3D printing of liquid crystal elastomeric actuators with spatially programed nematic order

This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi:10.1002/adma.201706164.Liquid crystal elastomers (LCEs) are soft materials capable of large, reversible shape changes, which may find potential application as artificial muscles, soft robots, and dynamic functional architectures. Here, the design and additive manufacturing of LCE actuators (LCEAs) with spatially programed nematic order that exhibit large, reversible, and repeatable contraction with high specific work capacity are reported. First, a photopolymerizable, solvent-free, main-chain LCE ink is created via aza-Michael addition with the appropriate viscoelastic properties for 3D printing. Next, high operating temperature direct ink writing of LCE inks is used to align their mesogen domains along the direction of the print path. To demonstrate the power of this additive manufacturing approach, shape-morphing LCEA architectures are fabricated, which undergo reversible planar-to-3D and 3D-to-3D′ transformations on demand, that can lift significantly more weight than other LCEAs reported to date.The authors gratefully acknowledge support from the National Science Foundation through the Harvard MRSEC (Grant No. DMR-1420570) and the DMREF (Grant No. DMR-1533985). A.K. and R.L.T. acknowledge support from their National Science Foundation Graduate Research Fellowships. J.A.L. acknowledges support from the Vannevar Bush Faculty Fellowship Program sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineering and funded by the Office of Naval Research Grant N00014-16-1-2823 as well as the generous donation from the GETTYLAB in support of our work. This work made use of the Shared Experimental Facilities supported in part by the MRSEC Program of the National Science Foundation under award number DMR-1419807. Finally, the authors thank L. K. Sanders and C. Settens for technical assistance and Brian Donovan and Tyler Guin (AFRL) for useful discussions. (DMR-1420570 - National Science Foundation through Harvard MRSEC; National Science Foundation; DMR-1533985 - DMREF; Vannevar Bush Faculty Fellowship Program - Basic Research Office of the Assistant Secretary of Defense for Research and Engineering; N00014-16-1-2823 - Office of Naval Research; DMR-1419807 - MRSEC Program of the National Science Foundation)Accepted manuscrip