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PUBLICATIONS

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Patents

Journals

  • 104

    rGO-ZnSnO3 Nanostructure-Embedded Triboelectric Polymer-Based Hybridized Nanogenerators

    Abstract

    Piezoelectric/ferroelectric zinc tin oxide (ZnSnO3) nanocubes (NCs) are synthesized via a hydrothermal synthesis process. Piezoelectric materials exhibit a superior dielectric property, strong electric dipole moment, and higher piezoelectric coefficient, which results in an improved electrical output of the nanogenerator. The synthesized ZnSnO3 NCs are embedded in triboelectric polydimethylsiloxane (PDMS) polymer to employ the synergistic effect of ZnSnO3/PDMS composite polymer matrix (CPM), which creates a hybrid nanogenerator (HNG). The proposed HNG reveals a high electrical performance due to the improved dielectric constant as well as the synergistic effect of piezoelectricity and triboelectricity. Besides, a conductive filler material such as reduced graphene oxide (rGO) is synthesized using a modified Hummer's method and is further utilized to prepare an rGO-ZnSnO3/PDMS CPM for improving the electrical output performance of the HNG. Furthermore, the ZnSnO3 NCs and rGO-ZnSnO3 with different amounts are embedded into PDMS polymeric film to optimize the electrical performance of the HNG. The durability test of the proposed HNG device along with the robustness is investigated. Finally, the proposed HNG device is employed to harvest mechanical movements from daily life human activities to power various portable electronics.

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  • 103

    Robust and flexible triboelectric nanogenerator using non-Newtonian fluid characteristics towards smart traffic and human-motion detecting system

    Abstract

    Due to the self-powered property of the triboelectric nanogenerator (TENG), development of the TENG based sensor is highly required to solve the major obstacles composed of the size and power consumption issues induced by external power source of the conventional Internet of Things (IoT) device. However, the conventional TENG based sensors are generally composed of thin films and these films can be easily damaged by external impact. With these damaged films, a malfunction of the conventional TENG based sensor can occur, which can induce an accident in a place where these sensors are utilized. Herein, the non-Newtonian fluid (NNF) with the shear thickening phenomenon (STP), which can increase its robustness as the applied external force to the NNF increases, is utilized to fabricate the TENG. Hence, the fabricated NNF with the STP based TENG (NNFT) is possessing the high resistance to impact as well as flexibility, simultaneously. The water-assisted oxidation is conducted to form the nanostructures on the surface of the Al electrode at the NNFT. Also, by adding the polyvinylidene fluoride powder into the NNFT (NNFT-P), the high open-circuit voltage of 260 V, short-circuit current of 11.2 μA, and power density of 37.5 mW/m2 are generated from the NNFT-P. As an application, the NNFT-P based self-powered traffic detection system (NSTDS) is implemented. With the NSTDS, the dangerous situation is successfully alerted to the pedestrian without significant damage in the NSTDS when the speeding vehicle is passing the NSTDS. Furthermore, the human motions including walking, running, and jumping are successfully detected with the proposed NNFT-P. Considering these results, the proposed NNFT-P is predicted to be utilized as the smart traffic system as well as human motion detecting sensor in near future.

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  • 102

    Switchless Oscillating Charge Pump-Based Triboelectric Nanogenerator and an Additional Electromagnetic Generator for Harvesting Vertical Vibration Energy

    Abstract

    According to energy crisis and increasing number of small electronics, energy harvesting is one of the most promising technologies for scavenging several types of wasted energy. Especially, with regard to vibrational energy harvesting, triboelectric nanogenerators and electromagnetic generators stand out due to their working mechanisms. Here, an oscillating charge pump-based hybrid generator with two triboelectric nanogenerators and an electromagnetic generator using a switching-free characteristic was fabricated with material optimization. To enhance the electrical output of the triboelectric nanogenerator, a concept of charge pumping with simply connecting an additional charge pump device and the nanostructure formation process on the contact metal layer were adopted. The electrical outputs were characterized as an output current of 9.17 μA with a current density of 83.2 mA m–3 in the triboelectric nanogenerator. The power density of the triboelectric nanogenerator reached 4.45 W m–3 with a 40 MΩ resistor. The electromagnetic generator showed an output current density of 0.91 A m–2. Moreover, with the cuboid structure, the device can sense the collision force with different angular displacements from 5 to 30°. The proposed hybrid generator with a simple structure can be applied to sensing applications with the one-point-fixed state.

