Opto-electric Droplet and Particle Physics

Steve Wereley, Professor, Mechanical Engineering, Purdue University

  • Room 223, Institute of Cyber-Systems & Control
  • 10:30 A.M., Nov 22, 2016

Recently my research group in the Microfluidics Laboratory at Purdue University has harnessed the power of light and electric fields to develop several novel ways for non-contact manipulation of droplets and particles with potential applications in the bio/medical/chemical/pharma industries. These are generally described as opto/electric droplet manipulation and opto/electric particle manipulation. I will present the fundamental principles behind these methods, what their capabilities are, and what their potential uses are.

Opto/electric droplet manipulation: using lasers and electric fields we can control and manipulate individual droplets to perform assays and other chemical operations. This method is similar to opto-electrowetting (OEW or EWOD) except that the “electrodes” used for the droplet manipulation are virtual electrodes whose locations are defined by dynamic laser light patterns rather than fixed, unmovable conventional electrodes.

Opto/electric particle manipulation: using lasers and electric fields we can capture, concentrate, manipulate and sort populations of micro- and nanometer-scaled “particles”. These “particles” range in size from single molecules (DNA, proteins, etc.) to nanoparticles (quantum dots, carbon nanotubes, nano-scaled polystyrene latex beads, etc.) to complex biological organisms (bacteria, mammalian cells, etc.). This novel technique called Rapid Electrokinetic Patterning (REP) combines features of optical trapping (OT) and dielectrophoresis (DEP) in an innovative, dynamic way using a simple parallel plate electrode configuration. Transparent Indium Tin Oxide (ITO) electrodes on glass substrates apply an electric field to the fluid carrying the particles but also to allow light into and out of the fluid. Near-IR laser illumination causes subtle localized heating, creating an electric permittivity gradient that in turn drives a global microscopic toroidal vortex. The vortex efficiently transports particles to a preferred location, usually the surface of the electrode where they are non-permanently collected. They can then be released or permanently fixed in place by the application of a low frequency electric field.


Professor Wereley completed his masters and doctoral research at Northwestern University. He joined the Purdue University faculty in August of 1999 after a two-year postdoctoral appointment at the University of California Santa Barbara. During his time at UCSB he worked with a group developing, patenting, and licensing to TSI, Inc., the micro-Particle Image Velocimetry technique. His current research interests include opto/electrokinetics, investigating microscopic biological flows, harnessing diffusion for sensing applications, and developing new ways of measuring flows at the smallest length scales. Professor Wereley is the co-author of Fundamentals and Applications of Microfluidics (Artech House, 2002 and 2006) and Particle Image Velocimetry: A Practical Guide (Springer, 2007). He is on the editorial board of Experiments in Fluids and is an Associate Editor of Springer’s Microfluidics and Nanofluidics. Professor Wereley has edited Springer’s recent Encyclopedia of Microfluidics and Nanofluidics and Kluwer’s BioMEMS and Biomedical Nanotechnology.