Department of Mechanical engineering

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Author: search.filters.author.Bhatt, GeetaSubject: search.filters.subject.Mechanical Engineering

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    Anisotropic Stick-Slip Behavior of Aqueous Drops on Lubricated Chemically Heterogeneous Slippery Surfaces
    (ARXIV, 2020-08) Bhatt, Geeta
    Conventional slippery surfaces show isotropic drop mobility in all directions, but many applications require directional drop motion along a particular path only. In previous studies, researchers used topographic substrates, together with different external stimuli, to demonstrate anisotropic drop motion, which is not very efficient and cost-effective. Herein, we report a novel approach to smartly control drop motion on lubricating fluid-coated chemically heterogeneous surfaces composed of alternating hydrophobic and hydrophilic stripes. Upon depositing an aqueous drop on such a surface, the underneath lubricating fluid dewets from the hydrophilic regions but remains intact on the hydrophobic ones, providing sticky and slippery areas for the drop. This results in remarkable anisotropic drop sliding behavior, from uniform motion along parallel to stripes to stick-slip motion along the perpendicular to them. Furthermore, we also demonstrate a phase diagram summarizing different dynamic situations exhibited by drops, sticking, or moving in one or both directions.
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    2022 Index IEEE Transactions on NanoBioscience Vol. 21
    (IEEE, 2022-10) Bhatt, Geeta
    This index covers all technical items—papers, correspondence, reviews, etc.—that appeared in this periodical during 2022, and items from previous years that were commented upon or corrected in 2022. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author’s name. The primary entry includes the coauthors’ names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author’s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.
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    Paper-Based Microfluidic Devices for the Detection of DNA
    (Springer, 2019-10) Bhatt, Geeta
    Microfluidic paper-based analytical devices are an attractive tool for point of care diagnostics as they facilitate fast detection without the need for any sophisticated instrumentation and skilled professional. These devices are disposable, portable, and affordable; hence, they are utilized in almost all the diagnostic domains for carrying out the detection. There are various aspects associated with the paper-based devices, namely working principle, reaction mechanism, fabrication schemes (2D/3D), detection sensitivity, and readout mechanism. Over the period, continuous progress is envisioned in all these domains to enhance the sensitivity of the detection and several variants, namely miniaturization, the inclusion of nanoparticles, multi-functionalization, etc. are also explored to make the detection more efficient. This chapter provides a state of the art review of the various aspects of paper-based microfluidic devices, including their fabrication scheme, sensing methodology, and their several applications in DNA detection domain. Also, advantages, disadvantages, and future aspects of these devices are also discussed.
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    Integrated DEP Assisted Detection of PCR Products With Metallic Nanoparticle Labels Through Impedance Spectroscopy
    (IEEE, 2022-10) Bhatt, Geeta
    Electrochemical impedance spectroscopy (EIS) is gaining immense popularity in the current times due to the ease of integration with microelectronics. Keeping this aspect in mind, various detection schemes have been developed to make impedance detection of nucleic acids more specific. In this context, the current work makes a strong case for specific DNA detection through EIS using nanoparticle labeling approach and also an added selectivity step through the use of dielectrophoresis (DEP), which enhances the detection sensitivity and specificity to match the detection capability of quantitative polymerase chain reaction (qPCR) in real-time context as compared to the individually amplified DNA (Liu et al. , 2008). The detection limit of the proposed biochip is observed to be 3–4 PCR cycles for 582 bp bacterial DNA, where the complete procedure of detection starts in less than 10 min. The process of integrated DEP capture of labeled products coming out of PCR and their impedance-assisted detection is carried out in an in-house micro-fabricated biochip. The gold nanoparticles, which possess excellent optical, chemical, electronic, and biocompatibility properties and are capable of generating lump-like DNA structure without modifying its basic impedance signature are introduced to the amplified DNA through the nanoparticle labeled primers.
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    Enhanced Fluorescence-Based Detection of Vibrio Cells Over Nanoporous Silica Substrate
    (Springer, 2019-04) Bhatt, Geeta
    The food and waterborne pathogens threaten the human health through porous borders that require immediate detection in real time. The present work reports the development of a nanoporous silica-based platform for the rapid detection of Vibrio cells. The nanoporous thin film has been developed over silicon substrate utilizing PMSSQ (polymethylsilsesquioxane, (CH3SiO1.5)n) and PPG (polypropylene glycol, CH((CH3)CH2O)n) combination in PGMEA (propylene glycol methyl ether acetate) solvent as provided earlier by Gangopadhyay et al. (Nanotechnology 20, 2009 [1]). The PPG acts as a porogen and evaporates on heat treatment giving a porous structure and assembles the PMSSQ nanoparticles. The films were characterized through FTIR, EDAX, and SEM microscopy, and it was found out that the functional groups like OH, CH3, Si–CH3, Si–O, and Si–O–Si were present abundantly in the porous structure, which can be further modified for its application in biology. An aliquot of 2.5 µl Vibrio cell solution was immobilized (over nanoporous silica film) to study its fluorescence intensity under an epifluorescence microscope. Vibrio (Vibrio harveyi (ATCC® 700106™)) cells possess self-fluorescing effects with bleaching characteristics. The fluorescence images (with the progression of time) are acquired and processed through Image J (courtesy NIH), and relative fluorescence of the cells are calculated as a function of time. A 1.7 times increase in the overall fluorescence intensity level is recorded in the presence of the porous silica layer as compared to uncoated silicon substrate showing immobilization capabilities of these films.
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    Analysis of graphene coated optical fiber for visible range refractive index sensing
    (Elsevier, 2023-02) Bhatt, Geeta
    In this work, graphene coated optical fiber structure has been exploited theoretically for refractive index sensing within visible operating region. A high refractive index polymer layer is also considered as a matching layer between graphene and the fiber core to generate lossy mode resonances in the desired spectrum. It is observed that multilayer graphene coating supports much sharper and narrower resonances than the graphene monolayer. Sensing characteristics with variation in number of graphene layers and polymer layer thickness are investigated with different polarizations of light. Calibration curves indicating change in resonant wavelength corresponding to the refractive index variation of sensing medium are also presented. It is observed that polymer layer act as the catalyst in enabling the structure to support resonances and shifting the operating region in visible spectrum. A maximum sensitivity of 300 nm/RIU for RI range of 1.33–1.40 is reported for p-polarization of light. It is believed that visible range operation of the proposed structure will make it cost effective and highly suitable for the development of bio-chemical sensors.