bluuebunny/crossref_metadata_2025 huggingface dataset:
Versatile Utilizations of Cellulose Nanofibers for High-Performance Silicon Anode in Lithium-Ion Batteries
Authors: Kim Jong Min , Piao Yuanzhe
Published: February 2020

Silicon is the most anticipated anode material in lithium-ion batteries due to its natural abundancy, low insertion voltage (<0.4 V vs. Li/Li+) and high specific capacity (<3579 mAh g-1). However, huge volume change (~ 300 %) during cycling which causes poor cycling stability and its insulating nature prohibit the practical use. In this research, cellulose nanofibers were utilized in various ways to enhance the performance of silicon nanoparticle anodes. As carbon sources, the ultrathin (~ 1.55 nm) cellulose nanofibers can provide an extensive conductive network to improve both the cycling stability and rate performance by mitigating the volume expansion of silicon and providing the efficient electron path. Furthermore, by using thicker (~ 30 nm) cellulose nanofibers as carbon sources, a porous conductive network can be achieved, which can provide both the efficient electron path and ion diffusion path. In addition, the void space generated by cellulose nanofibers became a buffer space which enhanced the cycling stability. Finally, as a binder additive, cellulose nanofiber can enhance the performance of carboxymethyl cellulose binder. It can act as both a filler and a binder to be utilized in an electrode composite, unlike the traditional reinforcing fillers. Therefore, the versatile, cheap and abundant cellulose nanofibers show great potential in lithium-ion batteries.
Design of Multifunctional Binder for High-Capacity Silicon Based Anodes
Authors: Cao Pengfei , Yang Guang , Nanda Jagjit , Saito Tomonori
Published: February 2020

The role of binder material for silicon (Si) and other metal alloy based anodes is critical for their long-term performance. Although several principles have been recognized to fabricate a “better” binder, there seems to be a lack of a rational design and synthesis approach that would meet the robust criteria required for metal alloy anodes. This presentation will discuss the synthesis and characterization of a novel polymer binder, a catechol-functionalized chitosan cross-linked by glutaraldehyde (CS-CG+GA), that serves dual functionalities: a) provides wetness-resistant adhesion capability via catechol grafting and b) possesses mechanical robustness via in-situ formation of a three-dimensional (3D) network. A Si nanoparticle (SiNP) based anode with the designed functional polymer network (CS-CG10%+6%GA) exhibits a capacity retention of 91.5% after 100 cycles (2144 ± 14 mAh/g). This study shows that traditional “better” properties including stronger adhesion strength and higher mechanical robustness do not always improve binder performance, but rather Si anode performance is governed by a delicate synergy of various polymer properties. The clear relationship between grafting density of adhesion groups and degree of crosslinking for ultimate electrochemical performance of polymer binders is established by assessing the rheological behavior of polymer solution, mechanical property of anode coating, adhesion force with SiNPs, peel stress of anode coating, morphology evolution of electrode, and the semi-quantitative evaluation on the scaling behavior and stiffness of the polymer backbone. This study provides a clear path for the rational design of high-performance functional polymer binders for not only Si-based electrodes, but also for other types of alloy and conversion-based electrodes.
Pre-Lithiatiated Carbon Composite Nanofibers Anodes and Their use in Rechargeable Lithium-ion Batteries
Authors: Alcoutlabi Mataz , Elizondo Antonio , Lopez Jorge , Gonzalez Gabriel
Published: February 2020

Prelithiation is a good method used to mitigate the loss of lithium caused by the formation of the solid electrolyte interface (SEI) layer and by the irreversible reactions at the first discharge cycle. The main goal of this work is to systematically study the effect of prelithiation and thermal treatment on the electrochemical performance of carbon fiber anodes for LIBs. We present results on the centrifugal spinning of Polyacrylonitrile (PAN) fibers and PAN/ceramic composite fibers subjected to thermal treatment under different temperature and environmental conditions. The carbon composite-fibers anodes treated under a nitrogen atmosphere showed better electrochemical performance than that treated under argon atmosphere. The pre-lithiation of carbon fiber anodes after the first cycle exhibited higher charge/discharge capacities and higher coulombic efficiency up to 98% than the pristine carbon fibers. The results show that the pre-lithiation and the creation of defects onto the carbon-fibers surface are the detrimental keys of achieving and designing anode materials with enhanced electrochemical performance.
Nano-Rod Gradient Li[Ni0.81Co0.06Mn0.13]O2: Preserving Cathode Structure for Long-Term Cycling (1000 Cycles) Li-Ion Batteries
Authors: Sun HoHyun , Yoon Chong seung , Heller Adam , Mullins Charles Buddie
Published: February 2020

