bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Stability of Quasi-Two-Dimensional β-Ga2O3 and Its Device Application
Authors: Kim Suhyun , Kim Janghyuk , Kim JiHyun
Published: February 2020

An ultra-wide bandgap of around 4.8-4.9 eV (at room temperature), high thermal and chemical stabilities are some of the attractive properties of β-gallium oxide (β-Ga2O3) for fabricating (opto)electronics. Its noticeably high dielectric breakdown field (Ebr) also has drawn attention; the theoretical value was calculated to be ~8 MV/cm and a recent report reached an experimental value of 3.8 MV/cm, which is higher than those of GaN and SiC. These advantages obviously led to various applications on power devices including metal-semiconductor field-effect transistors (MESFETs), metal-oxide-semiconductor field-effect transistors (MOSFETs) and Schottky barrier diodes.

Mechanically exfoliated β-Ga2O3 flakes were studied in our investigation. The mechanical exfoliation of β-Ga2O3 is possible although it is not formed by van der Waals interaction as its monoclinic structure allows cleavage into thin flakes along [100] direction. This new possibility of preparing β-Ga2O3 samples not only suggests that β-Ga2O3 can possess two-dimensional (2D) properties, but also offer a solution for low thermal conductivity of β-Ga2O3, which is a critical limitation when fabricating high power devices. Since it is only recently that mechanically exfoliated β-Ga2O3 gained attention, there still exists several characteristics to be investigated. Unlike bulk substrates, quasi-2D β-Ga2O3 needs more research on stability to be applied to devices such as sensors and high-power electronics that operate at high temperature. In this study, the thermal stability of β-Ga2O3 flakes was observed over time and the means to improve the stability were investigated. The optical and structural changes with time were measured as the samples were exposed to higher temperature (200 – 400 °C). MESFETs were also fabricated using β-Ga2O3 flake as the channel material to investigate the thermal effects on the device, especially the Schottky barrier between the channel and the gate metal. Different metals and an additional thermally conductive 2D layer was used to enhance the thermal stability of the device. This study shows the potential of quasi-2D material (β-Ga2O3) devices with long term stability at high temperature. Further results and discussion will be presented in detail.
Atomic Observation of Solid-State Reaction in Fe/ZnO Bilayer
Authors: Huang Chih-Yang , Tai Kuo-Lun , Lu Ming-Yen , Wu Wen-Wei
Published: February 2020

Transition metal oxides are of great interest due to their wide physical characteristics. Transition metal oxide heterostructure could even combine the functions of different metal oxides to perform superior properties. Therefore, the study of heterostructure formation is essential. In this work, the formation of metal oxide heterostruture through diffusional reaction was observed via in-situ transmission electron microscope (TEM). Single-crystal ZnO thin film and Fe metal were annealed at 650∘C, and then Fe3O4/ZnO heterostucture were formed by solid-state diffusion. The HRTEM results and corresponding FFT-DP demonstrated the reaction taking place along the basal plane of ZnO {0001} while Fe3O4 forms along planes {111}, which are both the closest-packing plane. Moreover, Fe3O4 twin defects were observed which composed of (111) spinel-law twin boundaries. The nanofabricated method provides a novel approach to produce transition metal oxides heterostructures for their wide range of applications.
Anomalous Electron Accumulation at Al2O3/in2O3 Interface Via Short-Range Ordered Two-Dimensional Electron Gas
Authors: Lee Sang Yeon , Seo Hyungtak
Published: February 2020

Transparent conducting oxide (TCO) films, which is one of the widely used as window electrodes at the various devices, fulfil high electrical conductivity and optical transparency in the visible region of spectrum. Conventional TCO films are formed by the tuning charge transport of wide band gap oxides like indium gallium zinc oxide (IGZO), zinc oxide (ZnO), tin dioxide (SnO2), and indium oxide (In2O3). Among the various TCO candidates, In2O3 is an attractive TCO candidate since In2O3 can satisfied the visible transparency and high carrier density via doping processes. To achieve the high mobility In2O3 films, doping processes with metal dopants such as Ti, Zr, Mo, and W have been suggested by many previous study. Intrinsic In2O3, however, has n-type semiconductor due to its native oxygen vacancy act as n-type donor and indium interstitial. As another approach to gain highly conductivity TCOs, two-dimensional electron gas (2DEG) channel can be suggested since 2DEG channel can be applied to increase the electrical conductivity of oxide semiconductors up to the metallic conduction level. The tuning of electrical and optical properties in oxides via surface and interfacial 2DEG channels is of great interest, as they reveal the extraordinary transition from insulating or semiconducting characteristics to metallic conduction or superconductivity enabled by the ballistic transport of spatially-confined electrons. Although most previous studies have been carried out in crystalline phase like single crystal SrTiO3 or III-V compound semiconductor, realizing practical aspects of this exotic phenomenon toward short-range ordered and air-stable 2DEG channels remains a great challenge.

