Stretchable and transparent ionic diode and logic gates

Inspired by the asymmetric ion transport phenomenon commonly seen in biology, in this article, we develop transparent and stretchable hydrogel-based ionic diode and logic gates. The ionic diode is made up of polyacrylamide hydrogel doped by two different polyelectrolytes with opposite fixed charges. Due to the asymmetric distribution of the fixed charges, the hydrogel diode shows ion rectification capability. Our experiments further show that large rectification ratio of the diode can be maintained when the diode is under moderate stretch. Using the ionic diode, we further successfully construct two types of ionic logic gates: OR gate and AND gate, which can perform logic operations on binary inputs and produce a single output. We hope the transparent and stretchable ionic diode, as well as the logic gates, can be used as the basic functional elements for advanced and integrated stretchable ionic circuit system.