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Articles 1 - 12 of 12
Full-Text Articles in Biomedical Engineering and Bioengineering
Polyelectrolyte Mediated Scalable Synthesis Of Highly Stable Silver Nanocubes In Less Than A Minute Using Microwave Irradiation, Subrata Kundu, Vivek C. Maheshwari, Sanjun Niu, Ravi F. Saraf
Polyelectrolyte Mediated Scalable Synthesis Of Highly Stable Silver Nanocubes In Less Than A Minute Using Microwave Irradiation, Subrata Kundu, Vivek C. Maheshwari, Sanjun Niu, Ravi F. Saraf
Ravi Saraf Publications
Silver nanocubes were synthesized for the first time in large quantities on gold seed in the presence of a polyelectrolyte using microwave heating for 60–120 s. Our experiment indicates that the polyelectrolyte directs the growth of the particle in a specified crystallographic direction resulting in the faceted particle, i.e. a nanocube. The nanocubes are stable for at least 2 months in ambient conditions.
Self-Assembly Of A Micrometers-Long One-Dimensional Network Of Cemented Au Nanoparticles, Vivek C. Maheshwari, Jennifer Kane, Ravi F. Saraf
Self-Assembly Of A Micrometers-Long One-Dimensional Network Of Cemented Au Nanoparticles, Vivek C. Maheshwari, Jennifer Kane, Ravi F. Saraf
Ravi Saraf Publications
One-dimensional Au nanoparticles connected by ionic linkers self-assemble into a micrometer-scale network. Reactions between linker ions reinforce the assembly and lead to the formation of a continuous network. This continuous network demonstrates room temperature Coulomb-blockade characteristics that are indicative of electron transport along the 1D pathways.
Linear Tactile Nanodevice With Resolution On Par With Human Finger, Ravi F. Saraf, Vivek C. Maheshwari, Chieu Nguyen
Linear Tactile Nanodevice With Resolution On Par With Human Finger, Ravi F. Saraf, Vivek C. Maheshwari, Chieu Nguyen
Ravi Saraf Publications
A large area thin-film nanodevice made by self-assembly containing electroluminescent nanoparticles is reported. The ~100 nm thick device on application of potential across the top and bottom surface of the film converts local pressure to light. The intensity of the electroluminescent light is linearly proportional to the applied local compressive stress. By imaging the light, the stress distribution over the area of contact is obtained at resolution on par with human finger.
Selective Assembly Of Nanoparticles On Block Copolymer By Surface Modification, Sanjun Niu, Ravi F. Saraf
Selective Assembly Of Nanoparticles On Block Copolymer By Surface Modification, Sanjun Niu, Ravi F. Saraf
Ravi Saraf Publications
We have developed a method to selectively deposit nanoparticles on the ordered nanoscale elements of PS–PI–PS (polystyrene– polyisoprene–polystyrene) block copolymer film. The process utilizes reactive ion plasma to selectively modify the PS surface with amine groups to electrostatically attract negatively charged Au nanoparticles. In spite of the strong interparticle Coulombic repulsion, the deposition on PS domains is significantly high. It is observed that the deposition at the edges of the domain is particularly high, forming a percolating nanoparticle necklace. The latter may lead to interesting avenues to fabricate electronic devices.
High-Resolution Thin-Film Device To Sense Texture By Touch, Vivek C. Maheshwari, Ravi F. Saraf
High-Resolution Thin-Film Device To Sense Texture By Touch, Vivek C. Maheshwari, Ravi F. Saraf
Ravi Saraf Publications
Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimum invasive surgery and humanoid robots increases. The spatial resolution of current large-area (greater than 1 cm2) tactile sensor lags by more than an order of magnitude compared with the human finger. By using metal and semiconducting nanoparticles, a ~100-nm-thick, large-area thin-film device is self-assembled such that the change in current density through the film and the electroluminescent light intensity are linearly proportional to the local stress. A stress image is obtained by pressing a copper grid and a United States …
Self-Assembly Of Nanoparticles On Live Bacterium: An Avenue To Fabricate Electronic Devices, Vikas Berry, Ravi F. Saraf
Self-Assembly Of Nanoparticles On Live Bacterium: An Avenue To Fabricate Electronic Devices, Vikas Berry, Ravi F. Saraf
Ravi Saraf Publications
Lysine-capped gold nanoparticles can be electrostatically assembled on the surface of Bacillus cerius, a Gram-Positive bacterium. The conductivity of the “gold-plated” bacteria assembly immobilized between electrodes is a function of the humidity experienced by the nanoparticles.
