Premium
4D Printing of Hygroscopic Liquid Crystal Elastomer Actuators
Author(s) -
Kim Keumbee,
Guo Yuanhang,
Bae Jaehee,
Choi Subi,
Song Hyeong Yong,
Park Sungmin,
Hyun Kyu,
Ahn SukKyun
Publication year - 2021
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.202100910
Subject(s) - materials science , liquid crystal , photopolymer , elastomer , actuator , monomer , chemical engineering , inkwell , polymer , humidity , composite material , nanotechnology , polymer chemistry , optoelectronics , electrical engineering , engineering , physics , thermodynamics
Liquid crystal elastomers (LCEs) are broadly recognized as programmable actuating materials that are responsive to external stimuli, typically heat or light. Yet, soft LCEs that respond to changes in environmental humidity are not reported, except a few examples based on rigid liquid crystal networks with limited processing. Herein, a new class of highly deformable hygroscopic LCE actuators that can be prepared by versatile processing methods, including surface alignment as well as 3D printing is presented. The dimethylamino‐functionalized LCE is prepared by the aza‐Michael addition reaction between a reactive LC monomer and N,N′‐dimethylethylenediamine as a chain extender, followed by photopolymerization. The humidity‐responsive properties are introduced by activating one of the LCE surfaces with an acidic solution, which generates cations on the surface and provides asymmetric hydrophilicity to the LCE. The resulting humidity‐responsive LCE undergoes programmed and reversible hygroscopic actuation, and its shape transformation can be directed by the cut angle with respect to a nematic director or by localizing activation regions in the LCE. Most importantly, various hygroscopic LCE actuators, including (porous) bilayers, a flower, a concentric square array, and a soft gripper, are successfully fabricated by using LC inks in UV‐assisted direct‐ink‐writing‐based 3D printing.