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Soft wearable flexible bioelectronics integrated with an anklefoot exoskeleton for estimation of metabolic costs and physical effort

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npj Flexible Electronics 2023年第1期7卷 535-544页

作者： Jihoon kim Prakyath Kantharaju Hoon Yi Michael Jacobson Hyungkeun Jeong hojoong kim Jinwoo Lee Jared Matthews Nathan Zavanelli Hyeonseok kim Heejin Jeong Myunghee kim Woon-Hong Yeo IEN Center for Human-Centric Interfaces and Engineering and George W.Woodruff School of Mechanical Engineering Georgia Institute of TechnologyAtlantaGA 30332USA Department of Mechanical and Industrial Engineering the University of Illinois at ChicagoChicagoIL 60607USA Department of Mechanical Roboticsand Energy EngineeringDongguk UniversitySeoulRepublic of Korea Human Systems Engineering The Polytechnic SchoolIra A.Fulton Schools of EngineeringArizona State UniversityMesaAZ 85212USA Wallace H.Coulter Department of Biomedical Engineering Georgia Institute of Technology and Emory University School of MedicineAtlantaGA 30332USA Institute for Robotics and Intelligent Machines Parker H.Petit Institute for Bioengineering and BiosciencesInstitute for MaterialsNeural Engineering CenterGeorgia Institute of TechnologyAtlantaGA 30332USA

Activities and physical effort have been commonly estimated using a metabolic rate through indirect calorimetry to capture breath *** physical effort represents the work hardness used to optimize wearable robotic ***,personalization and rapid optimization of the effort are *** respirometry is the gold standard for estimating metabolic costs,this method requires a heavy,bulky,and rigid system,limiting the system’s field ***,this paper reports a soft,flexible bioelectronic system that integrates a wearable ankle-foot exoskeleton,used to estimate metabolic costs and physical effort,demonstrating the potential for real-time wearable robot adjustments based on *** from a set of activities,including walking,running,and squatting with the biopatch and exoskeleton,determines the relationship between metabolic costs and heart rate variability root mean square of successive differences(HRV-RMSSD)(R=−0.758).Collectively,the exoskeleton-integrated wearable system shows potential to develop a field-deployable exoskeleton platform that can measure wireless real-time physiological signals.

关键词： skeleton wear estimation

Enhancing BiVO_(4)photoanode performance by insertion of an epitaxial BiFeO_(3)ferroelectric layer

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Journal of Energy Chemistry 2024年第2期89卷 71-78,I0003页

作者： Haejin Jang Yejoon kim hojoong Choi Jiwoong Yang Yoonsung Jung Sungkyun Choi Donghyeon Lee Ho Won Jang Sanghan Lee School of Materials Science and Engineering Gwangju Institute of Science and TechnologyGwangju 61005Republic of Korea Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea

BiVO_(4)(BVO)is a promising material as the photoanode for use in photoelectrochemical ***,the high charge recombination and slow charge transfer of the BVO have been obstacles to achieving satisfactory photoelectrochemical *** address this,various modifications have been attempted,including the use of ferroelectric *** materials can form a permanent polarization within the layer,enhancing the separation and transport of photo-excited electron-hole *** this study,we propose a novel approach by depositing an epitaxial BiFeO_(3)(BFO)thin film underneath the BVO thin film(BVO/BFO)to harness the ferroelectric property of *** self-polarization of the inserted BFO thin film simultaneously functions as a buffer layer to enhance charge transport and a hole-blocking layer to reduce charge *** a result,the BVO/BFO photoanodes showed more than 3.5 times higher photocurrent density(0.65 mA cm^(-2))at 1.23 V_(RHE)under the illumination compared to the bare BVO photoanodes(0.18 m A cm^(-2)),which is consistent with the increase of the applied bias photon-to-current conversion efficiencies(ABPE)and the result of electrochemical impedance spectroscopy(EIS)*** results can be attributed to the self-polarization exhibited by the inserted BFO thin film,which promoted the charge separation and transfer efficiency of the BVO photoanodes.

