Professor Jan Lagerwall, Department of Physics and Materials Science, Faculty of Science, Technology and Medicine, University of Luxembourg

Liquid crystal elastomer soft actuators and strain sensors

I will present our recent work on making liquid crystal elastomers of unconventional shapes, specifically shells, tubes and fibers, as well as our ideas of applying them, as microhearts and peristaltic pumps and as non-electronic sensors of mechanical strain.

Spectacular new properties emerge in liquid crystal elastomers (LCEs) from their unique combination of long-range orientational order with elasticity and shape programmability. In nematic LCEs, a heat- or light-induced transition from ordered to disordered state leads to a reversible macroscopic shape change up to 400%. Performance beyond that of human skeletal muscle has been demonstrated. Cholesteric LCEs show structural color due to a self-assembled helix structure with sub-micron period. The colour shifts visibly upon mechanical deformation, enabling optical strain measurement. Our lab has pioneered procedures for moulding LCEs into spherical and tubular shape^[1-2], exhibiting unique actuation modes, and to make CLCEs in sheets or fibres with unprecedented ease. ^[3-5] I will also present our work to apply these LCEs practically in innovative contexts.

LCEs uniquely connect our macroscopic world to the nanoscale, since they couple orientational order at the molecular (~nm) scale to the macroscopic shape of the object.

References 

[1] A. Sharma,  A.M. Stoffel, & J.P.F. Lagerwall. Liquid crystal elastomer shells with topological defect-defined actuation: Complex shape morphing, opening/closing, and unidirectional rotation. J. Appl. Phys. 129, 174701 (2021).
[2] Najiya, Popov, N., Jampani, V. S. R. & Lagerwall, J. P. F. Continuous Flow Microfluidic Production of Arbitrarily Long Tubular Liquid Crystal Elastomer Peristaltic Pump Actuators. Small 19, 2204693 (2022).
[3] Rijeesh Kizhakidathazhath et al. Facile Anisotropic Deswelling Method for Realizing Large‐Area Cholesteric Liquid Crystal Elastomers with Uniform Structural Color and Broad‐Range Mechanochromic Response. Adv. Funct. Mater. 30, 1909537 (2020).
[4] Y. Geng, R. Kizhakidathazhath. & J. P. F. Lagerwall, Robust cholesteric liquid crystal elastomer fibres for mechanochromic textiles. Nat. Mater. (2022). DOI: 10.1038/s41563-022-01355-6.
[5] Y. Geng, Y. & J. P. F. Lagerwall, Multiresponsive Cylindrically Symmetric Cholesteric Liquid Crystal Elastomer Fibers Templated by Tubular Confinement. Adv. Sci. e2301414 (2023).