To address the growing demand for both energy density and cycling stability, a layered nanorod gradient (NRG) Li[Ni0.81Co0.06Mn.0.13]O2 cathode was synthesized with a high Ni-content bulk and a radially columnar nano-rod comprised surface and benchmarked against the widely used constant concentration (CC) Li[Ni0.82Co0.14Al0.04]O2. The NRG cathode delivered a discharge capacity of 225 mAh g-1, equivalent to ~ 830 Wh kg-1 at the cathode level, with 91%

capacity retention in half-cells after 100 cycles (210 mAh g-1 and 79 % for CC cathode) and 88% capacity retention in full-cells after 1000 cycles (56 % for CC cathode). Through a combination of in-situ and time-resolved X-ray diffraction (XRD), cross-section scanning electron microscopy imaging (SEM), and high-resolution transmission electron microscopy (HR-TEM), we confirm that the exceptional electrochemical performance of the NRG material, both in energy density and cycling performance, is attributed to its radially columnar concentration graded nano-rods at the surface. These nano-rods function as a buffer to diminish abrupt stress from the high Ni-content bulk during the H2 → H3 phase transition by suppressing crack propagation to preserve particle coherency, enabling reversibility of the cathode particle. This is important because electrolyte infiltration into the reactive Ni-rich bulk and subsequent formation of the electrically insulating rocksalt nano-structure (NiO) along the cracks are prevented, thereby minimizing impedance increase during long-term cycling. Furthermore, the nano-rods also enhance the thermal stability by delaying the layered to rocksalt phase transition on the surface through an increased concentration of Mn on the exterior.
A New Formulation of the Pseudo2D Battery Model Coupling Macroscopic and Microscopic Deformations
Authors: Mai Weijie , Smith Kandler , Colclasure Andrew M.
Published: February 2020

High-capacity electrode materials such as silicon are promising in improving the capacity and energy densities of lithium ion battery (LIB). However, the broad application of such material is hindered by their large volume change during lithiation/delithiation, which not only causes active particle pulverization, but also leads to macroscale deformation that changes the dimension and porosity distribution of the cell. The objective of this work is to consistently reformulate the Pseudo2D battery model to incorporate the effect of large deformation during battery cycling, at both the particle and electrode levels.

In this work, the finite strain theory is used to approximate deformations in electrode by coupling it with the distribution of intercalation fraction within the cell. The porosity variation is approximated assuming conservation of the volume of the solid phase, which is then combined with the electrode deformation to consistently yield the magnitude of particle deformation at each position. The specific particle surface area is also consistently updated, which is ignored in most existing models. All transport equations are also reformulated in the reference frame but with the effect of large deformation incorporated.

Preliminary simulation results for a LIB with Si anode and NMC532 cathode show that porosities in both electrodes are notably reduced and become nonuniform when charged at a relatively high C rate. The increase of transport resistances and the gradual build-up of compressive stress due to active material volume change contribute to additional overpotentials that adversely affect the electrochemical performances of the cell, such as its accessible capacity/energy. In the future, this model will be used for cell design optimization in terms of electrode loadings, compromise between cell stress and strain, optimal range of Si SOC and possibly the optimal composition of a composite electrode, etc.
One Dimensional Nanomaterials for Emerging Energy Storage
Authors: Mai Liqiang
Published: February 2020

One-dimensional nanomaterials can offer large surface area, facile strain relaxation upon cycling and efficient electron transport pathway to achieve high electrochemical performance. Hence, nanowires have attracted increasing interest in energy related fields. We designed the single nanowire electrochemical device for in situ probing the direct relationship between electrical transport, structure, and electrochemical properties of the single nanowire electrode to understand intrinsic reason of capacity fading. The results show that during the electrochemical reaction, conductivity of the nanowire electrode decreased, which limits the cycle life of the devices. We have developed a facile and high-yield strategy for the oriented formation of CNTs from metal−organic frameworks (MOFs). The appropriate graphitic N doping and the confined metal nanoparticles in CNTs both increase the densities of states near the Fermi level and reduce the work function, hence efficiently enhancing its oxygen reduction activity. In addition, we demonstrated the critical role of structural H2O. The results suggest that the H2O-solvated Zn2+ possesses largely reduced effective charge and thus reduced electrostatic interactions with the V2O5 framework, effectively promoting its diffusion. We also identified the exciting electrochemical properties (including high electric conductivity, small volume change and self-preserving effect) and superior sodium storage performance of alkaline earth metal vanadates through preparing CaV4O9 nanowires. Furthermore, a novel assembled nanoarchitecture was also presented, which consists of V2O3 nanoparticles embedded in amorphous carbon nanotubes that are then coassembled within a reduced graphene oxide network. The naturally integrated advantages of each subunit exhibit highly stable and ultrafast sodium-ion storage. Our work presented here can inspire new thought in constructing novel one-dimensional structures and accelerate the development of energy storage applications.
Theoretical Study of Lithium Electrodeposition on Lithium Metal Anodes
Authors: Angarita-Gomez M Stefany , Balbuena Perla B.
Published: February 2020

