Surface Functionalization of Thermoplastic Polymers for the Fabrication of Microfluidic Devices by Photoinitiated Grafting


  • This work was supported by the Office of Nonproliferation Research and Engineering of the U.S. Department of Energy under contract No. DE-AC03-76SF00098 as part of a close collaboration with Sandia National Laboratory in Livermore, and, in part, by the National Institute of General Medical Sciences, National Institutes of Health (GM-48364). Support of T. R. by the Austrian Science Fund is gratefully acknowledged. We also thank Dr. Craig R. Tewell for his help in the determination of the UV-emission spectrum, Senol Mutlu for depositing Parylene C on chips, as well as Ticona and Bayer AG for samples of their polymers.


Photografting has been used for the surface modification of a wide range of commercial commodity polymers such as poly- styrene, poly(methyl methacrylate), poly(dimethyl siloxane), polycarbonate, Parylene C, polypropylene, cyclic olefin copolymer, and hydrogenated polystyrene that are useful substrate materials for the fabrication of microfluidic chips. Since the chain propagation is initiated after UV light-activated abstraction of a hydrogen atom from the surface of channels within the materials, their permeability for UV light was tested and polyolefins were found to be the best candidates. A number of monomers with a variety of functional groups such as perfluorinated, hydrophobic, hydrophilic, reactive, acidic, basic, and zwitterionic have been successfully grafted from the surface of selected substrates, and the grafting efficiency determined using X-ray photoemission spectroscopy. Layered surface structures were prepared by consecutive grafting of different monomers. Our approach also enables photolithographic patterning of surfaces and specific functionalization of confined areas within the microchannel.