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Electroactive Bi-functional Liquid Crystal Elastomer Actuators
Liquid crystal elastomers (LCEs) show promising potentials as smart actuators, for example, those contracting/expanding linearly like mammalian muscles.[1] Direct heating and light illumination are the most used activation mode in LCE actuators because LCEs are based on thermotropic or phototropic liquid crystals.[1,2,3] However, in the world of actuators, electrical energy is the most convenient and the most in demand stimuli. Indeed, the nature does use electrical impulses between nerves and muscles or skins for actuation or sensing with extraordinary efficacy, and electrical stimulation is also more widely utilizable as driving forces in industrial devices. Efforts have been made to achieve electroactive LCEs (eLCEs).
In this talk, I will present a trilayer electroactive LCE (eLCE) system by combining two smart materials, LCE and ionic electroactive polymer device (i-EAD), which is bi-functional and can perform either bending or contractile deformations under low voltage stimulation.[4] By applying a voltage of ±2 V at 0.1 Hz, the redox behavior and associated ionic motion in the two conducting polymer electrodes of i-EAD provide bending deformation of the device up to a bending strain difference of 0.8% for a sample of 0.5 mm thickness. On the other hand, by applying a voltage of ± 6V at 10 Hz, the ionic current-induced Joule heating triggers the muscle-like contractile response of the central ion-conducting LCE component, a linear contraction ratio of 20% being obtained without load. Moreover, a load of 270 times of the weight of trilayer eLCE film can be left with a strain of 20%. This approach of combining two smart polymer technologies, i.e., LCE and i-EAD, in a single device, is promising for the development of smart materials with multiple degrees of freedom in soft robotics, electronic devices, and sensors.
References
[1] M.-H. Li, P. Keller P., Artificial muscles based on liquid crystal elastomers, Phil. Trans. A. 364, 2763 (2006).
[2] B. Ni, G. Liu, M. Zhang, P. Keller, M. Tatoulian, M.-H. Li, Large-Size Honeycomb-Shaped and Iris-Like Liquid Crystal Elastomer Actuators, CCS Chemistry, 4, 847 (2022).
[3] B. Ni, G. Liu, M. Zhang, M. Tatoulian, P. Keller, M.-H. Li, Customizable Sophisticated 3D Shape Changes of Large-size Liquid Crystal Elastomer Actuators, ACS Appl. Mater. Interfaces, 13, 54439 (2021).
[4] G. Liu, Y. Deng, G. Nguyen, C. Vancaeyzeele, A. Brûlet, F. Vidal, C. Plesse, M.-H. Li, Electroactive Bi-functional Liquid Crystal Elastomer Actuators, Small, 2023, 2307565.