Embedded 3D Printing of Liquid Crystal Elastomers

Abstract

Embedded 3D printing is an emerging technique for printing previously impossible structures. Embedded printing uses a fluid support matrix to allow filament to be extruded anywhere in three-dimensional space as opposed to on a substrate. In these experiments, we combine this new technique with liquid crystal elastomers (LCEs), which can reversibly undergo physical changes when heated above and below the isotropic nematic transition temperature (TNI). LCEs use the forces involved with the printing process to align the mesogens within the LCE. Because of this, the acceptable printing parameters are more specific in LCE printing. Combining this with Embedded printing introduces new complications. In this thesis, it is established that reversible actuators can be created through embedded printing of LCEs. These actuators can undergo up to 50% actuation strain and maintain this ability for at least 20 heat cycles. The print outcomes and actuation strain of various samples was measured at three different print speeds. All print speeds resulted in a high degree of alignment but they varied drastically in print outcome. Both low print speeds and high print speeds were unideal. The matrix was rheologically analyzed to understand what about the matrix made it viable for embedded printing. It was determined that the rheological properties of the material of the matrix were not the only parameters that affected the printing process, as differences in matrix temperature changed print outcomes without changing rheological properties significantly.