ChBE Seminar: Orlin Velev, North Carolina State University
Tuesday, March 5, 2019
2110 Chem/Nuc (bldg #90), UMD College Park
Speaker: Orlin Velev, ChBE Professor, North Carolina State University
Title: Design of novel functional soft matter by interfacial templating and multiphasic capillary binding
We will discuss the principles and applications of a rich variety of colloidal structures and materials made from multiphasic liquid-liquid-polymer systems. The capillary forces originating at the liquid/liquid interfaces can serve for reconfigurable binding in numerous soft matter systems, including Pickering emulsions, novel responsive capillary gels, and compositions for 3D printing. Alternatively, the liquid/liquid interfaces can template the formation of a variety of polymer nanomaterials, including nanoparticles, nanofibers, nanoribbons, microrods and microsheets. Both approaches present numerous opportunities for engineering of novel colloidal structures. We will first present responsive structures made of filaments from lipid-coated magnetic nanoparticles suspended in water-oil systems. The nanocapillary binding results in ultra-high filament flexibility. Similar principles can be used in the assembly of Janus and patchy particles and in the making of self-repairing magnetic gels. As an example of the application of such structures, we will discuss the development of new 3D printing inks consisting of water, crosslinked PDMS microbeads and liquid PDMS phase. These Homocomposite Thixotropic Pastes (HTPs) can be directly extruded and shaped on a 3D printer. The curing of the PDMS bridges yields remarkably elastic and flexible structures. The HTP-3DP inks are biocompatible and enable new opportunities for making of “active” and reconfigurable structures. We will next introduce a new class of soft dendritic polymer colloids (“dendricolloids”) that have a hierarchical morphology similar to molecular-scale polymer dendrimers, but two orders of magnitude larger in scale. The polymer particulate materials with branched and fractal morphology are fabricated by a simple and scalable process of polymer precipitation in turbulently sheared liquid media. The dendricolloids combine the properties of two of the most fascinating and studied soft matter systems – the freely-suspended dendritic particles have very large excluded volume, while in contact their nanofiber corona possesses the highly adhesive abilities of the nanofiber-padded gecko legs. The fractal branching and contact splitting phenomena of the polymer dendricolloids enable a range of highly unusual properties – gelation at very low volume fractions, strong adhesion to surfaces and to each other, and ability to bind strongly into coatings, nonwoven sheets, and ultrasoft membranes.
Orlin Velev is a Frank and Doris Culberson Distinguished Professor at NC State University. Dr. Velev received M.Sc. and Ph.D. degrees from the University of Sofia, Bulgaria, while also spending one year as a researcher in Nagayama Protein Array Project in Japan. After graduating in 1996, Velev accepted a postdoctoral position and later became research assistant professor at the Department of Chemical Engineering, University of Delaware. In 2001 formed his new research group in the Department of Chemical and Biomolecular Engineering, NC State University, where he was promoted to chaired professor in 2009.
Velev has contributed more than 200 publications, which have been cited more than 21,000 times, and has presented more than 245 invited presentations at major conferences and at universities, government institutes and companies. His awards include among many others NSF Career, NC State Alcoa Distinguished Engineering Research, NC State Alumni Distinguished Professor, NC State R.J. Reynolds Award for Excellence, AIChE Andreas Acrivos Award for Professional Progress and ACS Langmuir Lecturer. Velev has been elected to an ACS Fellow and MRS Fellow.
Velev has established a record of innovative research in the areas of colloids and nanostructures with electrical and photonic functionality, biosensors, microfluidics and nanomanufacturing. He has been the first to synthesize "inverse opals", one of the most widely studied types of photonic materials today. Velev has also pioneered techniques for making novel nanoparticle materials, Janus particles, rod-like particles, and responsive foams. Technologies based on his research have formed the basis of two Research Triangle Area startup companies. He has been an advocate of incorporating the latest achievements in the areas of nanoscience and nanotechnology in the engineering curriculum.