Lithium metal anode is among the most promising anodes for the next generation of batteries due to its high theoretical energy density and capacity. Challenges such as high reactivity and lithium dendrite formation have kept lithium metal anodes away from practical applications in portable electronics and electric/hybrid vehicles. It is known that the lithium dendrite formation on anode surfaces during the charging process starts by the inhomogeneous deposition of metallic lithium during the electrochemical reduction of lithium cations. However, the underlying mechanisms of Li dendrite formation are still poorly understood. Therefore, gaining fundamental understanding of the early stages of lithium electrodeposition is crucial in order to overcome this challenge. In this work, Density Functional Theory (DFT) simulations were conducted to study the electron transfer between lithium metal slab Li (100) and the electrolyte. Here we explore the effect of multiple solvents and Li-salts on the electrodeposition of lithium. Ethylene carbonate (EC), 1,2-Dimethoxyethane (DME), 1,3-Dioxolane (DOL), and mixtures of them are used as solvents. These species compete with the salt anion and the Li cation for electron transfer from the surface. Our theoretical study provides new insights into lithium electrodeposition that advance the understanding of the process as a function of electrolyte composition and ionic concentration.
Hierarchical Bulk Nanoporous Aluminum for on-Board Hydrogen and Heat Generation By Hydrolysis in Pure Water
Authors: Corsi John S , Fu Jintao , Lee Timothy , Detsi Eric
Published: February 2020

Despite the remarkable key features of hydrogen energy technology such as the high gravimetric energy density of hydrogen, the zero-emissions electricity generated using fuel cells, and the high natural abundance of hydrogen resources (particularly in the form of water), there are still many scientific and engineering challenges that must be addressed before a true sustainable hydrogen economy can be realized. Two of these challenges include sustainable hydrogen generation without CO2 emissions and effective storage of this hydrogen for specific applications. In this presentation, I will present a sustainable method to produce hydrogen on-board, which could be used to overcome the two challenges mentioned above. Our approach involves: (i) Fabrication by selective alloy corrosion of hierarchical bulk nanoporous aluminum characterized by the coexistence of both macroscopic and mesoscopic ligament/pore structures, with the mesoscopic ligaments in the range of 10-20 nm. (ii) Recovery of the sacrificial material simultaneously during selective alloy corrosion, which contributes to sustainability of the process. (iii) Use of this hierarchical bulk nanoporous aluminum to produce hydrogen and heat on-board by hydrolysis with “pure” water, with a yield of ~52-85 % during hydrogen production without incorporation of any catalyst or reaction promoter in the aluminum-water system. Besides hydrogen and heat generations, I will demonstrate the combustion of this bulk nanoporous aluminum in air and under ambient conditions, which implies that this material could be attractive as a combustion fuel catalyst, e.g. to enhance the ignition and combustion of solid propellants. Thanks to a new carbon-free sustainable pathway to extract aluminum by Elysis (https://elysis.com/en), a joint venture composed of high-profile aluminum suppliers including Rio Tinto and Alcoa, and aluminum consumers including Apple, aluminum can be obtained by electrolysis of Al2O3 without CO2 emissions. The inclusion of this carbon-free aluminum in our process will make it possible to produce hydrogen from nanoporous aluminum and pure water without greenhouse gas emissions at any stage of the process.
(Invited) Fully-Coupled 3D Electrochemical-Thermal Modeling of Cylindrical Lithium-Ion Batteries
Authors: Gomadam Parthasarathy M.
Published: February 2020

A rigorous three-dimensional electrochemical-thermal model is developed without having to make dimension-reduction approximations to the electrochemical model. The fully-coupled model is developed for the spiral battery in the unwound form taking advantage of the coordinate-transformation technique published in Ref. 1. Key thermal model parameters such as heat capacity, entropy coefficient and hysteresis heating are obtained by direct measurements or by fitting simplified versions of the model to a host of experimental data. The thermodynamics software package – Advanced Electrolyte Model (AEM) – is used to obtain electrolyte transport parameters as functions of concentration and temperature. Exothermic chemical reactions that are triggered under high temperatures are included following Ref. 2-3. The chief safety feature of separator shutdown is modeled and its effects studied under a range of conditions. Model predictions for normal operations as well as under abuse such as internal and external shorts are presented. Comparisons between predictions and data are shown for some external short conditions, demonstrating the accuracy of the model.

References

M. Gomadam, R.E. White, and J.W. Weidner, J. Electrochem. Soc., 150, A1339 (2003).

G-H.Kim, A.Pesaran, and R.Spotnitz, Power Sources, 170, 476 (2007).

F.Lopez, J.A.Jeevarajan, and P.P.Mukherjee, J. Electrochem. Soc.,
162, A2163 (2015).

Fig. 1. Predicted temperature profile along before separator shutdown during an external short condition.

Figure 1
A Highly Efficient Computational Model of Energy Storage Systems for Microgrid Applications
Authors: Ajiboye Damola Martins , Kimball Jonathan , Landers Robert , Park Jonghyun
Published: February 2020

The need for an efficient approach to modeling and monitoring of the plethora of phenomena in battery applications cannot be overemphasized. On account of this, we present an approach that is computationally inexpensive and capable of predicting vital battery parameters in real-time especially for Microgrid applications. The chosen approach employs the Chebyshev-spectral method, which represents a cardinal shift from the traditional methods (finite difference, finite volume and finite element methods) along with a linearized charge transfer equation and a segregated solver. The attraction of this approach lies in its low computational cost, accuracy and real-time computations. By means of comparison with the conventional methods, we established the viability and efficiency of the Chebyshev spectral method for Microgrid applications.
(Invited) Β-Ga2O3 Traps: Materials to Devices
Authors: Arehart Aaron R , Farzana Esmat , McGlone Joe , Jackson Christine M , Ringel Steven A
Published: February 2020

