Guo Zhuanfei South University of Technology research group to make progress in flexible electronics technology transfer

In recent years, the development of flexible electronic material very quickly, and can be used for implantable electronic epidermis electronics, the field of wearable devices, new energy systems, software robots. However, the transfer of flexible electronic materials restricts the development of flexible electronics technology. Common transfer method requires the use of a seal (Stamp) which has been prepared in a flexible material or an electronic device is transferred from the stamp to the substrate, and then transferred to another substrate, or directly to the soft seal material is used as the substrate. The electronic device typically requires stretchable soft substrate. When a soft seal (PDMS common material such as silicone rubber elastic Ecoflex and the like) is transferred, since the seal material is very soft, so the peeling at the interface with the substrate it will have a great strain, there may be more than a flexible electronic tensile limits of the material, leading to the electronic structure of the flexible material is destroyed and loses its function (FIG. 1). Transfer using a hard seal approach can effectively avoid the problem, but can not be used and the hard substrate stretchable electronics. How to resolve this contradiction is a key issue for flexible electronics materials and flexible electronic devices transfer.

The relationship between the maximum material strain and stiffness of Figure 1. Along the flexible electronic material when it is subjected to transfer of

Recently, South University of Technology Guo Chuanfei TF through the method of regulation of the rigidity of the seal material is successfully solved this problem – when transferring the seal to maintain a high rigidity, to reduce the transfer process the electronic device in bear strain; after the transfer completion, then the seal materials soften, directly as a stretchable substrate. They used A variable stiffness, calcium ion doping silk fibroin material as a seal . Silk fibroin is cocoons left after removal of sericin native protein, which has a very large range of variable stiffness in different relative humidity, the Young\’s modulus may change from 134 KPa to 1.84 GPa, respectively, corresponding to a relative humidity of 84 % and 33%. Specific strategy: in a low humidity condition (RH in the range of 33% -49%, the elastic modulus of the seal material is maintained at 100 MPa to 1.84 GPa) for a flexible electronic transfer material; release after the silk fibroin was placed high humidity environment, so that it softens, reduced elastic modulus of 0.1 MPa to 2 MPa, andPretty skin, the epidermis can be used directly as an electrode (FIG. 2). Thanks to good silk protein and epidermal skin electrodes mechanical matching, it may be fused with perfect texture of the skin, in addition to having good tensile properties may be outside, it has a lower interface than conventional commercial Ag-AgCl gel electrode impedance and a higher signal to noise ratio of EMG (EMG). In addition, the skin attached to the skin electrodes 10 days did not produce significant adverse effects. Typically, a flexible electronic materials and devices will be transferred to human skin or other non-planar roughened surface is very difficult, and this work has provided a new idea and a simple method.

Figure 2. silk protein skin electrode adhesion to the skin effect and show

The work recently published online in the Advanced Functional Materials Journal on (Adv. Funct. Mater. 2020, 2001518). Guochuan Fei, associate professor as the sole author of the paper newsletter, South University of Technology is the first unit and the communication unit. The first author of the paper as a research assistant research group Huang Jun , he is also the 2019 session of the research group of graduate students graduate, post-doctoral research group Liu Wang have made important aspects of the work of the mechanics of the calculation contribution. The research was supported by the National Natural Science Foundation of China, Guangdong Zhujiang support innovation and entrepreneurial talent program team, Shenzhen, basic research projects such as the layout of disciplines. Papers link: https: //