ABSTRACT P.I.: Ain Sonin MIT CTS-9413026 Objects, materials or components may be built up by precise deposition and solidification of molten microdrops under controlled thermal conditions. This provides a means of true "digital micro-fabrication" or fabrication of 3D objects or materials in microdrop units under complete computer control, much in the same way that 2D hard copy is obtained by ink-jet printing. Shape can in principle be controlled accurately, properties can be tailored via the choice of melt materials, droplet size and thermal conditions, and there is no waste. Numerous applications are conceivable: rapid prototyping, customized parts produced directly under computer control, materials or parts with continuously varying or heterogeneous properties to meet special needs, etc. Particularly interesting possibilities arise in electronics packaging. Customized 3D microcircuits could in principle be fabricated, complete with simple components like resistors and with protective insulation. The purpose of the present research is to develop, via experimentation and theoretical modeling, a fundamental knowledge base for precise dropwise deposition and solidification at the microscale. This has until recently been a largely unresearched field. In this one year project, experiments will be performed which will lead to a basic understanding of the solidification angle in microscase melt deposition on subcooled targets. Insofar as discoveries permit, the results will be expressed in terms of universal scaling laws, and the physical processes controlling solidification will be identified. The second objective is to provide a theory for instabilities observed in earlier work on sweep deposition of beads on molten material onto substrate materials.
