bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Doping at the Extreme in Organic Semiconductors: Challenges and Opportunities
Authors: Kahn Antoine
Published: August 2024

Molecular doping is an effective tool to enhance bulk conductivity, increase carrier injection and de-activate electron or hole traps in organic molecular and polymer semiconductors. Considerable effort has been directed toward the synthesis of powerful and stable p-type and n-type molecular dopants over the past decade.[1,2] This talk reviews a range of molecular redox agents used in organic electronics, with focus on strong reductants and oxidants for organic semiconductors with low electron affinity (EA) and large ionization energy (IE), respectively. In particular, we look at air-stable dimers, e.g. [RuCp*Mes]2, formed of 19-electron organometallic sandwich compounds able to reduce organic semiconductors with EA well below 3 eV.[3] We review powerful single-electron molecular oxidants, e.g. F6-TCNNQ and CN6-CP, which can introduce holes in organic semiconductors with IE larger than 5.6 eV. Applications of these n- and p-dopants to improve the conductivity of carrier injection layers and create large gap semiconductor p-i-n structures are described.[4] The last part of the talk focuses on recent work on adduct-based p-doping of organic semiconductors, applicable to a range of hole transport materials.[5]

[1]S. Barlow, S.R. Marder, X. Lin, F. Zhang and A. Kahn, Electrical Doping of Organic Semiconductors with Molecular Oxidants and Reductants, Handbook of Conducting Polymers (2019)

[2] G. Song, S.B. Kim,S. Mohapatra, Y. Qi, T. Sajoto, A. Kahn, S.R. Marder, S. Barlow, n-Doping of Organic Electronic Materials Using Air-Stable Organometallics, Adv. Mat. 24, 699 (2012)

[3] X. Lin, B. Wegner, K. M. Lee, M. A. Fusella, F. Zhang, K. Moudgil, B. P. Rand, S. Barlow, S. R. Marder, N. Kochand A. Kahn, Beating the Thermodynamic Limit: Photo-Activation of n-Doping in Organic Semiconductors, Nature Materials 16, 1209 (2017)

[4] H. L. Smith, J. T. Dull, S. Mohapatra, S. Barlow, S. Marder, B. P. Rand, and A. Kahn, Powerful organic molecular oxidant and reductant enable a large gap, blue light-emitting organic homojunction diode, ACS Appl. Mat. Int. 14, 2381 (2022)

[5] N. Sakai, R. Warren, F. Zhang, S. Nayak, S. V. Kesava, Y.-H. Lin, H. S. Biswal, X. Lin, A. Kahn, M. Riede, P. K. Nayak and H. J. Snaith, Adduct-based p-doping of Organic Semiconductors, Nature Materials, 20, 1248 (2021)
Role of Dopant in Enabling Electrodeposition of Polymer Thin Films with High Solar Transmittance Modulation
Authors: Hahn Nathan T. , Grewal Simranjit , Grey John K. , Habteyes Terefe G. , Takele Wassie M. , Chen Dongchang
Published: August 2024

Buildings consume approximately one-third of the energy used in developed countries, with much of this energy tied to building heating and cooling. Electrochromic “smart” windows have the potential to mitigate some of this energy use through on-demand modulation of solar energy transmission. Therefore, electrochromic window devices based on low cost and facile solution-based processing routes are sought. In this work, we describe the electropolymerization and deposition of electrochromic poly(arylamine) thin films with exceptional broadband solar transmittance modulation, reaching ΔT
sol values of over 60% (Figure 1). Through high-resolution, near-field spectroscopic imaging we show that the structure of the acid dopant present in the electrodeposition solution plays a key templating role that determines the electrochromic performance of these films. Our findings indicate that polyanionic dopants are especially adept at directing polymer chain conformational order, which in turn improves charge delocalization and transport. These factors lead to films with high smoothness and optical clarity through the visible (T
lum > 80%) and near-infrared ranges. Further details regarding the cycling stability of these films and their integration into full electrochromic devices will be discussed. In summary, this work demonstrates the value of polyanionic dopants for templating high quality electrochromic polymer thin films capable of energy-relevant solar transmittance modulation for smart window applications.

