Entity

Time filter

Source Type


Bazaz S.A.,Ghulam Ishaq Khan Institute of Engineering Sciences and Technology | Khan F.,Ghulam Ishaq Khan Institute of Engineering Sciences and Technology | Shakoor R.I.,National Institute of Lasers and Optronics NILOP
Sensors and Actuators, A: Physical | Year: 2011

In this paper a detailed modeling, simulations and testing of a novel electrostatically actuated microgripper integrated with capacitive contact sensor is presented. Microgripper is actuated with lateral comb drive system and transverse comb system is used to sense contact between micro-object and microgripper jaws. The design is optimized in standard SOI-MUMPs micromachining process using L-Edit of MEMS-Pro. Finite element analysis of microgripper is performed in COVENTOR-WARE which shows total displacement of 15.5 μm at the tip of jaws when voltage of 50 Vdc is applied at the actuator. Finite element analysis of sensor part is performed and results are compared with analytical model. Modal analysis is performed to investigate mode shapes and natural frequencies of the microgripper. Microgripper is tested experimentally and total displacement of 17 μm is achieved at the tip of microgripper. The slight difference between finite element analysis and experimental results is due to small variations in the material properties, deposited during the fabrication process. The change in capacitance of capacitive contact sensor is linearly calibrated with the change in the displacement. The sensitivity of contact sensor is 90 fF/μm. The total size of microgripper is 5.03 mm × 6.5 mm. © 2011 Elsevier B.V. All rights reserved. Source


Khan T.M.,National Institute of Lasers and Optronics NILOP | Khan T.M.,Trinity College Dublin
Materials Chemistry and Physics | Year: 2015

In this paper a comprehensive study has been conducted to investigate the effect of palladium dopant (Pd) on the interior disordered properties of ZnO in terms of spatial correlation-length (L). Spatial correlation model is employed to explicate and gets insight of the broadening and asymmetry of the first-order optical phonon mode induced by the do-pant potential fluctuation. Apart from the conventional phonon modes associated with w-ZnO, origin of the additional local modes associated with Pd and subsequently dopant induced blue-shift in the principle E2 (high) phonon mode has been assessed. The system so - investigated is a chemically prepared composite Zn1-xPdxO (with x = 0, 2, 4 and 6 at %) nanopowder. Photoluminescence shows a blue-shift in the UV emission as a consequence of the extension of energy band-gap. The structural analysis based on X-ray diffraction reveals the absence of Pd-related secondary phases in contradicts to Raman analysis suggests Raman as the most sensitive technique. Crystallite size (D), dislocation density (δ) and optical band-gap (Eg) so-determined are correlated to spatial correlation-length "L" to account for the observed properties in photo-catalytic applications. © 2015 Elsevier B.V. All rights reserved. Source


Khan T.M.,National Institute of Lasers and Optronics NILOP
Journal of Materials Science: Materials in Electronics | Year: 2014

In this research work a comparative study of pure and In-doped ZnO polycrystalline thin films was made successfully deposited onto fused silica by reactive e-beam thermal evaporation at 300 °C. The structural and optical properties were assessed by employing X-ray diffraction (XRD), Raman spectroscopy, photoluminescence atomic force microscopy and spectroscopic ellipsometry (SE). XRD pattern, EDS and the principal Raman phonon band at 438 cm-1 confirmed purely polycrystalline wurtzite structured ZnO and incorporation of In at the Zn lattice sites. In studying the structural properties, the characteristic (002) plane was used as the focal point. Structural analysis showed that with In incorporation, the crystallites exhibited a preferential orientation along (002) c-plane perpendicular to the substrate. With In-doping (3.9 at.%), the optical band-gap increased and compressive strains were developed within the film. The prominent optical phonon mode at 587 cm-1 presented a low Raman intensity for the sample prepared in the oxygen environment and was assigned to oxygen vacancies. The film thickness and optical constants [refractive index (n), extinction coefficient (k)] were determined by SE study using Cauchy curve fitting model. PL emission spectra showed strong UV emission at 370-373 nm and a feeble visible (green) emission at 512-520 nm. The UV emission showed Stoke's shift with incorporation of In at the lattice sites as the emitted energy is lower that the band-gap energy of ZnO. The observed properties showed that ZnO can be made significantly important an electronic and optical material for various optoelectronic applications by incorporating In as the dopant material. © 2014 Springer Science+Business Media New York. Source


Firdous S.,National Institute of Lasers and Optronics NILOP | Anwar S.,National Institute of Lasers and Optronics NILOP
Laser Physics Letters | Year: 2015

Raman spectroscopy has been found useful for monitoring the dengue patient diagnostic and recovery after infection. In the present work, spectral changes that occurred in the blood sera of a dengue infected patient and their possible utilization for monitoring of infection and recovery were investigated using 532 nm wavelength of light. Raman spectrum peaks for normal and after recovery of dengue infection are observed at 1527, 1170, 1021 cm-1 attributed to guanine, adenine, TRP (protein) carbohydrates peak for solids, and skeletal C-C stretch of lipids acyl chains. Where in the dengue infected patient Raman peaks are at 1467, 1316, 1083, and 860 attributed to CH2/CH3 deformation of lipids and collagen, guanine (B, Z-marker), lipids and protein bands. Due to antibodies and antigen reactions the portions and lipids concentration totally changes in dengue viral infection compared to normal blood. These chemical changes in blood sera of dengue viral infection in human blood may be used as possible markers to indicate successful remission and suggest that Raman spectroscopy may provide a rapid optical method for continuous monitoring or evaluation of a protein bands and an antibodies population. Accumulate acquisition mode was used to reduce noise and thermal fluctuation and improve signal to noise ratio. This in vitro dengue infection monitoring methodology will lead in vivo noninvasive on-line monitoring and screening of viral infected patients and their recovery. © 2015 Astro Ltd. Source


Anwar S.,National Institute of Lasers and Optronics NILOP | Firdous S.,National Institute of Lasers and Optronics NILOP
Laser Physics Letters | Year: 2015

Hepatitis is the second most common disease worldwide with half of the cases arising in the developing world. The mortality associated with hepatitis B and C can be reduced if the disease is detected at the early stages of development. The aim of this study was to investigate the potential of Raman spectroscopy as a diagnostic tool to detect biochemical changes accompanying hepatitis progression. Raman spectra were acquired from 20 individuals with six hepatitis B infected patients, six hepatitis C infected patients and eight healthy patients in order to gain an insight into the determination of biochemical changes for early diagnostic. The human blood serum was examined at a 532 nm excitation laser source. Raman characteristic peaks were observed in normal sera at 1006, 1157 and 1513 cm-1, while in the case of hepatitis B and C these peaks were found to be blue shifted with decreased intensity. New Raman peaks appeared in HBV and HCV infected sera at 1194, 1302, 844, 905, 1065 and 1303 cm-1 respectively. A Mat lab subroutine and frequency domain filter program is developed and applied to signal processing of Raman scattering data. The algorithms have been successfully applied to remove the signal noise found in experimental scattering signals. The results show that Raman spectroscopy displays a high sensitivity to biochemical changes in blood sera during disease progression resulting in exceptional prediction accuracy when discriminating between normal and malignant. Raman spectroscopy shows enormous clinical potential as a rapid non-invasive diagnostic tool for hepatitis and other infectious diseases. © 2015 Astro Ltd. Source

Discover hidden collaborations