Fig. 3

Electromechanically tunable metasurfaces. a Tunable microbeam array actuated by electrostatic force [28]. Reproduced with permission from ©2013, Springer Nature. b Strain-induced tunable grating on a PDMS substrate [68]. Reproduced with permission from ©2018, American Chemical Society. c Micro-electro-mechanical-system-based metalens doublet [30]. Reproduced with permission from ©2018, Springer Nature