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(Invited) Nanohybrid Carbon Nanotube and P3HT Composite Semiconductor Materials for Solution Processed Optoelectronics
Authors: Andrews Joseph
Published: August 2024

Carbon nanotube networks have demonstrated promise for enabling printable transistors which can be utilized as switching elements within active matrices. Such active matrices have been utilized for controlling pixels and interrogating sensor elements. A new promising technology for imaging, called an active pixel matrix, aims to integrate both the underlying transistor and sensor element within a single device, namely a phototransistor. Carbon nanotubes are poised to enable printable active pixel matrices for sensing applications, however, due to minimal absorption a secondary material needs to be added as a photo synthesizer. Additionally, the material must be sufficiently electrically coupled with the carbon nanotube network to allow for efficient carrier extraction. Our lab has previously developed techniques for crystallizing P3HT directly onto carbon nanotubes using solution-phase soft epitaxy. In this work, the solution phased technique has been adapted to functional carbon nanotube networks already deposited onto a surface.

I will present the performance of a device that consists of a solution-processed carbon nanotube network, which acts as the carrier extraction layer, and a surface crystalized P3HT, which acts as the absorption element. First, I will detail the fabrication scheme and soft-epitaxial method of polymer crystallization. Next, I will overview how the P3HT crystallization affects the electronic performance of the devices, including the photo response. The device exhibits high responsivity, with a maximum responsivity value of 3 x 105. Additionally, the device exhibits a wide spectral response within the visible range, due to the exciton generation at the P3HT/CNT interface. I will also present the transient response of the device, which provides insight into the role of carrier injection/trapped states within the material.

Lastly, I will discuss the potential applications for an active matrix of phototransistors, including neuromorphic computing. In these specific applications, the semiconductor can be utilized as the functional material within an Organic Electrochemical Transistor (OECT), where it exhibits behavior associated with mixed ionic/electronic conduction (MEIC). I will benchmark the performance, and discuss various methods to fabricated charge trapped switches, a key memory/computational element for future neuromorphic architectures.
(Invited) A Neural Compact Model Based on Transfer Learning for Organic FETs
Authors: Cho Minsun , Lee O-Joun , Jung Sungyeop
Published: August 2024

Organic field-effect transistors (organic FETs) exhibit highly non-linear electrical characteristics due to their distinctive transport mechanism manifested by thermally-assisted hopping via localized states randomly distributed in both energy and space domains. This feature impedes the establishment of an analytical compact model. In this context, we present an approach to adopt artificial neural networks (ANN) for the development of a compact model, namely a neural compact model, by exploiting the powerful ability of the ANN to describe a non-linear function accurately. In addition, we evaluate the knowledge transfer method to reduce learning time and improve accuracy even when the data is scarce and costly. By technology computer-aided design simulation, we constructed a dataset of electrical characteristics of organic FETs with Gaussian disorder which is calibrated to the experimental measurement. Subsequently, we constructed and compared neural compact models based on conventional deep learning and transfer learning. We showed that the neural compact model with transfer learning provides an equivalent accuracy at a shorter modeling time. A complex dependence on the gate voltage, drain voltage, and temperature is successfully modeled over a wide range of operation regimes and temperatures.
(Digital Presentation) Synergistic Enhancement of Thermoelectric Performance through One-Dimensional Hybrid Nanocomposites: Wrapped Nickel Oxide-Decorated Multi-Walled Carbon Nanotubes with Polypyrrole
Authors: Bourenane Cherif Younes , Mekhalif Zineb , Abdous Slimane , Nedjar Linda , Mekki Ahmed
Published: August 2024

