Fig. 3: Gating threshold tests of the horizontal plain micropore membranes and the inclined membranes with tap-trigger microstructures.

a SEM images of four types of membranes with (i) 1 μm, (ii) 3 μm, (iii) 5 μm and (iv) 8 μm micropores. b Liquid columns where the liquids could not break through the four types of plain horizontal micropore membranes mounted at the bottom end of the long hollow tube. c Gating threshold tests of the four types of membranes inclined and contacted with tap-trigger microstructures. d Photomicrographs of the self-wetting process after triggering: the structure initially helped the liquid to penetrate (i) and then drew more liquid out to self-wet more membrane area (ii). e Comparative analysis of the gating threshold between the horizontal plain membranes and tap-triggered inclined membranes with four sizes of micropores. The black arrows indicate that the actual gating thresholds of the plain membranes were beyond the measured values in impassable statuses