Voxelated Additive Manufacturing of Liquid Crystal Elastomers

Responsive feedstocks for additive manufacturing have opened a new regime of material design & manufacturing, where printed architectures can morph from the as-printed state to a programmed state with exposure from a specific stimulus. Liquid crystal elastomers (LCEs) are being developed for additive manufacturing (AM) where programming can be instated during the printing of complex shapes and shape morphing can be triggered reversibly and repeatably over many cycles of stimuli exposure. Until recently, most AM of LCE efforts were focused on Direct Ink Write, limiting shape change programming to unidirectional liquid crystal alignment and part complexity. By using digital light projection platforms to not only print, but also address liquid crystal alignment on a voxel-level, complex printed architectures can exhibit repeatable, precise, and targeted three-dimensional shape change. Providing this capability will be a paradigm shift for applications such as soft robotics, stimuli-responsive control systems, anisotropic and tunable energy absorption, on-demand pumping for carbon capture and health care, and more.<br/><br/>Here we will report on two pathways of voxelated alignment digital light projection methods implemented at LLNL using either magnetic fields or photoalignment approaches. To achieve a targeted three-dimensional shape change, high performance computing simulation and design optimization at LLNL has informed the digital voxelated alignment maps applied during printing. In addition, liquid crystal elastomer resins have be optimized to flow during printing while maintaining a high degree of shape change. As a result, voxelated AM of LCEs will be presented, demonstrating 3D-to-3D targeted shape change.<br/><br/>This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS- LLNL-ABS-865922.