Traps in β-Ga2O3 keep devices, such as power transistors, photodetectors, and diodes, from working ideally. This manifests itself as short-term (ns to ms time scales) to longer term (day to week long) instabilities in terminal characteristics including dynamic on-resistance and threshold voltage and as increased leakage currents that degrade breakdown voltage and noise equivalent power. Using both conventional deep level transient and optical spectroscopies (DLTS/DLOS) and direct, quantitative defect spectroscopy on transistors namely constant drain current DLTS (CID-DLTS), the trap energies and concentrations in test structures and metal-semiconductor field effect transistors (MESFETs) are quantified and compared with the instabilities in the MESFET threshold voltage and dynamic on-resistance are correlated showing which traps matter in these MESFETs. A critical step in defect spectroscopy is to identify the sources of defects to enable strategies to eliminate the defects or bring them down to tolerable levels. Our group and the community have made great strides in beginning to identify the defects throughout the bandgap. Using high energy proton and neutron irradiation to create native defects and controlled studies with Fe, the two primary defects that cause threshold voltage instability in MESFETs will be discussed along with mitigation strategies.
(Invited) Top-Down Etching of III-Nitride Nanostructures
Authors: Wang George T , Leung Benjamin , Tsai Miao-Chan , Kazanowska Barbara A , Jones Kevin Scott , Sapkota Keshab R
Published: February 2020

Chemical etch processes for III-nitride (AlGaInN) materials and devices are significantly underdeveloped due to its apparent inertness to common wet etchants. To fully realize the potential of the III-nitrides in new electronic and photonic nano and micro device concepts, a more complete knowledge and development of anisotropic and three-dimensional top-down etch techniques are needed. Here, we explore the etch characteristics of GaN and AlGaN based materials using the general geometric principles of crystallographic dissolution processes to enable the prediction of facet-determined etch structures, including high aspect ratio nanowires and nanowalls. We perform the first complete nonpolar orientation-dependent etch rate measurements for GaN, and use them to predict the faceting of pillar structures with good agreement with experiment. We use these developments in wet etching to fabricate functional III-nitride-based optical nanowire and microcavity structures with control over the cross-sectional shape, where faceting enables sidewalls with near atomic-smoothness. Finally, we discuss a new fabrication method, quantum-size controlled photoelectrochemical etching, for the etching of InGaN quantum dots with high size uniformity from planar InGaN films.
Improved Output Power Behavior of Ultraviolet GaN-Based Light-Emitting Diode By Using Agpdcu Reflector
Authors: Sim Kee-Baek , Yoon Su-Jung , Seong Tae-Yeon
Published: February 2020

GaN-based ultraviolet UVLEDs have attracted a great deal of interest because of their applications in water and air purification and solid-state lighting. These applications have stimulated the technological development of high-efficiency UVLEDs. On the one hand, UVLEDs exhibit relatively lower external quantum efficiencies (EQEs) than visible LEDs. In particular, high-power UVLEDs should have high light extraction and heat dissipation efficiencies. For the flip-chip (FC) LEDs, the fabrication of high-performance p-type reflector with low contact resistance and high reflectivity is reqyired. Silver (Ag) is a commonly adopted p-type reflector for near UV LEDs but suffers from thermal instability, namely, agglomerated when annealed in air above 300 °C. In addition, electromigration (EM) is one of the major failure mechanisms of electronic interconnect under high current density (> ~105 A/cm2) stressing in microelectronics devices.

In this talk, we investigated the opto-electrical properties, and electromigration reliability of a Ag-Pd-Cu alloy (APC) reflector for near UV (385 nm)-LEDs as a function of temperature and compared with those of Ag only reflector. SEM results revealed that the Ag samples were less stable than the APC samples upon annealing. The contact resistivities of the Ag and APC contacts annealed at 500 °C were measured to be 2.59 × 10–
4 and 1.85 × 10–4 Wcm2, respectively. The Ga 2p core level for the APC sample shifted towards the lower binding-energies by 0.67 eV as compared to that of the as-deposited sample. The forward I-V properties of near UV LEDs fabricated with the Ag and APC reflectors were observe to be similar each other. Notably, the UV LEDs with the APC reflector produced 9.04% higher output at 100 mA than those with the Ag reflector. To investigate the device reliability, the EM behaviour of Ag and APC films were also characterised. The APC samples exhibited better EM resistance than the Ag samples. The APC samples yielded higher activation energies of the EM failures than the Ag sample. The better EM behaviour of the APC samples will be described and discussed on the basis of XRD pole figure and electron back scatter diffraction, phi scan, and inverse pole figures (IPFs) examination results.
Catalyst-Free Synthesis and Properties of Oxygen-Vacancy-Rich Tungsten Oxide Nanowires
Authors: Ting Chao-Wei , Yang Shu-Meng , Lu Kuo-Chang
Published: February 2020

