Hydrogel microparticles as dynamically tunable microlenses.

Tunable micro-optical elements were prepared by aqueous free-radical polymerization and electrostatic self-assembly techniques. Stimuli-responsive poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-AAc) microgels were used as lenses to generate dynamically tunable optical elements. By using optical microscopy to investigate the micrometer-scale dynamics of the self-assembled microlenses, we demonstrate focal length tuning through modulation of the solution pH and/or temperature.