PUBLICATIONS

PUBLICATIONS

Journals

Patents

Journals

  • 74

    Expressions for Resonant Frequency of Wirelessly Accessible Planar Mirrored-Coil Sensor in Biomedicine

    Abstract:

    Planar mirrored-coil structures are often used in the field of biomedicine as a sensor to measure physiological signals wirelessly. Although there are many studies on interrogation methodologies, research on the sensor itself remains understudied. In this article, we report an analytical formulation and a data-fitted formula to calculate the resonant frequency for a planar mirrored-coil sensor. Compared to the measured results, our analytical formula and data-fitted formula deviate by 13% and 9% median errors, respectively, which is much more accurate than the conventional one, 23%. It shows that both methods provide a way to quickly evaluate and design a planar mirrored-coil structure with high precision.
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  • 73

    Nickel-cobalt phosphate nanoparticle-layer shielded in-situ grown copper-nickel molybdate nanosheets for electrochemical energy storage

    Abstract

    Transition metal molybdates and phosphates are prominent electroactive materials for energy storage devices due to their high theoretical capacity, multiple valence states, good electrical conductivity, and natural abundance. Herein, we report in-situ grown high redox-active copper-nickel molybdate (CuNiMo) on copper foam (CF) via a one-pot solvothermal approach and the influence of reaction time on its morphology was studied in detail. The CuNiMo electrode prepared at a reaction time of 9 h (CuNiMo-9/CF) exhibited ultrathin nanosheets (UTNSs) that are vertically grown from CF substrate with the interconnected network. Owing to the advanced morphological features, the CuNiMo-9/CF electrode delivered a superior areal capacity of 387.5 µAh cm−2 (at 5 mA cm−2) to the other CuNiMo electrodes obtained at the reaction times of 6 and 12 h. In addition, the bare CF, CuNi-9/CF, and CuMo-9/CF electrodes were investigated for comparison. Next, Co-Ni phosphate (CoNiP) nanoparticle-layer was decorated on CuNiMo-9/CF UTNSs by a solution-immersion technique to enhance the redox chemistry. Exploiting the synergistic features of mixed metal molybdates and phosphates, the CoNiP@CuNiMo-9/CF composite material exhibited an exalted areal capacity of 666 µAh cm−2 at the same current density. Furthermore, the hybrid cell (HC) was assembled with the CoNiP@CuNiMo-9/CF as the positive electrode to explore its practical applicability. The assembled HC also exhibited maximum energy and power densities of 38.2 Wh kg−1 (1.09 mWh cm−2) and 2327.5 W kg−1 (66.5 mW cm−2), respectively. Also, the HC device demonstrated good cycling stability with a notable capacity retention of 87.7% after 3000 cycles. The real-time viability of HC was also tested by powering various electronic components.

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  • 72

    Designing of hierarchical lychee fruit-like cobalt-selenide heterostructures with enhanced performance for hybrid supercapacitors

    Abstract

    Hierarchical porous structured active materials for energy storage devices could increase the surface area, stimulate the charge transport kinetics, and regulate the volume changes during the charge/discharge process. Moreover, the fabrication of heterostructures would increase the interfacial electric field and modify the electronic structure. The features of hierarchical porous heterostructures are more beneficial to enhance the electrochemical properties and robustness of electrode materials for supercapacitors (SCs). Herein, novel hierarchical lychee fruit-like cobalt-oxide@coblat-selenide heterostructure composites (LF-CoO@CoSe HSCs) composed of three-dimensional nanoparticles were prepared via an efficient single-step hydrothermal approach followed by calcination treatment. The LF-CoO@CoSe HSC-500 electrode exhibited a high specific capacity value of 341.6 mAh g−1 (2146.2 F g−1) at a current density of 2 A g−1 compared to the other electrodes annealed at 400 and 600°C (LF-CoO@CoSe HSC-400 (307.2 mAh g−1) and LF-CoO@CoSe HSC-600 (131.8 mAh g−1)), respectively. The LF-CoO@CoSe HSC-500 electrode delivered good cycling stability (77.5%). Furthermore, the pouch-type aqueous hybrid SC (AHSC) was constructed with LF-CoO@CoSe HSC-500 as a positive electrode and porous activated carbon as a negative electrode. The assembled AHSC device delivered maximum energy and power density values of 37.01 Wh kg−1 and 9490 W kg−1, respectively with superior cycling stability of 134% even after 5000 cycles. Furthermore, the fabricated AHSC device was successfully powered a mini light-emitting diode bulb and a timer display. The prepared composites could be an efficient electro-active material for high-capacity SC applications.

