS的柔性导电薄膜及其制备方法 技术领域
本发明属于柔性导电薄膜技术领域，尤其涉及一种基于银粉和PDMS的柔性导电薄膜及其制备方法。
 背景技术
随着科学技术的发展和进步，柔性电子领域和可穿戴电子设备呈现出巨大的市场前景，全球主要的消费电子公司几乎都推出了各自的可穿戴产品，尤其在一些具有生理监测功能方面的应用得到广泛关注。由于这一类产品的工作环境在人体复杂不规则的皮肤表面，这就要求可穿戴设备的传感技术具有更大的灵活性和柔韧性，最好还要具有生物相适性，免于与人体产生不良反应。基于传统刚性基底的传感器显然与柔性的人体复杂的三维皮肤表面存在机械上的不匹配，这会影响用户的体验和测量结果。随着电子技术和材料科学的发展，满足上述特点的柔性传感器在此基础上应运而生。
目前的基于银粉和PDMS的可拉伸柔性导电薄膜的制备方法主要有以下几种：
1、将苯乙烯（St，48.5g)、二乙烯基苯(DVB,1.5g)和偶氮二异丁腈（AIBN，2.0g)的混合物加入500mL的四颈圆底烧瓶中，该烧瓶含有2g聚乙烯吡咯烷酮（PVP）、135g乙醇和15g水，将烧瓶置于油浴中，并保持在70℃。混合液通过鼓泡氮气脱氧，同时搅拌。24小时后，将烧瓶从油浴中取出，在空气中冷却。用去离子水对得到的交联聚苯乙烯/银粉(PS@Ag)微球进行多次离心纯化。将PDMS预聚物和固化剂以混合，然后添加制备的核壳PS@Ag填料，以2000rpm的速度混合5分钟。然后将混合物在真空下脱气10分钟，随后将粘性混合物浇注到模具中并刮平以制备导电膜，或用手工丝网印刷法直接印刷在基板上，以获得各种导电图案，然后在80℃下加热4小时固化。
2、将PDMS预聚物和固化剂(Sylgard® 184)混合。然后将二苯甲酮（3%重量比）和银粉(17%-22%体积比)加入PDMS混合物中并脱气15分钟。然后将制备的PDMS-Ag光刻胶混合物旋涂到柔性衬底(例如，聚酯或硅酮)上30秒。将旋涂的晶片加载到距离光掩模版50个间距的地方。12mW/cm的紫外线照射10分钟后，在120个重紫外线照射剂量(7200mJ/cm对于在银粒子的光透射显著衰减下诱导完全的光化学反应是必要的)下进行50秒的曝光后烘焙。在曝光后烘焙期间，未曝光区域完全交联，而曝光区域保持未固化。将未固化的PDMS置于甲苯中5秒以移除。显影后用2-丙醇冲洗，氮气流吹干。将柔性衬底上制备的图案层压或氧等离子体键合形成多层器件。最后，使用热压缩步骤将微加工装置模塑成用于生物医学应用的期望形状。
3、将PDMS的预聚物和固化剂混合。脱气后，将混合溶液倒入圆形模具中以制备可拉伸的基底。将模具中的混合溶液在60℃的恒温下固化超过1小时，以形成厚度约为300 的PDMS基底。将固化的PDMS基底从圆形模具上撕下，然后将PDMS基底切割成尺寸为4×2.5cm2的矩形。为了制造波状图案化的PDMS基底，将矩形PDMS基底的端部固定在基底支架上，并拉动PDMS基底的两端，直到达到所需的预应变条件。然后将预应变的PDMS基底的表面暴露于紫外光臭氧（UVO）下30分钟。在UVO处理之后，预应变PDMS基底以1mm/sec的速率释放，以在PDMS基底上形成波状图案。为了制造具有平滑屈曲的波状图案PDMS基底，将PDMS基底以20％的恒定预应变固定在基底支架上，同时增加紫外光臭氧处理时间40至60分钟。在波状图案化PDMS上对半透明银（Ag）膜进行直流反应磁控溅射（DC溅射）。使用DC溅射系统将各种厚度（10，15，20nm）的半透明Ag膜沉积在波状图案和平坦的PDMS基底上。在DC磁控溅射过程中，PDMS基底在室温下以20rpm的速度恒定旋转。半透明Ag膜在100W的恒定直流反应功率，2毫托的工作压力和20sccm（标准毫升/分钟）的氩（Ar）流速下生长。
虽然上述方式制备得到的柔性导电薄膜具有一定的导电性和拉伸性，但仍在存在一些不足：
