Electrostatic self-assembly of microsphere lens arrays

We propose a novel versatile method for the rapid and low-cost fabrication of microsphere arrays to be used as lenses of desired geometry and optical properties. Our method is based on the electrostatic self-assembly of dielectric microspheres in Parylene-C/glass well templates, with the array geometry patterned in the Parylene-C layer via standard clean room techniques. While different particle sizes and materials can be used to tune the light focusing properties of the microlenses, we demonstrate here a process that uses 3 μm size melamine spheres. We use optical tweezers to assess the electrostatic nature of the microsphere binding mechanism by manipulating the patterned spheres. We demonstrate that our method ensures extremely fast and reliable array formation and offers moreover the possibility to reversibly assemble and disassemble the lens array by tuning the pH of the microsphere patterning and washing solutions.