Given the drawbacks of organic materials’ thermoelectric (TE) conversion efficiency, an approach has been made in this study to synthesize a hybrid organic-inorganic material based on polypyrrole (PPy), multi-walled carbon nanotubes (MWCNTs) and nickel oxide nanoparticles (NiO). The nanocomposite is formed through three steps: MWCNTs functionalization via diazonium salt grafting of 5-amino-1,2,3-benzene tricarboxylic acid; in situ generation on their surfaces of NiO nanoparticles with a homogenous distribution; the chemical polymerization of pyrrole using methyl orange as templating and dopant to wrap the MWCNTs-(COOH)3-NiO. To explore the structural and physical properties of the fillers and the nanocomposites, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Raman spectrometer, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used. Thereby investigating the electrical conductivity (𝜎), Seebeck coefficient (S) and thermal conductivity (κ) at room temperature, a promising improvement was observed in PPy-MWCNTs-(COOH)3-NiO compared to pure PPy. The observed enhancements in TE properties (ZTPPy-MWCNTs-(COOH)3-NiO = 1.51×10-2) are attributed to the presence of NiO, which acts as a dopant and improves the charge carrier density in the nanocomposite; this result could be increased at higher temperatures. Overall, these results demonstrate the potential of our approach for developing high-performance TE materials with applications in energy harvesting and waste heat recovery. Furthermore, this approach offers the potential for scalability and reproducibility, making it a promising method for large-scale fabrication of high-performance composites.

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(Digital Presentation) Optimized Security: Enhancing the Modified Advanced Encryption Standard for Efficient Iot Application
Authors: Naik Jahnavi , Nyathikala Harika , Chiluka Sagar , Bevara Vasudeva
Published: August 2024

The Modified Advanced Encryption Standard (MAES) emerges as a robust solution tailored for the unique challenges posed by Internet of Things (IoT) applications. In this paradigm, where resource constraints and energy efficiency are paramount, MAES optimizes the Advanced Encryption Standard (AES) to meet the specific demands of IoT devices. This modification involves a judicious trade-off between security and computational complexity, ensuring a delicate balance suitable for the constrained nature of IoT environments. MAES not only maintains the formidable security features of AES but also introduces tailored enhancements that cater to the low-power, low-memory, and high-throughput requirements of IoT devices. This abstract highlight the crucial role MAES plays in fortifying the security landscape of IoT, making it a compelling choice for safeguarding sensitive data in the era of interconnected and resource-limited devices.

The test case bits will be used to pick the module. The key and input will then be chosen in accordance with the test case bit selection, and the module will generate the corresponding output and lower the clock cycles to 16 with 149.721W power dissipation. Verilog code was used to generate the MAES algorithm, which was intended for FPGA. Vivado tool is utilized for Synthesis and Simulation. The KINTEX-7 FPGA has successfully tested the design.
(Invited) Preparation of N-Type and P-Type Doped Single Crystal Diamonds with Laser-Induced Doping and Microwave Plasma Chemical Vapor Deposition
Authors: Guo Linhai , Tian Li , Wang Hui , Meng Lingxue , Feng Chujun
Published: August 2024

In this study, n-type doped single crystal diamonds were successfully prepared under normal temperature and pressure conditions using laser-induced doping. 248nm pulsed laser beams with nanosecond duration were irradiated on the single crystal diamond substrate immersing in an 85% phosphoric acid solution and it introduced phosphorus doping to form an n-type doped thin layer. The resistivity of the doped region significantly decreased compared to that of the single crystal diamond. After depositing a titanium electrode, the resistivity of the doped film obtained by Van der Pauw Technique was determined to be 1.3×10-6 Ω·m. Raman spectroscopy confirmed the absence of carbon or graphite phases in the laser-induced doped diamond, indicating that the enhanced conductivity was due to phosphorus incorporation.