1、制备工艺复杂，需要对导电材料-银粉做复杂的预处理，使得银粉表面改性；
2、制备过程涉及苯乙烯、二乙烯基苯、偶氮二异丁腈和二苯甲酮等对人体有危害的化学试剂；
3、对制备的设备要求较高，如直流反应磁控溅射；
4、上述方案制得的柔性导电薄膜在导电性和拉伸性上表现较弱。
 技术问题
本发明旨在至少解决上述技术问题之一，提供了一种基于银粉和PDMS的柔性导电薄膜及其制备方法，其制备工艺简单、不涉及有害化学试剂、对设备要求低，产品在导电性和拉伸性上表现较佳。
 技术解决方案
本发明的技术方案是：一种基于银粉和PDMS的柔性导电薄膜的制备方法，包括以下步骤：制备银粉、PDMS预聚物和PDMS固化剂，且所述银粉的直径小于12微米；
将所述银粉进行研磨、清洗、干燥后，加入所述PDMS预聚物中混匀再加入所述PDMS固化剂混匀得到液态柔性导电薄膜；
将所述液态柔性导电薄膜涂匀至设定厚度并固化后得到柔性导电薄膜。
可选地，其中，清洗步骤包括：
并向具有银粉的容器中加入5至10克乙醇，然后通过超声波装置将银粉和乙醇的混合溶液超声分散；
待所述银粉沉淀在容器的底部后，吸除银粉上方的乙醇并将剩余乙醇蒸发。
可选地，所述银粉的直径为2微米-3.5微米。
可选地，所述银粉与所述PDMS薄膜基体的重量比在150wt.%-200wt.%之间。
可选地，所述PDMS预聚物和PDMS固化剂之间的重量比为10：1。
可选地，所述液态柔性导电薄膜的固化包括以下步骤：
将混匀得到的所述液态柔性导电薄膜倒在硅片上，然后在匀胶机上进行旋涂形成待固化薄膜，所述匀胶机的旋涂速度为400-1000rpm，旋涂时间为15-25s；
将所述待固化薄膜与硅片一起放于加热板上，在60-100℃的环境下加热15-30分钟，所述待固化薄膜形成固化的柔性导电薄膜，待所述硅片及柔性导电薄膜冷却之后，将所述柔性导电薄膜自所述硅片上剥离。
本发明实施例还提供了一种基于银粉和PDMS的柔性导电薄膜，包括银粉和PDMS薄膜基体，所述银粉均匀分散于所述PDMS薄膜基体内，所述银粉的直径小于12微米。
可选地，所述银粉的直径为2微米-3.5微米。
可选地，所述银粉与所述PDMS薄膜基体的重量比在150wt.%-200wt.%之间。
 有益效果
本发明所提供的一种基于银粉和PDMS的柔性导电薄膜，柔性导电薄膜可以任意改变其形态，例如拉伸、弯曲、扭曲，这可以使其与任意曲面贴合使用，PDMS薄膜基体还具有生物相容性和无毒等特性，且具有较好与皮肤的贴服性，可广泛应用于可穿戴设备，且灵敏度高、使用效果好。制备流程更简单、快速，并且在制备过程中不需要任何强酸强碱等危险化学试剂及高精度，高技术的设备。除此之外，还通过实验验证了本发明所制备的柔性导电薄膜的灵敏度系数可以达到939，灵敏度远高于目前同类成品。
 附图说明
为了更清楚地说明本发明实施例中的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本发明实施例提供的一种基于银粉和PDMS的柔性导电薄膜的制备方法的参考流程示意图；
图2是本发明实施例提供的一种基于银粉和PDMS的柔性导电薄膜的拉伸过程中各阶段的GF值。
 本发明的实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
在具体实施方式中所描述的各个具体技术特征和各实施例，在不矛盾的情况下，可以通过任何合适的方式进行组合，例如通过不同的具体技术特征/实施例的组合可以形成不同的实施方式，为了避免不必要的重复，本发明中各个具体技术特征/实施例的各种可能的组合方式不再另行说明。
 实施例一：
