Pd-conformally coated, one-end-embedded gold nanowire percolation network for intrinsically stretchable, epidermal tattoo fuel cell

Soft, conformal and wearable epidermal fuel cells may offer promising energy solutions to power next-generation on-skin electronics on-demand anytime anywhere. However, it is non-trivial to design intrinsically stretchable electrode in order to maintain the fuel cell performance under real-world and dynamic mechanical deformations. Here, we present a tattoo-like epidermal fuel cell based on Pd conformally-coated, one-end-embedded percolation gold nanowire (EP-AuNW/EP-AuPdNW) networks, which are in essence the combination of in-plane percolation conductivity and out-plane anisotropic conductivity. Both EP-AuNW and EP-AuPdNW are intrinsically stretchable conductors for anode and cathode in fuel cell. Compared to non-conformal counterparts, a 6-times greater power density was achieved for conformal system. Importantly, EP-NW based fuel cell can function under various mechanical deformations including stretching, compression, bending, and twisting; the power density showed negligible changes to the tensile strain up to ∼50% and could maintain its 75% performance even under 80% strain. Furthermore, a dragon-tattoo epidermal fuel cell was fabricated, demonstrating on-demand power generation with real-world ethanol sources.