Oceanside, CA, United States
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Kiruthika S.,Jawaharlal Nehru Centre for Advanced Scientific Research | Kulkarni G.U.,Soft Science
Solar Energy Materials and Solar Cells | Year: 2017

Indoor light control using thermotropic materials is an active area of research. While active materials are available to switch transmittance with temperature, large area heaters with desired transparency are not easily affordable. In this paper, the fabrication of thermochromic devices using inexpensive Sn mesh electrodes (5 Ω/□, transmission, 80%) produced by crackle lithography with hydroxypropyl methyl cellulose (HPMC) as active material is reported. When laminated and coated on the inner surface of a PET window (8×8 cm2), the mesh served as a transparent heater to cause gelation in HPMC at ~40 °C to switch from water-clear transparency to paper-white opaqueness with 1 mm thickness of the active layer. The power consumption was only 0.2 W/cm2. Few drops of a color ink produced interesting effects in this smart window prototype. © 2017


Sarkar D.,Indian Institute of Science | Singh A.K.,Soft Science
Journal of Physical Chemistry C | Year: 2017

Nonvolatile resistive switching based resistive-random-access-memory (RRAM) is evolving rapidly among various other nanoscaled-semiconductor technologies. In this article, resistive switching mechanism in a solution-route-processed ZnO/α-Fe2O3 core-shell n-n heterojunction nanorods (NRs) is investigated for the first time. As fabricated nanostructured electrode shows resistive switching with compelling ON/OFF ratio at a significantly small reverse bias voltage (-0.55 V). Moreover, this core-shell nanorod-based resistive-switch exhibits an excellent time-retention (with relaxation constant (α) ∼ -0.0065 even after ∼103 s) and endurance (with a minute change in switching potential after 100 switching cycles). Resistive switching in this core-shell nanorods system arises due to the tuning of band-alignment at the heterojunction interface governed by fast and reversible migration of charge/ionic species on either side of the interface under reverse-bias condition, facilitating electron tunneling across the interface as supported by experimental observations, together with highly nonlinear dependency of the drift velocities of oxygen-vacancies on applied potential bias. Such understanding behind the high-degree and energy-efficient nonvolatile resistive switching in ZnO/α-Fe2O3 core-shell NRs make them a potential candidate in engineering next-generation nanoheterostructure based RRAM devices. © 2017 American Chemical Society.


Kikuchi M.,Japan Atomic Energy Agency | Azumi M.,Soft Science
Reviews of Modern Physics | Year: 2012

Tokamaks have demonstrated excellent plasma confinement capability because of their symmetry but has an intrinsic drawback because of their pulsed inductive operation. Efforts have been made in the past 20 years to realize steady-state operation, the most successful utilizing a bootstrap current. In this review, progress in understanding tokamak physics related to steady-state operation is described to investigate the scientific feasibility of a steady-state tokamak fusion power system. © 2012 American Physical Society.


Tsai F.-C.,Soft Science | Stuhrmann B.,Soft Science | Koenderink G.H.,Soft Science
Langmuir | Year: 2011

We demonstrate that cytoskeletal actin-myosin networks can be encapsulated with high efficiency in giant liposomes by hydration of lipids in an agarose hydrogel. The liposomes have cell-sized diameters of 10-20 μm and a uniform actin content. We show by measurements of membrane fluorescence intensity and bending rigidity that the majority of liposomes are unilamellar. We further demonstrate that the actin network can be specifically anchored to the membrane by biotin-streptavidin linkages. These protein-filled liposomes are useful model systems for quantitative studies of the physical mechanisms by which the cytoskeleton actively controls cell shape and mechanics. In a broader context, this new preparation method should be widely applicable to encapsulation of proteins and polymers, for instance, to create polymer-reinforced liposomes for drug delivery. © 2011 American Chemical Society.


Saha A.,Soft Science | Adamcik J.,Soft Science | Bolisetty S.,Soft Science | Mezzenga R.,Soft Science
Angewandte Chemie - International Edition | Year: 2015

Self-assembly of the naturally occurring sweetening agent, glycyrrhizic acid (GA) in water is studied by small-angle X-ray scattering and microscopic techniques. Statistical analysis on atomic force microscopy images reveals the formation of ultralong GA fibrils with uniform thickness of 2.5 nm and right-handed twist with a pitch of 9 nm, independently of GA concentration. Transparent nematic GA hydrogels are exploited to create functional hybrid materials. Two-fold and three-fold hybrids are developed by introducing graphene oxide (GO) and in situ-synthesized gold nanoparticles (Au NPs) in the hydrogel matrix for catalysis applications. In the presence of GO, the catalytic efficiency of Au NPs in the reduction of p-nitrophenol to p-aminophenol is enhanced by 2.5 times. Gold microplate single crystals are further synthesized in the GA hydrogel, expanding the scope of these hybrids and demonstrating their versatility in materials design. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Rajalakshmi R.,Soft Science | Angappane S.,Soft Science
Journal of Alloys and Compounds | Year: 2014