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  • 101

    Wide-range robust wireless power transfer using heterogeneously coupled and flippable neutrals in parity-time symmetry

    Abstract

    Recently, stationary wireless power transfer (WPT) has been widely adopted in commercial devices. However, the current WPT configuration is limited in its operational area and susceptible to operating condition changes, impeding its applications for dynamic environments. To overcome the limitations, we propose a WPT system with laterally aligned neutral elements in parity-time (PT) symmetry, which can widen the operational area with the number of neutrals N. Compared to the conventional multiple-input-single-output WPT, the dimension of system complexity is substantially reduced from R × CN to RN+1 because the neutral amplitudes are simply controlled by coupling capacitors. The operational frequency is automatically adjusted to a real eigenvalue of the PT-symmetric system to achieve high voltage gain and efficiency, making the system robust. The performance of the system calculated by the coupled-mode theory was experimentally verified with rigid and flexible types of receivers, confirming its potential in both industrial and biomedical electronics.

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  • 100

    Omni- and unidirectional data unit photolithography for high similarity and multiple angular segment display-based encoded microparticle fabrication

    Abstract

    In this study, we propose high similarity and multiple angular segment display-based encoded microparticle fabrication using omni- and unidirectional data unit photolithography systems. Uniform high-correlation values are obtained regardless of the decoding direction when an omnidirectional data unit is used. In addition, multiple display angles are analyzed based on unidirectional data units with varying slit widths. Finally, encoded microparticles for multiple angular segment displays are fabricated and selective information recognition is demonstrated.

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  • 99

    Hybridized generator to simultaneously harvest tribo-thermal energy induced by vibration of fluorine rich-beads

    Abstract

    With the growth of the issues related to the energy crisis and global warming, harvesting the vibration energy using the triboelectric nanogenerator (TENG) and thermal generator (TEG) can be regarded as a solution to suppress the both issues. This is because the carbon-free and renewable electrical energy can be generated from the mechanical energy and thermal energy, which are induced by the vibration with the aid of the TENG and TEG, respectively. Herein, the hybridized generator to simultaneously harvest tribo-thermal energy induced by the vibration and collision of the fluorine rich-beads (HG-TTB) is proposed, which is composed of the cylindrical TENG (C-TENG) and flexible TEG (F-TEG). The electrical power density generated from the proposed HG-TTB is 1.20 and 3.53 times higher than that from the C-TENG and F-TEG, respectively. Furthermore, HG-TTB can store 150.06 and 1.19 times more electrical energy than the F-TEG and C-TENG in the capacitor, respectively. The proposed HG-TTB can successfully supply an electrical energy to the rust removing system without any external power sources, which totally clean rusts grown on the surface of the metal. Considering these results, the proposed HG-TTB can be expected to be a promising alternative energy source in near future.

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  • 98

    Transition metal dichalcogenide nanostructured electrodes without calcination for aqueous asymmetric supercapacitors

    Summary

    The controlled development of mixed phases of transition metal dichalcogenide (TMDC) electrodes with hierarchical nanostructures overcomes the limited contribution of pure TMDC compositions, which is desirable to achieve superior electrochemical performance. Herein, the flower-like NiMo3S4/NiS2 (NMS/NS) nanostructures with mixed-phase nature were grown on conductive carbon cloth (ie, NMS/NS@CC-210) at 210°C (24 h) by a hydrothermal method. Importantly, the uniform flower-like nanostructured NMS/NS@CC-210 electrode revealed battery-like performance with a superior specific capacitance of 1448 F g−1 (480 C g−1 at 1 A g−1) than the other NMS/NS@CC (180°C, 190°C, and 200°C) electrodes at different reaction temperatures as well as single counterparts of MoS2 (MS)@CC-210 and NiS2(NS)@CC-210 electrodes. The presence of plenty of lattice defects in NMS/NS@CC-210 electrode structure is favored to the exposure of several electrochemical active sites for rapid transportation of electron and electrolyte diffusion, resulting in better cycling retention (83%) behavior than the pure MoS2@CC (50%) and NiS2@CC (68%) electrodes after successive 5000 cycles. Using the optimized NMS/NS@CC-210 electrode, an asymmetric electrochemical capacitor was fabricated, and its electrochemical behavior was evaluated in a two-electrode system. The NMS/NS@CC-210//activated carbon (AC)@CC device delivered its superior energy and power densities of 43.8 W h kg−1 and 12 853 W kg−1, respectively. Finally, two flexible NMS/NS@CC-210//AC@CC devices with similar features were made and successfully powered the 3-V-based light-emitting diodes and display portable electronics for practical applications.

