Department of Applied Mechanics

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

This study demonstrates a rapid, wash-free, dip-type plasmonic fiberoptic absorbance biosensor (P-FAB) capable of zeptomole analyte detection and 6-orders of wide dynamic range. It involves a sandwich immunoassay on a compact U-bent fiber optic probe surface that works by dipping an antibody-functionalized probe into a mixture of sample and gold nanoparticle (AuNP) label suspension. The U-bent fiberoptic probes with a high evanescent wave absorbance sensitivity allow detection of the high extinction AuNP labels measured in terms of light intensity change using a pair of LED and photodetector (PD). This simple and low-cost P-FAB gives an unprecedented detection limit of 0.17 zeptomole for human immunoglobulin G (HIgG) in 25 μL buffer in just 25 min. Further silver enhancement of AuNP labels for 5 min results in a limit of quantitation (LoQ) down to 0.17 zeptomole (∼100−150 molecules in 25 μL), making P-FAB a highly sensitive and low-cost technology for point-of-care diagnostics. © 2020 Elsevier B.V.

World University root node

Department Of Biotechnology

Sensors and Actuators, B: Chemical

U-bent fiber optic plasmonic biosensor platform for ultrasensitive analyte detection

In this paper, the development of weighted nonlinear beamformer, called as Filtered Delay Weighted Multiply and Sum (F-DwMAS) is reported. This method was investigated on Synthetic Transmit Aperture (STA) technique. The performance of the developed F-DwMAS method was compared with Delay and Sum (DAS) and recently introduced F-DMAS beamforming methods. Importantly, in the method proposed, an extra window stage is added after the delay stage in the F-DMAS method. The different methods of DAS, F-DMAS and F-DwMAS were compared in terms of the resulting image quality metrics, Lateral Resolution (LR), Axial Resolution (AR), Contrast Ratio (CR) and contrast-to-noise ratio (CNR), in experiments on tissue-mimicking phantoms. Experimental results show that, for STA technique, F-DwMAS resulted in improvements of AR by 46.91% and 30.19%, LR by 61.35% and 52.48%, CR by 84.68% and 27.51%, and CNR by 5.45% and 34.4% compared to those obtained using DAS and F-DMAS, respectively. Hence, it can be concluded that the image quality is improved by F-DwMAS compared to DAS and F-DMAS. © 2020 IEEE.

IEEE International Ultrasonics Symposium, IUS

A weighted non-linear beamformer for synthetic aperture ultrasound imaging

Currently, portal pressure is measured by the standard method known as hepatic venous pressure gradient (HVPG). But it is an invasive procedure; therefore, an alternative noninvasive technique to estimate portal pressure is required to monitor portal hypertension. In this work, a 3D portal vein model is developed to study the acoustic interaction with microbubbles in the portal vein. Ultrasound scattering by ultrasound contrast agent (UCA) is modelled and analyzed using finite element analysis in order to estimate portal pressure. It was found from the analysis that the subharmonic component dropped by 1.5 dB as the portal pressure raised from 0 mmHg to 10 mmHg. Over the same pressure range, the fundamental component reduced by only 0.2 dB. The results suggest that the subharmonic component from the nonlinear response of microbubble is strongly affected by the ambient pressure, and the proposed model may be used to estimate portal pressure noninvasively. Copyright © 2020 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

Department of Engineering Design

BIODEVICES 2020 - 13th International Conference on Biomedical Electronics and Devices, Proceedings; Part of 13th International Joint Conference on Biomedical Engineering Systems and Technologies, BIOSTEC 2020