关键词： Photoelectrochemical Photoanode BiVO_(4) Ferroelectric materials BiFeO_(3)

Hyperreflective photonic crystals created by shearing colloidal dispersions at ultrahigh volume fraction

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Microsystems & Nanoengineering 2024年第1期10卷 161-173页

作者： Minji kim Jong Bin kim Shin-Hyun kim Department of Chemical and Biomolecular Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea

Colloidal crystallization serves as one of the most economic and scalable production methods for photonic ***,insufficient optical performance,nonuniformity and low reproducibility remain challenges for advanced high-value *** this study,we optimally formulate a photocurable dispersion of silica particles and apply shear flow to unify the orientation of the colloidal crystals,ensuring high optical performance and *** silica particles experience strong repulsion at ultrahigh volume fractions of 50%but demonstrate low mobility,leading to polycrystalline *** shear flow to the dispersions allows the silica particles to rearrange into larger crystalline domains with a unidirectional orientation along the *** shear-induced structural change produces absolute reflectivity at the stopband as high as 90%and a high transparency of 90%at off-resonant wavelengths with minimal diffusive ***,the strong interparticle repulsion ensures a uniform volume fraction of particles throughout the dispersion,reducing deviations in the optical *** intricately micropattern the photocurable dispersions using ***,the photonic films and patterns can be stacked to form multiple layers,displaying mixed structural colors and multiple reflectance peaks without sacrificing *** superior photonic materials hold promise for various optical applications,including optical components and anticounterfeiting patches.

关键词： properties. dispersion reflectivity

Boosted Lithium-Ion Transport Kinetics in n-Type Siloxene Anodes Enabled by Selective Nucleophilic Substitution of Phosphorus

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Nano-Micro Letters 2024年第10期16卷 618-637页

作者： Se In kim Woong-Ju kim Jin Gu Kang Dong-Wan kim School of Civil Environmental and Architectural EngineeringKorea University02841 SeoulSouth Korea Nanophotonics Research Center Korea Institute of Science and Technology02792 SeoulSouth Korea

Doped two-dimensional(2D)materials hold significant promise for advancing many technologies,such as microelectronics,optoelectronics,and energy ***,n-type 2D oxidized Si nanosheets,namely n-type siloxene(n-SX),are employed as Li-ion battery *** thermal evaporation of sodium hypophosphite at 275℃,P atoms are effectively incorporated into siloxene(SX)without compromising its 2D layered morphology and unique Kautsky-type crystal ***,selective nucleophilic substitution occurs,with only Si atoms being replaced by P atoms in the O_(3)≡Si-H *** resulting n-SX possesses two delocalized electrons arising from the presence of two electron donor types:(i)P atoms residing in Si sites and(ii)H *** doping concentrations are varied by controlling the amount of precursors or their mean free *** at 2000 mA g^(-1),the n-SX electrode with the optimized doping concentration(6.7×10^(19) atoms cm^(-3))delivers a capacity of 594 mAh g^(-1) with a 73%capacity retention after 500 *** improvements originate from the enhanced kinetics of charge transport processes,including electronic conduction,charge transfer,and solid-state *** approach proposed herein offers an unprecedented route for engineering SX anodes to boost Li-ion storage.

关键词： Li-ion battery Two-dimensional N-type siloxene Doping mechanism Kinetics

Investigation of operation and degradation mechanisms in ZnTeSe blue quantum-dot light-emitting diodes by identifying recombination zone

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Nano Research 2024年第7期17卷 6527-6533页

作者： Oul Cho Sujin Park Hogeun Chang Jiwhan kim Jaekwon kim Sungwoo kim Taehyung kim Jeonghun Kwak Department of Electrical and Computer Engineering Inter-university Semiconductor Research Centerand Soft Foundry InstituteSeoul National UniversitySeoul 08826Republic of Korea Material Research Center Samsung Advanced Institute of TechnologySuwonGyeonggi-do 16419Republic of Korea