Furthermore, p-type doped single crystal diamonds were successfully prepared by introducing boron during the growth process using Microwave Plasma Chemical Vapor Deposition（MPCVD）. It was demonstrated that the proposed technique can introduce impurities into single crystal diamonds to form doped conductive thin layers, which has potential applications in the field of microdevices and integrated circuits.
E-Mode AlGaN/GaN HEMTs Using p-NiO Gates
Authors: Chiang Chao-Ching , Wan Hsiao-Hsuan , Li Jian-Sian , Ren Fan , Yoo Timothy Jinsoo , Kim Honggyu , Pearton Stephen J
Published: August 2024

Sputtered p-NiO films were used to suppress gate leakage and produce a positive shift in gate voltage of AlGaN/GaN high electron mobility transistors for e-mode operation. A direct comparison with Schottky gate devices fabricated on the same wafer shows the utility of the NiO in increasing the on-off ratio and shifting the threshold voltage from -0.95 V (Schottky gated) to +0.9 V (NiO gated). The breakdown voltage was 780 V for a 40 µm drain-source separation. The sub-threshold swing decreased from 181 mV/dec for Schottky gate HEMTs to 128 mV/dec on NiO-gated devices. The simple fabrication process without any annealing or passivation steps shows the promise of NiO-gates for e-mode AlGaN/GaN HEMT operation.

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The Electronic Impact of X-Ray on Atomically-Thin Oxide Semiconductor Devices
Authors: Lin Tzu-Jie , Tseng Robert , Chang Chan-Yuen , Chou Tsung-Te , Lien Der-Hsien
Published: August 2024

In the past few years, there has been a significant emphasis on atomically-thin metal oxide semiconductors (OS), driven by their adjustable electrical properties that open up a range of electronic applications [1.2]. However, the mechanisms of transport and electronic tunability in OS remain unclear [3]. X-ray characterization techniques, i.e. X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD), are considered as non-destructive and are widely used to quantify the chemical and electronic state of OS. In this work, we discovered that X-ray has significant impact on the electronic properties of OS. We observed that low energy X-ray (<2 keV) induces a negative V
T offset in OS devices [4]. The variation in V
T primarily originates from the chemical interaction of oxygen molecules on the channel surface. OS devices absorb the low-energy X-ray, generating the holes, and they subsequently react with O2
- on the channel surface, resulting in the production of oxygen and its removal from the channel surface, as shown in Fig 1a. The V
T shift caused by low energy X-ray will recover in air over time, as illustrated in Fig 1b. We incorporated the post low-energy X-ray devices into a vacuum environment with a pressure of 10-6 torr, and the V
T of the device exhibited no recovery over time, providing additional support for oxygen absorption mechanism. Time-resolved electrical measurements conducted in different atmospheric conditions reveal that the variations in V
T arise from the oxygen absorption mechanism. The research highlights the effect of X-ray on OS and analyzes the mechanism behind the increase in OS carrier concentration induced by the X-ray exposure.

[1] Si, M. et al. Scaled indium oxide transistors fabricated using atomic layer deposition. Nat. Electron. 5, 164–170 (2022).

[2] Charnas, Adam, et al. Extremely Thin Amorphous Indium Oxide Transistors. Adv. Mater. 2304044 (2023).

[3] Conley, J. F. Instabilities in amorphous oxide semiconductor thin-film transistors. IEEE Trans. Device Mater. Rel. 10, 460–475 (2010).

[4] Tseng, R., Wang, ST., Ahmed, T. et al. Wide-range and area-selective threshold voltage tunability in ultrathin indium oxide transistors. Nat. Commun. 14, 5243 (2023).

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(Digital Presentation) Doped ZnO Layer (ZnO-Ga) Window Layer Fabrication By Electrodeposition
Authors: Saeed Mahfouz
Published: August 2024

As an n-type semiconductor, zinc oxide (ZnO) is a conducting oxide for CIGS thin solid film 1 ZnO also possesses excellent stability, exceptional transparency, and high electron mobility, among other beneficial qualities 2-4. As in previous work for producing CIGS solar devices, this study presents the electrodeposited ZnO layer doped with gallium as a top layer. The substrate is undoped Zinc Oxide, and the electrochemical process was conducted at 72 °C. The electrolyte consists of Zn(NO3)2, GaCl3, and LiCl as a supporting electrolyte. This work is comparing both DC and pulsing electroplating to optimize the process parameters.

