ChBE Seminar Series: Robert F. Shepherd
Tuesday, April 3, 2012
11:00 a.m.-12:00 p.m.
Room 2110 Chemical and Nuclear Engineering Bldg.
Professor Srinivasa Raghavan
Engineering with Soft Matter: Bioscaffolds, Microfluidic Granulation, and Robots
Robert F. Shepherd
Elastomeric polymers, complex fluids, and granular media are typically soft (i.e., they are readily deformed at room temperature thermal energies). We have used the properties of these materials to create simple fabrication routes to sophisticated devices and machines (e.g., silicon microgears, bioscaffolds, and soft robots). Three fabrication routes that we have developed will be highlighted:
Direct Ink Writing of bioscaffolds. Currently, there is no practical method of fabricating 3D cell scaffolding with well defined, open architectures at the microscale. This limitation makes it difficult to deliver nutrients to supported cells, or remove waste accumulating around the cells. Additionally, precise control over pore size will be necessary to manage population growth during the division and differentiation of stem cells.We have designed solutions of entangled biopolymers that can be printed as 3D scaffolds with sub-micron feature sizes, and support the culture of a variety of cell types.
Microfluidic granulation. Micro/nano fabrication of ceramic and silicon components for optics, MEMS (e.g., microgears, accelerometers, and comb drives), and other emerging technologies (e.g., energy storage and flexible electronics) is typically performed by etching from bulk material. These etching processes are time consuming, prohibit control over internal nanostructure of the components, and require significant infrastructure/capital investment. We adapted a microfluidic technique (SFL) to optically pattern dense colloidal suspensions into arbitrary shapes. We patterned colloidal silica into microgears at rates of 100 Hz and converted the patterned microgears to silica glass or silicon via sintering or chemical reduction.
Soft lithography of robots. Advanced robots (e.g., Big Dog or PETMAN from Boston Dynamics) are typically comprised of complex assemblies of rigid components, requiring hundreds of custom designed parts that render these robots prohibitively expensive. Using only commercially available elastomers and simple soft lithography, we have fabricated open loop robotic manipulators that can grip and move delicate and irregularly shaped objects without damage, and mobile robots that can slither and crawl to navigate obstacles, as well as robots that can swim and jump.
About the Speaker
Robert Shepherd is a postdoctoral fellow at Harvard University, in the Whitesides Research Group. Prior to joining Harvards Department of Chemistry & Chemical Biology, Robert completed his undergraduate and graduate degrees (B.S. and Ph.D.) at University of Illinois, Urbana-Champaign in the Department of Materials Science. As a post-doctoral researcher, Robert has investigated manufacturing routes to soft robots, the effect of AC electric and static magnetic fields on flames, and using macroscopic, granular models of macromolecular (polymer) dynamics.While at Illinois, his graduate studies with Jennifer A. Lewis were focused on the Direct Ink Writing of complex fluids (e.g., entangled polymers and colloidal gels) and the microfluidic assembly of granular matter. His combined work in graduate and postdoctoral research has resulted in journal publications in PNAS, Adv. Mat., Soft Matter, Angew. Chem. Int. Ed., Langmuir, Current Opinion in Colloid and Interface Science (COCIS), and his work has been featured on BBC, CNN, WSJ, Scientific American's Top 50 Inventions (2008 & 2011), C&EN, and several other popular media outlets.