阅读说明：本技术 柔性电容传感器 (Flexible capacitive sensor ) 是由 邹强 马卓敏 于 2019-04-02 设计创作，主要内容包括：本发明公开柔性电容传感器,包括具有柱状微结构的PDMS介电层及两个ITO/PET导电膜构成的上下电极,PDMS介电层采用以下方式制作：将PDMS DC184、PDMS SE1700按预定比例混合制作成PMDS混合胶；分两次匀涂PMDS混合胶在载玻片上,第一次涂完后固化处理,继续匀涂,形成电容传感器初步介电层；将具有孔洞的PCET模板放在二次涂的PDMS膜上后抽真空处理,使PDMS进入PCET模板孔洞里,固化后形成柱状微结构；洗除PCTE模板,形成PDMS电容传感器介电层。本发明能达到理想高度,提高可压缩性,同时具有很好的稳定性,不易坍塌,使柔性电容传感器保持优异灵敏度。(The invention discloses a flexible capacitive sensor, which comprises a PDMS dielectric layer with a columnar microstructure and an upper electrode and a lower electrode formed by two ITO/PET conductive films, wherein the PDMS dielectric layer is manufactured by adopting the following method: mixing PDMS DC184 and PDMS SE1700 according to a predetermined proportion to prepare PMDS mixed glue; uniformly coating PMDS mixed glue on a glass slide twice, curing after the first coating, and continuously and uniformly coating to form a primary dielectric layer of the capacitive sensor; placing the PCET template with the holes on the secondarily coated PDMS film, and then vacuumizing the PCET template to enable PDMS to enter the holes of the PCET template, and forming a columnar microstructure after curing; and washing away the PCTE template to form the dielectric layer of the PDMS capacitive sensor. The invention can reach ideal height, improve compressibility, and has good stability, and is not easy to collapse, so that the flexible capacitance sensor keeps excellent sensitivity.)

1. The flexible capacitive sensor is characterized by comprising a PDMS dielectric layer with a columnar microstructure and electrodes formed by two ITO/PET conductive films positioned above and below the PDMS dielectric layer, wherein the PDMS dielectric layer is manufactured in the following mode:

mixing PDMS DC184 and PDMS SE1700 according to a predetermined proportion to prepare PMDS mixed glue;

uniformly coating PMDS mixed glue on a glass slide twice, curing after the first coating to obtain a first PDMS film, and continuously and uniformly coating to obtain a second PDMS film to form a primary dielectric layer of the capacitive sensor;

placing the PCET template with the holes on the second layer of PDMS film, vacuumizing the PCET template and the primary dielectric layer of the capacitive sensor to enable PDMS colloid to enter the holes of the PCET template, and forming a stable columnar microstructure after curing;

and washing away the PCTE template to form the PDMS capacitance sensor dielectric layer with the columnar microstructure.

2. The flexible capacitive sensor of claim 1, wherein the first layer of PDMS film has a thickness of 200um and the first layer of PDMS film has a thickness of 100 um.

3. The flexible capacitive sensor of claim 1, wherein the PCET template has a thickness of 13um and a pore size of 5um with randomly distributed pores on the surface.

4. The flexible capacitive sensor of claim 1, wherein the PCET template is removed using methylene chloride dissolution.

Technical Field

The invention relates to the technical field of flexible electronics, in particular to a flexible capacitive sensor.

Background

In recent years, the field of flexible electronics has evolved over the years. Flexible sensors are becoming important applications in future robotics, in vitro diagnostics and energy harvesting. According to recent advances in robotic systems, prostheses, and wearable medical devices, efforts to implement high-sensitivity flexible sensors with simple methods have become a research focus for experimenters. Moreover, while the field of flexible electronics is rapidly developing, advances in the fabrication of electronic devices are also needed.

