Ion-electron coupling-enabled mechanical ion transistor with ultralow subthreshold swing.

Biological mechanosensitive (BMS) ion channels can activate selective cationic permeation beyond a threshold driving force and switch sharply between on and off states that are essential for life functions. However, it remains a grand challenge to experimentally replicate such biological systems using artificial structures with distinct on-off states for life science, sensing, and energy applications. Here, we report a mechanical ion transistor that exhibits stepwise streaming-current versus pressure response through graphene nanochannels under electrostatic gating. The mechanical ion transistor exhibits an ultralow subthreshold swing (around 4.8 millibars per decade) defined by the minimum required pressure to increase the streaming current by 10 folds. Such a value is orders of magnitude lower than the current state-of-the-art of artificial structures and even sharper than most BMS channels. Our experimental observation of the threshold pressure and the current oscillation at the transition pressure evidences that the mechanical gating effect is attributed to the ionic Coulomb blockade induced by ion-electron coupling. The abrupt threshold transition behavior facilitates the mimicking of ultrasensitive detection of blood pressure pulsation in the olfactory bulb. The discovery here not only enables a better understanding of the functional mechanisms of BMS channels but also offers alternative routes for precise control of ion transport for applications in water filtration, energy harvesting, and neuromorphic sensing.