In this work, oxygen-vacancy-rich tungsten oxide nanowires were synthesized on Si via grain-by-grain thermal evaporation method without any catalyst; also, WO3-x nanowires were grown on W foils as comparison on their physical properties. High-resolution transmission electron microscopy studies show that the lattice arrays of oxygen-vacancy-rich tungsten oxide nanowires grown on Si were crystalline, while those of WO3-x nanowires grown on W foils were improved in terms of crystallization with increase of growth temperature. We demonstrated this result with x-ray diffraction analysis as well. For physical property measurements, the oxygen-vacancy-rich nanowire grown on Si had a very low resistivity of 4.55 x 10-3 Ω ‧ cm, while the resistivity of WO3-x nanowires grown on W foils decreased as the growth temperature rises. Additionally, we found that WO3-x nanowires exhibit different magnetic properties depending on the valence state of tungsten. Notably, the oxygen-vacancy-rich tungsten oxide nanowires grown on Si possessed special antiferromagnetic properties.
Detection and Analysis of Extracellular Vesicles in Physiological Salt Environment Using AlGaN/GaN High Electron Mobility Transistor Biosensors
Authors: Pulikkathodi Anil Kumar , Sarangadharan Indu , Lo Chiao-Yun , Chen Po-Hsuan , Chen Chih-Chen , Wang Yu-Lin
Published: February 2020

Extracellular vesicles (EVs) have emerged as a research area attracting intense investigation. The enumeration and surface marker analysis of EVs have been conducted using conventional techniques and correlated with incidence and metastasis of various cancers and risk assessment of cardiovascular diseases. With efforts to characterize EVs as specific diseases biomarkers, it is imperative to develop sensitive and robust detection techniques to monitor the presence of EVs in physiological fluids. Previously, we demonstrated direct protein detection from physiological fluids using high field modulated field effect transistor (FET) biosensor. In the present work, we have utilized antibody functionalized AlGaN/GaN high electron mobility transistor (HEMT) to capture EVs from high salt environment (1X PBS) and resulting change in electrical response of the sensor has been correlated with the concentration of EVs. The unique high field modulation applied to the sensor facilitates target detection overcoming Debye screening. Our sensor can achieve better sensitivity (detection limit of 107 EVs/mL) than the conventional technologies used for EV detection such as nanoparticle tracking analyzer. Furthermore, our sensor methodology can also be used to determine the surface markers present in the captured EVs. In our sensor, when EVs are captured by the immobilized anti-CD63, the solution capacitance varies as the applied potential drops across the solution, thereby modulating the HEMT drain current. When we employ a secondary antibody such as anti-CD9 to bind with CD9 which is abundantly present on the exosomal membrane, the impedance increases, resulting in more potential drop across the solution and therefore, a decrease in drain current (Figure 1). The results in Figure 1 indicate that our sensor can perform EV enumeration and exosomal surface marker analysis to establish a comprehensive diagnostic model for EVs in physiological fluids.

Figure 1
Development of the Drying Process of Antibody-Immobilized FET Sensors for Long Term Storage
Authors: Wu Chang-Run , Chen Po-Hsuan , Sarangadharan Indu , Wang Yu-Lin
Published: February 2020

The biomarker cardiac troponin I (cTnI) is a clinical marker used to diagnose acute myocardial infarction. In our work, we have developed an extended gate FET biosensor with high sensitivity, a wide dynamic range and high selectivity to detect cTnI from clinical samples. The biosensor allows a user to detect cTnI in 5 min from one drop of blood, without any prior training or knowledge of the assay.

However, antibody functionalized biomedical sensors face problems in practical implementations such as device preservation for long term and in transportation. Drying the antibody on the sensor can be a solution which avoids liquid handling. In this study, firstly, the activity of cTnI antibody that has been dried with different drying reagents (in-house recipes) and in different concentrations was analyzed using ELISA. We can get optimized reagent concentration from the ELISA results. Then, cTnI antibodies immobilized on the gold surface of extended gate FET biosensor were dried using different reagents. After drying, the antibodies were reactivated in 1X PBS. Following this, the electrical sensor measurement reveals that the antibody activity is maintained and calibration curve can be obtained. These results suggest that drying the sensor chip with these reagents maintains antibody activity and allows our sensor system to function as well as before drying. This is significant for practical implementation of our sensor as a homecare diagnostic device.

Figure 1
(Invited) Self-Powered Medical Electronics
Authors: Li Zhou
Published: February 2020

Recently, piezoelectric nanogenerator（PENG） and triboelectric nanogenerator (TENG) have attracted much attention and been considered as another potential solution for harvesting mechanical energy. With its high output performance, outstanding biocompatibility and low cost, nanogenerator（NG） has been studied for powering implantable and wearable electronic medical devices.

Here, we demonstrated a biomechanical-energy harvesting using a NG as a power source or an active sensor. The NGs can convert the mechanical energy from human motion into electricity and drive the implanted long-term self-powered medical devices or biosensors. An implantable triboelectric nanogenerator (iTENG) in a living animal has been developed to harvest energy from its periodic breathing. The energy generated from breathing and body moving was used to power a prototype pacemaker and a low-level laser cure (SPLC) system, respectively. Meanwhile, it was found that the self-powered system could regulate the heart rate of a rat and significantly accelerated the mouse embryonic osteoblasts' proliferation and differentiation. Real-time acquisition and wireless transmission of self-powered cardiac monitoring data was also demonstrated for the first time. Another NG based self-powered pulse sensor have been applied for antidiastole of coronary heart disease, atrial septal defect and atrial fibrillation from health. These works are concentrated on live-powered medical devices. It showed broad clinical applications of self-powered medical systems for disease detection and health care.
(Invited) Biomimetic Approaches for the Practical Utilization of Discrete Liquid-Solid Contact Electrification
Authors: Kim Dong Sung
Published: February 2020

The concept of “discrete liquid-solid contact electrification”, which is result of sequential process of the liquid contact on the solid surface and successive detachment of contact liquid from the solid surface, was reported. After the first report on discrete liquid-solid contact electrification inside the conventional pipet tip surface, the phenomenon is deeply investigated and explored with the help of utilization on a hydrophobic surfaces, which enables easy detachment of liquid from its surface. As a result, the phenomenon can be intentionally enhanced.

