Packaging technique for a tunable miniature liquid iris operated by electrowetting actuation

This paper presents a simple ultraviolet (UV) chemical sealant aided packaging technique for a tunable liquid iris actuated by electrowetting-on-dielectric (EWOD) principle. To evaluate the proposed UV chemical sealant aided packaging technique, a large number of tunable liquid iris samples (9×9×2 mm³) are prepared by standard MEMS fabrication processes. The optical functionality of the microfabricated tunable iris is firstly tested. When an electrical voltage is sequentially applied to patterned ITO electrodes inside the tunable iris, opaque liquid initially covering only in the rim of the iris shifts to the center of the iris, resulting that the aperture diameter of the iris is modified from 4.2 mm to 0.85 mm. To improve the packaging of the iris the optimum chemical sealant (TB3124M UV sealant, ThreeBond Inc.) is selected through heavy field tests of various chemical sealants. To verify the proposed packaging technique, the high thermal test of the iris with the UV chemical sealant aided packaging is conducted using a temperature chamber. The result shows that the iris with the UV chemical sealant aided packaging shows no liquid leakage and remains as it was, while the iris only with a mechanical packaging shows severe liquid leakage through the joint area of the iris. The proposed packaging is easy to use but provides reliable liquid packaging, which can be applied to various microfluidic devices without additional complicated microfabrication processes.