Microlens arrays (MLAs) are being used more and more in optical and lighting systems in applications such as fiber optics, image systems and illumination. Various fabrication methods for MLAs have been described. These include the reflow process, molds, laser-aided fabrication, lithography with a gray-scale mask, etching, and assembly by surface properties. Among these processes, molding has more advantages such as fast, high precision and mass product.  PMMA, SU-8, and PMGI have all been used for microlens fabrication

Any material in liquid state tends to exist in its lowest surface free energy, resulting in the least surface area, and spherical shape. The polymer particles on the smooth surface of a substrate will shrink into a hemispherical lens due to the surface tension when heated above their softening temperature. The key is to make sure of regular arrangement of lenses in a two dimensional plane. SU-8 can also be used as the micro-mold or stamp to form PDMS or PMMA microlenses.

PMMA, SU-8, PMGI Lenses: Benefits/Attributes

  • Excellent adhesion
  • Optical transparency
  • Spin-coatable

Basic steps of PMGI Microlens fabrication using an imaging resist and thermal reflow process based on surface tension.

Source: University of Washington
Fabrication of SU-8 Microlens array using a stamping method.
Source: S. Kuo & C. Lin, J. Micromech. Microeng. 18 (2008)
VCSEL with integrated PMGI Microlens to shape the laser output beam.
Source: Optoelectronics Dept.,
Univ. of Ulm