We have deposited ZnO and 3% Mn doped ZnO (ZnO:Mn) thin films of different thickness by RF magnetron sputtering and studied the structural and optical properties. The deposited films were characterized by a host of characterization techniques, such as, X-ray diffraction, scanning electron microscopy, UV-visible transmittance and photoluminescence. The X-ray diffraction measurements on all the films show a preferential growth along c axis and the intensity of (0 0 2) peak is found to increase with increase of thickness up to 80 and 90 nm for ZnO and ZnO:Mn films respectively and decreases thereafter. The FESEM images of the films illustrate a hexagonal granular surface morphology for lower thickness and a growth of pyramidal nanostructures for higher thickness. The calculated values of the optical band gaps are found to decrease upon increasing the film thickness. Markedly, the band edge emission is large for 80 and 90 nm films of ZnO and ZnO:Mn respectively. The obtained optimized sputtering growth conditions will facilitate to exploit these ZnO and ZnO:Mn thin films for various device applications. © 2014 Elsevier B.V. All rights reserved.


Krishnamurthy K.S.,Soft Science
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

The Bobylev-Pikin striped-pattern state induced by a homogeneous electric field is a volume flexoelectric instability, originating in the midregion of a planarly aligned nematic liquid crystal layer. We find that the instability acquires a spatiotemporal character upon excitation by a low frequency (<0.5 Hz) square wave field. This is demonstrated using a bent-core liquid crystal, initially in the 90°-twisted planar configuration. The flexoelectric modulation appears close to the cathode at each polarity reversal and, at low voltage amplitudes, decays completely as the field becomes steady. Correspondingly, at successive polarity changes, the stripe direction switches between the alignment directions at the two substrates. For large voltages, the stripes formed nearly along the alignment direction at the cathode gradually reorient toward the midplane director. These observations are generally attributed to inhomogeneous and time-dependent field conditions that come to exist after each polarity reversal. Polarity dependence of the instability is attributed to the formation of intrinsic double layers that bring about an asymmetry in surface fields. Momentary field elevation near the cathode following a voltage sign reversal and concomitant gradient flexoelectric polarization are considered the key factors in accounting for the surfacelike modulation observed at low voltages. © 2014 American Physical Society.


Schefer L.,Soft Science | Adamcik J.,Soft Science | Mezzenga R.,Soft Science
Angewandte Chemie - International Edition | Year: 2014

The structural conformations of the anionic carrageenan polysaccharides in the presence of monovalent salt close to physiological conditions are studied by atomic force microscopy. Iota-carrageenan undergoes a coil-helix transition at high ionic strength, whereas lambda-carrageenan remains in the coiled state. Polymer statistical analysis reveals an increase in persistence length from 22.6±0.2 nm in the random coil, to 26.4±0.2 nm in the ordered helical conformation, indicating an increased rigidity of the helical iota-carrageenan chains. The many decades-long debated issue on whether the ordered state can exist as single or double helix, is conclusively resolved by demonstrating the existence of a unimeric helix formed intramolecularly by a single polymer chain. The coil-helix transition within single chains of anionic carrageenan polysaccharides is resolved in situ by atomic force microscopy, as a result of the presence of monovalent ions close to physiological conditions (see picture). Polymer statistical analysis demonstrates a modulation of the rigidity and topological features of individual polyelectrolyte chains upon this conformational change. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.


Krishnamurthy K.S.,Soft Science
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

The electric Freedericksz transition is a second-order quadratic effect, which, in a planarly aligned nematic liquid crystal layer, manifests above a threshold field as a homogeneous symmetric distortion with maximum director-tilt in the midplane. We find that, upon excitation by a low frequency (<0.2Hz) square-wave field, the instability becomes spatially and temporally varying. This is demonstrated using calamitic liquid crystals, initially in the 90°-twisted planar configuration. The distortion occurs close to the negative electrode following each polarity switch and, for low-voltage amplitudes, decays completely in time. We use the elastically favorable geometry of Brochard-Leger walls to establish the location of maximum distortion. Thus, at successive polarity changes, the direction of extension of both annular and open walls switches between the alignment directions at the two substrates. For high voltages, this direction is largely along the midplane director, while remaining marginally oscillatory. These results are broadly understood by taking into account the time-varying and inhomogeneous field conditions that prevail soon after the polarity reverses. Polarity dependence of the instability is traced to the formation of intrinsic double layers that lead to an asymmetry in field distribution in the presence of an external bias. Momentary field elevation near the negative electrode following a voltage sign reversal leads to locally enhanced dielectric and gradient flexoelectric torques, which accounts for the surface-like phenomenon observed at low voltages. These spatiotemporal effects, also found earlier for other instabilities, are generic in nature. © 2015 American Physical Society. ©2015 American Physical Society.


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