In this study, we fabricated Al2O3/In2O3 heterojunction system on soda-lime glass consisting of In2O3 deposited by RF reactive sputter with a thickness from 8 to 100 nm and Al2O3 deposited by ALD with a thickness below 100 nm. We suggest that Al2O3/In2O3 heterojunction acts as short-range ordered 2DEG channel with a low temperature (~200 ℃). After deposition of Al2O3 layer, the heterojunction two-dimensional metallic channel was fabricated between Al2O3 and In2O3 interface as showing the metallic conduction with sheet charge density > 10 14/cm2, sheet resistance of 850 Ω/cm2, room temperature Hall mobility of 20.5cm2 V-1 sec-1 depending on the In2O3 thickness. To prove existence of 2DEG channel at the interface, we performed the I-V measurement, time of flight secondary ion mass spectrometry, ultraviolet-visible spectrophotometer, tunneling electron microscope–electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and Hall measurement.
Towards InGaAs MS-DRAM Memory Cells
Authors: Navarro Carlos , Navarro Santiago , Marquez Carlos , Sampedro Carlos , Donetti Luca , Karg Siegfried , Riel Heike , Gamiz Francisco
Published: February 2020

The need of a low-power, fast and low-cost CMOS compatible embedded DRAM cell is rising incessantly with the upcoming Internet of Things (IoT) era [1]. Capacitor-less DRAM cells [2, 3] have emerged as a promising solution since they do not require dedicated fabrication steps to deal with the storage node. Among this breeze of cells, the MSDRAM [4] can be highlighted due to the simpler manufacturing process.

The MSDRAM (Meta-Stable-Dip RAM) memory operation is based on inter-gate coupling [5] and non-equilibrium state [6]. The back gate (ground-plane) is biased positively to induce a virtual n-type back-channel while the front-gate voltage is negative to retain any available hole in the body. By modulating the hole population at the front-channel, the vertical top-gate induced electric field is screened (or not) so that the back electron-channel is maintained (or depleted). Depending upon the back-channel depletion degree different conductance values are achieved defining the logic ‘1’ and ‘0’ memory states. State programming is carried out by injecting holes by band-to-band tunneling at the drain edge (W1) or evacuating holes by top-gate capacitive coupling (W0)

In this work, a III-V InGaAs MSDRAM cell is built and its memory operation is demonstrated by TCAD numerical simulations in Synopsys [7, 8]. The detailed structure and the doping are shown in Fig.1. The basic memory operation is depicted in Fig. 2a for a W0-R-W1-R-W0-R sequence with W1/0 being the ‘1’/’0’ state programming and R the reading. The current after any W0 operation remains much lower than after W1. Figure 2b represents the body electron and hole densities after the first W0 and W1, respectively. Following W0, the hole density is limited underneath the top dielectric allowing a strong vertical field that depletes the back-channel from electrons leading to a drastic drop in the conductance and thus in the drain current. On the contrary, after generating holes by band-to-band tunneling during W1, the electron back-channel is reinforced enabling a larger current level while reading afterward.

In conclusion, preliminary TCAD results demonstrate the feasibility of implementing the MSDRAM concept on III-V materials.

REMINDER project (No 687931) is thanked for support.

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(Invited) Validation of the Ion-Responsive Urine Sensor for Prostate Cancer Detection
Authors: Lee Kwan Hyi
Published: February 2020

A noninvasive assay capable of quantifying prostate cancer biomarkers in untreated urine is an elusive diagnostic technique with various obstacles. Difficulties arise because untreated urine contains varying salt concentrations and pH levels even though they are from the same patient. Untreated urine also possesses a fewer number of cancer biomarkers than can be found in serum and a greater number of other biomolecules, which reduces the signal-to-noise ratio. Consequently, urine preconditioning processes and digital rectal examination (DRE) to increase cancer biomarker concentration is of utmost importance in current urine assays. To address these issues, an ion-responsive urine sensor (IRUS) measuring differential electrical signals is presented as a self-normalized detection method. FET biosensor with a disposable sensing gate forms the basis of the proposed IRUS and has the capability to detect prostate cancer biomarkers in untreated urine.
(Invited) Implantable Flexible Nanogenerators for Biomechanical Energy Harvesting
Authors: Wang Xudong
Published: February 2020

Harvesting mechanical energy from biological systems possesses great potential for in-vivo powering implantable electronic devices. Nanogenerator (NG) is a promising technology for harvesting biomechanical energy either in vivo or ex vivo. In this talk, I present a development of flexible piezoelectric nanogenerator (NG) based on mesoporous poly(vinylidene fluoride) (PVDF) films. Monolithic mesoporous PVDF was fabricated by a template-free sol-gel-based approach at room temperature. By filling the pores of PVDF network with poly(dimethylsiloxane) (PDMS) elastomer, the composite’s modulus was effectively tuned over a wide range down to the same level of biological systems. A close match of the modulus between NG and the surrounding biological component is critical to achieve practical integration. Upon deformation, the composite NG exhibited appreciable piezoelectric output that was comparable to or higher than other PVDF-based NGs. An artificial artery system was fabricated using PDMS with the composite NG integrated inside. Effective energy harvesting from simulated blood pressure fluctuation was successfully demonstrated. The simple and effective approach for fabricating mesoporous PVDF with tunable mechanical properties provided a promising route toward the development of self-powered implantable devices. In vivo biomechanical energy harvesting was further demonstrated. The PVDF NG was encapsulated by polydimethylsiloxane (PDMS) and embedded into rodents. No toxicity or incompatibility sign was found in the host after carrying the packaged NG for 6 months. Moreover, the electric output of this NG was extremely stable and exhibited no deterioration during the entire implantation period. The outstanding efficiency, magnificent durability and exceptional biocompatibility promise this mesoporous PVDF-based NG in accomplishing self-powered bioelectronics with potentially lifespan operation period.
(Invited) Piezoelectric Peptide-Based Energy Harvesters
Authors: Yang Rusen
Published: February 2020

