title: Polymer microfabrication by scanning based microstereolithography: optical design and material functionality.
abstract: Several research groups have attempted to optimize photopolymerization parameters to increase the throughput of scanning based microstereolithography (MSL) systems through modified beam scanning techniques. Efforts in reducing the curing line width have been implemented through high numerical aperture (NA) optical setups. However, the intensity contour symmetry and the depth of field of focus have led to grossly non-vertical and non-uniform curing profiles. This work tries to review the photopolymerization process in a scanning based MSL system from the aspect of material functionality and optical design. The focus has been to exploit the rich potential of photoreactor scanning system in achieving desired fabrication modalities (minimum curing width, uniform depth profile, and vertical curing profile) even with a reduced NA optical setup and a single movable stage. The present study tries to manipulate to its advantage the effect of optimized lower [c] (photoinitiator (PI) concentration) in reducing the minimum curing width to ~10-20 μm even with a higher spot size (~21.36 μm) through a judiciously chosen "monomer-PI" system. Optimization on grounds of increasing E(max) (maximum laser exposure energy at surface) by optimizing the scan rate provides enough time for the monomer or resin to get cured across the entire resist thickness (surface to substrate ~10-100 μm), leading to uniform depth profiles along the entire scan lengths.
authors.affiliation: Materials Research Centre, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Ankur
authors.initials: A
authors.lastname: Goswami
authors.forename: Arindam
authors.initials: A
authors.lastname: Phani
authors.forename: A M
authors.initials: AM
authors.lastname: Umarji
authors.forename: Giridhar
authors.initials: G
authors.lastname: Madras