Title: Humidity- and Photo-Induced Mechanical Actuation of Cross-Linked Liquid Crystal Polymers

Author: Yuyun Liu, Bo Xu, Shengtong Sun, Jia Wei, Limin Wu, Yanlei Yu*

Journal: Adv. Mater., 2017, 29(9), 1604792.

Abstract:

Azobenzene-containing cross-linked liquid crystal polymer films without hydrophilic groups exhibit dual-responsivity to humidity and UV light. The films realize not only a series of large and sophisticated contactless motions by utilizing moisture, including an inchworm walk, and tumbling locomotion, but also dual-mode actuation that can be applied in flexible electronics. 

Fulltext Link: https://www.onlinelibrary.wiley.com/doi/full/10.1002/adma.201604792

We successfully fabricated a hydrophobic CLCP film featuring dual-responsive actuation by utilizing humidity gradients and UV light. By means of the hydration of oxygen containing groups and LCs alignment, the CLCP film undergoes a fast reversible actuation in a predefined way, that is, perpendicular to the direction of LCs alignment, by exposure to humidity gradients, which is superior to other state-of the-art materials. The CLCP film also performed a series of sophisticated contactless motions by exposure to humidity gradients, including an inchworm walk, a sit-up motion by “tree”, and tumbling locomotions. In addition, the CLCP film also exhibited UV-responsive bending along the LCs alignment direction, which is orthogonal to the direction of the bending induced by humidity. Therefore, a touchless electronic device with dual-mode actuation was prepared to output different signals in response to humidity and UV light. This work not only provides new insights into the mechanism of humidity-responsive actuation of hydrophobic CLCP films but also broadens the potential applications of the dual-responsive CLCP films in electronic devices and sensors.