Orientation Of Self-Assembled Block Copolymer Cylinders Perpendicular To Electric Field In Mesoscale Film, S. Elhadj, J. W. Woody, V. S. Niu, Ravi F. Saraf
Orientation Of Self-Assembled Block Copolymer Cylinders Perpendicular To Electric Field In Mesoscale Film, S. Elhadj, J. W. Woody, V. S. Niu, Ravi F. Saraf
Ravi Saraf Publications
The possibility of using self-assembled films of block polymers as templates to fabricate nanoscale structures for devices has attracted great attention towards this class of material. Self-assembly of a block copolymer can be directed by using an electric field to orient features (i.e., ~10-nm-diam cylinders) parallel to the electric field, making the material more attractive as a nanoscale lithography mask. In this letter we describe an approach to influence the electric field orientation phenomena by interfacial effects. As a result, the 15-nm-diam polystyrene cylinders of the polystyrene–polyisoprene–polystyrene triblock copolymer orient perpendicular to the electric field. The described approach along with …
Spontaneous Planarization Of Nanoscale Phase Separated Thin Film, Ravi F. Saraf, Sanjun Niu, Eric Stumb
Spontaneous Planarization Of Nanoscale Phase Separated Thin Film, Ravi F. Saraf, Sanjun Niu, Eric Stumb
Ravi Saraf Publications
Structure of complex fluid at mesoscales is influenced by interfacial effects. We describe the dynamic response in such films to sudden change in interfacial tension. In a self-assembled block copolymer film, the monolayer of 15 nm diam cylindrical discrete phases close to the surface commence to sink at an average rate of 0.16 nm/day in response to the interfacial tension change. Surprisingly, this spontaneous planarization occurs, even though the cylinders are covalently stitched to the matrix. A simple model explains the observed behavior. The observation may lead to approaches to tailor the structure of mesoscale thin films of complex fluids …
An Approach To Sequence Dna Without Tagging, Sanjun Niu, Ravi F. Saraf
An Approach To Sequence Dna Without Tagging, Sanjun Niu, Ravi F. Saraf
Ravi Saraf Publications
Microarray technology is playing an increasingly important role in biology and medicine and its application to genomics for gene expression analysis has already reached the market with a variety of commercially available instruments. In these combinatorial analysis methods, known probe single-strand DNA (ssDNA) “primers” are attached in clusters of typically 100 μm × 100 μm pixels. Each pixel of the array has a slightly different sequence. On exposure to “unknown” target ssDNA, the pixels with the right complementary probe ssDNA sequence convert to double-stranded DNA (dsDNA) by a hybridization reaction. To transduct the conversion of the pixel to dsDNA, the …
Corrosion And Protection Of A Conductive Silver Paste, V. Brusic, G. S. Frankel, J. Roldan, Ravi F. Saraf
Corrosion And Protection Of A Conductive Silver Paste, V. Brusic, G. S. Frankel, J. Roldan, Ravi F. Saraf
Ravi Saraf Publications
One of the possible uses for a conductive paste is as an adhesive in interconnect technology that could replace PbSn solder. The interconnections are expected to perform under a variety of environmental conditions, and with an applied voltage. Thus knowledge of their corrosion and dissolution resistance is of utmost importance. This is a study of the dissolution and protection of polymer/metal composite films, prepared with a high loading of silver or gold particles. Electrochemical tests were conducted in a droplet of triple-distilled water with or without benzotriazole (BTA) and BTA derivatives. Results indicate that, in spite of some protection obtained …
Laser Assisted Pd Seeding For Electroless Plating On Siq2, A. G. Schrott, B. Braren, Ravi F. Saraf
Laser Assisted Pd Seeding For Electroless Plating On Siq2, A. G. Schrott, B. Braren, Ravi F. Saraf
Ravi Saraf Publications
Excimer laser pulses with wavelengths of 248 and 308 nm were used to selectively seed Pd on SiO2 surfaces, making them suitable for electroless plating. This novel seeding process for insulating materials is accomplished with the sample immersed in the seeding solution, and occurs only on the areas of the substrate that are illuminated (through the liquid) by the laser light. The Pd content of the seeded samples increased with the number of pulses, but was rather independent of repetition rate. The deposition rate showed a dependence with wavelength consistent with a defect driven mechanism for electron excitation through …
Simulated Crystalline Structures Of Aromatic Polyimides, Tze Wing Poon, B. David Silverman, Ravi F. Saraf, Angelo R. Rossi, Paul S. Ho
Simulated Crystalline Structures Of Aromatic Polyimides, Tze Wing Poon, B. David Silverman, Ravi F. Saraf, Angelo R. Rossi, Paul S. Ho
Ravi Saraf Publications
Semicrystalline structures involving molecular packing and optimized chain conformations of three polyimides have been obtained with the CHARMM moleculardynamics program, and their densities calculated. An eclipsed conformation of face-toface stacking of polymer chains with a relative shift is observed, and the shift is found to depend upon the molecular characteristics of the planar unit and chain linearity. Threedimensional structures obtained by calculating the optimized edge-on confirmation of the stacked units yield the smallest calculated density for PMDA-ODA, namely 1.515 g/cm3, followed by BPDA-PDA with 1.644 g/cm3 and PMDA-PDA with 1.712 g/cm3. Both PMDA-ODA and BPDA-PDA …