Tunable microlenses

The brittlestar Ophiocoma wendtii uses its entire skeleton not only for mechanical strength but as one big compound eye. Its body is covered with an array of calcitic microlenses tailored to such optical perfection that they are completely free of birefringence, spherical aberration, and distortion. Most strikingly, the brittlestar has built-in sunglasses it can cover itself with during the day and remove at night; these are piped in through an intricate porous network surrounding the lenses and consist of pigment-filled cells that modulate the refractive index and light transmission. This setup enables the brittlestar to adapt its light absorption based on the external light conditions, as well as to tune wavelength selection, increase focusing capability, and select light from a particular direction. 

The brittlestar’s unique combination of optical precision with adaptive tunability inspired us to design a synthetic adaptive optical network based on the same strategy. Using three-beam interference lithography, we constructed a polymeric analog of the hexagonally packed microlens array surrounded by pores.

Pumping different types of photoactive dyes through the pore network allows dynamic modulation of light transmission, as well as focal length, numerical aperture, and wavelength selectivity. We continue to extend this adaptive strategy to a variety of sensor, encryption, and other dynamic optical systems, particularly in conjunction with our recent development of self-assembly methods for complex nanoporous architectures.