Direct laser writing of liquid crystal elastomers oriented by a horizontal electric field

Abstract

Background: The ability to fabricate components capable of performing actuation in a reliable and controlled manner is one of the main research topics in the field of microelectromechanical systems (MEMS). However, the development of these technologies can be limited in many cases by 2D lithographic techniques employed in the fabrication process. Direct Laser Writing (DLW), a 3D microprinting technique based on two-photon polymerization, can offer novel solutions to prepare, both rapidly and reliably, 3D nano- and microstructures of arbitrary complexity. In addition, the use of functional materials in the printing process can result in the fabrication of smart and responsive devices. Methods: In this study, we present a novel methodology for the printing of 3D actuating microelements comprising Liquid Crystal Elastomers (LCEs) obtained by DLW. The alignment of the mesogens was performed using a static electric field (1.7 V/µm) generated by indium-tin oxide (ITO) electrodes patterned directly on the printing substrates. Results: When exposed to a temperature higher than 50°C, the printed microstructures actuated rapidly and reversibly of about 8% in the direction perpendicular to the director. Conclusions: A novel methodology was developed that allows the printing of directional actuators comprising LCEs via DLW. To impart the necessary alignment of the mesogens, a static electric field was applied before the printing process by making use of flat ITO electrodes present on the printing substrates. The resulting microelements showed a reversible change in shape when heated higher than 50 °C.

Three-dimensional blueprinting of molecular patterns in liquid crystalline polymers

“…In addition to the requirement for the manual work and the time consuming and inaccurate nature of the assembling procedure, this method also restricts the geometrical complexity of the structure. Inspired by our first published paper in this work, researchers demonstrated real voxel-by-voxel encoding alignment through combination of an external electric field with DLW photopolymerization technique [83,84]. While this method is desirable at this small scale, the electric field becomes much more inefficient than magnetic field at larger scales.…”

“…13 Superposition of electric fields with photopolymerization was used for voxel-by-voxel blueprinting of molecular order. 14,15 Guo et al applied two-photon polymerization technique to generate LCE freeforms. The alignment complexity was enhanced by fabricating microchannels on the walls 16 to modulate molecular order.…”