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Staszel C.,University of Illinois at Chicago | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | Sinha-Ray S.,Indian Institute of Technology Indore | And 2 more authors.
Polymer (United Kingdom) | Year: 2017

In this work, the adhesion energies of two dissimilar polymer films after thermal bonding are studied. The films were formed from the emulsions of polycaprolactone (PCL) and nylon-6 (N6) spin-coated onto metal substrates. After that, the solidified blend polymer films on the metal substrates were faced with additional PCL films on metal substrates and thermally bonded to them. The surface structure of blend films was elucidated prior to thermal bonding by staining them using Rhodamine B. The dye stained only N6 leaving PCL undyed and the exposed structure was analyzed using digital photography, which revealed the surface concentration of PCL, as well as the N6 and PCL distributions over the surfaces. It was discovered that PCL-N6 domains would remain partially mixed, influencing the adhesion energy measured. © 2017 Elsevier Ltd


Kolbasov A.,University of Illinois at Chicago | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | Sinha-Ray S.,Indian Institute of Technology Indore | And 2 more authors.
Journal of Membrane Science | Year: 2017

Nanofiber membranes containing such biopolymers as lignin, oats, soy protein, sodium alginate and chitosan used in this work were formed by solution blowing. The heavy metal adsorption on these membranes from aqueous solutions was studied in equilibrium in the batch experiments, as well as under the throughflow conditions. The mechanical properties of nylon-6-based biopolymer-containing membranes important under the throughflow conditions were also evaluated using tensile tests. A novel model of metal adsorption in the throughflow experiments was also proposed here and verified by the successful comparison with the present experimental data. The results revealed attractive capabilities of these inexpensive nano-textured biopolymer adsorbents formed from waste materials using the process scalable to the industrial level. The results also elucidated the physico-chemical mechanisms of heavy metal adsorption on biopolymers. © 2017 Elsevier B.V.


Zupancic S.,University of Illinois at Chicago | Zupancic S.,University of Ljubljana | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | And 4 more authors.
Molecular Pharmaceutics | Year: 2016

Nanofibers represent an attractive novel drug delivery system for prolonged and controlled release. However, sustained release of hydrophilic drugs, like ciprofloxacin hydrochloride (CIP), from polymeric nanofibers is not an easy task. The present study investigates the effect of different hydrophobic polymers (PCL and PMMA) alone in monolithic nanofibers or with hydrophilic polymers (PVA, PEO, and chitosan) in blended nanofibers aiming to achieve sustained CIP release. CIP release from PCL nanofibers was 46% and from PMMA just 1.5% over 40 day period. Thus, PMMA holds great promise for modification of CIP release from blended nanofibers. PMMA blends with 10% PEO, PVA, or chitosan were used to electrospin nanofibers from solution in the mixture of acetic and formic acid. These nanofibers exhibited different drug-release profiles: PEO containing nanofiber mats demonstrated high burst effect, chitosan containing mats revealed very slow gradual release, and PVA containing mats yielded smaller burst effect with favorable sustained release. We have also shown that gradual sustain release of antibiotic like CIP can be additionally tuned over 18 days with various blend ratios of PMMA with PVA or chitosan reaching almost 100%. A mathematical model in agreement with the experimental observation revealed that the sustained CIP release from the blended nanofibers corresponded to the two-stage desorption process. © 2015 American Chemical Society.


Zupancic S.,University of Illinois at Chicago | Zupancic S.,University of Ljubljana | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | And 4 more authors.
Molecular Pharmaceutics | Year: 2016

Sustained controlled drug release is one of the prominent contributions for more successful treatment outcomes in the case of several diseases. However, the incorporation of hydrophilic drugs into nanofibers, a promising novel delivery system, and achieving a long-term sustained release still pose a challenging task. In this work we demonstrated a robust method of avoiding burst release of drugs and achieving a sustained drug release from 2 to 4 weeks using core-shell nanofibers with poly(methyl methacrylate) (PMMA) shell and monolithic poly(vinyl alcohol) (PVA) core or a novel type of core-shell nanofibers with blended (PVA and PMMA) core loaded with ciprofloxacin hydrochloride (CIP). It is also shown that, for core-shell nanofibers with monolithic core, drug release can be manipulated by varying flow rate of the core PVA solution, whereas for core-shell nanofibers with blended core, drug release can be manipulated by varying the ratios between PMMA and PVA in the core. During coaxial electrospinning, when the solvent from the core evaporates in concert with the solvent from the shell, the interconnected pores spanning the core and the shell are formed. The release process is found to be desorption-limited and agrees with the two-stage desorption model. Ciprofloxacin-loaded nanofiber mats developed in the present work could be potentially used as local drug delivery systems for treatment of several medical conditions, including periodontal disease and skin, bone, and joint infections. © 2016 American Chemical Society.


Sahu R.P.,University of Illinois at Chicago | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | Sinha-Ray S.,Indian Institute of Technology Indore | And 2 more authors.
International Journal of Heat and Mass Transfer | Year: 2016

Pool boiling of Novec 7300 fluid and self-rewetting water-heptanol mixtures on bare copper surface and a copper surface coated with copper-plated nanofibers is studied experimentally. The experimental data revealed a significant increase in the heat removal rate up to the critical heat flux (CHF) on the copper-plated nanofiber surfaces in comparison with bare copper surfaces. Also, the critical heat flux increases on the copper-plated nanofiber surface, albeit it is reached at a lower surface superheat in comparison with bare copper surface. Prolong boiling in water facilitates oxidation of the layer of copper-plated nanofibers, and diminishes its roughness, albeit does not affect the heat transfer rate. © 2015 Elsevier Ltd. All rights reserved.


