All-Printed and Fully-Stretchable Organic Electrochemical Transistors Based on Hydrogel Electrolyte

Solution-processable organic materials are desirable for functionalized wearable devices. To maximize that feature of organic polymers, printing is one of the best methods to cast films or patterns. Herein, we fabricated fully-stretchable organic electrochemical transistors(OECTs) by a conventional PBC printer. To achieve the stretching of the whole body of the devices, a printed planar gate electrode and polyvinyl alcohol(PVA) hydrogel electrolyte were employed. The simplicity of the PCB printer made it possible to print a wide range of viscous inks, from an organic semiconductor to a hydrogel precursor. A Stretchable silver paste provided a soft feature to drain/source, gate and interconnect without any strategies to improve the stretchability of metallic components, such as pre-stretching methods and formation of stretchable patterns. Moreover, unlike reported studies of printed ion-gel electrolytes for transistors, a printed hydrogel electrolyte on OECTs has not been reported yet. The resulting OECTs showed decent performance comparable to ink-jet or screen-printed OECTs; the maximum transconductance and on/off ratio were 1.2mS and around 1400, respectively. The devices were stable in electromechanical behavior until 30% strain which is required for wearable electronics on the skin.