Recently, PDMS films often serve as flexible nano-dielectric layers for flexible capacitive sensors due to their excellent elastic and dielectric properties. In addition, it often serves as the base material for flexible electronic devices, such as the upper and lower electrodes of flexible capacitive sensors, due to its excellent biocompatibility, intrinsic high stretchability, chemical inertness, stability, and variable mechanical properties. To achieve high sensitivity of flexible capacitive sensors, two approaches are commonly used: (1) the conductive filler is added to the flexible polymer using percolation theory. Conductive particles are often filled with mainly metallic materials and carbon materials. Such as metal nanoparticles, metal nanowires, carbon nanotubes, graphite, and the like. (2) Dielectric layers with microstructures are prepared, i.e., air gaps are used to increase compressibility, such as pyramids, nanoneedles, and pillars, among others. The addition of metal nanowires to the PDMS film and the creation of microstructures can not only improve stretchability, but also give the flexible sensor higher sensitivity and faster response time. At the same time, researchers how to prepare a more prominent microstructure and maintain the flexibility of the structure well thought. For the columnar microstructure, the higher the height is, namely the columnar microstructure has great compressibility, and meanwhile, the columnar microstructure has more proper rigidity and is not easy to collapse, so that the high sensitivity and the stability of the flexible capacitance sensor can be realized. However, the preparation of the columnar structure conforming to the above characteristics has certain difficulty, and on one hand, the PDMS is a viscous liquid at normal temperature and becomes colloidal after being cured. Both of these states are easily deformed and not easily restored. On the other hand, since the columnar structure has a size of the order of micrometers, it is easily collapsed during the manufacturing process and the use process. Therefore, it is a difficult problem to be solved to prepare a high-columnar microstructure which has good stability and is not easy to collapse.

Therefore, there is an urgent need to provide a method for manufacturing a flexible capacitive sensor, which has a microstructure with high compressibility and a flexible electrode made of a conductive filling material, and can ensure that the sensor has stable and high sensitivity.

Disclosure of Invention

The invention aims to provide a flexible capacitive sensor aiming at the technical defects in the prior art, which not only has a microstructure with extremely high biocompatibility and great compressibility, but also can ensure that the sensor has stable and high sensitivity, and the manufacturing method has the advantages of simple operation, low cost and low requirement on the operating environment, and opens up a new way for the preparation process of the microstructure of the flexible sensor.

The technical scheme adopted for realizing the purpose of the invention is as follows:

the flexible capacitive sensor comprises a PDMS dielectric layer with a columnar microstructure and electrodes formed by two ITO/PET conductive films positioned above and below the PDMS dielectric layer, wherein the PDMS dielectric layer is manufactured in the following mode:

mixing PDMS DC184 and PDMS SE1700 according to a predetermined proportion to prepare PMDS mixed glue;

uniformly coating PMDS mixed glue on a glass slide twice, curing after the first coating to obtain a first PDMS film, and continuously and uniformly coating to obtain a second PDMS film to form a primary dielectric layer of the capacitive sensor;

placing the PCET template with the holes on the second layer of PDMS film, vacuumizing the PCET template and the primary dielectric layer of the capacitive sensor to enable PDMS colloid to enter the holes of the PCET template, and forming a stable columnar microstructure after curing;

and washing away the PCTE template to form the PDMS capacitance sensor dielectric layer with the columnar microstructure.

The thickness of first layer PDMS membrane is 200um, the thickness of first layer PDMS membrane is 100 um.

The PCET template is characterized in that the thickness of the PCET template is 13um, and the pore diameter of the randomly distributed pores on the surface is 5 um.

And removing the PCET template by adopting a dichloromethane dissolving method.

Compared with the prior art, the invention has the beneficial effects that:

the invention adopts PDMS SE1700 and PDMS DC184 with two different models of PDMS glue and different Young modulus to prepare the dielectric layer with the columnar microstructure, the rigidity of the material is marked by the Young modulus, and the larger the Young modulus is, the more difficult the material is to deform. Therefore, the prepared microstructure can reach the ideal height, the compressibility is improved, and meanwhile, the microstructure has good stability and is not easy to collapse, so that the flexible capacitive sensor keeps excellent sensitivity.

Drawings

FIG. 1 is a schematic diagram of the preparation of the dielectric material of the flexible capacitive sensor provided by the present invention;

FIG. 2 is a schematic diagram of a process for manufacturing a flexible capacitive sensor according to the present invention;

FIG. 3 is a schematic diagram of a PCET template used in the fabrication of a flexible capacitive sensor provided by the present invention;

