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Shekhar S.,Center for Nano Science and Engineering | Ananthasuresh G.K.,Indian Institute of Science
Sensors and Transducers | Year: 2011

This paper explains the reason behind pull-in time being more than pull-up time of many Radio Frequency Micro-Electro-Mechanical Systems (RF MEMS) switches at actuation voltages comparable to the pull-in voltage. Analytical expressions for pull-in and pull-up time are also presented. Experimental data as well as finite element simulations of electrostatically actuated beams used in RF-MEMS switches show that the pull-in time is generally more than the pull-up time. Pull-in time being more than pull-up time is somewhat counter-intuitive because there is a much larger electrostatic force during pull-in than the restoring mechanical force during the release. We investigated this issue analytically and numerically using a 1D model for various applied voltages and attribute this to energetics, the rate at which the forces change with time, and softening of the overall effective stiffness of the electromechanical system. 3D finite element analysis is also done to support the 1D model-based analyses. © 2011 IFSA.

Hegde G.,Center for Nano Science and Engineering | Srinivas T.,Indian Institute of Science
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Silicon-On-Insulator (SOI) technology has huge potential in fabricating compact devices for various applications such as integrated optic waveguides, directional couplers, resonators etc. In this work, we present the analysis of a biosensor based on an integrated optic racetrack resonator, interrogated by a bus waveguide. The biomaterial is applied as a cladding layer. Here we analyze the coupling between the resonator and the bus waveguide, and its dependence on the bio layer. In traditional analysis, the effective refractive index and resonator total path length are the factors influencing the resonant wavelength. Our analysis shows that all parametric values decrease with increase in waveguide width and spacing. The inclusion of waveguide mode overlap and perturbation in coupled mode equation results in enhanced resonator sensitivity of an order of magnitude.

Vinayakumar K.B.,Indian Institute of Science | Kulkarni P.G.,Central Animal Facility | Nayak M.M.,Center for Nano Science and Engineering | Dinesh N.S.,Indian Institute of Science | And 2 more authors.
Journal of Micromechanics and Microengineering | Year: 2016

A novel fabrication process has been described for the development of a hollow stainless steel microneedle array using femto second laser micromachining. Using this method, a complicated microstructure can be fabricated in a single process step without using masks. The mechanical stability of the fabricated microneedle array was measured for axial and transverse loading. Skin histology was carried out to study the microneedle penetration into the rat skin. Fluid flow through the microneedle array was studied for different inlet pressures. The packaging of the microneedle array, to protect the microneedle bore blockage from dust and other atmospheric contaminations, was also considered. Finally, the microneedle array was tested and studied in vivo for insulin delivery to a diabetic rat. The results obtained were compared with the standard subcutaneous delivery with the same dose rate and were found to be in good agreement. © 2016 IOP Publishing Ltd.

Ghosh P.,Materials Research Center | Kumar S.,Center for Nano Science and Engineering | Ramalingam G.,University of Virginia | Kochat V.,Stanford University | And 6 more authors.
Journal of Physical Chemistry C | Year: 2015

The grain size of monolayer large area graphene is key to its performance. Microstructural design for the desired grain size requires a fundamental understanding of graphene nucleation and growth. The two levers that can be used to control these aspects are the defect density, whose population can be controlled by annealing, and the gas-phase supersaturation for activation of nucleation at the defect sites. We observe that defects on copper surface, namely dislocations, grain boundaries, triple points, and rolling marks, initiate nucleation of graphene. We show that among these defects dislocations are the most potent nucleation sites, as they get activated at lowest supersaturation. As an illustration, we tailor the defect density and supersaturation to change the domain size of graphene from <1 μm2 to >100 μm2. Growth data reported in the literature has been summarized on a supersaturation plot, and a regime for defect-dominated growth has been identified. In this growth regime, we demonstrate the spatial control over nucleation at intentionally introduced defects, paving the way for patterned growth of graphene. Our results provide a unified framework for understanding the role of defects in graphene nucleation and can be used as a guideline for controlled growth of graphene. © 2015 American Chemical Society.

Kumar S.,Center for Nano Science and Engineering | Purohit R.,MANIT | Malik M.M.,Center for Nano Science and Engineering
Materials Today: Proceedings | Year: 2015

In the field of nanotechnology, polymer based nanocomposites have become an important area of current research and development. This paper includes detail preparation methods, properties of polymer based nanocomposite materials in different areas such as flammability resistance, electrical, electronic, mechanical and fuel cell applications. This review is designed to be comprehensive source for recent advances in polymermatrix nanocomposites and their applications in mechanical, electrical and electronics industries. Physical and mechanical properties of conducting polymer matrix nanocomposites for application in nano-diodes, field effect transistors, field emission super-capacitors and energy storage are reviewed. © 2015 Elsevier Ltd.

Talukder S.,Center for Nano Science and Engineering | Kumar P.,Indian Institute of Science | Pratap R.,Center for Nano Science and Engineering
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

Electric field can induce long range flow in liquid materials. This phenomenon is known as liquid electromigration. In particular case of Cr thin film deposited on an insulating substrate, application of high electric-field between two point electrodes results in liquefaction and subsequent flow of the liquefied material in a radially symmetric fashion away from the cathode. This electric field driven material transport phenomenon has been used for a new patterning technique, named electrolithography. A negatively biased scanning probe is used to etch a thin Cr film according to a desired pattern. Then the pattern is transferred to new materials using a polymer layer below the metal film. Electrolithography does not need any UV or e-beam source, and can be performed in ambient condition. We have achieved pattern resolutions of 9 nm on the polymer and 40 nm on transferring the pattern to other materials. In this work, with the help of electrolithography, we have patterned large areas using vector scan technique. This improves throughput of the process by a significant order. © 2016 COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

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