On-Chip Droplet and Particle Manipulation by Electric Fields: Application in Microbioassays and Microfluidic Device

Date: Wednesday September 26
Time: 3:30 pm
Place:Ross Hall Rm. 136

Orlin D. Velev
Department of Chemical and Biomolecular Engineering
North Carolina State University

Biography

Dr. Orlin Velev studies and develops nanostructures with electrical and photonic functionality, biosensors and microfluidic devices. He has been the first to synthesize "inverse opals", one of the most widely studied types of photonic materials today. He also pioneered principles for microscopic biosensors with direct electrical detection, discovered novel types of self-assembling microwires and designed new microfluidic chips. He 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 accepted a postdoctoral position with Profs. Eric Kaler and Abraham Lenhoff at the Dept. of Chemical Engineering, University of Delaware. He initiated there an innovative program in colloidal assembly and was promoted to research faculty in 1998. In 2001 formed his new research group as an assistant professor in the Dept. of Chemical Engineering, North Carolina State University, where he was promoted to an Associate Professor with tenure in 2006. He has contributed more than 90 publications, which have been cited more than 3300 times, and has presented more than 90 invited presentations at major conferences and at many universities and companies. Recent awards include NSF Career, Camille Dreyfus Teacher-Scholar, Sigma Xi, Ralph E. Powe, and others.

Abstract

On-Chip Droplet and Particle Manipulation by Electric Fields: Application in Microbioassays and Microfluidic Device
Dielectrophoresis, particle interaction with external AC fields, could be used to manipulate and assemble colloidal particles on any size scale. Examples of dielectrophoretic manipulation of nanoparticles, microparticles, live cells and droplets by planar electrodes will be presented. The structures that could be assembled on a chip include microwires from metallic nanoparticles, switchable photonic crystals, and biocomposite membranes from live cells. Two new applications of this method will be presented in detail. First, we will focus on a technique for electric field on-chip manipulation of freely suspended droplets and particles. Evaporation from water droplets leads to particle microseparation processes driven by Marangoni instabilities. The levitated droplets could serve as self-contained assembly templates and microreactors with controlled on-chip mixing, drying and polymerization. These droplet microfluidic chips could also serve as containers for microbioassays. Second, we will demonstrate how an additional level of complexity can be engineered to turn particles floating between the electrodes into prototypes of self-propelling micromachines and micropumps. Various types of miniature semiconductor diodes suspended in water propel themselves electroosmotically when a uniform alternating electric field is applied across the container. These diode "active particles" suggest rudimentary solutions to problems facing self-propelling microdevices, including harvesting power from external sources, internally controlled movement, and potential for a range of additional functions. We demonstrate how semiconductor diodes attached to the walls of microfluidic channels provide locally distributed pumping and mixing functions powered by a global external field.