Nanoscale energy harvester holds promise for the development of self-powered nanosystems, while molecular self-assembly of bio-inspired materials has attracted much research effort in recent years. Here we report the controlled growth of vertically aligned FF peptide microrods and their application in nanogenerators. The peptide has recently been demonstrated as a sustainable and smart material for piezoelectric energy conversion. Utilizing both piezoelectric and triboelectric effects is of significant research interest due to their complementary energy conversion mechanisms. We discovered a simple and efficient approach to integrate the piezoelectric nanogenerator with triboelectric nanogenerator. The stacking one layer atop the piezoelectric peptide-based nanogenerator to form the single-electrode triboelectric nanogenerator eliminate the needed extra electrode and complicated connection found in other devices. The energy conversion process is simplified and improved. This work demonstrated the first biomaterial-based hybrid nanogenerator and significantly advanced the study of smart biomaterials. Our work can enable new applications of bio-inspired materials in areas such as energy harvesting and storage, electromechanical sensing and actuation, drug delivery, as well as fundamental studies of FF-based structures.
(Invited) Printed Flexible Sensor-Integrated Wearable Healthcare Patch
Authors: Takei Kuniharu
Published: February 2020

Wearable healthcare device allows us to monitor continuous daily health conditions if multiple sensors to detect physical and chemical information from a body can be integrated on a flexible sheet. Simultaneous detections of a variety of health conditions from body during daily life are most likely only realized by attaching the devices directly onto skin. By considering hygiene concerns for the direct attachment, the device should be disposable like a bandage or contact lenses. To spread this concept to many users widely, the device needs to be low cost due to that reason. To realize both multi-functionality and low cost process on a macroscale film, printing techniques to form active materials are promising as a next class of electronics. In fact, recently, many printed flexible sensors and transistors have been reported by using inorganic and/or organic materials. As the one of approaches, in this talk, a printed flexible multi-functional healthcare patch will be introduced. Furthermore, the fundamental properties of each sensor such as skin temperature, motion, and electrocardiogram signal sensors will be discussed. Although there are still a lot of challenges to realize the wearable healthcare patch, this progress may be able to help the progress on this field in near future.
Development of Portable Self-Powered Disinfection Systems Based on Triboelectric and Thermoelectric Effects
Authors: Chiu Che Min , Lin Zong-Hong
Published: February 2020

Pathogenic bacteria that give rise to infection remain a major health concern over the past several decades. In this study, we proposed a concept of self-powered active disinfection system for wearing clothes. The system was mainly composed of a power generator to convert either biomechanical energy or thermal energy into electricity, and conductive fabrics as electrodes to build a wearable disinfection cell. Based on different power sources, we develop two types of self-powered antibacterial fabrics. For the use of biomechanical energy as a power supply, we applied triboelectric nanogenerator (TENG) to effectively harvest energy from human motions; for converting thermal energy into electricity, a Te-Ag2Te hybrid thermoelectric nanogenerator was used. The working principle of the system was based on hybrid effects of H2O2 production and electroporation, showing good disinfection effect toward Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). In addition, we also demonstrated the presence of one-dimensional (1D) Te nanowires on fabrics would increase the strength of the local electric field and enhanced the system disinfection performance. To conclude, the self-powered active disinfection system behaves as an ideal candidate to combat with pathogenic bacteria in biomedical and environmental applications.
(Invited) All-Solid Hybrid Energy Fabric for Wearable Electronics
Authors: Fan Xing
Published: February 2020

The demand for wearable power sources has been growing rapidly in the modern era of portable electronics. It is essential to make these power sources more comfortable and fit for the human body, especially for some medical applications in which case we need to wear it day and night. Energy harvesting and storage devices in the form of a common-looking fabric is thus of a great interests in recent years. Herein, we have successfully woven out a type of micro-cable power textile for simultaneously harvesting energy from ambient sunshine and mechanical movement. Solar cells fabricated from lightweight polymer fibers into micro cables are then woven via a scalable shuttle-flying process with fiber-based triboelectric nanogenerators to create a hybrid energy harvesting fabric. The hybrid power fabric is just 320 µm thick, fabricated with a size of 4 cm by 5 cm, was demonstrated to charge a 2 mF commercial capacitor up to 2 V in 1 min under ambient sunlight in the presence of mechanical excitation, such as human motion and wind blowing. Based on the similar strategy, a novel solid solar energy harvesting and storage hybrid textile combining both photovoltaic cells and super-capacitors were also designed and realized, in order to provide power at dark condition within a single textile. With such features as low-cost, thinness, light-weight, being flexible and wearable, as well as colorful appearance, this work represents a significant step towards the development of large scale energy harvesting and storage for wearable electronics and self-powered home technology. Some recent publications were selected as “Research Highlights” by Nature and the “9 most impressive social innovation goods from October” of Yahoo News in 2016.

