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Published May 5, 2020 | Published + Supplemental Material
Journal Article Open

A nonlinear beam model of photomotile structures


Actuation remains a significant challenge in soft robotics. Actuation by light has important advantages: Objects can be actuated from a distance, distinct frequencies can be used to actuate and control distinct modes with minimal interference, and significant power can be transmitted over long distances through corrosion-free, lightweight fiber optic cables. Photochemical processes that directly convert photons to configurational changes are particularly attractive for actuation. Various works have reported light-induced actuation with liquid crystal elastomers combined with azobenzene photochromes. We present a simple modeling framework and a series of examples that study actuation by light. Of particular interest is the generation of cyclic or periodic motion under steady illumination. We show that this emerges as a result of a coupling between light absorption and deformation. As the structure absorbs light and deforms, the conditions of illumination change, and this, in turn, changes the nature of further deformation. This coupling can be exploited in either closed structures or with structural instabilities to generate cyclic motion.

Additional Information

© 2020 National Academy of Sciences. Published under the PNAS license. Edited by John A. Rogers, Northwestern University, Evanston, IL, and approved March 18, 2020 (received for review September 9, 2019). PNAS first published April 16, 2020. This work started while B.A. visited California Institute of Technology as a Moore Distinguished Scholar in 2017–2018. K.K., A.S.K., K.B., and R.C.H. gratefully acknowledge the support of the US Office of Naval Research through Multi-investigator University Research Initiative Grant ONR N00014-18-1-2624. K.K. also acknowledges the support of the NSF Graduate Research Fellowship under Grant DGE-1745301. Data Availability: All data needed to evaluate the conclusions in this paper are available in the main text or in SI Appendix. Author contributions: K.K., B.A., and K.B. designed research; K.K., A.S.K., and R.C.H. performed research; K.K., B.A., and K.B. analyzed data; and K.K., B.A., and K.B. wrote the paper. The authors declare no competing interest. This article is a PNAS Direct Submission. This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1915374117/-/DCSupplemental.

Attached Files

Published - 9762.full.pdf

Supplemental Material - pnas.1915374117.sapp.pdf

Supplemental Material - pnas.1915374117.sm01.mp4

Supplemental Material - pnas.1915374117.sm02.mp4


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