MTU Laser-Based Direct-Write Techniques: Recent Development and Nanoparticles Patterning Results
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MTU Laser-Based Direct-Write Techniques: Recent Development and Nanoparticles Patterning Results Edward M. Nadgorny1, Changgong Zhou1, Jaroslaw Drelich2, 3, and Randy Zahn2 1 Department of Physics, 2Department of Materials Science and Engineering, and 3Engineering Research Center for Wireless Integrated Microsystems, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, U.S.A. ABSTRACT Two laser-based direct-write techniques to guide particles from a mist source to a target substrate by laser beams were recently developed at Michigan Tech. The laser-guided directwrite (LGDW) technique uses a hollow optical fiber, while the laser-guided microsensor patterning (LGMP) technique uses a micrometer-sized aperture. The techniques are suggested to be utilized for patterning microstructures made of nanoparticles that are either crystallized from liquid precursors or directly deposited from nanoparticle-in-liquid suspensions. The computational results based on the paraxial Fraunhofer approximation of a Gaussian beam diffracted by a circular aperture and experimental measurements of corresponding deposition rate under different conditions suggest several factors for setup optimization of LGMP. The results indicate that among the most important factors are the aperture size relative to the laser beam-waist size and the divergence of the beam near the aperture. Examples of gold-thiolate, protein-coated polystyrene, and carbon-polymer composites deposition are presented. INTRODUCTION Laser-based guidance of nanoparticles is one of many techniques in the new emerging field of direct-write technologies allowing effective and advanced patterning of various materials for the fabrication of sensors and electronics (see an extensive review [1] for more details). Two laser-based techniques have recently been developed at MTU, LGDW and LGMP [2-6]. Both of the techniques use laser-induced optical forces to transport particles from a supply source and deposit them on a substrate mounted on a translation stage. They are differentiated mainly by the method of focusing the particles before depositing on the substrate: LGDW uses a hollow optical fiber while LGMP an aperture and lens-controlled narrow laser beam. These techniques are quite general and enable one to deposit almost any material that can be atomized to produce micron or submicron-sized carriers, i.e. liquid droplets. Such droplets may be in the form of liquid precursors, single-phase liquid solutions or colloidal suspensions of solid particles. Complex structures can be patterned by repeatedly depositing individual particles on the translated substrate. The techniques can operate over a wide range of particles sizes, from several nm to about one micron. So far, a variety of structures have been constructed on different substrates using metals, dielectrics, semiconductors, piezoelectric and ionic crystals, as well as living cells and proteins [2-7]. Unlike well-known optical trapping techniques, the laser-based direct-write techniques utilize optical
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