@article{kleinert_kim_velev_2012, title={Electric-Field-Controlled Flow in Nanoscale-Thin Wetting Films}, volume={28}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863050366&partnerID=MN8TOARS}, DOI={10.1021/la204774s}, abstractNote={A novel nanofluidic system based on electroosmotic flow in nanoscale-thin aqueous wetting films is reported. The water films formed spontaneously on mica substrates in a saturation humidity environment. The film thickness was determined to be a few tens of nanometers by optical interference and fluorescence intensity measurements and was consistent with a theoretical evaluation of the thickness of a film based on the competing forces of electrostatic repulsion and capillary pressure. Lateral flow was induced by applying a dc electric field tangential to the film and characterized by tracking the position of a fluorescent probe. The mobilities of the thin fluid layer and the flow marker were lower than the predictions of the electrokinetic theory, which may be a result of adsorption of the fluorescent molecules to the mica. Confinement of the film to two-dimensional "channels" was achieved by microcontact printing of patterned hydrophobic monolayers onto the substrate. This system has the advantage of simple and inexpensive fabrication in comparison to nanofluidic devices made by traditional lithography techniques.}, number={5}, journal={LANGMUIR}, author={Kleinert, Jairus and Kim, Sejong and Velev, Orlin D.}, year={2012}, month={Feb}, pages={3037–3044} }
 @article{kleinert_kim_velev_2010, title={Electric-Field-Assisted Convective Assembly of Colloidal Crystal Coatings}, volume={26}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78649279091&partnerID=MN8TOARS}, DOI={10.1021/la100119m}, abstractNote={A new technique that combines evaporative convective deposition of colloidal crystal coatings with an electric field to achieve more rapid assembly and reduce the defects in the crystal structure is reported. When an ac voltage is applied across the particle suspension and the substrate in the convective assembly process, a longer film spreads from the meniscus by the electrowetting-on-dielectric (EWOD) effect. The data suggest that the EWOD-increased liquid surface area results in increased evaporation-driven particle flux and crystal assembly that is up to five times more rapid. The extended drying film also provides more time for particle rearrangement before the structure becomes fixed, resulting in formation of crystal domains an order of magnitude larger than those deposited by convective assembly alone. The results demonstrate that EWOD is a facile tool for controlling particle assembly processes in wetting films. The technique could be used in improved large-scale colloidal crystal coating processes.}, number={12}, journal={LANGMUIR}, author={Kleinert, Jairus and Kim, Sejong and Velev, Orlin D.}, year={2010}, month={Jun}, pages={10380–10385} }
 @article{kim_barraza_velev_2009, title={Intense and selective coloration of foams stabilized with functionalized particles}, volume={19}, ISSN={["1364-5501"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349345796&partnerID=MN8TOARS}, DOI={10.1039/b908054f}, abstractNote={We report a new method for intense and selective coloring of foams stabilized by particles from cellulose derivatives. The addition of pH-sensitive dyes during the process of formation of hydrophobically modified cellulose (HMC) particles by a pH-jump leads to co-precipitation and strong adsorption of the pH-sensitive dyes on the cellulose particle surfaces at low pH. These strongly colored HMC particles not only act as strong stabilizers of the foams, but also allow their intense and selective coloration without any coloring of the solution medium. We characterized quantitatively the color intensity of these foams, analyzed the adsorption behavior of pH-sensitive dyes on the cellulose particles and showed that it follows well the Langmuir isotherm model. Lower pH of the media leads to stronger adsorption of the pH-sensitive dyes on the HMC particles due to the hydrophobic attraction under reduced electrostatic repulsion. The results illustrate how particle stabilizers can be used to impart additional functionality to foams and prepare dispersion systems of unusual properties.}, number={38}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Kim, Sejong and Barraza, Harry and Velev, Orlin D.}, year={2009}, pages={7043–7049} }
 @article{wege_kim_paunov_zhong_velev_2008, title={Long-term stabilization of foams and emulsions with in-situ formed microparticles from hydrophobic cellulose}, volume={24}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-51449120260&partnerID=MN8TOARS}, DOI={10.1021/la801634j}, abstractNote={We report a simple method to produce foams and emulsions of extraordinary stability by using hydrophobic cellulose microparticles, which are formed in situ by a liquid-liquid dispersion technique. The hydrophobic cellulose derivative, hypromellose phthalate (HP), was initially dissolved in water-miscible solvents such as acetone and ethanol/water mixtures. As these HP stock solutions were sheared in aqueous media, micron sized cellulose particles formed by the solvent attrition. We also designed and investigated an effective and simple process for making HP particles without any organic solvents, where both the solvent and antisolvent were aqueous buffer solutions at different pH. Consequently, the HP particles adsorbed onto the water/air or water/oil interfaces created during shear blending, resulting in highly stable foams or foam/emulsions. The formation of HP particles and their ability for short-term and long-term stabilization of interfaces strongly depended on the HP concentration in stock solutions, as well as the solvent chemistry of both stock solutions and continuous phase media. Some foams and emulsion samples formed in the presence of ca. 1 wt% HP were stable for months. This new class of nontoxic inexpensive cellulose-based particle stabilizers has the potential to substitute conventional synthetic surfactants, especially in edible, pharmaceutical and biodegradable products.}, number={17}, journal={LANGMUIR}, author={Wege, Hartmut A. and Kim, Sejong and Paunov, Vesselin N. and Zhong, Qixin and Velev, Orlin D.}, year={2008}, month={Sep}, pages={9245–9253} }