本发明实施例提供了一种基于银粉和PDMS的柔性导电薄膜的制备方法，包括以下步骤：制备银粉、PDMS（聚二甲基硅氧烷，polydimethylsiloxane）预聚物和PDMS固化剂，且所述银粉的直径小于12微米，以保证灵敏度；
将所述银粉进行研磨、清洗、干燥后，加入所述PDMS预聚物中混匀再加入所述PDMS固化剂混匀得到液态柔性导电薄膜，即通过两次混匀的方式使PDMS的混匀效果更好，银粉的分布也更均匀，制得的柔性导电薄膜的传感精度更高；
将所述液态柔性导电薄膜涂匀至设定厚度并固化后得到柔性导电薄膜，制备方法简单、快速，在制备过程中不需要任何强酸强碱等危险化学试剂及高精度，高技术的设备，制备成本低且成品效果好。
具体地，其中，清洗步骤包括：
并向具有银粉的容器中加入5至10克乙醇，然后通过超声波装置将银粉和乙醇的混合溶液超声分散；
待所述银粉沉淀在容器的底部后，吸除银粉上方的乙醇并将剩余乙醇蒸发。
优选地，银粉的直径为1.5微米-5微米，本实施例中，所述银粉的直径为2微米-3.5微米。
具体地，所述银粉与所述PDMS薄膜基体的重量比在150wt.%-200wt.%之间。
具体地，所述PDMS预聚物和PDMS固化剂之间的重量比为10：1。
具体地，所述液态柔性导电薄膜的固化包括以下步骤：
将混匀得到的所述液态柔性导电薄膜倒在硅片上，然后在匀胶机上进行旋涂形成待固化薄膜，所述匀胶机的旋涂速度为400-1000rpm，旋涂时间为15-25s；硅片上可预先喷涂有脱模剂。
将所述待固化薄膜与硅片一起放于加热板上，在60-100℃的环境下加热15-30分钟，所述待固化薄膜形成固化的柔性导电薄膜，待所述硅片及柔性导电薄膜冷却之后，将所述柔性导电薄膜自所述硅片上剥离，该Ag/PDMS薄膜以高柔性的PDMS作为基底材料，混入颗粒分散较均匀的银粉，通过超声、搅拌、旋涂及加热固化等方式制得。通过控制银粉与PDMS基底的重量比和旋涂速度与时间，可以得到不同特性的柔性导电薄膜。
本实施例中，针对目前柔性导电薄膜制备工艺复杂，设备要求高，制备过程中使用的化学试剂对人体有害，拉伸性和导电性不足等问题，提供了一种简单、快速的制备基于银粉和PDMS的柔性导电薄膜的方法，在制备过程中不需要任何强酸强碱等危险化学试剂及高精度、高技术的设备。该柔性导电薄膜通过控制银粉和PDMS的重量比及旋涂速度和时间来控制薄膜的导电性和厚度，制得的薄膜可以满足不同应用需求，具有较大重量比和旋涂速度的柔性导电薄膜可以应用于灵敏度较低但测量范围较大的柔性传感器。相反，具有较小重量比和旋涂速度的柔性导电薄膜可用于需要高灵敏度但小测量范围的柔性传感器
具体应用中，导电柔性导电薄膜的制备流程可参考如图1所示。
第一步（a）：首先对银粉（直径2-3.5微米，纯度99.9％以上）进行初处理，即将银粉放在研钵中研磨，以使结块的银粉细化。随后将研磨后的银粉转入到容器中，并向其中加入5-10g乙醇。最后通过超声波机将银粉和乙醇的混合溶液超声分散15-30分钟，然后静置，银粉沉淀于容器的底部。
第二步（b）：首先用吸管去除容器内漂浮在银粉上部的乙醇溶液。随后待乙醇完全蒸发后（可以室温下蒸发），将PDMS预聚物加入容器中（银粉与PDMS的重量比在150wt.%-200wt.%。当重量比低于150wt.%时，薄膜导电性较差；当重量比高于200wt.%时，银粉/PDMS混合物较粘稠，不易均匀旋涂到硅片上）。然后，将银粉/PDMS混合物在行星式搅拌机中以2000-2200rpm的速度混合3-5分钟，这一步的目的是使得银粉在PDMS基底中分散的更均匀，得到混匀物。
第三步（c）：向上一步得到的混匀物中加入PDMS固化剂（PDMS预聚物和固化剂之间的重量比为10：1），再次在行星式搅拌机中以2000-2200rpm的速度搅拌混合1.5-3分钟，使得固化剂与PDMS预聚物完全混合。
