title: Caulking polydimethylsiloxane molecular networks by thermal chemical vapor deposition of Parylene-C.
abstract: Surface functionalization of polydimethylsiloxane (PDMS) is important in developing high-performance microfluidic devices. This work applied the thermal chemical vapor deposition (t-CVD) of Parylene-C onto PDMS to caulk the molecular network while retaining the original surface properties for the oxygen plasma bonding. The very low deposition rates (for example, a nominal rate of 0.12 Å min-1at 135 °C) of Parylene-C at elevated substrate temperatures enabled the reactive Parylene-C monomers to penetrate into the PDMS matrix up to 4.6 ± 0.1 μm (135 °C), which was verified for the first time by a scanning electron microscope with an energy dispersive X-ray analysis (SEM-EDAX). The Parylene-C caulked in the molecular network of PDMS matrix guaranteed an excellent resistance to small molecule permeations. Meanwhile, only discrete nucleation islands were formed on the top surface rather than a continuous Parylene-C layer as observed under the AFM scan, which made the processed PDMS surface ready for device assembly. This surface functionalization method has better long-term stability than the other wet-type rivals. The barrier for oxygen plasma bonding in previously reported dry surface treatments was also avoided, thereby, facilitating the device assembly. The present work successfully developed a novel pcPDMS (Parylene-C caulked PDMS) technique, which overcame the bonding difficulty in the previous works but retained the low small molecule permeability as before. Caulking a molecular network through the t-CVD of Parylene-C also demonstrated a new strategy of functionalizing polymer surfaces and preparing new hybrid materials for wide lab-on-a-chip applications.
authors.affiliation: Institute of Microelectronics, Peking University, 100871, Beijing, China. w.wang@pku.edu.cn.
authors.forename: Yaoping
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Institute of Microelectronics, Peking University, 100871, Beijing, China. w.wang@pku.edu.cn.
authors.forename: Lingqian
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, AML, Tsinghua University, 100084, Beijing, China.
authors.forename: Chi
authors.initials: C
authors.lastname: Mo
authors.affiliation: Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, AML, Tsinghua University, 100084, Beijing, China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Institute of Microelectronics, Peking University, 100871, Beijing, China. w.wang@pku.edu.cn and National Key Laboratory of Science and Technology on Micro/Nano Fabrication, 100871, Beijing, China and Innovation Center for Micro-Nano-electronics and Integrated System, 100871, Beijing, China.
authors.forename: Wengang
authors.initials: W
authors.lastname: Wu
authors.affiliation: Institute of Microelectronics, Peking University, 100871, Beijing, China. w.wang@pku.edu.cn and National Key Laboratory of Science and Technology on Micro/Nano Fabrication, 100871, Beijing, China and Innovation Center for Micro-Nano-electronics and Integrated System, 100871, Beijing, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang