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1. The Design and SAR Analysis of a UWB Bow-tie Antenna for Wireless Wearable Sensors

   Kakaraparty, Karthik; Mahbub, Ifana (January 2022, THE USNC-URSI 2022 National Radio Science Meeting)

   Kakaraparty, Karthik; Mahbub, Ifana (Ed.)

   This paper presents design of a wearable flexible patch antenna and its corresponding SAR (specific absorption rate) analysis when placed on a human body. The substrate material used is polyimide with a thickness of 0.1 mm, and gold is used for the patch and ground material with 200 nm thickness. The di-electric constant and the tangent loss of the polyimide substrate are 3.5 and 0.0002, respectively. The dimensions of the proposed antenna are 30×30×0.1004 mm3. The designed antenna has the resonating frequency at 3.45 GHz and a bandwidth of 2.6 GHz. The far field gain of the designed antenna is 7.5 dBi. The SAR analysis generated an SAR value of 0.174 W/kg, which is within the safe limit of 2W/kg averaged over 10g of tissue as specified by the ICNIRP (International Commission of Non-Ionization Radiation Protection). This suggests that the designed antenna is safe and can be utilized for wireless wearable sensors. 

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2. Design of a Compact 24 GHz Antenna Array for Unmanned Aerial Vehicle-to-Vehicle (V2V) Communication

   https://doi.org/10.1109/AP-S/USNC-URSI47032.2022.9886200  

   Kakaraparty, Karthik; Roy, Sunanda; Mahbub, Ifana (September 2022, 2022 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (AP-S/URSI))

   This paper presents the design of a compact 4 × 4 antenna array suitable for unmanned aerial vehicle-to-vehicle (V2V) communication applications. The proposed antenna array can offer a narrow beamwidth, high gain, wide beam steering capability and is highly compact. The substrate material used is Rogers 5880 with a thickness of 0.2 mm, and copper is used for the patch and ground material with 0.14 mm thickness. The di-electric constant and the tangent loss of the Rogers substrate are 2.2 and 0.0004, respectively. 45° phase shifters are incorporated in the feeding paths to facilitate the beamsteering. The dimensions of the proposed antenna array are 32 × 32 × 0.48 mm 3 . The designed antenna array has the resonating frequency at 24 GHz and has a bandwidth of 0.83 GHz (3.5% fractional bandwidth). The measured far field gain of the designed antenna array is 16.7 dBi. The beamwidth derived from the array’s far-field radiation pattern is 14.6°, and the maximum beam steering range of the array is 102° along the θ axis. 

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3. Design and Performance Analysis of a 24 GHz Series-Fed $$1 \times 5$$ Antenna Array with Material Deformation for D2D Applications

   https://doi.org/10.1109/USNC-URSI52151.2023.10238054  

   Kakaraparty, Karthik; Mahbub, Ifana (July 2023, 2023 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (USNC-URSI))

   This paper presents the design and simulation of a 24 GHz 1×5 series-fed microstrip patch antenna array and its performance analysis with structural deformation. The optimized design comprises of 5 antenna elements arranged in series, where the entire design is symmetric about the center antenna element. The parameters such as S11 , gain vs. theta plots are analyzed with and without the material deformation. The shape deformation analysis is indeed needed to determine the performance efficiency of the designed antenna when deployed on drones, where the antenna needs to be flexible enough to be aligned with the curvature of drone's body. The simulation results are analyzed to see how best can the proposed antenna array can perform with the structural deformation. 

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4. DESIGN OF A WEARABLE ULTRASOUND PATCH WITH SOFT AND CONFORMAL MATCHING LAYER

   https://doi.org/10.1115/DMD2023-8253  

   Krings, Ethan J; Truong, Sequoia L; Reeser, Kiersten A; Hage, Benjamin D; Bashford, Gregory R; Markvicka, Eric J (April 2023, American Society of Mechanical Engineers)

   Abstract Ultrasound is a safe, noninvasive diagnostic technique used to measure internal structures such as blood vessels and the velocity of blood flow in the human body. The ability to continuously measure blood flow in major cerebral arteries would enable the early detection of medical problems such as stroke. However, current ultrasound technology consists of rigid, hand-held probes that are arduous to use, sensitive to movement, and are primarily designed for intermittent, instead of continuous use. Here, we describe the design of a wearable ultrasound patch for continuously measuring blood flow velocity through the middle cerebral artery (MCA) that can be assessed from the temple region of the head. The wearable ultrasound patch is composed of an array of piezoelectric elements that are wired together using flexible electrical conductors and encapsulated in an elastic substrate. To improve ultrasound energy transfer, a soft and conformal composite matching layer is introduced. The matching layer consists of gallium-based liquid metal (LM) microdroplets dispersed in a silicone elastomer. The acoustic impedance of the matching layer can be tuned by varying the volume loading of LM. The wearable ultrasound patch will provide new opportunities to continuously measure blood flow velocity and ultimately enable early detection of medical problems such as stroke. 

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5. On efficient asymptotic modelling of thin films on thermally conductive substrates

   https://doi.org/10.1017/jfm.2021.157  

   Allaire, Ryan H.; Cummings, Linda J.; Kondic, Lou (May 2021, Journal of Fluid Mechanics)

   We consider a free-surface thin film placed on a thermally conductive substrate and exposed to an external heat source in a set-up where the heat absorption depends on the local film thickness. Our focus is on modelling film evolution while the film is molten. The evolution of the film modifies local heat flow, which in turn may influence the film surface evolution through thermal variation of the film's material properties. Thermal conductivity of the substrate plays an important role in determining the heat flow and the temperature field in the evolving film and in the substrate itself. In order to reach a tractable formulation, we use asymptotic analysis to develop a novel thermal model that is accurate, computationally efficient, and that accounts for the heat flow in both the in-plane and out-of-plane directions. We apply this model to metal films of nanoscale thickness exposed to heating and melting by laser pulses, a set-up commonly used for self and directed assembly of various metal geometries via dewetting while the films are in the liquid phase. We find that thermal effects play an important role, and in particular that the inclusion of temperature dependence in the metal viscosity modifies the time scale of the evolution significantly. On the other hand, in the considered set-up the Marangoni (thermocapillary) effect turns out to be insignificant. 

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