References

[1] J. Chen#, Y. Huang#, N. Zhang, H. Zou, R. Liu, C. Tao, X. Fan*, Z. L. Wang*, Nature Energy. 2016, 1, 16138.

[2] N. Zhang#, J. Chen#, Y. Huang, W. Guo, J. Yang, J. Du, X. Fan*, C. Tao*, A Wearable All‐Solid Photovoltaic Textile, Advanced Materials, 2016, 28 (2), 263-269

[3] Z. Chai#, N. Zhang#, P. Sun, Y. Huang, C. Zhao, H. Fan, X. Fan*, W. Mai*, ACS Nano. 10 (2016) 9201–9207.
Heavy Metal Ion Detection from Whole Blood Using Ion Selective FET Sensor
Authors: Wang Shin-Li , Sukesan Revathi , Hsieh Ching-Yen , Wang Yu-Lin
Published: February 2020

In our daily life, there are various sources of pollution that adversely affect our health. Heavy metal is one of the main contaminants surrounding everyone in an ecosystem. Since lead ions cannot be metabolized by liver, it will stay in the blood, and if medical intervention is not provided, it can cause adverse health effects to nervous system, due to gradually accumulating lead ion concentration. Nowadays, there are several technologies that can detect lead ion concentration, but most of them will take long time or are not easy to operate, because they require laboratory based bulky equipment. Examples of such methodologies are inductively coupled plasma- mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS), which are the most commonly employed heavy metal ion detection techniques. However, this is not desirable for every-day use or ‘in field’ monitoring. Based on the idea of homecare diagnostics, we have developed a heavy metal ion sensor to detect lead ions in whole blood, with high sensitivity, selectivity, wide dynamic range and great ease of operation. High electron mobility transistor (HEMT) based sensor has been widely used in various applications, because it has high sensitivity, stability in harsh environments and fast response times. The fabrication of HEMT chip has 4 steps: ICP mesa etching, ohmic contact metal deposition, interconnect metal deposition and SU8 passivation. The 1mm2 HEMT chip is packaged by embedding in epoxy substrate in the shape and form of micro SD card. Ion selective membrane (ISM) is selectively immobilized on the channel. Using high field operation, the changes in ISM capacitance due to lead ion capture, is amplified by the HEMT and we can obtain a drain current signal that is proportional to the lead ion concentration, in whole blood. We can thus obtain high sensitivity and low detection limit, which is comparable to the traditional technologies such as ICP-MS (detection limit of Pb2+: 10-10 M)

Figure 1
(Invited) Multifunctional Nano-Array Integrated Monolithic Devices: Toward Rational Engineered Nanomaterials Design and Scalable Nanomanufacturing
Authors: Gao Pu-Xian
Published: February 2020

The scalable three-dimensional (3-D) integration of functional nanostructures into applicable platforms represents a promising technology to meet the ever-increasing demands of fabricating high performance devices featuring cost-effectiveness, structural sophistication and multi-functional enabling. Such an integration process generally involves a diverse array of nanostructural entities (nano-entities) consisting of dissimilar nanoscale building blocks such as nanoparticles, nanowires, and nanofilms made of metals, ceramics, or polymers. Various synthetic strategies and integration methods have enabled the successful assembly of both structurally and functionally tailored nano-arrays into a unique class of monolithic devices. The performance of nano-array based monolithic devices is dictated by a few important factors such as materials substrate selection, nanostructure composition and nano-architecture geometry. Therefore, the rational material selection and nano-entity manipulation during the nano-array integration process, aiming to exploit the advantageous characteristics of nanostructures and their ensembles, are critical steps towards bridging the design of nanostructure integrated monolithic devices with various practical applications. In this talk, we highlight the latest research progress of the two-dimensional (2-D) and 3-D metal and metal oxide based nanostructural integrations into prototype devices and systems applicable with ultrahigh efficiency, good robustness and improved functionality. Selective examples of nano-array integration, scalable nanomanufacturing and representative monolithic devices will be highlighted, including automotive catalytic converters, thermo-catalytic and photo-activated reactors for fuel/chemical production, and sensors, with practical nanotechnology implications ranging from energy, environmental, to chemical and biotechnology areas.
Plasmonic Nanopore Fabrication for Single Molecule Bio Sensor By Using Electron Beam Irradation
Authors: Choi Seong Soo , Park Myoung Jin , Han Chul Hee , Oh Sae-Joong , Kim Hyun-Tae , Choi Soo Bong , Kim Yong-Sang
Published: February 2020

Recently the portable device called MINion for single molecule analysis was developed by Oxford Nanopore Technology. The electrical detection technique for the solid state device was utilized for single molecule detection . However, the large error rates were reported by several journals, even though the significant error reduction was developed after the invention of the portable nanopore device. In this report, we introduce the optical nanopore fabrication by using plasmonic optical enhancement effect. First, the Au thin films were vacuum-deposited on the nanometer thin SiN film, followed by removal of SiN film and by drilling Au apertures by using focused ion beam (FIB) technique. Then, electron beam irradiations on the specimens either by using low energy field emission electron beam microscopy (FESEM) or high energy Transmission electron beam microscopy (TEM). In addition, the periodic grooves, or the periodic Au aperture array were fabricated on the Au sample in order to provide strong plamonic optical enhancements. During the electron irradiation on the fabricated Au surface, we observed the diffused binary Au-C membrane due to Ostwald ripening and also the unstable Au-C mixed phase change via spinodal decomposition. We also found that the Au cluster diffusion would depend upon the electron beam fluence. However, the exact understanding of this phenomenon is still on-going investigation.

