Simple and easily controllable parabolic-shaped microlenses printed on polymeric mesas

A simple and easy shape-controllable approach is demonstrated for the fabrication of parabolic-shaped polymer microlenses (mu-lenses), which are widely used in bio-imaging systems such as microfluidic and lab-on-a-chip systems for improving the image quality due to their ability to efficiently focus light into the devices. The mu-lenses were printed directly on micro-structured polymeric SU-8 mesas and they were formed on these mesas using a photo-curable organic-inorganic hybrid material (H-resist) using a drop-on-demand (DOD) ink-jet printing technique. The parabolic-shape mu-lenses with a fixed diameter resulting from the micro-structured SU-8 mesas are controlled by surface wetting conditions (i.e., the comparison between hydrophobic and hydrophilic) that efficiently improve the boundary confinement effect, and by printing different numbers of drops per m-lens. The influence of the geometrical changes on the optical properties is also investigated. The high numerical aperture (NA) parabolic-shaped mu-lenses controlled by the hydrophobic surface-treated micro-structured polymeric SU-8 mesas, which are able to confine the drops at the edge, can be integrated on a microfluidic system and they allow high resolution image quality.