Two-dimensional electrophoretic microlens alignment

An adaptive alignment technique is presented that provides precise control and active positioning of sub-millimeter-sized spherical lenses in two-dimensions through the application of electrophoretic forces in a microfluidic well. The device is comprised of a lithographically patterned microfluidic well and electrodes that can be addressed to position or align the spherical microlens to the corresponding beam source. The motion of the microlens is controlled using CMOS compatible voltages (3V - 1μA) that are applied to opposite electrodes in the microfluidic well, creating an electrical field in the solution. By applying voltages to opposite electrode pairs, we have demonstrated the movement of spherical microlenses with sizes ranging from 0.87μm to 40μm in directions parallel to the electrode surface. Under a bias of 3 volts, the microspheres had an experimentally measured electrophoretic velocities ranging from 13 to 16 μm/s. Optical alignment of the spherical or ball microlens can be accomplished using feedback from a photo detector to position the lens for maximum efficiency. Using this device, it is possible to actively align microlenses to optical fibers, VCSELs, LEDs, photodetectors, etc.