Self-Assembled High NA Microball Lens Arrays

In this paper, we demonstrated an innovative self-assembly method to fabricate microball lens arrays based on the generation of global energy wells where microballs can be precisely located and positioned. This method uses dielectrophoresis (DEP) and gravitational forces to produce global energy wells in space to self-assemble microballs in the desired positions. The additional localized variable DEP forces were used to further manipulate microballs locally to fill up the vacancies or sweep out the excess microballs in the microball lens arrays. The array demonstrated has 40 × 40 microball lenses (i.e. 1.8mm × 1.8mm). The diameter of microball is 25 μm and the pitch of two microballs is 45 μm. Microball lens arrays formed by this method have numerical aperture (NA) of 0.78 and the interference pattern suggests that the uniformity of microball lenses are good.