Complete electrodeposited devices with quantum efficiencies greater than 0.63 and efficiencies ranging from 3.2 to 6.3% were formed and evaluated. This work provides the electrochemical behavior and agitation effects of the deposit chemical composition. The deposit adhesion to the substrate was tested by applying the peeling test. For each of the three doped ZnO layers, sample polarization curves at 400 rpm electrode rotation speed is given (figure 1).

With the use of XRD and the energy-dispersive X-ray spectroscopy technique (EDS), the final composition, oxide concentrations, crystallography, and oxide effects on the deposit were ascertained (figure 2). To measure the thickness of the deposit, a profilometer was employed.

References

[1] Saeed, M. Peña,.G. Nanomaterials 2021, 11,

911.

[2] Rousset, J. Saucedo, E. Lincot, D. Chemistry

of Materials 21 (2009) 534-978.

[3] Machado. G, Guerra. D, Leinen. J, Ramos. R, Marotti. A, Dalchiele, Thin Solid

Films 490 (2005) 124 – 131.

[4] Chikoidze, E. Nolan, M. Modreanu, M. Sallet, V.

Galtier, P. Thin Solid Films 518 (2008) 8146.

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A Comparative Study of Ambipolar Material in Conventional and Access Region-Based Devices
Authors: Hsiao Hsin-Lu , Lin Shu-Ping
Published: August 2024

Neuromorphic devices utilizing atomically thin 2D materials show promise for large-scale computing by emulating biological neural networks. Floating gate transistors (FGTs) typically fall into two categories based on the selection of the semiconductor channel layer material. One category involves unipolar semiconductors that transmit only one type of majority carrier, while the second category consists of ambipolar semiconductors, tunable to switch the type of majority carrier. This flexibility enables devices to switch modes and respond to specific stimulation, such as molybdenum ditelluride (MoTe2), proven to be valid as a channel material [1]. Here, MoTe2, hexagonal boron nitride (h-BN), and graphene (Gr) were applied to construct the ambipolar FGT (AFGT). Additionally, access regions (ARs) were introduced in the AFGT to fabricate AR-based AFGT (AR-AFGT), altering the transmission mechanism of carriers in the channel layer compared with the AFGT device [2].2D van der Waal materials were stacked in the order of Gr/h-BN/MoTe2 to fabricate AFGTs with source/drain electrodes overlapping the Gr, serving as the floating gate (FG), with a channel length of about 2 µm. Gr/h-BN/MoTe2 AR-AFGTs were fabricated by placing ARs, which do not overlap with FG, in proximity to source/drain electrodes with a channel length of 10 µm. We measured and compared the transfer characteristic of AFGT and AR-AFGT devices. The AFGT exhibited obvious ambipolar behavior with dominant n-branch and p-branch. However, in the case of AR-AFGT, a significant n-branch portion was observed. These phenomena may arise from the AR increasing the distance from the electrode to the storage layer, indicating that MoTe2 acts as a unipolar material. Our study compared AFGT and AR-AFGT devices, highlighting their unique traits. While AFGT exhibited significant ambipolar behavior, AR-AFGT, influenced by the increased distance, displayed a distinct unipolar profile with an emphasis on the n-branch. The integration of AR stands out as a key factor for creating adaptable neuromorphic devices.

References

Wu, E., et al., Tunable and nonvolatile multibit data storage memory based on MoTe2/boron nitride/graphene heterostructures through contact engineering. Nanotechnology, 2020. 31(48): p. 485205.

Sasaki, T., et al., Material and Device Structure Designs for 2D Memory Devices Based on the Floating Gate Voltage Trajectory. ACS Nano, 2021. 15(4): p. 6658-6668.