Recently, discrete liquid-solid contact electrification has been utilized as a fundamental operation mechanism of the energy harvester, called triboelectric nanogenerator (TENG), which utilizes the contact electrification phenomenon with electrical induction to efficiently convert ambient mechanical energy to electrical energy.

In this presentation, the history from the discovery of discrete liquid-solid contact electrification to its application as a TENG is introduced. Especially, the biomimetic approaches (mimicking natural lotus leaf and moth's eye) in the fabrication the TENG are introduced not only to enhance the electrical output as an energy harvester, but also to give an additional function for practical utilization. The present study would broaden the applications of discrete liquid-solid contact electrification, which is ubiquitous but previously inconspicuous in our daily life.
(Invited) nanopore-Nanoelectrode Multifunctional Nanopipette for Single Entity and Single Cell Analysis and Imaging
Authors: He Jin
Published: February 2020

Nanopiptte, made from the glass or quartz capillary, has emerged as a versatile tool to probe nanoworld. We have fabricated nanopore-nanoelectrode nanopipette, which can integrate multiple techniques, including nanopore, nanoelectrode and surface enhanced Raman spectroscopy (SERS) techniques, at the apex of nanopipette for sensitive and selective detection. In this talk, I will introduce our recent work of using nanopore-nanoelectrode multifunctional nanopipette for single protein, nanoparticle and cell studies. We manipulated and probed the collision and translocation motions of single entity near the nanopipette apex. The nanopipette has also been used as the probe of scanning ion conductance microscopy (SICM) for topography and surface potential/charge mapping of live cells with nanometer scale spatial resolution.
(Invited) Electrically Conductive Silver Nanowire Coatings on Textiles for Personal Thermal Management
Authors: D'Angelo Paola A. , Orlando Joseph , Lum June S. , Hirst Elizabeth
Published: February 2020

Protection from arctic cold weather has been an ongoing need in military clothing. Current garment systems are problematic due to overdressing, poor moisture management, discomfort following strenuous activity, loss of dexterity and risk of pain and frostbite. All these challenges must be balanced to improve the mobility of Soldiers while reducing pain, hypothermia, and risk of frostbite. In this work, we develop an electrically conductive coating for military uniform fabrics based on synthesized networks of silver nanowires (AgNWs). The nanowire network provides thermal insulation through increased infrared (IR) heat retention as well active Joule heating of the fabric. Long silver nanowires were synthesized using the polyol method where silver nitrate is reduced in the presence of iron chloride seeds, ethylene glycol, and polyvinyl pyrrolidone. Different fabrics including polyester, polypropylene, cotton, and NyCo (50/50 blend of cotton and nylon) were coated with the nanowire ink, and thermal properties were examined. Fourier Transform Infrared (FTIR) spectroscopy revealed a highly thermally insulating coating with an IR reflectance of ~24 % for 100% cotton. Joule heating experiments were carried out and revealed that the temperature of the AgNW-coated textile could be increased by up to 109 °C with 3 V in under one minute. The sheet resistance of the coated fabric was measured using a IV-point probe and found to be significantly lower than the sheet resistance of untreated fabric suggesting the development of a highly conductive textile. Thermal images were also studied and thermal radiation of AgNW-coated fabric was decreased by ~3 °C, indicating that the coated textile appeared cold while being worn. The moisture vapor transmission rate (MVTR) of the coated fabric was investigated and results suggested that coating the different material fabric with AgNW networks does not affect the breathability of the textile since no significant changes in MVTR were observed for any of the fabrics. The results of our research suggest that AgNW-coated textiles could provide passive and active thermal management solutions to offer Soldiers protection from extreme climatic operating environments.
Prestress-Driven Optical Modulations of Flexible Oxide Thin Films Processed in Stretching Mode
Authors: Choi Hong Je , Jung Ye Seul , Soon Aloysius , Cho Yong Soo
Published: February 2020

