Research Interests

Research in Professor Tilton's group addresses biopharmaceutical formulations, microfluidic biotechnologies, and nanotechnologies for environmental remediation, as well as fundamental studies of the influence of surfaces on macromolecular structure, dynamics and function. These diverse applications are linked in the sense that each of them is controlled by interfacial physical chemistry. The following are examples of current projects.

Microfluidic Cell Sorting
Micropatterned electrode technologies are being developed to sort different cell types, vesicles and/or colloidal particles in microfluidic devices. Cells adopt particular locations in nonuniform fields based on a coupling of dielectrophoretic and electrohydrodynamic forces. In this way, cell mixtures can be sorted for diagnostic purposes on the basis of differences in their dielectric properties. These ideas are being extended to microfluidic bioreactors based on biofunctionalized colloids and vesicles.

Targeted Remediation of Chlorinated Solvent Residuals in Groundwater
Inspired by targeted drug delivery technologies, we are developing polymer-functionalized iron nanoparticles that transport through microporous aquifers and preferentially accumulate at the interface between water and chlorinated organic solvent residuals. This effectively concentrates the contaminant remediation at the underground source, promising more rapid decontamination than current "pump and treat" technologies can offer.

PEG-Modified Proteins
The pharmaceutical efficacy of many protein therapeutics is significantly enhanced by grafting poly(ethylene glycol) chains to the proteins. We are investigating how PEG modification alters the underlying colloidal and interfacial behaviors of proteins and using the information to optimally formulate PEG-proteins for sustained release drug delivery.

Representative Publications

S.B. Velegol, R.D. Tilton, "A Connection between Interfacial Self-Assembly and the Inhibition of Hexadecyltrimethylammonium Bromide Adsorption on Silica by Poly- L -lysine," Langmuir 17 , 219 (2001).

M.L. Sun, R.D. Tilton "Coadsorption of Protein/Surfactant Complexes to the Air/Water Interface," Colloids and Surfaces B: Biointerfaces 20 , 281 (2001).

A.D. Braem , D.C. Prieve, R.D. Tilton, "Electrostatically Tunable Coadsorption of Sodium Dodecylsulfate and Poly(Ethylene Oxide)-b-Poly(Propylene Oxide)-b-Poly(Ethylene Oxide) Triblock Copolymer to Silica," Langmuir 17 , 883 (2001).

B.B. Luokkala, S. Garoff, R.D. Tilton, R.M. Suter, "Interfacial Structure and Rearrangement of Nonionic Surfactants near a Moving Contact Line," Langmuir 17 , 5917 (2001).

V. Brisson, R.D. Tilton, "Self-Assembly and Two-Dimensional Patterning of Cell Arrays by Electrophoretic Deposition," Biotechnology and Bioengineering 77 , 290-295 (2002)

S.B. Velegol, R.D. Tilton, "Specific Counterion Effects on the Competitive Co-Adsorption of Polyelectrolytes and Ionic Surfactants," Journal of Colloid and Interface Science 249 , 282-289 (2002).

E.A.S. Doherty, K.D. Berglund, B.A. Buchholz, I.V. Kourkine, T.M. Przybycien, R.D. Tilton, A.E. Barron, "Critical Factors for High-Performance Physically Adsorbed (Dynamic) Polymeric Wall Coatings for Microchannel Electrophoresis of DNA," Electrophoresis 23 , 2766-2776 (2002).

K.D. Berglund, A. Timko, T.M. Przybycien, R.D. Tilton, "Use of Nonionic Ethylene Oxide Surfactants as Phase Transfer Catalysts for Poly(Acrylic Acid) Adsorption to Silica against an Electrostatic Repulsion," Progress in Colloid and Polymer Science 122 , 56-66 (2003).

K.D. Berglund, T.M. Przybycien, R.D. Tilton, "Coadsorption of Sodium Dodecylsulfate with Hydrophobically Modified Nonionic Cellulose Polymers I: Role of Polymer Hydrophobic Modification," Langmuir 19 , 2705-2713 (2003).

K.D. Berglund, T.M. Przybycien, R.D. Tilton, "Coadsorption of Sodium Dodecylsulfate with Hydrophobically Modified Nonionic Cellulose Polymers II: Role of Surface Selectivity in Adsorption Hysteresis," Langmuir 19 , 2714-2721 (2003).

A.D. Braem, S. Biggs, D.C. Prieve, R.D. Tilton, Control of Persistent Nonequilibrium Adsorbed Polymer Layer Structure by Transient Exposure to Surfactants," Langmuir 19 , 2736 (2003).

S. Daly, T.M. Przybycien, R.D. Tilton, "Coverage Dependent Orientation of Lysozyme Adsorbed on Silica," Langmuir 19 , 3848 (2003).

N. Kumar, K. Varanasi, R.D. Tilton, S. Garoff, "Surfactant Self-Assembly ahead of the Contact Line on a Hydrophobic Surface and its Implications for Wetting," Langmuir 19 , 5366 (2003).

E. J. Choi, M.D. Foster, S. Daly, R. Tilton, T. Przybycien, C.F. Majkrzak, P. Witte, H. Menzel, "Effect of Flow on Human Serum Albumin Adsorption to Self-Assembled Monolayers of Varying Packing Density, " Langmuir 19 , 5464 (2003).

K. D. Berglund, M. T. Truong, R. D. Tilton and L. M. Walker, "Rheology of Transient Networks Containing Hydrophobically Modified Cellulose, Anionic Surfactant and Colloidal Silica: Role of Selective Adsorption," Rheol. Acta 43, 50 - 61 (2004)

O.J. Rojas, P.M. Claesson, K.D. Berglund, and R.D. Tilton, "Coadsorption and Surface Forces for Selective Surfaces in Contact with Aqueous Mixtures of Oppositely Charged Surfactants and Low Charge Density Polyelectrolytes," Langmuir , 20 , 3221-3230 (2004).

N. Kumar , S. Garoff, and R.D. Tilton, "Experimental Observations on the Scaling of Adsorption Isotherms for Nonionic Surfactants at a Hydrophobic Solid-Water Interface," Langmuir 20 , 4446-4451 (2004).

N. Kumar and R.D. Tilton, "A Unified Model to Predict Self-Assembly of Nonionic Surfactants in Solution and Adsorption on Solid or Fluid Hydrophobic Surfaces: Effect of Molecular Structure," Langmuir 20, 4452-4464 (2004).

I.N. Nnebe, R.D. Tilton, and J.W. Schneider, "Direct Measurement of the Stability of Poly(ethylene glycol)-Poly(ethylenimine) Graft Films," Journal of Colloid and Interface Science 276 , 306-316 (2004).

Y.Liu, S. Majetich, K. Matyjaszewski, R.D. Tilton, D. Sholl, and G.V. Lowry, "TCE Dechlorination Rates, Pathways, and Efficiency of Nanoscale Iron Particles with Different Properties," Environmental Science and Technology , 39 , 1338-1335 (2005).

S. Daly, T.M. Przybycien, and R.D. Tilton, "Adsorption of poly(ethylene glycol) modified lysozyme to silica," Langmuir 21 , 1328-1337 (2005).

H. Zhou, M.A. Preston, R.D. Tilton, and L.R. White, "Calculation of the electric polarizability of a charged spherical dielectric particle by the theory of colloidal electrokinetics," Journal of Colloid and Interface Science 285 , 845-856 (2004).

H. Zhou, L.R. White and R.D. Tilton, "Lateral separation of colloids or cells by dielectrophoresis augmented by AC electroosmosis," Journal of Colloid and Interface Science 285 , 179-191 (2005).