Fig. 1

Formulation of bioinspired conductive ink for writing electronics and sensors. a A vial-based do-it-yourself (DIY) pen loaded with P/G ink. b The DIY pen tip is a 10-μL pipette microtip punched in a vial cap. c, d P/G ink can controllably flow in the DIY pen tip. e–h Conductive texts written on transparent Kapton film and paper. i P/G ink written on skin and fingernail as a conductive tattoo. j Image showing the sensors of the P/G@paper and P/G@Kapton. The initial resistance (R₀) of the P/G@paper is 45.3 kΩ and of the P/G@kapton is 77.3 kΩ. k–n Resistance responses of the P/G@paper and P/G@Kapton to temperature (25–51 °C), light (6.5–310 mW cm⁻²), air pressure (793–868 Torr), and relative humidity (10.6–64%). Note: decreases in resistances of the P/G@paper and P/G@Kapton with the increasing temperatures or light powers can be attributed to the thermoconductive or photoconductive features of the P/G ink, whereas air pressure or relative humidity increase the resistances of the P/G@paper and P/G@Kapton