Pulsed Laser Imaging Demonstrates the Mechanism of Current Rectification at a Hydrogel Interface

The accumulation or depletion of charge carriers at a p-n junction results in electronic rectification.¹ Similarly, we show that accumulation or depletion of ions underlies ionic rectification at a single hydroge.-electrolyte interface. We monitored the rapid formation and collapse of ionic gradients at the hydrogel-electrolyte interface of natural²′³ and synthetic⁴ charged microparticles by the use of pulsed-laser microscopy.^5,6 We conclude that the flow of the current is determined by the charge of the hydrogel and the geometry of the electric field applied to it. Our findings can be utilized to design hydrogel-based microswitches and “wet” integrated circuits.