Showing papers by "Rajib Chakraborty published in 2017"

MWCNT reinforced bone like calcium phosphate—Hydroxyapatite composite coating developed through pulsed electrodeposition with varying amount of apatite phase and crystallinity to promote superior osteoconduction, cytocompatibility and corrosion protection performance compared to bare metallic implant surface

Abstract: Inconsistent growth of tissues and poor osteoconduction performance on the metallic implant surfaces due to variation of surface energy are major contributing factors for failure of most metallic implant on account of lack of stronger attachment with surrounding bone or tissues. In this study, composite coating of hydroxyapatite, calcium hydrogen phosphate and MWCNT was developed on SS316 surface with varying amount of calcium phosphate-hydroxyapatite phase and crystallinity by pulsed electrodeposition. TEM study revealed that the MWCNTs were bonded strongly with the in situ deposition phases and thus act as reinforcement in the deposited coating similar to the collagen fiber in natural bone structure. Presence of MWCNT reinforcement increased the overall coating modulus of elasticity in the range of 6–10 GPa similar to that of natural bone. Different coating surfaces with varied amount of phase and crystallinity exhibits altogether different phenomena and growth geometry of apatite formation during osteoconduction period under contact with SBF. Coatings with highest amount of hydroxyapatite phase exhibit formation of porous spherical (~ 1 μm) and rod like (~ 600 nm) scaffold structure along with presence of nanopores (~ 100 nm) all along the contact surfaces. Cell proliferation study indicated uniform and fast spreading of cells over the coating surfaces as compared to bare metallic implant. EIS study illustrated five times high corrosion resistance capability along with formation of passivation layer under contact with SBF for coating comes with 66% of hydroxyapatite phase.

Digital Camera-Based Spectrometry for the Development of Point-of-Care Anemia Detection on Ultra-Low Volume Whole Blood Sample

Abstract: Objective of this paper: Early detection of anemia (low hemoglobin count) at point-of-care (PoC) in a low resource setting is challenging given the associated capital and recurring costs of the device. In this paper, we have developed a faster and reliable method to screen the hemoglobin level in the whole blood in a resource limited point of care setting. We have also investigated a simple scattering-based technique to predict the overall morphology of the red blood cells. Methods: In this paper, we have developed and validated a digital camera-based spectrometer for the early detection of anemia with the whole blood of 10- $\mu \text{L}$ volume in a low resource PoC setting. The developed device consists of two LEDs [Green (570 nm) and Red (631 nm)], a web camera, a fluid sensing chamber (cuvette holder), and associate electronics. Validation of Beer–Lambert law using the blood of various degree of dilution has been achieved in this in vitro experiment. Major results: A significant number of human subjects (300) having a wide range of hemoglobin counts in a hospital is tested and found to reproduce results from a gold standard automated hematology analyzer. Our developed microcuvette requires only 10- $\mu \text{L}$ unprocessed whole blood sample for the device. Conclusions: The device is expected to serve as a minimally invasive e-health care device for the anemia screening in any resource-limited point of care setting.

Realization of mode independent multichannel transmission filter by controlling the photon localization in symmetric cavities

Abstract: Modern optical communication system requires multiple channel transmission in different spectral band for different applications. Here we are proposing a microresonator structure for closely spaced, mode independent multiple channel transmission in 3rd transmission window by controlling the localization of photons in its cavity. To design the proposed structure, the spectral filtering properties of a single cavity planar microresonator are studied initially. In conventional multilayer dielectric filter, the localization of light in the microcavity is generally controlled by controlling the number of layers. Here we have shown that application of electric field across the structure, designed with suitable materials can also affect the localization of light in the cavity as well as the Q values of the transmission spectra. The mode independent characteristic of the structure is found from the study of its transmittance characteristics at different angle of incidence of light. It is found that the results of single cavity structure hold well for multicavity resonator structure also, in the regime of optical communication wavelength range. A method to increase the number of transmission channels is also proposed here keeping the fabrication perspective in mind.

Efficient splitting of broadband LED light into narrowbands using superlensing effect and defects on its top 2D photonic crystal

Abstract: In this work, design of a photonic crystal (PhC) based structure is proposed for efficient splitting of light from broadband Light Emitting Diode (LED) into multiple narrowband sources. InP based transverse junction LED is considered. A vertical stack of two-dimensional (2D) square lattice PhC made up of GaAs/air is placed on top of this LED. 2D periodicity of the PhC is in the vertical plane of the top surface of the LED. On removal of a few GaAs rods the broadband light is focussed by effect of superlensing on the resulting T-type channel. The simulated result is studied by creation of curved air hole on the superlensing PhC. Only TM polarized light of specific wavelength ranges from the LED source is considered for narrowbands splitting as the TE polarized light does not have suitable bandgap there.

Analysis of photonic spot profile converter and bridge structure on SOI platform for horizontal and vertical integration

Abstract: Horizontal spot size converter required for horizontal light coupling and vertical bridge structure required for vertical integration are designed on high index contrast SOI platform in order to form more compact integrated photonic circuits. Both the structures are based on the concept of multimode interference. The spot size converter can be realized by successive integration of multimode interference structures with reducing dimension on horizontal plane, whereas the optical bridge structure consists of a number of vertical multimode interference structure connected by single mode sections. The spot size converter can be modified to a spot profile converter when the final single mode waveguide is replaced by a slot waveguide. Analysis have shown that by using three multimode sections in a spot size converter, an Gaussian input having spot diameter of 2.51 μm can be converted to a spot diameter of 0.25 μm. If the output single mode section is replaced by a slot waveguide, this input profile can be converted to a flat top profile of width 50 nm. Similarly, vertical displacement of 8μm is possible by using a combination of two multimode sections and three single mode sections in the vertical bridge structure. The analyses of these two structures are carried out for both TE and TM modes at 1550 nm wavelength using the semi analytical matrix method which is simple and fast in computation time and memory. This work shows that the matrix method is equally applicable for analysis of horizontally as well as vertically integrated photonic circuit.