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Handheld, Graphene Multiplexed Sensor for Wastewater-Based Epidemiology
Authors: Geiwitz Michael , Kumar Narendra , Burch Ken
Published: August 2024

Wastewater-based epidemiology (WBE) is emerging as a vital tool for early detection of the emergence of diseases without the need for individual testing and reporting. This is enabled via virus shedding through bodily waste, which can be present up to two days before symptoms appear in infected individuals, albeit at low levels. Current detection methods, such as HPLC-MS and PCR, are time-consuming and require specialized equipment with highly trained personnel. This drives up the cost and turnaround time while limiting the widespread implementation of WBE for local detection, especially in resource-limited settings. Therefore, a fast, cost-effective, multiplexing, and sensitive viral wastewater detection platform could help health officials effectively implement measures to mitigate the spread of diseases. Here, I will present our recently developed handheld, graphene-based multiplexed platform utilizing high-specificity aptamers for rapid, sensitive, and simultaneous detection of virus proteins for SARS-CoV-2, Influenza A, and RSV in wastewater to accurately assess infected individuals in municipal communities. In addition, the device allows normalizing to the population, contributing to the signal by simultaneously measuring the presence of virus proteins and caffeine in wastewater. These results will highlight the selectivity and specificity of the platform in wastewater as well as the limits of detection.
(Invited) Multi-Modal Solid-State Gas Sensors-Based Breath Analysis System with Convolutional Neural Network (CNN) for Early Detection of Lung Cancer
Authors: Lee DaeSik
Published: August 2024

Currently, digital healthcare technologies based on Internet of Things (IOT) are emerging, and the market for digital healthcare was estimated to be 151.5 billion dollars by 2020. Among the digital healthcare technologies, disease diagnosis is attracting maximum attention. Traditional diagnostic methods, such as radiology and human biological material analysis, have limitations of long study time, high cost, radiation exposure, and pain. Therefore, non-invasive diagnostics methods, for early diagnosis of specific diseases and personal healthcare management, have attracted attention.

Breath sensors are one of the promising candidates for the realization of non-invasive diagnosis owing to their ease of use, safety, and cost effectiveness. The exhaled breath analysis technique holds great promise as a non-invasive method for diagnosing lung cancer. In the breath of lung cancer patients, various volatile organic compounds (VOCs) markers are generated during metabolic processes. Analyzing these VOCs markers presents a compelling avenue for early and non-invasive lung cancer diagnosis. Solid state gas sensors capable of measuring specific VOCs are currently being researched and utilized as commercial gas sensors for this purpose. However, the concentration of lung cancer VOCs markers in exhaled breath is commonly very low, and individual commercial gas sensors often lack the necessary sensitivity and selectivity to accurately diagnose lung cancer. In this study, we propose a multimodal solid state electronic biosensor system designed to differentiate lung cancer VOCs characteristics among multiple VOCs, enabling exhalation-based lung cancer diagnosis. Initially, we developed multimodal biosensors using more than 20 gas sensors, consisting of metal oxide semiconductor sensors, electrochemical sensors, photoionized detectors, metalorganic frame sensors and so on. And each exhibiting varying sensitivity profiles for complex gas mixtures. Additionally, we designed a classification algorithm based on convolutional neural networks (CNN) and multi-layered perceptron (MLP) to distinguish between lung cancer patients and healthy individuals using the output from these diverse multimodal gas sensors. To evaluate the system's performance, we collected exhaled air samples from 74 lung cancer patients and 107 normal subjects, conducting clinical trials with our developed system. We did model evaluation with confusion matrix and ROC curve. The results of these tests confirmed that our system achieved a high predictive accuracy of over 95% in classifying lung cancer patients. The simplicity of the sensor configuration in our developed system makes it suitable for large-scale screening tests to identify potential candidates for precise lung cancer diagnosis. This technology has the potential to contribute to reduced national welfare costs and improved patient survival rates through early diagnosis.
(Invited) Molecular Engineering of Field-Effect Transistor-Based Biosensors
Authors: Chen Junhong
Published: August 2024

