Soft lithography of microfluidics channels using SU-8 mould on glass substrate for low cost fabrication

Abstract

Soft lithography describes the moulding of polymers using master templates, a technology that is widely used in microfluidics fabrication. This study outlines a quick and low cost soft lithography processing using negative photoresist (PR) SU-8 on glass substrate to create a master template for subsequent Polydimethylsiloxane (PDMS) replication in overall microfluidics fabrication. Two types of negative PR, SU-8 5 and SU-8 2015 are used in this study to increase the adhesion of the resist. Inkjet transparent mask is used as microfluidic photomask instead of expensive chrome mask and the design was made on AutoCAD software. Results from high power microscopy (HPM) and 3D profilometer show successful fabrication with <;0.1 mm variance between the dimensions in the original design and the dimensions after the lithography process. The thickness and surface roughness of micro channels in SU-8 master template and PDMS replicate is ~100 μm and ≤0.15 μm for both fabricates, respectively. SU-8 was chosen for master template for its superior properties and low cost fabrication with short processing time.