A fully integrated optofluidic micro-iris

We report on a novel type of tunable optofluidic micro-iris composed of a microfluidic chamber filled with two immiscible liquid phases, a highly absorbing aqueous pigment dispersion and a mixture of transparent silicone oils. The pigment dispersion, which is forced to assume a ring shape using a combination of changes in surface wettability and topography, defines a circular optical aperture of high contrast. Using integrated electrowetting actuation, the aperture diameter can be tuned in four discrete steps. The advantages of the concept are the absence of any moving parts, compactness of design, low power consumption (<; 5 mW), moderate drive voltage (75 V), high uniform transmission (>; 86 %) and highly reliable and repeatable tunability.