Hydrogel-actuated tunable-focus microlens arrays mimicking compound eyes

Inspired by the structure of natural compound eyes, a liquid tunable-focus microlens array omnidirectionally arranged on a transparent hemispherical dome is demonstrated. Benefiting from the dome structure, this microlens array exceeds traditional planar ones with wide field of view (FOV). Each microlens in this microlens array was formed by a curved water-oil meniscus. The focal length of the microlenses could be individually tuned by a thermo-responsive hydrogel microactuator. Planar and hemispherical microlens arrays were tested and the focal length of the hemispherical microlens array varied from 3 mm to 32 mm. Focused images from the microlens arrays were recorded by a CCD-coupled stereoscope.