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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 22: Gels, Polymer Networks and Elastomers I

CPP 22.2: Talk

Wednesday, March 20, 2024, 10:00–10:15, H 0106

Predicting birefringence patterns and actuation of 3D-printed structures of liquid crystalline elastomers — •Santiago Gomez Melo, Li-Yun Hsu, Clara Vazquez-Matel, Rasmus Schröder, Eva Blasco, Falko Ziebert, and Ulrich Schwarz — Heidelberg University, Heidelberg, Germany

Liquid crystalline elastomers (LCEs) are a promising class of material to achieve autonomous deformation in response to external stimuli. Their actuation stems from the nematic-isotropic transition of a programmed molecular orientation, in which the LCE locally strains differently along the parallel and perpendicular directions. Recently, interest in this system has increased due to the possibility to 3D-print such materials as structures with arbitrary shapes. Here we show that the orientation in the sample can be controlled by positioning PDMS-scaffolds at the boundaries. Because they introduce strong anchoring boundary conditions, they determine the minimal energy solution of the Landau-de Gennes free energy of the LCE. We show both theoretically and experimentally that the use of suitable scaffold geometries allows for the engineering of diverse textures of the director field, which are then imprinted into the LCE by direct laser writing. To demonstrate successful design, we show that the calculated and measured birefringence patterns agree very well with each other. A similar test can be performed for mechanical actuation by temperature changes, which is predicted by modelling the LCE-microdevice as neo-Hookean material with an active deformation contribution.