Figure 1
(Invited) Wireless Photoelectrochemical Control of Neuronal Activity with Coaxial Silicon Nanowires
Authors: Tian Bozhi
Published: February 2020

Optical methods for modulating cellular behavior are promising for both fundamental and clinical applications. However, most available methods are either mechanically invasive, require genetic manipulation of target cells, or cannot provide sub-cellular specificity. Here, we address all these issues by showing optical neuromodulation with free-standing coaxial p-type/intrinsic/n-type silicon nanowires (PIN-SiNWs). We revealed the presence of atomic gold on the nanowire surfaces, likely due to gold diffusion during the material growth. To evaluate how surface gold impacts the photoelectrochemical properties of single PIN-SiNWs, we used modified quartz pipettes from a patch clamp and recorded sustained cathodic photocurrents from single PIN-SiNWs. We show that these currents can elicit action potentials in primary rat dorsal root ganglion neurons through a primarily atomic gold-enhanced photoelectrochemical process. This work shows that wireless and non-genetic photoelectrochemical neuromodulation with single nanostructures is possible, and has implications for both basic research and photo-responsive therapies for neurodegenerative diseases.
(Invited) Transparent Bioelectronics for Electrical and Optical Measurements of Embryonic Stem Cell Derived Cardiomyocytes
Authors: Cohen-Karni Tzahi , Rastogi Sahil , Shiwarski Daniel , Bliley Jacqueline , Feinberg Adam
Published: February 2020

Understanding cellular electrical communication is of growing interest in stem cell biology. Electrical properties have been linked to specification and differentiation of stem cells into targeted progeny such as neurons and cardiomyocytes. Basic research at the tissue level of the heart and brain electrical activity has led to the development of tools to treat various ailments, such as pacemaker and deep brain stimulation electrodes for the treatment of cardiac arrhythmias and Parkinson’s disease respectively. Currently, there is a critical need and tremendous interest in developing new ways to complement fluorescent indicators such as voltage and Ca2+-sensitive dyes, for direct electrophysiological measurements of cells and tissue. Graphene, a honeycomb sp2 hybridized two-dimensional (2D) carbon lattice is a promising bioelectronic building block due to its outstanding electrical conductivity (charge carrier mobility up-to 200,000 cm2 V-1 s-1), mechanical flexibility, and optical properties (optical transmittance of ~97.7%). Here we report a unique transparent graphene-based electrical platform that enables concurrent electrical and optical investigation of ES-derived cardiomyocytes’ intracellular processes and intercellular communication. The graphene-based bioelectronics platform is also shown to be biocompatible in terms of adhesion, viability and cell stress. Our presented approach will greatly impact our basic understanding of signal transduction in complex cellular assemblies, and create new avenues for bidirectional communication (sensing and stimulation) with electrically active tissues. The developed nanomaterials-based measurement platform will set the ground for further investigations of the relationship between electrical signals and reported diseases such as Alzheimer, Parkinson’s disease and Arrhythmias.
(Invited) Plasmonic Patch Nanoantennas for Reproducible and High-Sensitivity Chemical Detection with Surface-Enhanced Raman Spectroscopy
Authors: Wang Feng , Joshi Bhuwan P , Chakrabarty Ayan , Zhang Hailiang , Wei Qi-Huo
Published: February 2020

Excitations of surface plasmon polaritons at metal/dielectric interfaces can lead to a number of interesting optical effects in nonlinear harmonics generation, nanofocusing, enhanced optical scattering and emission. In particular, Raman signals from molecules in contact with or close proximity of metallic nanostructures can be enhanced by many orders of magnitudes, a phenomenon called surface-enhanced Raman scattering (SERS). Studies have shown that with certain plasmonic nanostructures, the SERS signals are detectable even in single molecular level, making SERS a potential label-free and high-sensitivity bio/chemical sensing modality. However, it is challenging to reach single molecule SERS in a reproducible way, as nanogaps between plasmonic nanostructures are commonly required. While nanopatterning techniques such as electron beam lithography are versatile in creating various nanostructures, creating nanogaps below 20nm reducibly remains a challenge. Here we present plasmonic patch antennas as a platform for SERS applications. The patch antennas are made of metallic patches on the top of a metal film separated by a dielectric layer. This vertical metal-dielectric-metal design makes it possible to reproducibly control the gap size in nanometers by using thin film deposition techniques such as atomic layer deposition. In this talk, we will present numerical and experimental studies on resonant cavity modes of these plasmonic patch antennas, a simple expression relating the cavity resonant frequencies with the geometric parameters of the antennas. We will also present experimental tests on SERS enhancement factors by the plasmonic patch antennas, and a comparison of their performances with commercial SERS substrates.
(Invited) Charge Carriers, Defects and Interfaces in Two-Dimensional Materials and Devices
Authors: Liu Yuanyue
Published: February 2020

Two-dimensional semiconductors show great promise for next-generation electronics and optoelectronics, yet they still face significant challenges to realize their potential. Here I will discuss our recent theoretical/computational studies on the charges carriers, defects and interfaces in two-dimensional materials and devices. Specifically, I will show (i) how to estimate the electron/hole mobility with reasonable accuracy; (ii) the role of defects and how to passivate the harmful ones [1,2]; and (ii) how to lower the metal-semiconductor resistance [3,4].

