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22 January 2007 Creation of embedded structures in SU-8
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Two methods were investigated for the creation of encapsulated micro-fluidic channels and bridges in negative tone SU-8 photoresist. The first uses two exposures at different wavelengths to create the channel sidewalls and microchannel encapsulation layer; the other method creates both using a single I-line (365 nm) exposure and a grayscale photomask. These methods can define structures with vertical dimensions ranging to hundreds of microns and introduces very little extra processing complexity. For the dual wavelength method, an I-line light source is used to define the channel walls while a non-collimated deep-UV (254 nm) light source provides a large energy dose to the top surface of the SU-8 to produce a membrane over all the channels. Using the dual wavelength method allows SU-8 to be used as the material for the channels and the encapsulation method is self-limiting avoiding the requirement for precise control over the exposure dose. The rate of UV dose and the post-exposure baking parameters are critical to the quality and strength of the micro-channels. Properly designed channels have been successfully developed in lengths up to 1 cm. Alternatively using a grayscale Zn/Al bimetallic photomask and a single I-line exposure, 3D bridge micro-structures were successfully made on SU-8. The use of grayscale masks for both techniques also provides the possibility of shaping the channel. With the ability to create micro-bridges, further research will be performed to investigate how well the single exposure technique can be used to produce micro-channels of various sizes and dimensions.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
James M. Dykes, David K. Poon, Jun Wang, Dan Sameoto, Jimmy T. K. Tsui, Chinheng Choo, Glenn H. Chapman, Ash M. Parameswaren, and Bonnie L. Gray "Creation of embedded structures in SU-8", Proc. SPIE 6465, Microfluidics, BioMEMS, and Medical Microsystems V, 64650N (22 January 2007);

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