Kim D.-Y.,Korea University | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | Park J.-J.,Korea University | And 9 more authors.
Advanced Functional Materials | Year: 2014

The industrial scale application of graphene and other functional materials in the field of electronics has been limited by inherent defects, and the lack of simple deposition methods. A simple spray deposition method is developed that uses a supersonic air jet for a commercially available reduced graphene oxide (r-GO) suspension. The r-GO flakes are used as received, which are pre-annealed and pre-hydrazine-treated, and do not undergo any post-treatment. A part of the considerable kinetic energy of the r-GO flakes entrained by the supersonic jet is used in stretching the flakes upon impact with the substrate. The resulting "frozen elastic strains" heal the defects (topological defects, namely Stone-Wales defect and C2 vacancies) in the r-GO flakes, which is reflected in the reduced ratio of the intensities of the D and G bands in the deposited film. The defects can also be regenerated by annealing. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Sahu R.P.,University of Illinois at Chicago | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | Sinha-Ray S.,Indian Institute of Technology Indore | And 2 more authors.
International Journal of Heat and Mass Transfer | Year: 2015

Pool boiling of ethanol, water and their binary mixtures on nano-textured surfaces comprised of copper-plated nanofibers was studied experimentally. The nanofiber-covered surfaces were formed using polymer nanofibers produced by the electrically-assisted supersonic solution blowing process followed by copper-plating. The pool boiling data on the nano-textured surfaces did not follow the standard boiling curve and showed a sharp deviation. In particular, the heat flux and accordingly, the heat transfer coefficient, were found to be significantly higher at low surface superheats. It was also demonstrated that the nano-textured surfaces developed in the present work are robust and do not deteriorate after several cycles of pool boiling experiments. The process features uncovered in the present experiments are attractive for cooling of high-power microelectronics. A novel theoretical approach to pool boiling modeling introduced in this work revealed several detailed morphologies of fluid motion in the pool boiling process observed experimentally. © 2015 Elsevier Inc. All rights reserved.


Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | Sinha-Ray S.,Indian Institute of Technology Indore | Yarin A.L.,University of Illinois at Chicago | And 2 more authors.
Journal of Membrane Science | Year: 2015

In this work filtration efficiency of commercially available filter media with fiber/pore sizes of the scale of 10. μm is dramatically increased by not only adding electrospun nanofibers, as is usually done, but also a layer of ultrafine supersonically blown 20-50. nm nanofibers. Three different commercially available base filters were modified with (i) electrospun nanofibers alone, (ii) solution-blown 20-50. nm nanofibers alone, and (iii) the dual coating with electrospun nanofibers deposited first and the solution-blown 20-50. nm nanofibers deposited on top of them. Detailed observations of nanoparticle removal by these base and the above-mentioned modified filters revealed that the filters with dual electrospun nanofibers (deposited first) and the solution-blown 20-50. nm nanofibers deposited on top of them are the most effective in removing the below-200. nm Cu nanoparticles/clusters from aqueous suspensions. Experiments were conducted in two different time ranges: (a) for 8-15. s, and (b) for 8. min. It was found that the efficiency of the dual-coated filters containing 20-50. nm fibers was significantly higher than those of the others at the lowest nanoparticle concentrations of 0.2-0.5. ppm in suspension. The experiments conducted for longer time revealed that the smallest nanofibers were as efficient in particle retention as in the shorter-time experiments, and there was no visible breakage pattern of these nanofibers. The theory developed in the present work explains and describes how the smallest solution-blown nanofibers introduce a novel physical mechanism of nanoparticle interception (the attractive van der Waals forces) and become significantly more efficient collectors compared to the larger electrospun nanofibers. The theory predicts the domain of nanoparticle collection due to the van der Waals forces. The theory also elucidates the morphology of the nanoparticle clusters being accumulated at the smallest nanofiber surfaces, including the clusters growing at the windward side, or in some cases also on the leeward side of a nanofiber. © 2015 Elsevier B.V.


Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | Sinha-Ray S.,Indian Institute of Technology Indore | Yarin A.L.,University of Illinois at Chicago | And 2 more authors.
Polymer (United Kingdom) | Year: 2015

This work describes a comprehensive numerical model of solution blowing process of multiple three-dimensional polymer jets issued from a die nosepiece into a high-speed air flow and deposited onto a moving screen. The model solves the quasi-one-dimensional equations of the mechanics of free liquid jets with the jet axis configuration being three-dimensional. It accounts for the polymer solution viscoelasticity, jet interaction with the surrounding high-speed air flow, and solvent evaporation and jet solidi fication. The results include the polymer jet configurations in flight as well the detailed information on the pattern in which the oncoming polymer jets are deposited on the moving screen (the so-called lay-down), and its characteristics, in particular, the fiber-size distributions obtained under different conditions. The work also describes experiments on solution blowing and comparison of the numerical and experimental data. © 2014 Elsevier Ltd. All rights reserved.


Sett S.,University of Illinois at Chicago | Sahu R.P.,University of Illinois at Chicago | Sinha-Ray S.,University of Illinois at Chicago | Sinha-Ray S.,Corporate Innovation Center | And 3 more authors.
Electrochimica Acta | Year: 2016

Gravitational drainage of vertical films of ionic surfactants supported on a frame with the upper and lower parts being electrodes is studied experimentally. The electric field introduces three additional physical phenomena: (i) the surface charge redistribution, which eventually changes surface elasticity, (ii) the electroosmotic flow in the diffuse layer, and (iii) pressure build-up near the electrode toward which the electroosmotic flow is directed. It is shown that stabilization of the films is possible either due to the traction imposed by the electroosmotic flow directed upward (against gravity), or due to the pressure build-up near the lower end of the frame, in cases where the electroosmotic flow is directed downward (in the gravity direction) and enters a dead end at the lower electrode. © 2015 Elsevier Ltd. All rights reserved.

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