Stretch tuning of the Debye ring for 2D photonic crystals on a dielectric elastomer membrane.

The tunable diffracted pattern (Debye ring) of the well-ordered close-packed 2D photonic crystal (PC) is achieved via large deformation of the dielectric elastomer (DE) membrane for the first time. Two deformation models are proposed, the in-plane deformation driven by voltage and the out-of-plane deformation actuated by pressure. Both experimental and theoretical analyses are conducted to explore the tunability of the DE stretch on the Debye ring of the 2D PC, by voltage and pressure. An excellent agreement is found between the experimental and analytical results. This study shows that tuning the size of the Debye ring by voltage driven in-plane deformation is easy to operate and space-saving. However, it needs a high voltage and the adjustable range is relatively small. On the other hand, the pneumatic tuning by out-of-plane deformation has a widely adjustable range compared with the electric one and the pressure needed is only hundreds to less than two thousand pascal, which is energy-saving. This work may pave the way for the design of various smart sensors and soft displays with the combination of PCs and DEs.