A Bidirectionally Focus-Tunable Optofluidic Microlens With Miniature Thermoelectric Coolers

The design and fabrication of a novel bidirectionally optofluidic tunable microlens actuated by thermoelectric coolers (TECs) are reported. A high-resolution three-dimensional printing technology is adopted to fabricate the truly three-dimensional structure of an optofluidic chip. Owing to the bidirectional thermal property of the TECs, both upward and downward membrane profiles are available under the control of a programmable direct-current power supply. The focal length of the liquid lens decreases from 25 to 5 mm as the voltage is increased from 0.2 to 1.1 V whereas the focal length changes from −25 to −5 mm as the current is applied in the opposite direction. A finite element simulation with COMSOL software is conducted to assess the temperature distribution on the device. The response functions of the TECs are investigated for the heating and cooling processes, and the imaging properties are characterized.