第四步（d）：将之前得到的混合物倒在硅片上，然后在匀胶机上进行旋涂。在这一步中，可以通过控制旋涂速度和时间来控制薄膜的厚度。本实施例中旋涂速度是400-1000rpm，旋涂时间是15-25s。
第五步（e）：将旋涂均匀的薄膜，与硅片一起放于加热板上，在60-100℃的环境下加热15-30分钟。随后待硅片及薄膜冷却之后（可在室温下冷却），柔性导电薄膜可以从硅片上轻松剥离。
第六步（f）：将柔性导电薄膜从硅片上剥离后，得到基于银粉和PDMS的柔性导电薄膜。
可对柔性导电薄膜进行拉伸实验，即通过测量柔性导电薄膜的初始电阻值和初始尺寸，并测量其拉伸后的尺寸及对应尺寸的电阻值。具体应用中，可以将柔性导电薄膜的两端接上导线，将导线连接于电阻测量装置（例如SMU源表）等。通过拉伸设备的夹具夹持于柔性导电薄膜的两端，并通过拉伸设备开始对柔性导电薄膜进行逐步拉伸，并记录对应拉伸尺寸下的电阻值，直至柔性导电薄膜断裂失效，图2为柔性导电薄膜在拉伸过程中各阶段的GF值，总体GF值为939。
本发明实施例通过对上述柔性导电薄膜的拉伸实验，证明此柔性导电薄膜具有良好的导电性和拉伸性，最大拉伸率为48%，最大灵敏度（GF）可以达到939。其中GF（gauge factor）为应变灵敏度系数, 定义为GF=[（R- R 0）/ R 0]/[（L- L 0）/ L 0]。R 0和R分别代表柔性导电薄膜的初始电阻和拉伸后的电阻值；L 0和L分别代表柔性导电薄膜的初始长度和被拉伸后的长度。本发明实施例所提供的一种基于银粉和PDMS的柔性导电薄膜及其制备方法，制备流程更简单、快速，并且在制备过程中不需要任何强酸强碱等危险化学试剂及高精度，高技术的设备。除此之外，还通过实验验证了本发明所制备的银粉/PDMS薄膜（柔性导电薄膜）的灵敏度系数可以达到939，灵敏度远高于目前同类成品。
实施例二：
本发明实施例提供的一种基于银粉和PDMS的柔性导电薄膜，可由实施例一的制备方法制得并可用于穿戴设备的传感器，包括银粉和PDMS薄膜基体（PDMS薄膜基体），PDMS即polydimethylsiloxane，其无味、透明度高，具有高拉伸性、耐热性、耐寒性，且黏度随温度变化小。所述银粉均匀分散于所述PDMS薄膜基体内，所述银粉的直径可小于12微米，银粉的导电效果佳，且微米级的粒径可以保证柔性导电薄膜的灵敏度，由于银粉均匀分散于所述PDMS薄膜基体内，且PDMS薄膜基体可随意形变，当柔性导电薄膜受到外力变形时，在变形处，银粉的局部间距、局部密度将发生变化，从而导致柔性导电薄膜的阻值变化，进而使流经柔性导电薄膜的电流或/和施加于柔性导电薄膜的电压变化，其灵敏度高（超灵敏度）。
具体地，所述银粉的直径可小于10微米，例如银粉的直径可为1至6微米，以保证其灵敏度。
具体地，所述银粉的直径可为1-4.5微米，优选地，银粉的直径可为2微米-3.5微米。
具体地，所述银粉与所述PDMS薄膜基体的重量比可在100wt.%-300wt.%之间。
本实施例中，所述银粉与所述PDMS薄膜基体的重量比在150wt.%-200wt.%之间。当重量比低于150wt.%时，薄膜导电性相对较差；当重量比高于200wt.%时，银粉和PDMS混合物较粘稠，不易后续的均匀旋涂，成型性能欠佳。
具体应用中，可以在PDMS薄膜基体的两侧插设或贴设或夹设有导电电极。导电电极可以连接于电阻值测量装置。
具体应用中，可以在PDMS薄膜基体的表面设置柔性保护层，柔性保护层可为耐磨、抗撕拉、抗腐蚀的保护层，例如硅胶保护层等。
具体应用中，PDMS薄膜基体可呈多边形（矩形、三角形）、圆形、圆柱形、圆筒形等。