ZnTeSe quantum dots(QDs),recognized as promising eco-friendly blue electroluminescent emitters,remain under-explored in light-emitting diode(LED)***,to elucidate the operation and degradation mechanisms of ZnTeSe blue QD-LEDs,stacked ZnTeSe QD layers with discernable luminescence are designed by varying Te doping concentrations,and the recombination zones(RZs)of the blue QD-LEDs are *** RZs are identified near the hole-transport layer(HTL),confirmed by angular-dependent electroluminescence measurements and optical *** addition,in order to investigate carrier dynamics in the process of recombination,the transient electroluminescence(tr-EL)signals of the dichromatic QD-LEDs are *** a result,it is inferred that the RZ initially formed near the electron-transport layer(ETL)due to the high injection barriers of ***,due to the fast electron mobility,the RZ shifts toward the HTL as the operating current *** the device lifetime tests,the RZ remains stationary while the photoluminescence(PL)corresponding to the RZ undergoes a substantial decrease,indicating that the degradation is accelerated by the concentrated *** this study contributes to a deeper understanding of the operational mechanisms of ZnTeSe blue QD-LEDs.

关键词： quantum dots light-emitting diodes degradation recombination zones carrier dynamics

Dragonfly Interaction Algorithm for Optimization of Queuing Delay in Industrial Wireless Networks

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Journal of Bionic Engineering 2024年第1期21卷 447-485页

作者： Sanjay Bhardwaj Da-Hye kim Dong-Seong kim Department of IT Convergence Engineering ICT Convergence Research CenterKumoh National Institute of TechnologyGumiSouth Korea

In industrial wireless networks,data transmitted from source to destination are highly *** often leads to the queuing of the data,and poor management of the queued data results in excessive delays,increased energy consumption,and packet ***,a nature-inspired-based Dragonfly Interaction Optimization Algorithm(DMOA)is proposed for optimization of the queue delay in industrial wireless *** term“interaction”herein used is the characterization of the“flying movement”of the dragonfly towards damselflies(female dragonflies)for *** a result,interaction is represented as the flow of transmitted data packets,or traffic,from the source to the base *** includes each and every feature of dragonfly movement as well as awareness of the rival dragonflies,predators,and damselflies for the desired optimization of the queue *** features are juxtaposed as noise and interference,which are further used in the calculation of industrial wireless metrics:latency,error rate(reliability),throughput,energy efficiency,and fairness for the optimization of the queue *** analysis,convergence analysis,the Wilcoxon test,the Friedman test,and the classical as well as the 2014 IEEE Congress of Evolutionary Computation(CEC)on the benchmark functions are also used for the evaluation of DMOA in terms of its robustness and *** results demonstrate the robustness of the proposed algorithm for both classical and benchmarking functions of the IEEE CEC ***,the accuracy and efficacy of DMOA were demonstrated by means of the convergence rate,Wilcoxon testing,and ***,fairness using Jain’s index in queue delay optimization in terms of throughput and latency,along with computational complexity,is also evaluated and compared with other *** results show that DMOA exceeds other bio-inspired optimization algorithms in terms of fairness in queue delay management and average packet *** proposed a

关键词： Dragonfly Damselfly Interaction Queuing delay Optimization Industrial wireless networks

Ag-GST/HfO_(x)-based unidirectional threshold switching selector with low leakage current and threshold voltage distribution for high-density cross-point arrays

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Rare Metals 2024年第1期43卷 280-288页

作者： Kyoung-Joung Yoo Dae-Yun Kang Nahyun kim Ho-Jin Lee Ta-Hyeong kim Taeho kim Tae Geun kim School of Electrical Engineering Korea UniversitySeoul 02841Republic of Korea

