Three-Dimensional Silicon Micromachining and Its Application in Cancer Diagnosis

Masoud Agah, Ph.D.,
Assistant Professor,
Bradley Department of Electrical and Computer Engineering,
Virginia Tech University

After a brief review of different research thrusts at VT MEMS Lab ( µGC, chip cooling, and bioMEMS), in the first part, we present a single-mask process based on reactive ion etching lag and its dependence on geometrical patterns which is capable of three-dimensional (3-D) design control for microfluidic structures. Predictable results are achieved by the development of a complex Langmuir model relating the exposed surface geometry to the depth and width of microfabricated channels. The technique is based on the most complex surface pattern to date, composed of five independent geometric variables and provides the capability for vast networks of microcapillary channels and large, low aspect ratio cavities to be created on the same wafer requiring a single SF6 etch step. In the second part, we present the response of normal human fibroblast cells and breast cancer cells, two key cell types in tumor microenvironments, to artificial 3D microenvironments fabricated in silicon using the aforementioned technique. In these microenvironments, breast cancer cells formed stable adhesions with the curved sidewalls while fibroblasts stretched and elongated their cytoskeleton. Statistical analysis revealed that fibroblast cells grew on both flat silicon surfaces and inside the microenvironments. However, the localization of breast cancer cells in these same substrates was dependent on the depth. After 72 hours in culture, less than 5% of the breast cancer cells grew on the flat surfaces of the chips containing microenvironments with depths of >75 µm. The distinct behavior of the two cell types can be attributed to their different biomechanical properties and can be used to isolate live populations of normal and cancer cells from breast tumor biopsy samples.
Masoud Agah received his B.S. and M.S. degrees in electrical engineering from Sharif University of Technology (SUT), Iran, in 1996 and 1998, respectively, and his Ph.D. degree from the University of Michigan, Ann Arbor, in 2005. He began his undergraduate studies in 1992 after being awarded by the President of Iran for achieving the first rank in the Nationwide Iranian University Entrance Examination. During his studies, he received numerous awards, including the Iranian Exemplary Graduate Student Honor, awarded by President Khatami in 1998.. In 2000, he joined the NSF Center for Wireless Integrated MicroSystems (WIMS ERC), University of Michigan, where he developed MEMS-based gas chromatography columns for environmental monitoring applications. He was the recipient of the 2nd place DAC/ISSCC Student Design Contest Award at the 40th Design Automation Conference, 2003. He joined the faculty of Virginia Tech in August 2005, where he is currently an assistant professor in the Bradley Department of Electrical and Computer Engineering with a courtesy appointment in the Department of Mechanical Engineering. He established the VT MEMS Laboratory in 2005 and has focused his research on environmental and biomedical applications of MEMS. Dr. Agah received the NSF CAREER Award in 2008 for his proposed work entitled, "gC Matrix, a Microsystem Approach for Complex Gas Analysis." He is a member of the Institute of Electrical and Electronic Engineers (IEEE), as well as its Electron Devices and its Solid-State Circuits Societies, and a member of the American Chemical Society (ACS).