Noninvasive portal pressure estimation model using finite element analysis

Tuberculosis (TB) is a resurgent infectious disease affecting a large number of people in the developing countries. An on-site, affordable diagnostic screening at an early-stage for an immediate anti-TB treatment is known to tremendously minimize the high mortality rates. Lipoarabinomannan (LAM), a surface glycolipid, has been identified as a potential TB biomarker present in urine at ultra-low concentrations of a few fg/mL. Here, we report a plasmonic fiber optic absorbance biosensor (P-FAB) strategy for mannosylated LAM (Man-LAM or Mtb LAM) detection down to attomolar concentrations. It involves a plasmonic sandwich immunoassay on a U-bent fiber optic probe with gold plasmonic (AuNP) labels functionalized with anti-Mtb LAM immunoglobulin M (IgM) and anti-Mtb LAM IgG respectively. The Mtb LAM is quantified in terms of absorption of light passing through the fiber probe using a green LED and a photodetector. The choice of fiber optic probes (fused silica versus polymer), the optimum size (20, 40, 60 and 80&nbsp;nm) and concentration (2&nbsp;×&nbsp;, 10&nbsp;×&nbsp;, and 20&nbsp;×&nbsp;) of AuNP labels were investigated to obtain high sensitivity and lower limits of analyte detection (LoD). P-FAB with a simple LED-photodetector pair, 200&nbsp;μm fused silica U-bent fiber probe and 60&nbsp;nm (20&nbsp;×&nbsp;) AuNP labels gave LoDs down to 1&nbsp;fg/mL and 10&nbsp;fg/mL in the buffer and synthetic urine respectively. Moreover, the anti-Mtb LAM IgM bound sensor probes and the AuNP reagent stored at 4&nbsp;°C were stable up to 45 days. P-FAB based Mtb LAM sensor demonstrates its potential for an on-site TB diagnosis.

Department of Aerospace Engineering

Fulltext

Biosensors and Bioelectronics

A plasmonic fiberoptic absorbance biosensor for mannose-capped lipoarabinomannan based tuberculosis diagnosis

Uni-axial compressive failure of silica-epoxy based heterogeneous honeycombs is investigated in detail for a range of volume fractions. Introduction of heterogeneity in compression of staggered-square honeycomb is seen to result in damage initiation at multiple locations and subsequent damage growth to be more stable compared to pure epoxy in which damage was observed to be localized until peak load when catastrophic failure of the honeycomb specimen occurs. The increase in stiffness and comparative stability of the response is accompanied with reduction in strength, however, between 0 and 5% the total work of compressive failure is comparable. From the elastic-plastic analysis it is evident that the non-linearity in the response of pure honeycombs, prior to peak load, is largely due to formation of plastic hinges near corners of cells, whereas in case of heterogeneous honeycomb the non-linearity is mostly due to debonding of hard filler particles and matrix cracking leading to damage growth in cell walls. © 2020 Elsevier Ltd

Department of Ocean Engineering

Composite Structures

Effect of heterogeneity on crushing failure of disordered staggered-square honeycombs

Understanding the breakup morphology of an expelled respiratory liquid is an emerging interest in diverse fields to enhance the efficacious strategies to attenuate disease transmission. In this paper, we present the possible hydrodynamic instabilities associated with expelling the respiratory liquid by a human. For this purpose, we have performed experiments with a cylindrical soap film and air. The sequence of the chain of events was captured with high-speed imaging. We have identified three mechanisms, namely, Kelvin-Helmholtz (K-H) instability, Rayleigh-Taylor (R-T) instability, and Plateau-Rayleigh (P-R) instability, which are likely to occur in sequence. Furthermore, we discuss the multiple processes responsible for drop fragmentation. The processes such as breakup length, rupture, ligament, and drop formation are documented with a scaling factor. The breakup length scales with We-0.17, and the number of ligaments scales as Bo. In addition, the thickness of the ligaments scales as We-0.5. Here, We and Bo represent the Weber and Bond numbers, respectively. It was also demonstrated that the flapping of the liquid sheet is the result of the K-H mechanism, and the ligaments formed on the edge of the rim appear due to the R-T mechanism, and finally, the hanging drop fragmentation is the result of the P-R instability. Our study highlights that the multiple instabilities play a significant role in determining the size of the droplets while expelling a respiratory liquid. This understanding is crucial to combat disease transmission through droplets. © 2020 Author(s).

