Electrochemically Controlled Hydrogels with Electrotunable Permeability And Uniaxial Actuation.

The unique properties of hydrogels enable the design of life-like soft intelligent systems. However, stimuli-responsive hydrogels still suffer from limited actuation control. Direct electronic control of electronically conductive hydrogels could solve this challenge and allow direct integration with modern electronic systems. W e demonstrate an electrochemically controlled nanowire composite hydrogel with high in-plane conductivity that stimulates a uniaxial electrochemical osmotic expansion. This materials system allows precisely controlled shape-morphing at only -1 V, where capacitive charging of the hydrogel bulk leads to a large uniaxial expansion of up to 300%, caused by the ingress of ∼700 water molecules per electron-ion pair. The material retains its state when turned off, which is ideal for electrotunable membranes as the inherent coupling between the expansion and mesoporosity enables electronic control of permeability for adaptive separation, fractionation, and distribution. Used as electrochemical osmotic hydrogel actuators, they achieve an electroactive pressure of up to 0.7 MPa (1.4 MPa versus dry) and a work density of ∼150 kJ m (2 MJ m  versus dry). This new materials system paves the way to integrate actuation, sensing, and controlled permeation into advanced soft intelligent systems. This article is protected by copyright. All rights reserved.