Fabrication of Textured 3D Microstructures Using ‘Bulk Lithography’

This paper presents the method of fabrication of textured three dimensional (3D) microstructures in single scan of laser beam. The textured 3D microstructures are obtained on one of the free surface (surface opposite to the substrate) of the microstructure. Fabrication of textured 3D microstructure is achieved using newly developed 3D microfabrication process termed as ‘Bulk lithography’. In this process the required depth variation is obtained during fabrication by allowing unconstrained depth photopolymerization and varying laser exposure while scanning. Hence, representative experimental results of dimensionless cured depth against dimensionless energy were obtained. Three different regimes of cured depth namely absorption, transition and scattering were observed under wide energy exposure. A predefined texture can be incorporated in CAD model itself and the structures can be fabricated when restricted to absorption dominant regime. However, the novelty of the proposed method lies in a distinct phenomenon observed in transition and scattering regime based on characteristic multiple scattering leading to textured surfaces in these regimes.. Further, it is observed experimentally that these textures are function of the exposure energy and are hypothyzed because of scattering of light.