Engineering Research Seminar Series 22, 2012: Anti-sticking, Low Friction Coatings on Silicon Micromolds for Quality Control in Replication of Polymer Microfluidic Devices

Dr Liu Erjia, Associate Professor from Nanyang Technology University (NTU), Singapore

Date: 2012-10-05
Time: 16:00 to 17:00
Venue: Lecturer Theatre 6-0-09


Micro-hot-embossing and micro-injection-molding are among the most promising thermal plastic fabrication processes for mass production of microfluidic devices. However, both workpiece and micromold are susceptible to structural damage due to high thermal stress, stiction and friction between the workpiece and micromold during molding and demolding processes. The lifetime of an uncoated silicon (Si) micromold is usually very short even though it has good fidelity. A major constraint for Si micromolds is their inability to withstand a prolonged sliding surface contact due to high sidewall friction or high surface energy. Thus, the surface of an ideal micromold should have low adhesion and friction along with high hardness and wear resistance. This work deals with the impact of anti-sticking, low friction coatings deposited on Si micromolds on their durability and quality in replication of polymer (e.g. polymethylmethacrylate, PMMA) microfluidic devices, which involved different coating processes (e.g. magnetron sputtering and dipping), coating materials (e.g. diamond-like carbon (DLC) thin films, MoS2:Ti nanocomposite coatings, and octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) coatings), and properties of coated surfaces (e.g. structural, mechanical, thermal and tribological properties). Applied load, sliding velocity and temperature had significant effects on the friction behavior of the coated micromolds. All the coatings employed in this study reduced the surface adhesion and friction of the coated Si micromolds, leading to better replication quality and durability of the micromolds.

About the Speaker

Dr Liu Erjia has been with Nanyang Technological University (NTU), Singapore since 1997 and is currently an associate professor and the leader of the Knowledge Domain of Tribology with the School of Mechanical and Aerospace Engineering (MAE). He received his bachelor degree in materials engineering from Harbin University of Science & Technology in 1982, master degree in materials engineering from Harbin Institute of Technology in 1987, and PhD degree in metallurgy and materials engineering from Katholieke Universiteit Leuven (KUL), Belgium in 1997. He is an EXCO member of the Institute of Materials (IoM), East Asia. His research interests include thin films and coatings, carbon materials, nanocomposites, nanotribology, and electrochemistry. He has authored or coauthored more than 100 refereed journal papers, more than 100 conference papers, 11 books or chapters, and 2 patents filed. He has chaired the Symposium of Electrochemistry of Thin Films cum the 1st through 6th International Conferences on Technological Advances of Thin Films and Coatings (ThinFilms2002 - 2012), and has been the organization committee members of several international conferences (e.g. ThinFilms2002 - 2012, Intentional Conferences on Advanced Tribology (iCAT2004 & 2008)). He has been the associate editors of the journals “The Scientific World Journal” and “Research & Reviews in ElectroChemistry”, and the guest editors of the journals “Journal of Nanoscience and Nanotechnology (JNN)”, “Nanoscience and Nanotechnology Letters (NNL)”, and “Thin Solid Films (TSF)”.