The effects of stress in inorganic thin films have been long studied to minimize the negative influences of thermally-mismatched substrates mainly in terms of crystal growth and mechanical failure. Although it is well known that extra stress in thin films can affect optical properties, like bandgap, via the theoretical calculations of electronic structure, however, experimental verification of the optical modulation has not been available in the flexible systems. Here, we are dealing with a flexible semiconducting inorganic thin film which can be a fairly good representative for any semiconductor-involved flexible devices or components. We intentionally induced extra compressive stress in wide bandgap ZnO thin films by unique in situ stress-driven deposition processing that utilizes a uniaxial stretching mode of polymer substrate. The stretching mode provides homogeneous but biaxial stresses in the hexagonal wurtzite structure, leading to the extension of c-axis and the contraction of a-axis. The asymmetric consequences affect unexpectedly the energy levels of band structure, which is the origin of the in situ stress-driven optical modulations. We verify such changes successfully by using both the experimental and theoretical methods. The in situ deposition process of flexible thin films under a stretching mode provides compressive strain up to ~4.87%, which corresponds to an in-plane stress of less than ~9 GPa. The existence of the compressive stress induces distortion of the hexagonal unit cell as verified by high-resolution TEM images. We experimentally demonstrate the reduction of the optical bandgap by ~150 meV with the maximum compressive strain of ~4.87%. The experimental evidences of optical modulations were supported by the theoretical calculations using density functional theory. The reduced strong interactions between Zn 3d and O 2p orbitals are assumed to be responsible for the bandgap narrowing.
A Spectroelectrochemical Sweat Sensor for Improved Management of Diabetes Mellitus
Authors: Parr Daniel Lee , Leddy Johna
Published: February 2020

Despite recent attention, wearable ﬁtness tracking devices (e.g., Garmin®, Fitbit® and Apple Watch®) remain unable to monitor overall human and animal health in real time. Continuous measurement enables: (1) alerts of abnormal status and (2) collection of large datasets to beget better models of human health. Here, we focus on continuous measurement of diabetic status. Presently, diabetic status is assessed through invasive and expensive blood glucose measurements. As such, continuous measurement in this way is impractical. Often, insuﬃcient measurements are collected and diabetic excursions are undetected (especially in children and animals) which can result in severe complications including death. Some noninvasive techniques exist (e.g., Breath - Ketonix® and Urine) and rely on high levels of blood ketone bodies (e.g., acetoacetate (acac), β-hydroxybutyrate (bhb), and acetone) present with dysregulated diabetes. Blood ketone bodies partition into breath, tears, and sweat and enable noninvasive measurement. However, modern noninvasive techniques are subject to signiﬁcant irreproducibility and inaccuracy which limits their use by diabetic patients. Alternatively, we describe spectroelectrochemical measurement of acac and bhb in sweat through complexation with metal cations generated at the electrode surface. This concept is advantageous as it may enable continuous quantitative measurement by small portable electronics (such as a cell phone or smart watch). Furthermore, this platform may be extended to other biomarkers that partition into sweat that give insight into other aspects of human health (e.g., heart and kidney failure, exercise intensity, and weight loss).
(Invited) Ultraflexible Organic Photonic Devices
Authors: Yokota Tomoyuki , Someya Takao
Published: February 2020

Recently, flexible electronics has much attracted to realize bio medical application for their flexibility and conformability [1-3]. To improve these characteristics, reducing the thickness of the device is very effective [4]. We have developed ultra-flexible and lightweight organic electronics and photonics devices with few micron substrates. We fabricated the 2-V operational organic transistor and circuits which has very thin gate dielectric layers. The gate dielectrics were composed of thin aluminum oxide layer and self-assembled monolayers (SAMs). Due to the very thin substrate and neutral position, our device shows the highly flexibility and conformability. The device doesn’t be broken after crumpling.

And also we fabricated highly efficient, ultra-flexible, air-stable, three-color, polymer light-emitting diodes (PLEDs) have been manufactured on one-micrometer-thick parylene substrates. The total thickness of the devices, including the substrate and encapsulation layer, is only three micrometers, which is one order of magnitude thinner than the epidermal layer of the human skin. The PLEDs are directly laminated on the surface of skin and are used as indicators/displays owing to their amazing conformability as their superthin characteristics. Three-color PLEDs exhibit a high external quantum efficiency (EQE) (12, 14, and 6% for red, green and blue, respectively) and large luminescence (over 10,000 candelas per square meter at 10 V). The PLEDs are integrated with organic photodetectors and are used as pulse oximeter.

References

[1] D. Khodagholy et al., Nature Commun. 4 1575 (2013).

[2] G. Schwartz et al., Nature Commun. 4, 1859 (2013).

[3] L. Xu et al., Nature Commun. 5 3329 (2014).

[4] D. H. Kim et al., Nat. Mater., 9, 511 (2011).
(Invited) Molecular Sensors for Human Performance Monitoring and Protection
Authors: Brothers Michael , Sim Daniel , Islam Ahmad , Slocik Joseph , Maruyama Benji , Rubenstein Mitchell , Naik Rajesh , Kim Steve
Published: February 2020

Human performance monitoring and health protection requires precise monitoring of chemical and biochemical biomarkers. The biomarker detection in physiologically relevant media, such as sweat, saliva, and exhaled breath faces significant challenges ranging from chemical interference to environmental extremity. This presentation will provide an in-depth look on the factors governing in the biomarker sensor development. Specific attention will be given to the bio recognition element (BRE) design, biotic-abiotic interface, surface BRE packing density, and the electronic/electrochemical detection mode to mitigate the challenges in the biomarker sensor development. We will conclude this paper by opening up the discussion on the path towards ultrasensitive and selective electronic/electrochemical biomarker sensor development and its effective operation-relevant test and evaluation.
Electrodeposited Iron Phosphide Film As an Efficient Electrocatalyst for Hydrogen Evolution Reaction
Authors: Lu Zhipeng , Sepunaru Lior
Published: February 2020

