Faculty Publications
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Item Needle in a Haystack: Detecting Subtle Malicious Edits to Additive Manufacturing G-Code Files(Institute of Electrical and Electronics Engineers Inc., 2022) Beckwith, C.; Naicker, H.S.; Mehta, S.; Udupa, V.R.; Nim, N.T.; Gadre, V.; Pearce, H.; Mac, G.; Gupta, N.Increasing usage of digital manufacturing (DM) in safety-critical domains is increasing attention on the cybersecurity of the manufacturing process, as malicious third parties might aim to introduce defects in digital designs. In general, the DM process involves creating a digital object (as CAD files) before using a slicer program to convert the models into printing instructions (e.g., g-code) suitable for the target printer. As the g-code is an intermediate machine format, malicious edits may be difficult to detect, especially when the golden (original) models are not available to the manufacturer. In this work, we aim to quantify this hypothesis through a red team/blue team case study, whereby the red team aims to introduce subtle defects that would impact the properties (strengths) of the 3-D printed parts, and the blue team aims to detect these modifications in the absence of the golden models. The case study had two sets of models, the first with 180 designs (with two compromised using two methods) and the second with 4320 designs (with 60 compromised using six methods). Using statistical modeling and machine learning (ML), the blue team was able to detect all the compromises in the first set of data, and 50 of the compromises in the second. © 2009-2012 IEEE.Item Sensitivity improvement of photonic crystal refractive index sensor using porous silicon nano rods(Elsevier Ltd, 2023) Mehta, S.; Vankalkunti, S.; Kachhap, P.K.; Gautam, P.R.; Singh, M.This work proposes a photonic crystal refractive-index sensor for detecting volatile organic compounds (VOC). Two sensor designs are analyzed with Y-splitter photonic crystal waveguide using the finite-difference time-domain (FDTD) method. Also, simultaneous monitoring of two different analytes is possible across the arms of the Y-splitter. The porous silicon (p-Si) rods with a porosity of 25% are used to create a variable refractive index sensing region, which induces a relative shift in the resonant wavelength of the traveling mode. The response at the output ports is monitored in terms of transmittance power versus wavelength plot. The numerical simulations confirm ∼195.83 nm/RIU sensitivity and ∼24.482 RIU−1 figure-of-merit in the presence of hazardous alcohols. © 2023 Elsevier LtdItem Engineering Porous Silicon-Based Plasmonic Microdisk Resonator for Highly Sensitive Methanol Sensing(Institute of Electrical and Electronics Engineers Inc., 2024) Mehta, S.; Nakul Nayak, V.B.; Singh, M.This study introduces a novel application of a plasmonic microdisk resonator as a highly sensitive sensor for detecting methanol vapor. Leveraging the inherent advantages of plasmonic nanostructures, the microdisk resonator demonstrates a remarkable capability to detect minute concentrations of methanol. In this work, we modeled a novel 3-D porous-silicon (p-Si)-based hybrid plasmonic aperture-coupled microdisk resonator (HPACMR) with specific dimensions and porosity to optimize the sensitivity toward methanol vapor detection. The resonator's design incorporates a thin layer of copper on a dielectric microdisk, creating a plasmonic cavity that supports localized surface plasmon resonances. Finite element method-based simulations predict strong interactions between the resonator's plasmonic field and methanol molecules, leading to detectable shifts in the resonant frequency. By tuning the layout dimensions and p-Si properties, we achieved an altitudinous sensitivity of 569.52 nm/RIU and a Q-factor of nearly 370. The sensors' miniature footprint and potential for integration into portable devices make it an attractive candidate for field-deployable applications. © 2001-2012 IEEE.Item High-Q Plasmonic Resonator for Volatile Organic Compound Detection(Institute of Electrical and Electronics Engineers Inc., 2025) Mehta, S.; Shivaputra, S.; Ramesh, S.; Mandi, M.V.; Singh, M.A hybrid plasmonic waveguide (HPWG)-based resonator designs are studied for on-chip detection of volatile organic compounds (VOCs). The HPWG, which combines dielectric and metallic layers, significantly enhances the confinement of electromagnetic field, leading to increased interaction between the guided light and the surrounding analytes. The system achieves high spectral sensitivity and narrow linewidth by integrating multiple microring resonators in a cascaded configuration. This is critical for distinguishing small changes in the refractive index (RI) associated with different VOCs. Finite element method (FEM) simulations demonstrate the superior sensing performance of a proposed device, showing a spectral sensitivity of 469.5 nm/RIU and a quality factor (QF) of 518.75. The compact design and high sensitivity make this sensor an excellent candidate for on-chip VOC monitoring in industrial safety, as well as portable breath sensors to detect VOC biomarkers for early disease diagnosis. © IEEE. 1973-2012 IEEE.