Field-effect transistor (FET) biosensors based on two-dimensional (2D) nanomaterials have attracted significant attention over the last decade due to their rapid response, high sensitivity, lower limit of detection, miniaturized sensor chip, and digital readout. This talk will present a powerful approach to real-time biological sensing through molecular engineering of 2D nanomaterials in a FET platform. The working principle of the sensor is that the conductivity of 2D nanomaterial channel changes upon binding of biological species to molecular probes anchored on the nanomaterial surface. As such, the presence and the concentration of analytes (e.g., proteins, bacteria, viruses) can be determined by measuring the sensor resistance or impedance change. The talk will focus on the molecular engineering aspects of the biosensor device (e.g., engineering nanomaterial channel, molecular probe, and device passivation) through both theoretical and experimental approaches. The resulting FET platform sensing technology enables real-time detection of biological species with high sensitivity and selectivity.
(Invited) Seeing the Sound: An Ultrasound-Mediated Intravascular Light Source for Noninvasive Brain Modulation
Authors: Hong Guosong
Published: August 2024

Light is used in a wide range of methods in biology and medicine, such as fluorescence imaging, optogenetics, photoactivatable gene editing, photothermal and photodynamic therapies to treat cancers, and photochemotherapy to inactivate viruses in vivo. A critical challenge of applying light in vivo, such as deep-brain optogenetic neuromodulation and photochemotherapy in deep organs, arises from the poor penetration of photons in biological tissue due to scattering and absorption. Therefore, delivering light deep into the body requires invasive procedures, such as the insertion of optical fibers and endoscopes, as well as surgical removal of overlying tissues. The very invasiveness of these procedures also precludes easy repositioning and volume adjustment of the illuminated region in the same subject. To address these challenges, our lab has developed an ultrasound-mediated intravascular light source, leveraging the deep-tissue penetration of focused ultrasound. We capitalized on mechanoluminescent nanotransducers (MLNTs), which are colloidal nanoparticles of mechanoluminescent materials synthesized via a biomineral-inspired suppressed dissolution approach. These MLNTs can be delivered intravenously into blood circulation and emit light locally at the ultrasound focus. Owing to the deep penetration and fast temporal kinetics of ultrasound, we have demonstrated that this method can produce on-demand and dynamically programmable light emission patterns at elevated depths in different organs of live mice with millisecond precision. This ultrasound-mediated intravascular light source has allowed us to perform noninvasive “sono-optogenetic” neuromodulation in live mice, as well as brain-wide “scanning optogenetics” that activate different brain regions of the same mouse brain. Our development of the ultrasound-mediated intravascular light source has been published in PNAS (2019), Science (2020), Science Advances (2022), JACS (2022), JACS (2023), and Nature Protocols (2023).
(Invited) Point-of-Care Biomembrane-Based Electronic Sensors
Authors: Pappa Anna Maria
Published: August 2024

The development of medical devices that comply with the soft mechanics of biological systems at different length and complexity levels is highly desirable. With the emergence of conducting polymers exciting directions opened up in bioelectronics research, bridging the gap between traditional electronics and biology. With the ultimate goal of fully integrated devices, organic bioelectronic technologies have been heavily explored the past decade resulting in novel materials/device configurations. Multiplexing capability, ability to adopt to complex performance requirements in biological fluids, sensitivity, stability, literal flexibility and compatibility with large-area processes are only some of the merits of this technology for biomedical applications. A recent example of a bio-integrated electronic device, the BiOET, is based on polymeric semiconductor technology and is fabricated using nano/micro-fabrication methods in conjunction with synthetic biology approaches to incorporate hierarchically organized biological models of the cell membrane. Despite their significance, cell membranes are still an underexplored target for studying the mechanisms of diseases or drug therapies. Cell-free commercially available technologies for cell membrane studies have been limited to synthetic membranes that lack the inherent complexity found in the membrane of the cell. In this talk I will describe a method to create native cell membranes, using vesicles derived from live cells, on top of conducting polymer- based microfabricated electrodes and transistors. The activity of transmembrane proteins in response to different stimuli can be electrically monitored, offering a direct means to characterize drug toxicity or potency at the critical first contact point: membrane interaction.
(Invited) Organic Electrochemical Transistors for Marine Sensing
Authors: Ng Tse Nga
Published: August 2024

