Fig. 1. Schematic of the measuring procedure for suspicious powder samples at a wearable fingertip device. (A) The fingertip exhibiting the surface of screen-printed electrode onto a flexible nitrile finger cot (bottom left inset), as well as a conductive gel immobilized upon the thumb (bottom right inset); (B) swiping method of sampling to collect the target powder directly onto the electrode; (C) completion of the electrochemical cell by joining the index finger with electrodes to the thumb coated with the conductive gel electrolyte.