Browsing by Author "Hassan, Sakib"

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    Efficiency Limit of Far- and Near-field Thermophotovoltaic Energy Conversion
    (2019-07-31) Hassan, Sakib; Naik, Gururaj V
    Thesis Title: Efficiency Limit of Far- and Near-field Thermophotovoltaic Energy Conversion Ever increasing energy demand worldwide coupled with environmental concern forces the current fossil-fuel based energy paradigm to be shifted to alternative or renewable energy sources. Heat energy is such an alternative potential energy source that is abundant in industries as a form of waste heat, which is approximately 20-50\% of consumed energy. Utilizing this huge waste energy can lead to a sustainable, efficient, and clean energy production system. For this purpose, solid-state devices are most suitable. Thermophotovoltaic energy conversion (TPV) is a solid-state technology of converting thermal radiation from hot emitter directly into electricity without any moving parts. It has widespread applications in the defense, space, energy, and microelectronics because it is compact, lightweight, and robust. Despite their prospects, TPV devices have not been widely used only due to their poor efficiency. The poor efficiency of TPV device stems from two factors: spectral mismatch between emitter and PV cell, and high dark current in low bandgap PV cells. Additionally, parasitic absorption in the phonon band also reduces efficiency. In other words, the emission spectrum from the emitter holds the key for high-efficiency TPV system. Hence, spectrally selective thermal emission or enhanced near-field radiative heat transfer allows TPV cells to operate at efficiencies much higher than the current record of about 7 %. Here in this thesis, we optimize the design parameters of the thermal emitter together with the PV cell to find out the desired optoelectronic characteristics of a TPV device for any given operating temperature. We also find out the ultimate TPV conversion efficiency possible in real systems operating in the far and near-field configurations. Our analysis shows that sub-bandgap emission suppression and bandgap emission enhancement are the key parameters for high-efficiency operation. High suppression of undesired photons, even with moderate emission in the desired band, is more important for high efficiency. Our study shows that suppression of at least 20 dB and enhancement of at least 100 is necessary for achieving 60 % of Carnot efficiency at 1300 K. Using realistic properties of materials that make emitters, we show that Mo and W are good choices for thermal emitters. Our design framework should serve as a practical design guideline for the development of high-performance TPV system.
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    Functional wood for carbon dioxide capture
    (Cell Press, 2023) Roy, Soumyabrata; Philip, Firuz Alam; Oliveira, Eliezer Fernando; Singh, Gurwinder; Joseph, Stalin; Yadav, Ram Manohar; Adumbumkulath, Aparna; Hassan, Sakib; Khater, Ali; Wu, Xiaowei; Bollini, Praveen; Vinu, Ajayan; Shimizu, George; Ajayan, Pulickel M.; Kibria, Md Golam; Rahman, Muhammad M.
    With increasing global climate change, integrated concepts to innovate sustainable structures that can multiaxially address CO2 mitigation are crucial. Here, we fabricate a functional wood structure with enhanced mechanical performance via a top-down approach incorporating a high-performance metal-organic framework (MOF), Calgary framework 20 (CALF-20). The functional wood with 10% (w/w) CALF-20 can capture CO2 with an overall gravimetric capacity of 0.45 mmol/g at 1 bar and 303 K that scales linearly with the MOF loading. Interestingly, the functional wood surpasses the calculated normalized adsorption capacity of CALF-20 stemming from the mesoporous wood framework, pore geometry modulation in CALF-20, and favorable CO2 uptake interactions. Density functional theory (DFT) calculations elucidate strong interactions between CALF-20 and the cellulose backbone and an understanding of how such interactions can favorably modulate the pore geometry and CO2 physisorption energies. Thus, our work opens an avenue for developing sustainable composites that can be utilized in CO2 capture and structural applications.
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    Real-time In Vitro and In Vivo Biosensing using Photonic Microring Resonators
    (2023-04-18) Hassan, Sakib; Robinson, Jacob
    Real-time in vivo detection of different bioanalyte and biomarkers, particularly nitric oxide (NO) and temperature, is of utmost importance for critical healthcare monitoring, therapeutic dosing, and fundamental understanding of their role in regulating many physiological processes. However, the detection of NO in a biological medium is challenging due to its short lifetime and low concentration. Traditional methods of detecting bioanalyte and biomarkers suffer from many limitations such as complex sample preparation, complicated and expensive instrumentation, electromagnetic interference, etc. Here, we demonstrate for the first time that photonic Micro Ring Resonators (MRRs) can provide real-time, direct, and in vivo detection of NO in a mouse wound model. The MRR encodes the NO concentration information into its transfer function in the form of a resonance wavelength shift. We show that these functionalized MRRs, fabricated using CMOS-compatible processes, can achieve sensitive detection of NO (sub-µM) with excellent specificity, and no apparent performance degradation over more than 24 hours of operation in the biological medium. In another study, we show that this MRR can measure magnetic nanoparticle heating with high precision and fast temporal resolution (10 µs). MRR has negligible thermal mass and is not affected by electromagnetic interference; therefore, it can provide a more accurate measurement of specific absorption rate for sample volume as small as a few µL. We also demonstrate that MRR can measure the temperature gradient of a sample substrate with high spatial resolution and is capable of measuring the multiplexing capability of dual-channel magnetic nanoparticles. Finally, we could successfully measure the temperature of the targeted region of the brain slice during AMF stimulation which is not possible with traditional methods. Therefore, with alternative functionalization, this compact lab-on-chip optical sensing platform could support the real-time detection of myriad biochemical species and biomarkers and can revolutionize the field of biomedical science and healthcare monitoring.