Investigation of phase change, liquid flow, and heat transfer during laser micromachining

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ABSTRACTNational Science FoundationProposal Number: CTS-0500401Principal Investigator: Willis, David A.Affiliation: Southern Methodist UniversityProposal Title: Investigation of phase change, liquid flow, and heat transfer during laser micromachiningThis research program is a combined experimental and mathematical modeling effort that will investigate thermal-fluid processes during laser micromachining. Laser melting of thin films on a substrate induce surface-tension driven flows that can result in the formation of holes in the film. The laser-induced hole formation process is useful for micromachining, with applications to micro- and nano-technology. Two closely related sets of problems are addressed. The first one involves a model of fluid motion in the thin film of molten metal. The flow is coupled to evaporation from the surface and heat losses to the substrate. The proposed model will address the motion of the contact line formed on the substrate, as well as re-solidification in the film after the laser pulse ends. In addition, computation of the time scales of heat/mass transfer and estimates of the range of values of laser intensities appropriate for particular applications, i.e. the process window, will result in optimizing the micromachining procedures. Time resolved experiments with nanosecond resolution will be conducted to verify different aspects of the mathematical model, such as the time scale of melting and melt flow processes. The second set of problems involves lasers focused on the boundary between the film and the substrate. This configuration is used for laser induced forward transfer, in which material is ejected from a heated thin film for micro- and nano-particle deposition. Theoretical studies of laser induced forward transfer will provide reliable estimates of the sizes of particles deposited on the acceptor substrate for a range of values of laser intensities and material properties of the film. The proposed project will promote learning through research and interdisciplinary scientific collaborations between the Department of Mathematics and the Department of Mechanical Engineering. Under-represented groups will be recruited in the research program, both at the graduate and undergraduate level by working with two programs at SMU, the Gender Parity Initiative and Minority Recruitment Initiative. The PIs will use these initiatives to advertise research positions, in order to ensure that under-represented groups have the opportunity to apply to the PI's research program.