Surface-control enhanced crater-like electrode in a gelatin/polyvinyl alcohol/carbon composite for biodegradable multi-modal sensing systems with human-affinity

Numerous research fields adopting breathable, human-affinity, and biodegradable biopolymers for various applications have emerged. As one of the most common biopolymers due to its water-soluble and biodegradable properties, and being harmless to the human body, gelatin has a triple helix structure in its solid-state capable of forming a self-assembly. Here, the pore size (4 to 16 μm) of the gelatin/polyvinyl alcohol (PVA)/carbon (GPC) blend can be modified through the PVA content which is configurable to obtain different properties like air/light transmissivity, high conductivity with the blend of graphite and carbon black (40 to 50 S cm −1 ), with only carbon black (10 to 20 S cm −1 ), surface energy, and strain (5 to 11%) for several applications. In this study, a new secret tag application based on a GPC blend porous structure is presented for the first time. The optimized GPC aqueous solution may not only be coated directly on human skin to form an emotion sensor or breathable touchpad without causing irritation but could also be made into a multi-modal sensor for human activity with biodegradability. The GPC free-standing electrode film also yields a stable triboelectric output (75 V) when used as a triboelectric nanogenerator (TENG) by varying the surface area. The pore formation mechanism and variation of pore size in gelatin-PVA-carbon system was studied. As pore size changes, different conductivity, strain and air/light transmittance can meet the needs of human-affinity and biodegradable applications.