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Research Abstracts Online
January 2009 - March 2010

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University of Minnesota Twin Cities
Institute of Technology
Department of Chemical Engineering and Materials Science

PI: Michael Tsapatsis
Co-PI: Satish Kumar

Colloidal Lithography via Silica Sol Adsorption at Charged Surfaces

Colloidal adsorption at electrostatically charged and charge-patterned surfaces is a fundamental process whose applications include optical coatings, separation membranes, environmental remediation, and biological imaging. Electrostatic repulsion and attraction between surfaces are central phenomena in most aqueous systems, while van der Waals and Brownian forces also play a role in many cases. These researchers incorporate these interactions amongst colloidal particles and the adsorbing surface in a dynamic simulation methodology. Experimental observations at a series of electrostatic screening strengths were used as a basis of comparison with simulations, and the researchers found that adjustment of the colloid and surface charge characteristics enabled them to quantitatively match the coverage and achieve qualitative agreement with the pair distance distribution between adjacent particles. Discrepancies in the structural characterization were attributed to drying effects following the adsorption process.  Additional simulations of adsorption to charge-patterned surfaces revealed that the local "lattice parameter” of ordered structures would decrease when confined in two-dimensional regions, or result in transition to disordered structures.

Group Members

Nicole Atchison, Graduate Student
M.A. Arunagirinathan, Visiting Researcher
Damien Brewer, Graduate Student
Leon Cassidy, Undergraduate Student
Bahman Elyassi, Visiting Researcher
Wei Fan, Visiting Researcher
Missy Gettel, Undergraduate Student
Xuefeng Guo, Visiting Researcher
Parveen Kumar, Visiting Researcher
Sandeep Kumar, Graduate Student
J. Alex Lee, Graduate Student
Dongxia Liu, Visiting Researcher
Milan Kanti Naskar, Visiting Researcher
Pyung-Soo Lee, Graduate Student
Sudeep Maheshwari, Graduate Student
Elizabeth Mallon, Graduate Student
Aruna Ramkrishnan, Graduate Student
Chun-Yi Sung, Visiting Researcher
Rajiv Ranjan, Graduate Student
Joshua Sheffel, Graduate Student
Jared Stoeger, Graduate Student
Ana Torres, Graduate Student
Virany Yuwono, Visiting Researcher
Varun Kumar, Graduate Student
Jim Wydra, Graduate Student
Xueyi Zhang, Graduate Student