[Biomicrofluidics] Flow lithography in ultraviolet-curable polydimethylsiloxane microfluidic chips
Flow Lithography (FL) is the technique used for the synthesis of hydrogel microparticles with various complex shapes and distinct chemical compositions by combining microfluidics with photolithography. Although polydimethylsiloxane (PDMS) has been used most widely as almost the sole material for FL, PDMS microfluidic chips have limitations: (1) undesired shrinkage due to the thermal expansion of masters used for replica molding and (2) interfacial delamination between two thermally cured PDMS layers. Here, we propose the utilization of ultraviolet (UV)-curable PDMS (X-34-4184) for FL as an excellent alternative material of the conventional PDMS. Our proposed utilization of the UV-curable PDMS offers three key advantages, observed in our study: (1) UV-curable PDMS exhibited almost the same oxygen permeability as the conventional PDMS. (2) The almost complete absence of shrinkage facilitated the fabrication of more precise reverse duplication of microstructures. (3) UV-cured PDMS microfluidic chips were capable of much stronger interfacial bonding so that the burst pressure increased to ∼0.9 MPa. Owing to these benefits, we demonstrated a substantial improvement of productivity in synthesizing polyethylene glycol diacrylate microparticles via stop flow lithography, by applying a flow time (40 ms) an order of magnitude shorter. Our results suggest that UV-cured PDMS chips can be used as a general platform for various types of flow lithography and also be employed readily in other applications where very precise replication of structures on micro- or sub-micrometer scales and/or strong interfacial bonding are desirable.
Junbeom Kim1,2, Heseong An1,3, Yoojin Seo4,5, Youngmee Jung4,6, Jong Suk Lee3,7, Nakwon Choi2,6,a),b), and Ki Wan Bong1,a),b)lessHide Affiliations 1Department of Chemical and Biological Engineering, Korea University, Seoul 02841, South Korea 2Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea 3Materials Architecturing Research Center, Materials and Life Science Research Division, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea 4Center for Biomaterials, Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea 5NBIT, KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, South Korea 6Division of Bio-Medical Science & Technology (Biomedical Engineering), KIST School, Korea University of Science and Technology (UST), Daejeon 34113, South Korea 7Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 04107, South Korea a)N. Choi and K. W. Bong contributed equally to this work.