Highly flexible vertical electrolyte-gated metal oxide transistors for neuromorphic electronics

Metal oxide-based electrolyte-gated transistors (EGTs) are attractive for low-power biosensors and neuromorphic systems, but their electrical characteristics has been constrained by a fundamental trade-off between channel downscaling and electrical double layer (EDL) capacitance, resulting in limited transconductance and metrics inferior to that of organic counterparts. Here, we report high-performance and ultraflexible indium gallium zinc oxide (IGZO) EGTs enabled by a vertical device architecture and a nanoscale channel length. We systematically examined how device geometries-including the IGZO-electrode contact area, IGZO thickness, and semiconductor-electrode interface-affect the electrical properties and EDL capacitance, thereby revealing how the vertical structure decouples the channel length from the EDL formation area. Optimized vertical EGTs (vEGTs) exhibit a transconductance of up to 22.5 mS, an on/off current ratio of ~10⁵, ultralow operating voltages below 0.5 V, and pronounced ultraflexibility, maintaining stable performance when bent to a radius of 0.3 mm. Furthermore, vEGTs were integrated into inverter, NOR, and NAND logic circuits operating at voltages as low as 0.1 V. Finally, we demonstrate a closed-loop neuromorphic system in which the slow attenuation of the paired-pulse facilitation index enables adaptive and wireless control of a wearable display in response to a skin-interfaced sensor.