title: Real-time monitoring of two-photon photopolymerization for use in fabrication of microfluidic devices.
abstract: We report an improved method for production of microfluidic device masters using two-photon photopolymerization of SU-8 negative photoresist, which relies on a two-photon microscope (TPM) commonly used in imaging of biological samples. The device masters serve as negative relief structures for polydimethylsiloxane-based microfluidic devices. We observed that not only did the two-photon excitation of the SU-8 photoresist initiate crosslinking of the material in the region of the focus of the near-infrared laser beam (as expected) but it also resulted in emission of fluorescence in the visible range. The detected emission of SU-8 photoresist undergoing two-photon excitation displayed a strong correlation with the size of the polymerized objects produced during the exposure; this allowed the progress of the microfluidic master production process to be monitored in real-time. We demonstrate the use of the fluorescence detection during two-photon photopolymerization in the production of microfluidic devices, which were designed to trap individual yeast cells to be imaged with the same TPM used for microfluidic master writing.
authors.affiliation: Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Stoneman
authors.forename: Michael
authors.initials: M
authors.lastname: Fox
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Zeng
authors.forename: Valerică
authors.initials: V
authors.lastname: Raicu
mesh_terms: D004852:Epoxy Compounds / Q000737:chemistry*; D005453:Fluorescence; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D017785:Photons; D011108:Polymers / Q000737:chemistry*
chemical_list: D004852:Epoxy Compounds; D011108:Polymers; C520895:SU-8 compound