A continuous tilting of micromolds for fabricating polymeric microstructures in microinjection.

We demonstrate a practical design and integration of multidirectional tilted UV lithography and microinjection molding for microstructure-based microfluidic devices. The previously reported undercut (or T-profile) problem of photoresist causes the imperfect mirror image duplication of the microstructures to the Ni mold. This issue inevitably leads to the unstable molds in the production of microstructure-based microfluidic devices. This study presents a simple route for the successful fabrication of microstructure-based microfluidic devices by multidirectional tilted UV lithography. By changing slope angles of microstructures through tilting the chuck during the UV exposure, the slope angles (up to 30°) around the microstructures allow the effective prevention of the undercut problems of photoresist and facilitate easy releasing of the device with high durability. This technique can be easily used for the production of the microstructure-based microfluidic devices in microanalysis and lab-on-chip applications.