本发明实施例通过对上述柔性导电薄膜的拉伸实验，证明此柔性导电薄膜具有良好的导电性和拉伸性，最大拉伸率为48%，最大灵敏度（GF）可以达到939。其中GF（gauge factor）为应变灵敏度系数, 定义为GF=[（R- R 0）/ R 0]/[（L- L 0）/ L 0] ，即GF=[（R- R 0）/ R 0]除以[（L- L 0）/ L 0]。R 0和R分别代表柔性导电薄膜的初始电阻和拉伸后的电阻值；L 0和L分别代表柔性导电薄膜的初始长度和被拉伸后的长度。本发明实施例所提供的一种基于银粉和PDMS的柔性导电薄膜及其制备方法，制备流程更简单、快速，并且在制备过程中不需要任何强酸强碱等危险化学试剂及高精度，高技术的设备。除此之外，还通过实验验证了本发明所制备的银粉/PDMS薄膜（柔性导电薄膜）的灵敏度系数可以达到939，灵敏度远高于目前同类成品。
具体应用中，上述柔性导电薄膜（PDMS薄膜基体）的厚度可为0.05至5mm或其它合适厚度。例如上述柔性导电薄膜的厚度为0.1至2mm。
本发明实施例所提供的一种基于银粉和PDMS的柔性导电薄膜， 柔性导电薄膜可以任意改变其形态，例如拉伸、弯曲、扭曲，这可以使其与任意曲面贴合使用，PDMS薄膜基体还具有生物相容性和无毒等特性，且具有较好与皮肤的贴服性，可广泛应用于可穿戴设备，且灵敏度高、使用效果好。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换或改进等，均应包含在本发明的保护范围之内。

Claims (9)

  1. 一种基于银粉和PDMS的柔性导电薄膜的制备方法，其特征在于，制备银粉、PDMS预聚物和PDMS固化剂，且所述银粉的直径小于12微米；
    将所述银粉进行研磨、清洗、干燥后，加入所述PDMS预聚物中混匀再加入所述PDMS固化剂混匀得到液态柔性导电薄膜；
    将所述液态柔性导电薄膜涂匀至设定厚度并固化后得到柔性导电薄膜。
  2. 如权利要求1所述的一种基于银粉和PDMS的柔性导电薄膜的制备方法，其特征在于，其中，清洗步骤包括：
    并向具有银粉的容器中加入5至10克乙醇，然后通过超声波装置将银粉和乙醇的混合溶液超声分散；
    待所述银粉沉淀在容器的底部后，吸除银粉上方的乙醇并将剩余乙醇蒸发。
  3. 如权利要求1所述的一种基于银粉和PDMS的柔性导电薄膜的制备方法，其特征在于，所述银粉的直径为2微米-3.5微米。
  4. 如权利要求1所述的一种基于银粉和PDMS的柔性导电薄膜的制备方法，其特征在于，所述银粉与所述PDMS薄膜基体的重量比在150wt.%-200wt.%之间。
  5. 如权利要求1所述的一种基于银粉和PDMS的柔性导电薄膜的制备方法，其特征在于，所述PDMS预聚物和PDMS固化剂之间的重量比为10：1。
  6. 如权利要求1至5中任一茂所述的一种基于银粉和PDMS的柔性导电薄膜的制备方法，其特征在于，所述液态柔性导电薄膜的固化包括以下步骤：
    将混匀得到的所述液态柔性导电薄膜倒在硅片上，然后在匀胶机上进行旋涂形成待固化薄膜，所述匀胶机的旋涂速度为400-1000rpm，旋涂时间为15-25s；
    将所述待固化薄膜与硅片一起放于加热板上，在60-100℃的环境下加热15-30分钟，所述待固化薄膜形成固化的柔性导电薄膜，待所述硅片及柔性导电薄膜冷却之后，将所述柔性导电薄膜自所述硅片上剥离。
  7. 一种基于银粉和PDMS的柔性导电薄膜，其特征在于，包括银粉和PDMS薄膜基体，所述银粉均匀分散于所述PDMS薄膜基体内，所述银粉的直径小于12微米。
  8. 如权利要求7所述的一种基于银粉和PDMS的柔性导电薄膜，其特征在于，所述银粉的直径为2微米-3.5微米。
  9. 如权利要求7或8所述的一种基于银粉和PDMS的柔性导电薄膜，其特征在于，所述银粉与所述PDMS薄膜基体的重量比在150wt.%-200wt.%之间。
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