Physics of Fluids

Breakup morphology of expelled respiratory liquid: From the perspective of hydrodynamic instabilities

Atomization of a jet in air cross flow has numerous applications in industrial and natural systems. In this study, spray characteristics (i.e., droplet mean diameter, Sauter mean diameter, and volume flux distribution) generated from perpendicularly interacting air jet of 7.5-mm diameter and water jet of 0.8-mm diameter are characterized using a phase Doppler particle analyzer (PDPA) in a forward scattering mode. The investigation is done for seven momentum ratios (q), where the momentum ratios are varied by varying the jet flow rate while keeping air flow rate constant. The jet Weber number is calculated to be 42.56, which is constant for all the cases and falls under the multimode breakup regime. PDPA measurements are done at different spatial locations, 40 mm below the tip of the injector to avoid ligaments and to ensure stable droplets. From the experimental results, it is found that for all flow conditions, volume flux is maximum near the geometric center of the spray and decreases towards the edges indicating the solid cone structure of the spray. The volume flux also increases with increase in q. The maximum of mean droplet diameter (D10) and Sauter mean diameter (SMD or D32) is found at the geometric center of the spray in the x direction, whereas in the y direction the maximum D10 and D32 are shifted towards the windward side of the jet. The diameter–velocity correlation is negative at the center of the spray and positive at the edges for both x and y directions. The correlation model for volume flux is found to be in accordance with the experimental data, while a few outliers are found in the diameter model due to the presence of large droplets that skew the data. © 2020 by Begell House, Inc.

Journal of Flow Visualization and Image Processing

Phase doppler particle analyser (PDPA) characterization and modeling of sprays from orthogonally interacting water and air jets

A large Magnetoelectric (ME) response at room temperature in CoFe2O4 - BaTiO3 core shell composite is crucial for the biomedical application because of its biocompatibility. Good ME response of coreâ€“shell system is directly related to synthesis conditions as it determines extent of coupling between core and shell structures. In this work, CoFe2O4 - BaTiO3 core shell structures with improved ME response were prepared through hydrothermal and citric gel synthesis. Reitveld refinement analysis and microscopic images confirmed the successful formation of CoFe2O4 - BaTiO3 core shell structure. The core shell sample is composed of tetragonal BaTiO3 and cubic spinel CoFe2O4 phases. CoFe2O4 was found to exhibit both positive and negative magnetostriction at room temperature. ME coefficient of 12.38 mV/cm Oe was observed at room temperature, which is quite high and can enhance the efficiency of targeted drug delivery. Â© 2020 Elsevier B.V.

Materials Letters

Improved room temperature magnetoelectric response in CoFe2O4-BaTiO3 core shell and bipolar magnetostrictive properties in CoFe2O4

In the last three decades of developments, the technique of Digital Photoelasticity (DP) has been stabilized and the methodology has been successfully applied to a wide range of problems in Engineering and science. This review succinctly summarizes both the techniques and their applications. Sufficient attention is paid to bring out the problem-solving capability of photoelasticity in each of the domains so as to motivate the reader to extrapolate these ideas to the uncharted territory of new problems they may come across in their domains. © 2020 Elsevier Ltd

Optics and Lasers in Engineering

Digital photoelasticity: Recent developments and diverse applications

The surface of a rectangular wing is morphed numerically at high angles of attack such that it still operates at the reduced coefficient of lift at which the baseline wing operates but while the flow is separated on the baseline wing, it remains attached on the morphed wing. The aerodynamic characteristics of the baseline wing are obtained experimentally and that of the morphed wing is obtained numerically. The morphed surface at high angles of attack is obtained using a novel ‘decambering’ technique, which accounts for the deviation of the coefficients of lift and pitching moment from that predicted by the potential flow. Two wings with different airfoil sections, N ACA0012 and N ACA4415 are tested and compared at high α. Numerical morphing of wing surface for design coefficient of lift (CL ) (in terms of percentage increment) is presented at angles of attack 50 and 150 . This concept of design CL of a morphing wing is one of the possible solutions to fly at different flight conditions with corresponding targets and maneuvering requirements. A significant addition to the present numerical approach is to provide some comparison of the flow separation behavior with CFD at the root section of both the wing sections. The effects of morphed surfaces on drag penalty, coefficient of lift and post-stall angles of attack are studied and compared in terms of aerodynamic performance. © 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.