[1] Y. Liu, P. Stradins, S. Wei, Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201508828

[2] Y. Liu, H. Xiao, W. A. Goddard III, Nano Lett. 2016, 16, 3335

[3] Y. Liu, P. Stradins, S. Wei, Science Advances 2016, 2, e1600069

[4] Y. Liu, H. Xiao, W. A. Goddard III, JACS, 2016, 138, 15853
(Invited) Indium Gallium Phosphide Photodiode with 50% Increased External Quantum Efficiency and Higher Signal to Noise Ratio for Blood Pressure Measurement
Authors: Kao Yung-Hua , Chao Chang-Po , Kumar Amarendra , Lin Yi-Chieh , Hsu Chia-Liang
Published: February 2020

Measurement of blood pressure is one of the most important parameters for personal healthcare. Arteries are responsible for carrying blood from the heart to all parts of the body and the pressure of blood in arteries is measured in many abnormalities. The blood pressure is explained by two parameters. The highest blood pressure during heart pumping is measured by systolic pressure whereas the diastolic pressure measures the lowest blood pressure when the heart is not pumping the blood. For current work, the principle of light absorption is used to measure blood pressure in arteries. Light is more strongly absorbed by blood compared to skin or tissues and therefore, blood flow change can be detected by the change in intensity of light. This blood flow change is proportional to blood pressure and hence the blood pressure can be measured by measurement of change in light intensity.

In this work, we have developed the InGaP photodiode module with higher signal to noise ratio for blood pressure measurement. The InGaP photodiode External Quantum Efficiency (EQE) is 50% higher than Silicon (Si) photodiode. The EQE is ever higher than Si photodiode equipped with the filter as shown in Fig. 1(a). The newly developed InGaP photodiode has the advantage of selective EQE at different wavelength. The photodiode has almost zero EQE outside the desired region of wavelength (300 nm- 700 nm) where the Si photodiode EQE is spread in the longer wavelength region (300 nm - 1200 m). This higher region of EQE can lower the signal to noise ratio. The InGaP photodiode has an increased signal to noise ratio (24.8) compared to other photodiodes (24.0) due to the smaller wavelength region of EQE. Both systolic blood pressure and diastolic blood pressure measurement was compared for actual value and predicted value. The R2 correlation value for systolic and diastolic blood pressure is measured to be 0.86 and 0.91 respectively as shown in Fig. 1(b) and Fig. 1(c).

This works explore new doorway for LED and photodiode application in the field of biomedical sensors. The application of our new photodiode with enhanced EQE and the wide range of LED has numerous possibilities. The higher possibility of multichip design with Flip chip packaging technique can provide a single module for measurement of blood pressure, blood glucose, blood lipid and other parameters using LED of different wavelength.

Figure 1
(Invited) Mid-IR Metamaterial Absorber Platform for Gas and Chemical Sensing Applications
Authors: Lee Chengkuo , Hasan Dihan
Published: February 2020

Metamaterial based optical nanostructures refer to engineered material with properties not readily available in nature, and diversified sensing applications have been investigated. For example, metamaterial absorber is gaining attention for energy efficient Nondispersive Infrared sensor for large scale green-house CO2 gas monitoring applications. However, miniaturization of the technology remains a major issue. Integration with smart, gas selective material toward the realization of “hybrid metamaterial” absorber is believed to be a viable approach for the system miniaturization. Here, we present a novel hybrid polymer-metamaterial absorber approach for miniaturized and selective optical sensing of CO2 gas in the 5-8 μm mid IR (Infrared) spectral window for the first time. The new class of sensor offers ppm-level limit of detection at ambient temperature, fast response time (~2 minutes) and large differential change for all-optical monitoring on a small foot print (20μm by 20μm). As proof-of-concept, we report net absorption enhancement of 0.0282%/ppm and wavelength shift of 0.5319 nm/ppm. The gas selective smart material is found to enable dual-mode multiplexed sensing for cross checking and validation of gas concentration on the single platform. The obtained results will pave the way for physical understanding of metamaterial based sensing when integrated with mid-IR detector for on-chip readout and extending the mid-IR functionalities of selective materials for the detection of technologically relevant gases. Meanwhile, the feasibility of using this platform for chemical sensing and biomolecule detection will be highlighted as well.
Sensitivity Enhancement Techniques for Black Phosphorus-Based Gas Sensors
Authors: Lee Geonyeop , Kim Suhyun , Jung Sunwoo , Jang Soohwan , Kim JiHyun
Published: February 2020

Two-dimensional materials (2DMs) have been widely studied as sensing materials because their distinct 2D structure allows their entire volume to adsorb gas molecules. Black phosphorus (BP) has received much attention in recent years as one of the promising 2DMs. BP has direct band gap (0.3-2.0 eV), high carrier mobility (~1,000 cm2/V∙s) and high current on/off ratio (104-105). In addition, the unique properties of BP such as puckered structure, lone pair electrons on the surface and high charge transfer rate results in high sensitivity toward gas molecules. It is reported that BP shows higher sensitivity compared to graphene and MoS2. However, the sensitivity of BP-based gas sensor still requires better performance for the practical use.