FIG. 4 is a schematic perspective view of a flexible capacitive sensor provided by the present invention;

in the figure: the structure comprises a substrate, a first PDMS film 1 with the thickness of 200um, a preliminary dielectric layer 2 with two PDMS films, a PCTE template 3 with holes which are randomly distributed and have the same aperture, a PDMS cylinder embedded in the PCTE template, a columnar microstructure 5, a PDMS dielectric layer 6 with the columnar microstructure, and holes 7 which are randomly distributed on the PCET template and have the same aperture; 8 is an upper polar plate of the flexible capacitance sensor, 9 is a lower polar plate of the flexible capacitance sensor, 10 is a PDMS SE1700 sample, 11 is a PDMSDC184 sample, and 12 is a mixed PDMS sample which is mixed and stirred uniformly according to the proportion.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1 to 4, the high-sensitivity flexible capacitive sensor with embedded AgNWs and PDMS based on the dielectric material mixing ratio provided by the present invention includes a PDMS dielectric layer with a columnar microstructure and electrodes formed by two ITO/PET conductive films located above and below the PDMS dielectric layer, wherein the PDMS dielectric layer is manufactured in the following manner:

first, a mixed PMDS sample was prepared. The small young's modulus of the PDMS DC184, which is often used, may cause some difficulties in the post-fabrication of the columnar microstructure. And because the height of the columnar structure can influence the sensitivity of the sensor, a mixed gel sample of the PDMS DC184 and the PDMS SE1700 is prepared according to the sensitivity which is required to be realized by the sensor, so that a foundation is laid for preparing the columnar structure with high stability, and the mass mixing ratio of the PDMS DC184 and the PDMS SE1700 is 4:1-2: 1.

Next, the PMDS samples were pan-mixed. The dielectric material PDMS was spread over the slide two times. And (3) uniformly coating 200um mixed PMDS samples on the glass slide for the first time, and then carrying out curing treatment to obtain a first layer of PDMS film. On this basis, the 100um mixed PMDS sample was continued to be homogenized without any treatment to obtain a second layer of PDMS film. The two PDMS films together form the primary dielectric layer of the capacitive sensor.

Thereafter, a microstructure was prepared using a PCET template. The PCET template prepared in advance was gently placed on the previously treated primary dielectric layer of which the two PDMS films together constitute the capacitive sensor. Wherein, the PCET template with proper thickness is selected according to the height of the columnar structure to be realized.

The PCET template with the thickness of 13um is selected, and holes with the aperture of 5um are randomly distributed on the surface of the PCET template. And then, vacuumizing the template and the PDMS sample. Thus, air pressure can be used to force the PDMS gel under the PCET template into the holes in the template. Because the holes have a certain height, the columnar microstructure can be stably formed on the PDMS after the sample is cured again.

Finally, the PCTE template is washed away. Since dichloromethane has a very strong dissolving capacity, while keeping the PDMS columnar microstructure undamaged, dichloromethane reagent is used to wash away the PCTE template, so that the sample consists of only the columnar PDMS and the PDMS film. Thus, the preparation of the dielectric layer of the capacitance sensor with the columnar microstructure is finished.

The upper and lower electrodes of the capacitor are formed of ITO/PET (indium tin oxide/polyethylene terephthalate) conductive films. The ITO conductive film is obtained by adopting a magnetron sputtering method and performing high-temperature annealing treatment on a transparent ITO conductive film coating. The ITO/PET conductive film can be well fixed on the prepared dielectric layer, is not easy to fall off and has good stability, so the ITO/PET conductive film is selected as an electrode.

Compared with the prior art, the flexible sensor has the following beneficial effects:

1. the columnar microstructure has high sensitivity, large Young modulus, relatively large height and great compressibility. Meanwhile, the dielectric constant of the AgNWS particles added into the flexible electrode can also be increased, so that the sensitivity of the flexible capacitive sensor can be improved to a great extent;

2. the column micro-structure can be compressed for multiple times, is not easy to collapse, has high stability and reliability, and has a long service cycle;

3. the preparation method is simple to operate, the two PDMS adhesives with different Young's moduli are mixed according to a certain proportion, and meanwhile, the preparation of the flexible electrode does not need complex processes such as magnetron sputtering, high-temperature annealing and the like, so that the experimental steps are simple and easy to operate;

4. the requirement on the operating environment is low, an ultra-clean environment is not needed when the PCTE template is used and washed away, and the experiment can be completed in a common experiment environment;

5. the cost is low, and the PDMS SE1700, the PDMS DC184 and the flexible electrode used in the invention are all common cheap materials in experiments.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.