Fig. 3

Through-tissue light actuation of ion transport. a An integrated OEIP with OPV array laminated on the finger of the experimenter, with hand placed over a red LED emitting at 630 nm. A light intensity of around 2 mW/cm² penetrates through the finger. b I(V) curves measured with the device illuminated through the finger, compared with a measurement registered using a similar light intensity. c Validation of successful light-driven H⁺ pumping. 0.1 M HCl is added to the reservoir on the right, while the methyl red pH indicator is put in the left side reservoir. The pH gradient (lower pH on the right) is faintly observable at 1 min. The red light is shone through the finger and turned off at 1-min intervals, at which point photographs were taken.