In our study, we have tried to enhance the sensing properties of BP-based gas sensors toward NO2, NH3, and H2. BP-based gas sensors were fabricated by using a dry-transfer technique. BP flakes mechanically exfoliated from the bulk sample were transferred on to source-drain electrodes; the electrodes (Ti/Au) were pre-patterned on a SiO2/Si substrate. We performed two different approaches to improve the sensitivity of the sensors. First, we altered the supported structure to suspended structure to use both sides as the sensing area and eliminate the substrate effect such as charge scattering. We also functionalized BP sensors with Pt nanoparticles to improve its hydrogen sensing ability. We measured the resistive sensitivity and confirmed that sensing performance of treated sensors was higher than that of the untreated samples. The details of our experiment conditions and results will be presented at the meeting.
(Invited) Triboelectric Nanogenerator for Self-Powered Flexible Electronics and Internet of Things
Authors: Wang Zhong Lin , Wang Aurelia Chi
Published: February 2020

Triboelectrification is an effect known to society ever since the ancient Greek era, but it is usually considered a negative effect and avoided in many technologies. We have recently invented a triboelectric nanogenerator (TENG) that is used to convert mechanical energy into electricity by a conjunction of triboelectrification and electrostatic induction. As for this power generation unit, in the inner circuit, a potential is created by the triboelectric effect due to the charge transfer between two thin organic/inorganic films that exhibit opposite tribo-polarity; in the outer circuit, electrons are driven to flow between two electrodes attached on the back sides of the films in order to balance the potential. Ever since the first report of the TENG in January 2012, the output power density of TENG has been improved for five orders of magnitude within 12 months. The area power density reaches 500 W/m2 , and a conversion efficiency of ~50-85% has been demonstrated. The TENG can be applied to harvest all kind mechanical energy that is available but wasted in our daily life, such as human motion, walking, vibration, mechanical triggering, rotating tire, wind, flowing water and more. Alternatively, TENG can also be used as a self-powered sensor for actively detecting the static and dynamic processes arising from mechanical agitation using the voltage and current output signals of the TENG, respectively, with potential applications for touch pad and smart skin technologies. The TENG is possible not only for self-powered portable electronics, but also as a new energy technology with a potential of contributing to the world energy in the near future.

[1] Z.L. Wang, Materials Today, 20 (2017) 74-82.

[2] “Nanogenerators for Self-Powered Devices and Systems”, by Z.L. Wang, published by Georgia Institute of Technology (first book for free online download): http://smartech.gatech.edu/handle/1853/39262

[3] Z.L. Wang, L. Lin, J. Chen. S.M. Niu, Y.L. Zi “Triboelectric Nanogenerators”, Springer, 2016. http://www.springer.com/us/book/9783319400389

[4] Z.L. Wang “Triboelectric Nanogenerators as New Energy Technology for Self-Powered Systems and as Active Mechanical and Chemical Sensors”, ACS Nano 7 (2013) 9533-9557.

[5] Z.L. Wang, J. Chen, L. Lin “Progress in triboelectric nanogenerators as new energy technology and self-powered sensors”, Energy & Environmental Sci, 8 (2015) 2250-2282.
(Invited) Design of Silicon Structures for Optically-Controlled Biointerfaces
Authors: Tian Bozhi
Published: February 2020

Silicon (Si)-based materials have a wide range of utilities in biophysical and biomedical research. Remotely-controlled Si configurations, however, are rarely explored due to a limited fundamental understanding of the complex physicochemical processes that occur at Si-biology interfaces. Here, we formulated a biology-guided rational design principle for establishing intra-, inter- and extracellular Si-based interfaces, where Si and biological targets have matched properties. We demonstrated the utility of these interfaces by showing light-controlled non-genetic modulations of intracellular calcium dynamics, cytoskeleton-based transport and structures, cellular excitability, and brain activities in vivo.
(Invited) Flexible Organic Sensors for Biomechanical Measurements
Authors: Amit Moran , Zhai Yichen , Wu Zhenghui , Ng Tse Nga
Published: February 2020

This presentation shows an example of an instrumented glove for augmenting movement disorder assessments. The system is based on capacitive pressure sensing, and the validation allows an objective, repeatable metric that improve resolution over the current best practices. The glove measures the power required to move a patient’s arm and shows reduced inter- and intra-rater variability. Our approach using wearable sensors offers an objective route for the characterization of movement patterns, which would permit the effective evaluation of intervention outcomes, as well as provide a platform for novel motor interventions in the future.

