Graduate Student Researcher Texas A&M University College Station, Texas, United States
Introduction:: The development of curved, wearable electronics is an ongoing challenge due to the difficulty of fabricating electrodes onto 3D structures matching the contours of the human body. Liquid crystal elastomers (LCEs) are a class of shape-programmable materials which can be synthesized as a 2D film and induced to actuate into complex 3D shapes via external stimuli. Here, we describe the synthesis of an electronically patterned, high-strain LCE programmed to adopt a hemispherical shape for interfacing with the curved surfaces of the body.
Materials and Methods:: The fabrication of shape-tunable hemispherical electronics is achieved via patterned spray-coating of silver conductive inks onto a planar LCE film which conform into a static, 3D curved surface at body temperature. The LCE film is programmed via surface alignment to adopt a positive gaussian curvature when cooled below the crosslinking temperature. Copolymerization of high nematic-isotropic transition (TNI) temperature liquid crystal monomers allows for high-strain shape change and increases the glass transition of the LCE above body temperature, allowing the desired shape to remain static at target operating temperatures.
Results, Conclusions, and Discussions:: Hemispherical LCE shape change was quantified as radius of curvature adopted at room temperature. By altering the crosslinking temperature of the LCE film, the thickness of deposited metal traces, and the number of gaussian domains programmed into the film, a tunable radius of curvature was achieved. A library of fabricated electronic curved surfaces was created, with hemisphere radii ranging from 21.55 millimeters to 41.69 millimeters.
