Interpenetrating Liquid Crystal Elastomer and Ionogel as Tunable Electroactive Actuators and Sensors

Abstract

Electroactive liquid crystal elastomers (eLCEs) are used to make actuators and soft robotics. However, most eLCEs are monofunctional with one type of deformation (bending or contraction). Recently, a trilayer eLCE are reported by combining ion-conducting LCE and ionic electroactive polymer device (i-EAD). This i-EAD-LCE is bifunctional and performs either bending or contractile deformation by controlling low-voltage stimulation. Nevertheless, it has a Young's modulus of only 1.63 MPa. To improve the mechanical performance, the i-EAD-IPN-LCE is prepared here, whose central membrane is composed of interpenetrating LCE and ionogel (i-IPN-LCE) instead of a single ion-conducting LCE. This i-EAD-IPN-LCE with a typical thickness of 0.5 mm can function not only as linear and bending actuators, but also as a sensor. As a linear actuator, its Young's modulus, actuation stress, and strain are 51.6 MPa, 0.14 MPa and 9%, respectively, reaching skeletal muscles’ values. As a bending actuator, its bending strain difference Δε is 1.18% with 3 mN output force. It can also operate as a sensor producing 0.4 mV Open-Circuit-Voltage to respond to bending deformation (Δε = 9%). Therefore, this i-EAD-IPN-LCE is a promising system for the fabrication of robust electroactive devices and sensors with multiple degrees of freedom.