arXiv subjects

M. Rashed Khan

Publications and source records attributed to M. Rashed Khan.

4 recordsLinked to original sources

arXiv2024

A Modified T-Mixer Simulation, Fabrication, and Characterization For 1D Diffusion Controlled Studies

Here, we describe a simple and unique architecture of a microfluidic mixer that can mix two streams (Water and Fluorescein Isothiocyanate (FITC) buffer) with 30% efficiency. The overall mixing in this design is dominated by 1D diffusion, and to enhance mixing, we used three different types of geometric obstacles inside the channel. Comsol multiphysics simulation software was used to validate the theoretical mixing efficiency (at Reynolds Number, Re ~ 0.1, 1, and 10) of this device. We utilized soft lithography and replica molding techniques to fabricate the device out of Polydimethylsiloxane (PDMS, a commonly used polymer) on a glass substrate. The effective length of our microfluidic mixer is 5mm, and the channel width is about 200 microns with 50 micron height. It is composed of three different shapes of obstacles (e.g., 6 cones, 3 arrays of rectangular bars, and 5 circular posts), and all of these are placed inside the main channel. FITC buffer (Diffusion co-efficient, D = 0.5 x 10-9 m2/s) and DI water were used to investigate the mixer performance at Re~1. Simulated and experimental results are based on approximately 1.1 mm2 flow area and suggest that 30% mixing is achievable with the current design.

physics.med-ph↗

arXiv2024

Gold Nanoparticles Coated Optical Fiber for Real-time Localized Surface Plasmon Resonance Analysis of In-situ Light-Matter Interactions

In situ measurement of analytes for in vivo or in vitro systems has been challenging due to the bulky size of traditional analytical instruments. Also, frequent in vitro concentration measurements rely on fluorescence-based methods or direct slicing of the matrix for analyses. These traditional approaches become unreliable if localized and in situ analyses are needed. In contrast, for in situ and real-time analysis of target analytes, surface-engineered optical fibers can be leveraged as a powerful miniaturized tool, which has shown promise from bio to environmental studies. Herein, we demonstrate an optical fiber functionalized with gold nanoparticles using a dip-coating process to investigate the interaction of light with molecules at or near the surface of the optical fiber. Localized surface plasmon resonance from the light-matter interaction enables the detection of minute changes in the refractive index of the surrounding medium. We used this principle to assess the in situ molecular distribution of a synthetic drug (methylene blue) in an in vitro matrix (agarose gel) having varying concentrations. Leveraging the probed Z-height in diffused analytes, combined with its in silico data, our platform shows the feasibility of a simple optofluidic tool. Such straightforward in situ measurements of analytes with optical fiber hold potential for real-time molecular diffusion and molecular perturbation analyses relevant to biomedical and clinical studies.

physics.optics↗

arXiv2023

Data-driven Investigation of Cotton Fabric Behavior Modified by Straight and Zig-Zag Stitches

In this article, we demonstrate a data-driven approach to investigate the behavior of cotton fabric modified by straight and zig-zag stitches. Existing literature in understanding the mechanical behavior of soft materials (e.g., textile-based fibers or fabrics) heavily relies on stress-strain analyses. However, the strain-induced deformation behavior can be further analyzed by taking advantage of data-driven constitutive models. Such an approach reveals intermolecular parameters that can be utilized further in design and development analyses. For that, we exhibit the altered mechanics of base cotton fabric induced by two types of singular stitches (straight and zig-zag). We have sewn simple straight and zig-zag cotton stitches to investigate the mechanics of the base cotton fabrics using uniaxial stress-strain experimental data. Then, we leveraged the constitutive models (i.e., three-network model, TNM) obtained from MCalibration software to reveal eleven intermolecular parameters for data-driven investigations. Our experimental analyses, combined with the data, suggest a 99.99% confidence in assessing the mechanical impact of stitches on cotton fabrics. We have also used distributed strain energy to analyze the mechanics and failure of the base and stitched fabrics. Once adopted, our study may contribute to an improved understanding of the production of smart wearables and e-textiles.

cond-mat.mtrl-sci↗

arXiv2022

Confining Eutectic Gallium Indium (eGaIn) in Expired Artificial Kidneys to Unveil Nanoporous Conductive Wires

Nanoporous membranes have gained considerable interest in drug delivery1, ion transportation2, micro/nanofluidics3, molecular sensing4, and separation science5. Artificial kidneys, also known as dialyzers, reject pathogens and other unwanted substances from the blood, utilize hundreds of soft and nanoporous polymeric microtubes, and slowly become a burden to the environment with the growing number of dialysis patients worldwide. We demonstrate the fabrication of nanoporous conductive wires utilizing empty polysulfone microtubes collected from expired and unused artificial kidneys, also known as medical wastes. Injecting a fluidic, highly conductive, and room temperature liquid alloy (eutectic gallium indium-eGaIn$_6$, 75% Ga, 25% In) into microtubes of a twenty years old dialyzer, here, we have revealed a new class of nanoporous and conductive functional materials. These conductive fibers upcycle a medical waste, do not require expensive and conventional fabrication processes, and still provide the quintessential metal-oxide/metal framework due to the presence of the native surface oxide (i.e., Gallium Oxide, Ga2O3) of eGaIn at the nanoconfinement (i.e., nanopores) for nano/biosensing. We harnessed these new materials to sense and differentiate microliter volumes of deionized (DI) water, 1M hydrochloric acid (HCl), and 95% ethanol (EtOH), leveraging their electrical signatures. This new class of soft nanomaterials has the potential to become the paradigm-shift platforms for the next-generation of biomedical, bioelectronics, nanoelectronics, and sensor devices.

physics.med-ph↗