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  • 71

    An Efficient Power Management System Using Dynamically Configured Multiple Triboelectric Nanogenerators and Dual-Parameter Maximum Power Point Tracking

    Abstract

    Triboelectric nanogenerators (TENGs) have shown great potential as sustainable energy sources with the advantages of a lightweight, low cost, simple fabrication, and small size. Nevertheless, schemes for efficient power extraction from TENGs remains difficult, partly because of their short, high-voltage (HV) pulse output. The available power from a single TENG is not usually enough for practical applications. An efficient power management system for TENGs using a dynamically reconfigured combining method and dual-parameter maximum power point tracking (MPPT) is proposed. A series to parallel/parallel to series (SPPS) adaptive control method, which dynamically reconfigures the connection of multiple TENGs, efficiently combines the outputs. An MPPT method, which adjusts the dual parameters in a closed-loop, provides a wide range for matching the high output impedance (≈MΩ) of TENGs. The proposed technique is implemented using a 416 nW energy harvester interface integrated circuit (EHI-IC), realized using a 180 nm, 48 V Bipolar-CMOS-DMOS (BCD) process. Measured results show that the proposed approach achieves a 159-fold improvement in power extraction compared to the results without EHI-IC. Finally, a triboelectric energy harvesting ball (T-EHB), which combines 12 TENG pairs for multi-axis excitation, and several examples of device powering are presented using the T-EHB.

     

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  • 70

    Nanosilver-Particles Integrated Ni3Sn2S2-CoS Composite as an Advanced Electrode for High Energy Density Hybrid Cell

    Abstract

    An ion-exchange process is a promising approach to design advanced electrode materials for high-performance energy storage devices. Herein, a nanostructured Ni3Sn2S2-CoS (NSS-CS) composite is fabricated by successive hydrothermal and ion-exchange processes. Since the incorporation of redox-rich cobalt element enables the NSS-CS composite to be more electrochemically active, its impact on the electrochemical performance is therefore extensively studied. Particularly, the NSS-CS-0.2 g electrode material delivered a high areal capacity of 830.4 µAh cm−2 at 5 mA cm−2. Additionally, a room-temperature wet-chemical approach is employed to anchor nanosilver (nAg)-particles on the NSS-CS-0.2 g (nAg@NSS-CS-0.2 g) to further exalt its electrokinetics. Consequently, the nAg@NSS-CS-0.2 g electrode shows a higher areal capacity of 948.5 µAh cm−2 (193.5 mAh g−1) than that of the NSS-CS-0.2 g. Furthermore, its practicability is also examined by assembling a hybrid cell. The assembled hybrid cell delivers a high areal capacity of 969.2 µAh cm−2 (49.2 mAh g−1) at 7 mA cm−2 and maximum areal energies and power densities of 0.784 mWh cm−2 (40.8 Wh kg−1) and 45 mW cm−2 (2347.4 W kg−1), respectively. The efficiency of the hybrid cells is also tested by harvesting solar energy, followed by energizing electronic components. This work can pave the way for significant attraction in designing advanced electrodes for energy-related fields.

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  • 69

    Batteryless, Miniaturized Implantable Glucose Sensor Using a Fluorescent Hydrogel

    Abstract

    We propose a biomedical sensor system for continuous monitoring of glucose concentration. Despite recent advances in implantable biomedical devices, mm sized devices have yet to be developed due to the power limitation of the device in a tissue. We here present a mm sized wireless system with backscattered frequency-modulation communication that enables a low-power operation to read the glucose level from a fluorescent hydrogel sensor. The configuration of the reader structure is optimized for an efficient wireless power transfer and data communication, miniaturizing the entire implantable device to 3 × 6 mm 2 size. The operation distance between the reader and the implantable device reaches 2 mm with a transmission power of 33 dBm. We demonstrate that the frequency of backscattered signals changes according to the light intensity of the fluorescent glucose sensor. We envision that the present wireless interface can be applied to other fluorescence-based biosensors to make them highly comfortable, biocompatible, and stable within a body.

    Keywords: WPT; batteryless; fluorescent; glucose; implantable; wireless.

