Browsing by Author "Kim, Seonghwan (Sam)"

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    A Novel Scalable Approach to Solid Metal Microneedle Fabrication via an Automated Modified Wire Bonding Process
    (2024-01-15) Haider, Syed Kazim; Dalton, Colin; Kim, Seonghwan (Sam); Jones, Steven; Park, Simon
    Hypodermic needles have played a pivotal role in medical treatments; however, their use often incites fear due to pain and tissue trauma. Microneedle arrays present a promising alternative, with their smaller size resulting in reduced pain and trauma, however they have faced manufacturing scale-up challenges due to the complex microfabrication processes involved, precluding their widespread adoption into clinical practice. This research introduces a novel microneedle fabrication method utilizing a modified wire bonding process, enabling rapid iteration of designs on a single automated system. Key fabrication parameters, such as loop settings and wire bonding capillary shape, were explored to understand their impact on microneedle geometry. This study finds how specific wire bonding parameters can influence microneedle tip sharpness, crucial for efficient skin penetration. Additionally, the research delves into how these parameters affect microneedle length, a crucial factor for delivering drugs to a sufficient depth below skin. A significant aspect of this work involved investigating three different bonding wire diameters (25, 33, and 50 µm). The findings revealed that the largest diameter, 50 µm, exhibited optimal performance in terms of robustness, and had the least tendency to bend upon insertion into porcine skin tissue, and the lowest failure rate during microneedle fabrication. Initial tests on porcine skin validated the effective penetration ability of the wire bonded microneedles. A computational simulation was also developed to illustrate how the unique tip shapes, achievable through wire bonding, can enhance skin penetration. This iterative process, encompassing simulation, fabrication, and testing, underscores the potential of this novel fabrication method as a versatile platform technology. This research lays a solid foundation for broad applications, paving the way for future optimizations and adaptations tailored to specific microneedle requirements for different applications.
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    Development of 3D MOF Nanocomposites with Semiconducting Behavior for Resistive Gas Sensors and Photodetectors Applications
    (2023-12-05) Himayoonnia, Setareh; Kim, Seonghwan (Sam); Du, Ke; Kim, Keekyoung Kim
    This thesis presents a comprehensive exploration of three distinct projects involving novel nanocomposites consisting of metal-organic frameworks (MOFs) combined with multiwall carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs). These projects encompass methane (CH4) detection, the application of MOF composites for diabetes diagnosis through acetone detection, and their utilization as advanced photodetectors. In the first project, addressing the critical issue of CH4 detection, an innovative MOF/MWCNTs-based resistive sensor was developed. CH4 detection is crucial due to its environmental and safety implications. Existing detection methods often struggle with low concentrations of CH4 at room temperature (RT), typically within the range of a few parts per million (ppm). The developed sensor offers cost-efficiency, reliability, high sensitivity, and selectivity, presenting a breakthrough technology with the potential to significantly enhance environmental monitoring and industrial safety. The second project focuses on diabetes management, a global health concern. Traditional invasive blood glucose measurements can be cumbersome. To simplify and improve diabetes monitoring, the research investigates non-invasive nanomaterial-based gas sensors for detecting acetone, a diabetes biomarker. The developed MOF/MWCNTs nanocomposite resistive sensor offers selective detection of acetone at RT and atmospheric pressure, exhibiting remarkable sensitivity. The limit of detection is three orders of magnitude lower than the concentration of acetone in the exhaled breath of diabetic patients. The third project explores the application of MOF/CNF nanocomposites in photodetectors, crucial components in various technological domains. Traditional photodetectors face limitations, such as broadband absorption and the need for costly optical filters in narrowband applications. The introduced MOF/CNF nanocomposites address these challenges, combining the strengths of MOFs and CNFs while mitigating their weaknesses. This research not only overcomes limitations in traditional and recent nanomaterials-based photodetectors but also extends the capabilities of three-dimensional (3D) MOFs in narrowband photodetection applications, potentially revolutionizing photodetection technology. Overall, this thesis explores the potential of MOF-based nanocomposites in addressing critical challenges in CH4 detection, diabetes management, and photodetection, holding promise for environmental preservation, healthcare, and technological advancements.
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    Enhancing the Sensitivity of NDIR Spectroscopy Using Plasmonic Crystal Structures
    (2016) Ahmed, Amr Elsayed Shebl Mahmoud; Kim, Seonghwan (Sam); Mohamad, Abdulmajeed; Murari, Kartikeya; Sanati Nezhad, Amir
    Monitoring the concentration of methane is of crucial importance for health, safety, and maintenance. NDIR spectroscopy is a widely used commercially available method of monitoring the concentration of Gases. Enhancing the sensitivity of the IR detector enhances the limit of detection of NDIR sensors. Plasmonic crystal structures have been shown to enhance the absorption of EM radiation at certain wavelengths depending on their dimensions. In this thesis, a 13 fold enhancement in the LOD of a methane NDIR gas sensor was achieved by designing a plasmonic crystal structure. The structure is a layer of gold with a two dimensional array of micro sized holes. The dimensions of the structure were optimized by COMSOL simulations to get maximum absorption at λ=7.7 µm. The structure was fabricated and the NDIR sensor was developed to experimentally show the enhancement. The experimental results showed good agreement with the simulations and achieved the expected enhancement.
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    Multi-modal, Ultrasensitive Detection of Trace Explosives Using MEMS Devices
    (2016-01-15) Zandieh, Omid; Kim, Seonghwan (Sam); Mohamad, Abdulmajeed; Murari, Kartikeya; Park, Simon
    Multi-modal chemical sensors based on microelectromechanical systems (MEMS) have been developed with an electrical readout. Opto-calorimetric infrared (IR) spectroscopy, capable of obtaining molecular signatures of extremely small quantities of adsorbed explosive molecules, has been realized with a microthermometer/microheater device using a widely tunable quantum cascade laser. A microthermometer/microheater device responds to the heat generated by non-radiative decay process when the adsorbed explosive molecules are resonantly excited with IR light. Monitoring the variation in microthermometer signal as a function of illuminating IR wavelengths corresponds to the conventional IR absorption spectrum of the adsorbed molecules. In addition, micro differential thermal analysis, which can be used to differentiate the exothermic or endothermic reaction of heated molecules, has been performed with the same device to provide additional orthogonal signal for trace explosive detection and sensor surface regeneration. We have demonstrated the successful detection, differentiation, and quantification of trace amounts of explosive molecules and their mixtures.