Human skin, composed of complex neural networks, provides an excellent interface for converting external stimuli into electrical signals for transmission to the brain. Electronic skin (E-skin) research is active all over the world for mimic human skin, such as an electronic device for next–generation healthcare for collecting and analyzing bio–signals in real time by attaching or inserting them into the human body is actively performed.
However, common polymers are mismatched to imitate human skin due to biocompatibility, biofunctionality and permeability issues for a wide range of chemicals and biomolecules. To overcome the mismatch, in this study, first describes fabrication and application of electronic skin that is stable on wet and deformed biotissue by using protein, which is one of the biocomponents, as substrate of flexible E-skin.
The silk protein hydrogel is designed to have high stretchability and stability in the hydric environment by adding Ca2+ ions, and glycerol is added to enhance stability. Metal wires made of nano-size are suitable materials to mimic the nerves of the living body. Constructing the electrodes with the nanowires allows the nanowires to be continuously connected, even if the constructed electrodes are stretched. Silver nanowire (AgNW) can used as a substitute for neural networks in E-skin and these are buried in silk hydrogel membranes. This structure exhibit stable operability in communication between the environment and the electrodes, even under the same conditions as the actual skin experiences. In addition, AgNW can be made into various types of electrodes through simple lithography process without the use of chemicals and aligners.
The E-skin fabricated in this study was applied to various devices such as the flexible LED circuit with silk film, electrode for electrocardiogram (ECG) detection which can be attached to skin, RF antenna that can be used like a sensor, and we have confirmed the stable operation of these devices.