Multiple fabrications of sacrificial layers to enhance the dimensional accuracy of microstructures in maskless projection microstereolithography

Abstract

Microstereolithography (MSL) is a promising technology for producing fully three-dimensional microstructures with overhanging features and high-aspect ratios. In conventional stereolithography (SL), a layer thickness of ≈50–100 μm is obtained by using a recoater. However, a recoater cannot be used in MSL, where the layer thickness is typically ≈10 μm or less, since resin flow may break or distort the pre-fabricated layers. In most MSL systems, the resin surface (or layer thickness) is controlled by a free surface technique that employs resin gravity to refresh the resin surface over a given settling time. In addition, a sacrificial layer must be fabricated in MSL to create a flat initial surface and provide support, just as in SL. In this paper, the fabrication methodology and functionality of the sacrificial layer is investigated for microstereolithography microstructures fabricated using the free surface technique. Experimental data are presented that indicate the greater the number of sacrificial layers, the sharper the dimensional accuracy of the microstructures in the building direction. This is because multiple fabrications of the sacrificial layer affect the resin ‘wetting’ status on the substrate or pre-cured surfaces. Several microstructures were fabricated to verify the effect of multiple fabrications of the sacrificial layer on dimensional accuracy in the building direction.