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  • 97

    Efficient Co-Ni oxysulfide nanoarchitectured materials for long-lasting electrochemical cells: Biodegradable parafilm assisted pouch-type cells for portable electronic applications

    Abstract

    An advance of highly efficient transition metal chalcogenides-based electroactive material for electrochemical cells (ECCs) is of high significance for endorsing large-scale sustainable fabrication of energy storage devices. Herein, the binary metal chalcogenide fish scales-like structures (FSSs) were directly grown on the conductive current collector (nickel foam) using a single-step sulfurization process. In this process, the reaction temperature plays a key role in generating the cobalt-nickel oxyhydroxide (Co–Ni)OH FSSs at a constant reaction time. As result, the as-designed (Co–Ni)OH-140 exhibited higher electrochemical performance than the other ones prepared at different reaction temperatures (i.e., 120 and 160 °C). Furthermore, the sulfur (S) dopant suggestively not only enhances the electrical conductivity but also improves the electrochemical performance of the electrode. The resulting Co–Ni oxysulfide ((Co–Ni)OS) FSS electrode exhibited significantly improved electrochemical activity with outstanding cycling retention of 116% even after 20000 cycles. Moreover, by utilizing the charge storage properties of the (Co–Ni)OS FSS electrode, an ECC was assembled, which is fabricated by using a biodegradable parafilm as the pouch. The as-fabricated ECC exhibited maximum areal/specific energy density (0.44 mWh cm−2/65.9 Wh kg−1) and power density (51.5 mW cm−2/7.6 kW kg−1) with a high rate capability of 59.1% even at a higher current density of 60 mA cm−2. Furthermore, the self-powering work station with the wind turbine for energy conversion and the ECCs for charge storage was designed to drive portable electronic devices. The simple and cost-effective strategies of hierarchically connected nanomaterials provide a new path for the development of high-efficient ECCs.

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  • 96

    Regulating Dendrite-Free Zinc Deposition by Red Phosphorous-Derived Artificial Protective Layer for Zinc Metal Batteries

    Abstract

    Rational architecture design of the artificial protective layer on the zinc (Zn) anode surface is a promising strategy to achieve uniform Zn deposition and inhibit the uncontrolled growth of Zn dendrites. Herein, a red phosphorous-derived artificial protective layer combined with a conductive N-doped carbon framework is designed to achieve dendrite-free Zn deposition. The Zn–phosphorus (ZnP) solid solution alloy artificial protective layer is formed during Zn plating. Meanwhile, the dynamic evolution mechanism of the ZnP on the Zn anode is successfully revealed. The concentration gradient of the electrolyte on the electrode surface can be redistributed by this protective layer, thereby achieving a uniform Zn-ion flux. The fabricated Zn symmetrical battery delivers a dendrite-free plating/stripping for 1100 h at the current density of 2.0 mA cm–2. Furthermore, aqueous Zn//MnO2 full cell exhibits a reversible capacity of 200 mAh g–1 after 350 cycles at 1.0 A g–1. This study suggests an effective solution for the suppression of Zn dendrites in Zn metal batteries, which is expected to provide a deep insight into the design of high-performance rechargeable aqueous Zn-ion batteries.

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  • 95

    High-Efficiency Poly(Vinylidene Fluoride-Co-Hexafluoropropylene) Loaded 3D Marigold Flower-Like Bismuth Tungstate Triboelectric Films for Mechanical Energy Harvesting and Sensing Applications

    Abstract

    Triboelectric nanogenerators (TENGs) are one of the most trending energy harvesting devices because of their efficient and simple mechanism in harvesting mechanical energy from the environment into electricity. Herein, ferroelectric and dielectric bismuth tungstate (Bi2WO6 (BWO)) with a marigold flower-like structure is prepared via a hydrothermal method, which is embedded in poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), forming a PVDF-HFP/BWO composite polymer film (CPF) to fabricate TENGs. Generally, the ferroelectric materials exhibit a large piezoelectric coefficient, high electrostatic dipole moment, and high dielectric constant. The prepared PVDF-HFP/BWO CPF reveals a high polar crystalline β-phase which leads to enhanced piezoelectric and ferroelectric properties of the CPF, thus resulting in the increased electrical performance of the fabricated TENG. The electrical output performance of the proposed TENG is systematically investigated by varying the amount of BWO material embedded in the PVDF-HFP polymer. The fabricated PVDF-HFP/2.5 wt% BWO CPF-based TENG device exhibits the highest electrical output performance. Additionally, the robust test of the TENG device is conducted to investigate the electrical performance for long-term durability and mechanical stability. Finally, the proposed TENG is operated as a self-powered sensor, harvesting mechanical energy from daily life human activities, and powering various low-power portable electronics.

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