Optimized SU-8 processing for low-cost microstructures fabrication without cleanroom facilities

The study and optimization of epoxy-based negative photoresist (SU-8) microstructures through a low-cost process and without the need for cleanroom facility is presented in this paper. It is demonstrated that the Ultraviolet Rays (UV) exposure equipment, commonly used in the Printed Circuit Board (PCB) industry, can replace the more expensive and less available equipment, as the Mask Aligner that has been used in the last 15 years for SU-8 patterning. Moreover, high transparency masks, printed in a photomask, are used, instead of expensive chromium masks. The fabrication of well-defined SU-8 microstructures with aspect ratios more than 20 is successfully demonstrated with those facilities. The viability of using the gray-scale technology in the photomasks for the fabrication of 3D microstructures is also reported. Moreover, SU-8 microstructures for different applications are shown throughout the paper.Work supported by FEDER funds through the Eixo I do Programa Operacional Fatores de Competitividade (POFC) QREN, project reference COMPETE: FCOMP-01-0124-FEDER-020241, and by FCT- Fundação para a Ciência e a Tecnologia, project reference PTDC/EBB-EBI/120334/2010. Vânia C. Pinto thanks the FCT for the SFRH/BD/81526/2011 grant. Paulo J. Sousa thanks the FCT for the SFRH/BD/81562/2011 grant. Vanessa F. Cardoso thanks the FCT for the SFRH/BPD/98109/2013 gran