Jairus Kleinert

PhD, Chemical Engineering, 2013
North Carolina State University

M.S., Chemical Engineering, 2008
North Carolina State University

B.S., Chemical Engineering, 2006
Michigan State University, East Lansing, Michigan

Research Focus: Assembly and Manipulation of Particles and Molecules in Thin Wetting Films Using Electric Fields

Our work is focused on electric field control of flow in thin wetting films to assemble colloidal structures and characterize individual molecules. We have developed an enhanced method for colloidal crystal coating deposition by convective assembly in an electric field. The primary effect of the electric field is electrowetting on dielectric, which extends the length of the liquid film in which particles are packed into a crystal structure. Film extension increases the evaporation-driven flux of particles to the growing crystal and allows more space for particle rearrangement to form more uniform crystals. We have observed a six-fold increase in the crystal assembly rate and an order of magnitude increase in crystal domain size with this new method compared to convective assembly without an electric field.

Figure 1: Graph of increasing colloidal crystal coating thickness with applied voltage (left) and images of crystal domains formed with and without applied voltage (right), demonstrating advantages of our method of convective assembly in an electric field.

We have also developed a novel nanofluidic system based on flow in aqueous wetting films less than 100 nm thick. Flow in the films is driven by electroosmosis and is readily controlled by modulating the electric field polarity and intensity. Film flow can be directed along defined pathways by microcontact printing of hydrophobic silane patches on the substrate. We plan to apply this nanofluidics methodology to study the effects of confinement and electric field actuation on polymer brush monolayers and to demonstrate transporting, positioning, and stretching of individual DNA molecules.

Figure 2: Images of flow of a fluorescent marker in a nanoscale thin wetting film observed by fluorescent (left and right) and reflective (center) microscopy. The film is too thin to be seen optically without a fluorescent marker. The left and center images are of the same area.


Kleinert, J.; Kim, S.; Velev, O. D. Electric-field-assisted convective assembly of colloidal crystal coatings. Langmuir 2010, 26, 10380–10385.