Tunable liquid microlens actuated by infrared light-responsive hydrogel

We report on liquid-based tunable microlenses actuated by infrared (IR) light. Multiple micropost structures, made of IR light-responsive hydrogel with entrapped gold nanoparticles, are photopatterned around a lens aperture. The volumetric change in the hydrogel, controlled by IR light, regulates the curvature of a liquid-liquid interface forming the microlens at the aperture and its focal length. The focal length of the microlens can be tuned from -17.4 mm to +8.0 +/- 0.4 mm in seconds under IR irradiation. This microlens can be integrated into optical systems, for instance, for fiber endoscopy.