A Wearable Second Skin‐Like Multifunctional Supercapacitor with Vertical Gold Nanowires and Electrochromic Polyaniline

Abstract An ideal wearable/implantable bio‐diagnostics can be powered by second skin‐like energy devices in that they offer advantages such as conformal attachment/integration, lightweightness, and moduli‐matching properties. Past several years have witnessed encouraging progresses in soft stretchable supercapacitors by various material combinations and design strategies; however, it remains nontrivial to achieve highly flexible high‐performance supercapacitors in a skin‐thin layout yet with multifunctionality. Here, such a second skin‐like electrochromic supercapacitor is demonstrated using self‐assembled vertical gold nanowires (v‐AuNWs) and electrodeposited polyaniline (PANI). The v‐AuNW film is highly conductive yet offers great flexibility and deformability, while PANI plays a dual role in enhancing capacitance and as charge/discharge‐level indicator. The assembled supercapacitors offer superior skin‐conformability and could achieve an areal specific capacitance of 11.76 mF cm⁻² (scan rate of 10 mV s⁻¹) with high durability. A second skin‐like wearable tattoo energy device can be designed with negligible performance deterioration under multiple hand movements and skin deformations.