Direct Writing of 3D Microstructures Using a Scanning Laser System
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DIRECT WRITING OF 3D MICROSTRUCTURES USING A SCANNING LASER SYSTEM Hui Yu, Alexander Grüntzig, Yi Zhao, André Sharon, Biao Li and Xin Zhang Department of Manufacturing Engineering and Fraunhofer USA Center for Manufacturing Innovation, Boston University, Boston, MA 02215, USA ABSTRACT In this paper, a new revolutionary 3D manufacturing approach to rapid processing of 3D microstructures in both soft (SU-8) and rigid (Si) materials is introduced. This technique facilitates very fast prototyping without the need of masks, resulting in a low-cost, short-turnaround flexible fabrication process. INTRODUCTION Recently, the interest in microstructures with true 3D geometries has dramatically increased in microsystems applications [1]. These microstructures promise to be of great importance for the numerous applications including those for the coming biotechnology revolution. Advanced lithographic techniques have been developed to create multidimensional 3D structures and SU-8 thick film photoresist has been employed to fabricate embedded micro-fluidic channels [2,3], structural parts of micro motors [4] for (bio-) chemical and medical applications. Those 3D microstructures are fabricated with lithography masks but with tedious fabrication processes. Proton beam has also been adopted as direct writing micro-machining method to form embedded micro-channels; however, it requires costly facility [5]. Performance, cost and environmental impact are important measures of processes for industrial applications. Material processing with lasers is an expanding field [6] since it not only makes manufacturing cheaper, faster, cleaner, and more accurate but also opens up entirely new technologies and manufacturing methods that are simply not available using standard techniques. In this paper, we demonstrate a simple beam-scanning laser system for rapid prototyping of 3D microstructures in both soft (SU-8) and rigid (Si) materials. In addition, an apparatus has been built for precise multilevel microstructure alignment, enabling manufacturing of a large number of multi-layered, complex microstructures. Due to its maskless property, this technique provides several specific benefits for µ-TAS or lab-on-chip system. First, it simplifies the fabrication process and facilitates very fast prototyping. Second, it avoids the errors transferred from mask and errors due to diffraction. Third and finally, it results in a low-cost, short-turn-around flexible fabrication approach. EXPERIMENT SETUP Figure 1a describes experimental apparatus. A diode-pumped, high repetition rate (~100kHz), nanosecond pulse duration 3rd harmonic Nd:YAG laser BL8-355Q operating at a wavelength of 355 nm is used as the light source. The laser produces a maximum average power of larger than 400 mW at 20 kHz. The output energy can be adjusted by varying the pump diode current or by altering the repetition rate. An x-y-z-θ stage was built to translate a sample in four degrees-of-freedom. The laser light is directed through a 2-axis Scan Head before it reaches the sam
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