Mechanochromics of stretchable nano metasurfaces: Non-close-packed hexagonal lattices and tunable structural coloration

Under the bio-mechanism of a chameleon's color change, in this letter, a 2D nano metasurface, mechanical-strain-Actuated photonic crystal, is proposed. The lattice, a nano hexagon with non-close-packed cylinder holes, is analyzed via a mechanochromic coupling model and plane wave transmission to verify the optical structural color in strain. The metasurface material was fabricated by soft lithography on a stretchable substrate. The strain versus reflectivity spectra were measured, showing a full visible range color change, at a strain of 29%. The RGB colors in the strained state were maintained after 2000 repeated loading/unloading cycles, illustrating fatigue insensitivity.