Fabrication and characterization of polymer microprisms

Abstract

An increasing interest in low-cost polymer micro-fabrication techniques demands an increasing necessity for characterizing such techniques. In this research, polymethylmethacrylate (PMMA) and polydimethylsiloxane (PDMS) microprisms were realized by hot embossing and replica molding processes, respectively. In both replication methods, the polymer microprisms were patterned with the same brass master mold. This mold was fabricated via high precision micro-milling, which accommodates a wide range of achievable sidewall angles and a large workable surface area relative to lithographic fabrication technologies. The pattern designed for replication contained a microprism array of 20 parallel, equal length prisms, grouped into four sets of distinct prism geometries. The four geometries include three triangular microprisms with varying interior angles and one semicircular microprism with a radius of 500 μm. The polymer microprisms replicated by PMMA hot embossing and PDMS replica molding were found to exhibit interior angle reductions relative to the brass master mold dimensions. This paper includes a description and analysis of a surface treatment process by which the RMS surface roughness of the mentioned PMMA microprisms was shown to reduce by 28 % after controlled thermal exposures just above their glass transition temperature.