The use of electrochemical-metallization-based volatile threshold switching selectors in cross-point arrays has been widely explored owing to their high on-off ratios and simple ***,these devices are unsuitable for cross-point architectures because of the difficulty in controlling the random filament formation that results in large fluctuations in the threshold voltage during *** this study,we investigated the unidirectional threshold transition characteristics associated with an Ag/GST/HfO_(x)/Pt-based bilayer selector and demonstrated the occurrence of a low leakage current(<1×10^(-11) A) and low distribution of the threshold voltage(Δ0.11 V).The bilayer structure could control the filament formation in the intermediate state through the insertion of an HfO_(x) tunneling *** stacking a bilayer selector with NiO_(x)based resistive random-access memory,the leakage and programming currents of the device could be significantly *** the crossbar array configuration,we performed equivalent circuit analysis of a one-selector oneresistor(1S1R) devices and estimated the optimal array size to demonstrate the applicability of the proposed *** maximum acceptable crossbar array size of the 1S1R device with the Ag/GST/HfO_(x)/Pt/Ti/NiO_(x)/Pt structure was 5.29×10^(14)(N^(2),N=2.3×10^(7)).

关键词： Selector device Tunneling barrier Threshold switching Sputtering 1S1R Cross-point array

Trend of Developing Aqueous Liquid and Gel Electrolytes for Sustainable,Safe,and High‑Performance Li‑Ion Batteries

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Nano-Micro Letters 2024年第1期16卷 17-34页

作者： Donghwan Ji Jaeyun kim School of Chemical Engineering Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Department of Health Sciences and Technology Samsung Advanced Institute for Health Sciences&Technology(SAIHST)Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Biomedical Institute for Convergence at SKKU(BICS) Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Institute of Quantum Biophysics(IQB) Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Present Address:Department of NanoEngineering University of California San DiegoLa JollaSan DiegoCA 92093USA

Current lithium-ion batteries(LIBs)rely on organic liquid electrolytes that pose significant risks due to their flammability and *** potential for environmental pollution and explosions resulting from battery damage or fracture is a critical ***-based(aqueous)electrolytes have been receiving attention as an alternative to organic ***,a narrow electrochemicalstability window,water decomposition,and the consequent low battery operating voltage and energy density hinder the practical use of aqueous ***,developing novel aqueous electrolytes for sustainable,safe,high-performance LIBs remains *** Review first commences by summarizing the roles and requirements of electrolytes–separators and then delineates the progression of aqueous electrolytes for LIBs,encompassing aqueous liquid and gel electrolyte development trends along with detailed principles of the *** aqueous electrolytes are progressed based on strategies using superconcentrated salts,concentrated diluents,polymer additives,polymer networks,and artificial passivation layers,which are used for suppressing water decomposition and widening the electrochemical stability window of water of the *** addition,this Review discusses potential strategies for the implementation of aqueous Li-metal batteries with improved electrolyte–electrode interfaces.A comprehensive understanding of each strategy in the aqueous system will assist in the design of an aqueous electrolyte and the development of sustainable and safe high-performance batteries.

关键词： Lithium-ion battery(LIB) Aqueous electrolyte Gel electrolyte Electrochemical stability window Li dendrite

CFD-based hull optimization in calm water using adaptive grid deformation method

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Journal of Hydrodynamics 2024年第2期36卷 241-262页

作者： Shuguang Wang Yonghwan kim Department of Naval Architecture and Ocean Engineering Seoul National UniversitySeoulKorea

This paper presents an adaptive grid deformation technique for optimizing ship hull forms using computational fluid dynamics(CFD).The proposed method enables accurate and smooth updates of the hull surface and 3-D CFD grids in response to design *** technique incorporates a two-level point-transformation approach to move the grid points by a few design ***,generic B-splines are utilized to transform grid points according to the displacements of the control points within a defined control *** ensures surface modification accuracy and smoothness,similar to those provided by non-uniform rational ***,radial basis functions are used to interpolate the movements of the control points with a limited set of design *** developed method effectively maintains the mesh quality and simulation *** applying this method to surface and grid adaptation,a regression model is proposed in the form of a second-order polynomial to represent the relationship between the geometric parameters and design *** polynomial is then used to introduce geometric ***,a radial basis function surrogate model for the calm-water resistance is constructed to approximate the objective *** enhanced optimization framework is proposed for CFD–based hull optimization and applied to KVLCC2 to validate its feasibility and efficiency.

关键词： Hull-form optimization adaptive grid deformation ship resistance OpenFOAM radial basis function(RBF)surrogate model