To scale up hydrogen evolution reaction from electrochemical water splitting, a remaining challenge is to replace precious Pt catalysts with cost-effective catalysts. Recently, iron phosphide (FeP) was discovered to be a good substitute for platinum because of the extreme abundance and low cost of iron. Unfortunately, the synthesis of FeP typically requires harsh conditions, which usually cause the decomposition of phosphide precursors and the generation of highly corrosive and flammable phosphorus. Herein, we developed a straightforward and cost-effective method to electrodeposit FeP film on copper electrode at room temperature. The prepared FeP film only requires an overpotential of 66 mV in 0.5 M H2SO4, 131 mV in 1.0 M PBS and 110 mV in 1.0 M KOH, to achieve the current density of 10 mA/cm2, as well as Tafel slope of 55 mV/dec, 108 mV/dec, 60 mV/dec, respectively. In addition, the FeP shows excellent stability over 24 hours and gives about 100% Faradaic efficiency.
Tuning and Mechanistic Insights of Metal Chalcogenide Molecular Catalysts for the Hydrogen-Evolution Reaction
Authors: McAllister James , Miras Haralampos , Bandeira Nuno , Bo Carles , McGlynn Jessica C , Ganin Alexey Y , Song Yu-Fei
Published: February 2020

The production of hydrogen through water splitting using earth-abundant metal catalysts is a promising pathway for converting solar energy into chemical fuels. However, existing approaches for fine stoichiometric control, structural and catalytic modification of materials by appropriate choice of earth abundant elements are either limited or challenging. One promising strategy is the design of molybdenum sulfide nanoclusters which mimic the catalytically active sites found in MoS2. These molecules have the unique property of exposing a high degree of active edge sites leading to improved catalytic activity. Here, we explore the implementation of new design principles for the development of efficient molecular HER catalysts.

In this work, we prepared [Mo2O2(µ-S)2(S2)2]2–
(1)
, [Mo2O2(µ-S)2(S2)(S4)]2–
(2) and [W2O2(µ-S)2(S2)(S4)]2–
(3) by wet-chemical methods and investigated their HER electroactivity. Specifically, we aim to investigate the effects of stoichiometric and structural control resulting from the appropriate choice of the chalcogen elements and their ratio (e.g. O2-/S2
2-, O2-/S2
2-/S4
2-) within the coordination sphere of earth abundant transition metals (e.g. Mo or W). We evaluate the performance of these molecular catalysts for the hydrogen evolution reaction while we propose potential mechanistic pathways in relation to the interaction between catalysts and substrate.

The employed design principles offer the opportunity to bridge the gap between molecular and solid-state heterogeneous catalysts when immobilized on a carbon electrode surface. These molecular species represent an exciting class of low-cost earth-abundant materials and display great promise as HER electrocatalysts. Both molybdenum-based catalysts were shown to be exceptionally active towards the HER, with a reported overpotential of just –114 3 mV (at j = 10 mA cm–2) and no catalyst degradation over 1000 cycles. Density functional calculations reveal the effect of the electronic and structural features and confer plausibility to the existence of a unimolecular mechanism in the HER process based on the tested hypotheses. We anticipate these findings to be a starting point for further exploration of molecular catalytic systems.

Figure 1
(Invited) Development of Standards and Best Practices for Materials Testing in Low Temperature Electrolysis
Authors: Ayers Katherine E. , Capuano Christopher B , Motz Andrew R , Mani Prasanna
Published: February 2020

As part of any overall strategy for environmental sustainability, a source of renewable hydrogen is needed, as a chemical feedstock as well as part of the portfolio of energy storage solutions. Currently over 95% of hydrogen is made from fossil fuels through natural gas reforming or coal gasification. However, water electrolysis has decreased significantly in capital cost and increased in scale. At the same time, renewable electricity costs have also dropped, especially in periods of high capacity, providing a potential pathway for competitively priced “green” hydrogen from water splitting. Still, continued materials and manufacturing research is essential to achieve cost parity with fossil fuels and produce renewable hydrogen at scale.

As new materials are developed, it is important to make accurate comparisons to a common baseline, to understand the potential for improvement over existing technology and to compare different pathways. Currently, research on electrolysis materials published in the scientific literature tends to be scattered across a range of test conditions and configurations, making these comparisons difficult. For example, catalysts may be tested with a range of membranes, at different temperatures, with different counter electrodes, and different electrolytes. In addition, test configurations can impact performance and cause variation in results even for the same materials. Having a standard baseline set of conditions can ground the results, even if additional tests are also performed to look at benefits of specific conditions for specific materials.

There are currently efforts in both Europe and the United States to select common standards and define test parameters and configurations for low temperature electrolysis. The U.S. Department of Energy is funding a team to coordinate similar work across all of the major water splitting pathways: low temperature electrolysis (primarily ion exchange membrane-based), high temperature electrolysis (primarily solid oxide), solar thermochemical water splitting (STCH), and direct photoelectrochemical water splitting (PEC). This talk will describe status of this project, including a workshop held in October 2018 and follow up work for specific materials tests.