Edge effect of strained bilayer nanofilms for tunable multistability and actuation

Inspired by the need to develop reconfigurable materials at the micro- and nano- scales that are capable of exhibiting more than one stable configuration, we employed both theoretical and computational models supported by experiments to study the multistable behavior of a Si/Cr microclaw and uncover the mechanical principles involved. Our results indicated that besides the biaxial strain that serves as the primary driving force for scrolling, residual edge stresses due to the etching process play an important mechanical role in inducing bistability. Our study showed that individual Si/Cr microclaws demonstrate either monostability or bistability as the magnitude of the edge effect is varied and the computational results are consistent with experiments. More importantly, this work provide a means to guiding the on-demand design of microscale structures with tunable multistability and actuating capability using a strained-engineering approach. Programming multistability into nano-electromechanical or micro-electromechanical systems will allow for microscale manipulation and robotic operation for biomedical applications. 

This paper will appear in Nanoscale as a featured back cover article; DOI: 10.1039/C6NR08770A.