@article{chang_ucar_swindlehurst_bradley_renk_velev_2009, title={Materials of Controlled Shape and Stiffness with Photocurable Microfluidic Endoskeleton}, volume={21}, ISSN={["1521-4095"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67651108709&partnerID=MN8TOARS}, DOI={10.1002/adma.200803638}, number={27}, journal={ADVANCED MATERIALS}, author={Chang, Suk Tai and Ucar, Ahmet Burak and Swindlehurst, Garrett R. and Bradley, Robert O., IV and Renk, Frederick J. and Velev, Orlin D.}, year={2009}, month={Jul}, pages={2803-+} }
 @article{chang_beaumont_petsev_velev_2008, title={Remotely powered distributed microfluidic pumps and mixers based on miniature diodes}, volume={8}, ISSN={["1473-0189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-37349032809&partnerID=MN8TOARS}, DOI={10.1039/b712108c}, abstractNote={We demonstrate new principles of microfluidic pumping and mixing by electronic components integrated into a microfluidic chip. The miniature diodes embedded into the microchannel walls rectify the voltage induced between their electrodes from an external alternating electric field. The resulting electroosmotic flows, developed in the vicinity of the diode surfaces, were utilized for pumping or mixing of the fluid in the microfluidic channel. The flow velocity of liquid pumped by the diodes facing in the same direction linearly increased with the magnitude of the applied voltage and the pumping direction could be controlled by the pH of the solutions. The transverse flow driven by the localized electroosmotic flux between diodes oriented oppositely on the microchannel was used in microfluidic mixers. The experimental results were interpreted by numerical simulations of the electrohydrodynamic flows. The techniques may be used in novel actively controlled microfluidic-electronic chips.}, number={1}, journal={LAB ON A CHIP}, author={Chang, Suk Tai and Beaumont, Erin and Petsev, Dimiter N. and Velev, Orlin D.}, year={2008}, pages={117–124} }
 @article{cayre_chang_velev_2007, title={Polyelectrolyte diode: Nonlinear current response of a junction between aqueous ionic gels}, volume={129}, ISSN={["1520-5126"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35948967966&partnerID=MN8TOARS}, DOI={10.1021/ja072449z}, abstractNote={We demonstrate that a fixed junction between two aqueous gels containing oppositely charged polyelectrolytes could rectify electric current. The agarose-based gels were "doped" with sodium poly(styrene sulfonic acid) and poly(diallyl dimethylammonium chloride). The unidirectional current response of the interface between the cationic and anionic gels originates directly from anisotropy in the mobile ionic charges in the gels. The current depends on the concentration of polyelectrolyte, the background ionic concentration, and the distance traveled by the ions. The I-V curves from the devices demonstrated a combination of transient and stationary rectification effects. The current densities achieved were comparable to or higher than those obtained with previously reported organic semiconductor diodes. The diodes had good long-term stability in both DC and AC conduction modes. The materials and the process of preparation of these devices are simple, inexpensive, and scalable. They could be used in flexible and biocompatible electronic circuits.}, number={35}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Cayre, Olivier J. and Chang, Suk Tai and Velev, Orlin D.}, year={2007}, month={Sep}, pages={10801–10806} }
 @article{chang_paunov_petsev_velev_2007, title={Remotely powered self-propelling particles and micropumps based on miniature diodes}, volume={6}, ISSN={["1476-4660"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33847678889&partnerID=MN8TOARS}, DOI={10.1038/nmat1843}, number={3}, journal={NATURE MATERIALS}, author={Chang, Suk Tai and Paunov, Vesselin N. and Petsev, Dimiter N. and Velev, Orlin D.}, year={2007}, month={Mar}, pages={235–240} }
 @article{chang_velev_2006, title={Evaporation-induced particle microseparations inside droplets floating on a chip}, volume={22}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33644552476&partnerID=MN8TOARS}, DOI={10.1021/la052695t}, abstractNote={We describe phenomena of colloidal particle transport and separation inside single microdroplets of water floating on the surface of dense fluorinated oil. The experiments were performed on microfluidic chips, where single droplets were manipulated with alternating electric fields applied to arrays of electrodes below the oil. The particles suspended in the droplets were collected in their top region during the evaporation process. Experimental results and numerical simulations show that this microsepration occurs as a result of a series of processes driven by mass and heat transfer. An interfacial tension gradient develops on the surface of the droplet as a result of the nonuniform temperature distribution during the evaporation. This gradient generates an internal convective Marangoni flow. The colloidal particles transported by the flow are collected in the top of the droplets by the hydrodynamic flux, compensating for evaporation through the exposed top surface. The internal flow pattern and temperature distribution within evaporating droplets were simulated using finite element calculations. The results of the simulation were consistent with experiments using tracer particles. Such microseparation processes can be used for on-chip synthesis of advanced particles and innovative microbioassays.}, number={4}, journal={LANGMUIR}, author={Chang, ST and Velev, OD}, year={2006}, month={Feb}, pages={1459–1468} }