In addition, another type of biomechanical measurements involving blood pulsations is being developed using photosensors responsive to the short wavelength infrared (SWIR) spectra. Currently conventional SWIR sensors are limited by complex die transfer and bonding processing. Here we are advancing SWIR photodiodes by using a new generation of narrow bandgap conjugated polymers that are processed by solution processing techniques and allow simple direct deposition. The polymers are processed into bulk heterojunction photodiodes with photoresponse up to wavelength of 1.7 micron. The performances of devices with different polymer structures were compared through metrics including detectivity, quantum efficiency, response time and rectification ratio. Example applications including blood pulse measurements and spectroscopic identification will be demonstrated.
(Invited) Soft/Hard Interface for Energy Materials and Skin-like Electronics Toward Healthcare Monitoring
Authors: Lee Jung Woo
Published: February 2020

Power supply represents a critical challenge in the development of body-integrated electronic technologies. Although recent research establishes an impressive variety of options in energy storage (batteries and supercapacitors) and generation (triboelectric, piezoelectric, thermoelectric, and photovoltaic devices), the modest electrical performance and/or the absence of soft, biocompatible mechanical properties limit their practical use. The results presented here form the basis of soft, skin-compatible means for efficient photovoltaic generation and high-capacity storage of electrical power using dual-junction, compound semiconductor solar cells and chip-scale, rechargeable lithium-ion batteries, respectively. Miniaturized components, deformable interconnects, optimized array layouts, and dual-composition elastomer substrates, superstrates, and encapsulation layers represent key features. Systematic studies of the materials and mechanics identify optimized designs, including unusual configurations that exploit a folded, multilayer construct to improve the functional density without adversely affecting the soft, stretchable characteristics. System-level examples exploit such technologies in fully wireless sensors for precision skin thermography, with capabilities in continuous data logging and local processing, validated through demonstrations on volunteer subjects in various realistic scenarios.
(Invited) Enzymatic Bioelectrodes for a Contact Lens Lactate Biofuel Cell: Design and Analysis
Authors: Reid Russell C. , Minteer Shelley D. , Gale Bruce K.
Published: February 2020

Implantable and wearable ocular devices require a compact continuous power source that does not interfere with vision or regular physical activity. An enzymatic biofuel cell fits this description provided it has sufficient power density and stability. Two proof-of-concept contact lens lactate biofuel cell prototypes were designed and fabricated to investigate making enzymatic bioelectrodes that are flexible, have high surface area and conductivity and that could be integrated into a contact lens. The first prototype utilized a bilirubin oxidase biocathode and a lactate dehydrogenase bioanode. When tested in conditions similar to those found on the eye, this prototype produced more power (3 µW at ~0.2 V) than the second prototype but it did not sustain appreciable electrical activity for more than 4 hours due to poor cofactor/mediator immobilization. The second prototype used lactate oxidase at the anode and the device was stable for at least 24 hours of continuous operation but had lower power output (0.5 µW at ~0.2 V) than the first prototype because of lower electrode surface area (but increased biocompatibility). Both prototypes were limited by the oxygen reduction reaction (ORR) at the air-breathing biocathode. Oxygen concentration and transport are commonly blamed for low cathodic current but it is less understood how carbon nanotube (CNT) networking and CNT surface activity might affect catalytic current. For the second prototype, Monte Carlo and numerical simulations revealed that only 20% of the CNTs were networked to the current collector and, within that fraction, only ~5% of the CNT surfaces contributed to current output. These results have implications for enzymatic biofuel cells in general through two conclusions: 1) enzymatic electrode films that are thicker or having more CNTs may not be beneficial and 2) there is much opportunity to improve enzyme-CNT electron transfer.

Figure 1. Contact lens biofuel cell prototype with leads attached to it (right). On the left is a schematic to show that an electrode reaction (in this case oxygen reduction at a cathode) may be limited by poor connectivity between carbon nanotube clusters and the electrode.

Figure 1
(Invited) Smart Textile for Energy Harvesting and Self-Powered Sensing Applications
Authors: Lin Zong-Hong
Published: February 2020

Since the introduction of the first expounded triboelectric nanogenerator (TENG) in 2012, the theoretical and practical aspects of the TENG have been researched as an alternative energy harvesting technology to convert mechanical energy into electricity efficiently. Numerous self-powered sensing systems have adopted the TENG as a power source to further explore its versatile applications toward different targets. In this study, we employed a TENG to replace a traditional power supply for synthesizing different metallic nanoparticles using an electrochemical approach. Carbon fibers were adopted as the conductive substrates to grow the metallic nanoparticles, where the size and density of the nanoparticles on carbon fibers can be controlled by the electric output of the TENG. Additionally, we demonstrated that the as-prepared carbon modified and integrated with the TENG to construct a wearable self-powered sensing system exhibited significant selectivity and sensitivity toward lactate detection. Furthermore, the design of the sensing unit was favorable regarding its adaptability and flexibility to fit human body shapes and postures. As demonstrated in this study, the as-prepared self-powered sensing system could detect the lactate concentration in human perspiration, which can be an ideal wearable device for end users who seek real-time monitoring of their physical condition. This study concludes with a proposal for noninvasive biosensors, which provide boundless potential for future cross-field applications.

References

T-H. Chang, Y.-W. Peng, C.-H. Chen, T.-W. Chang, J.-Y. Wu, J.-C. Hwang, J.-Y. Gan and Z.-H. Lin, Nano Energy 2016, 21, 238–246.

T-W. Chang, C.-W. Wang, C.-H. Chen, Y.-C. Li, C.-L. Hsu, H.-T. Chang and Z.-H. Lin, Nano Energy 2016, 22, 564-571.

C.-H. Choi, P.-W. Lee, Y.-H. Tsao and Z.-H. Lin, Nano Energy 2017, In Press (https://doi.org/10.1016/j.nanoen.2017.10.064).