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  • 68

    Hybrid energy harvesting system based on Stirling engine towards next-generation heat recovery system in industrial fields

    Abstract

    Tremendous energy is being wasted without any proper utilization despite the energy crisis and global warming. Especially, enormous thermal energy is wasted, which is generated from the industrial fields. To handle this issue, technology is highly desired to harvest this wasted thermal energy. Herein, a hybridized energy harvesting system based on Stirling engine (HESS) is proposed in order to harvest the wasted thermal energy in industrial fields. The developed HESS is composed of a disk triboelectric nanogenerator (disk TENG) and electromagnetic generator (EMG) based on Stirling engine that converts thermal energy into mechanical energy. Hence, the HESS can harvest the electricity from the mechanical energy converted from the thermal energy owing to the Stirling engine and shows its great stability of the performance by generating electrical output for more than 2 h without any specific degradation. Each part of the single EMG and the disk TENG in the HESS respectively generates an output power of 0.384 μW at 60 Ω and 1.2 μW at 30 MΩ, and the HESS can generate 1.4 μW at 9 MΩ by integrating each generated power. Moreover, the fabricated HESS generates 14.51 times more electrical energy than generated electrical energy through the single EMG. Considering these results, the next-generation heat recovery system can be implemented with the HESS by converting the wasted thermal energy into electrical energy in the industrial fields.

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  • 67

    Enhanced self-host blue emission of CaSrSb2O7 materials via Bi3+ ion doping for high CRI WLEDs, security inks and flexible displays

    Abstract

    Luminescent materials are indispensable in our daily lives and have already been widely applied in various fields. Herein, novel self-host blue-emitting CaSrSb2O7 and CaSrSb2O7:Bi3+ phosphors with orthorhombic space group Imma (74) were successfully prepared. The phase purity, elemental composition, morphology, luminescent behaviors, etc. were investigated in detail. To compare the luminescence properties of rare-earth-activated phosphors, the self-host blue-emitting CaSrSb2O7 phosphor with unique performance exhibited a good quantum yield (QY) of 39.81%, and its emission intensity and QY could also be improved by doping Bi3+ ions. The CaSrSb2O7:Bi3+ phosphor was located in the pure blue region with the Commission Internationale de I'Eclairage chromaticity coordinate of (0.151, 0.058) and good color purity of 89.35%. For identifying its potential applications, the packaged white light-emitting diode device emitted a high color rendering index value of 93.66 under a forward current of 300 mA, and it would be further applied in security inks and flexible displays owing to its strong emission by the naked eyes. These results suggest that novel self-host blue-emitting CaSrSb2O7:Bi3+ phosphors could be used in multifunctional applications.

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  • 66

    Quantifying and dispensing of magnetic particles in a self-assembled magnetic particle array

    Abstract

    We develop a low-cost, mass-production process for creating rod-shaped glass-coated magnetic particles consisting of a magnetic metal core and glass shell structure. We investigate their magnetic properties by analyzing their optical absorbance in suspension as a function of the orientation of a 1 mT magnetic field. From the response we derive that the magnetization of the particles is 0.1 MA/m. We demonstrate an automated system that quantifies and dispenses a large amount of RGMPs by magnetic self-assembly on a high-volume plate patterned with an array of holes. This automatic dispenser can provide packaging forms with the smallest unit of RGMPs for in-vitro diagnostics and is expected to reduce the time and effort required for the assembly and packaging process.

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  • 65

    Two-dimensional porous NiCo2O4 nanostructures for use as advanced high-performance anode material in lithium-ion batteries

    Abstract

    Two-dimensional (2D) porous NiCo2O4 nanostructures (NCO NSs) were investigated for use as an anode material in lithium-ion batteries (LIBs). The 2D porous NCO NSs were synthesized using a solvothermal technique, followed by annealing at different temperatures of 300, 400, and 500 °C (referred to as NCO-300, NCO-400, and NCO-500, respectively). High-resolution scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses were used to examine the synthesized NCO NSs. The initial lithiation/de-lithiation capacities of the NCO-300, NCO-400, and NCO-500 electrodes were 1068.05 mA h g−1/816.55 mA h g−1, 1061.08 mA h g−1/805.78 mA h g−1, and 904.73 mA h g−1/701.95 mA h g−1, respectively at 100 mA g−1. The NCO-400 electrode displayed relatively excellent rate performance and outstanding reversibility compared with the other two electrodes because of its ultrafine thickness and highly porous structure. According to our electrochemical results, the 2D porous NCO-400 electrode appears to be very promising for use as an advanced anode in high-performance LIBs.

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