Fig. 2

Polymer-based optical metamaterials. a A large-area (8.7 cm × 8.7 cm) flexible PDMS based Ag negative index metamaterial (NIM) that shows negative index of refraction at optical frequencies. PDMS has the advantage of enabling direct pattern transfer, benefiting from PDMS’s low surface energy. b The transmission (T) and reflection (R) spectra of the large-area PDMS-based Ag NIM metamaterial. The metamaterial shows negative RI at a wavelength range of 1.7 µm to 2.4 µm. c An illustration of a flexible metamaterial consists of Au nanodisk array on top of an SU-8 substrate. SU-8 has high chemical and thermal resistance and good mechanical properties, rendering it useful as a flexible metamaterial substrate. d The reflection and transmission spectra of a flat (left) and a bent (right) SU-8-based flexible gold nanodisk metamaterial. The reflection is dependent on bending, but transmission of this flexible metamaterial is invariant of bending. e A scanning electron microscopy (SEM) image of a PEN-based Au split ring resonator (SRR) metamaterial. PEN has a high glass transition temperature and is transparent in visible and near-infrared (NIR) wavelength ranges. f The transmission spectra across visible and NIR wavelength ranges of a PEN-based Au SRR metamaterial with and without an applied out-of-plane strain. Given a strain of 1232 Pa, the electric peak shifts from 894 to 973 nm, showing a sensitivity of 0.06 nm/Pa. a, b Reprinted with permission from [81], Copyright (2011) Nature Publishing Group. c, d Reprinted with permission from [89], Copyright (2011) AIP Publishing LLC. e, f Reprinted with permission from [91], Copyright (2011) ACS Publications