Electrohydrodynamic Assembly of Multiscale PDMS Microlens Arrays

In this paper, we introduce an easy multiscale approach for the fabrication of polymer microlens arrays through a self-assembling process driven by the electrohydrodynamic (EHD) pressure. This method represents a simple alternative to the conventional soft lithography techniques. A thin layer of liquid polymer is deposited on a microengineered ferroelectric crystal and can be self-assembled and cross-linked in a single-step process as a consequence of the pyroelectric effect activated by simply heating the substrate. Although the EHD instability induced by the pyroelectric effect was discovered in principle few years ago, here we demonstrate a systematic investigation for fabrication of microlens arrays in a multiscale range (i.e., between 25 to 200 mu m diameter) with high degree of uniformity. By controlling the polymer instability driven by EHD, we report on two different microoptical shapes can be obtained spontaneously, i.e., spherical or toroidal. Here, we show how the geometrical properties and the focal length of the lens array are modulated by controlling two appropriate parameters. Such microlenses can be useful also as polymer patterned arrayed microstructures for optical data interconnections, OLEDs efficient light extraction, concentrating light in energy solar cells, imaging and 3-D display solutions, and other photonics applications.