With our marine ecosystems under threat from climate change, there is an urgent need to continuously monitor marine conditions. One key indicator is the dissolved oxygen level, but existing sensors are limited by size and costs that preclude widespread non-intrusive monitoring. This work reports a new dual-gate design based on organic electrochemical transistors (OECTs) to track dissolved oxygen concentration in seawater, a highly challenging matrix owing to its high ionic strength and multitude of chemical interferents. We present the novel operating principle, by deriving the channel conductance with respect to potentials on the two gates. The dual-gate OECT was highly sensitive and stable compared to the conventional OECT structure, as the dual-gate configuration extended the device stability window by preventing undesirable reactions at the OECT channel. Specifically, the sensor achieved a detection limit of 0.5 ppm dissolved oxygen concentration in seawater. The device demonstrated reliable operation over five days and was capable of monitoring oxygenation changes arising from the photosynthesis cycles of saltwater macro-algae. In addition, we also engineer a system to monitor the correlation of oyster movement with dissolved oxygen in its environment, and it offers a new design to realize compact, highly sensitive, economical in-situ sensors for harsh marine environments.
(Keynote) Skin-Inspired Electronics for Sensing in the Brain and Guts
Authors: Bao Zhenan
Published: August 2024

In this talk, I will discuss preparation of sensors, electronics and integration into high-density and high resolution electronics for sensing in brain and guts. The combination of pressure, neurochemical, electrophysiological sensing and electrical stimulation together with soft integrated circuits generates a new generation of biocompatible soft electronic sensing tools.
(Invited) Orbit Symmetry Breaking in Mxene Implements Enhanced Soft Bioelectronic Systems
Authors: Bai Wubin
Published: August 2024

Bioelectronic systems with soft mechanics, stable biocompatibility, and high-performance electronic recording and stimulation interfaces to internal organs offer paradigm-shifting potentials for advancing biomedical implants such as those for cardiovascular disease. Yet, challenges remain in the development of biocompatible materials with practical scalability for constructing bioelectronic systems that leverage performance and interfacial attributes to not only functionally approach those of conventional wafer-based technologies but also biologically compatible for long-term in-body operation. Here, we present the orbit symmetry breaking in MXene (a low-cost scalable, flexible, and conductive 2D layered material), implementing the improved electrode-tissue interface impedance, which stems from the out-of-plane charge transfer, and coupling with in-plane high conductivity comparable to precious metals. Besides, we compare MXene bioelectronics with commercial biotraces (gold, graphene oxide, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), emphasizing its enhanced biocompatibility, durability, and imaging visibility in bioelectronic systems. Accordingly, we introduce an epicardial patch based on orbit-symmetry-broken MXene that integrates the matrix mapping of electrophysiological activity and therapeutic capabilities across large areas at high-fidelity spatiotemporal resolution. Last, a wireless and battery-free MXene module, combined with real-time recording and closed-loop stimulation, demonstrates high signal-to-noise ratio data transmission, and wireless power transfer within bioelectronic systems.
(Invited) Cardiac Engineering: Optical Mapping in Cellular Communication
Authors: Sung Yen-Ling , Tsai Yuan-Si , Chang Chu-Ling , Chen Chih-Kuan , Wang Chih-Hua , Lin Yi-Chun
Published: August 2024

Microfluidic platforms have emerged as valuable tools for replicating the adverse effects of chemotherapy drugs on cardiac and non-cardiac cells in vitro. However, these systems currently fall short of comprehensively capturing the intricate nature of human responses to chemotherapy, necessitating further validation to enhance model accuracy. While innovative chip systems provide insightful means for screening cardiac toxicity, they encounter challenges in addressing individual variations in drug responses and the influence of patient-specific factors.

A novel cardiac chip incorporating intracellular electrophysiological techniques was developed to monitor acute hypoxia-induced responses in cardiac cells. Despite its promising potential, the model exhibits limitations inherent to its simplified two-dimensional microfluidic system, warranting additional validation and optimization efforts to enhance physiological relevance and facilitate applications in clinical translation.

Moreover, previous research has proposed the formation of functional connections between human neurons and myocardial cells in a microfluidic chip. However, this study primarily focused on one-way connections between neurons and myocardial cells, overlooking the complexities of bidirectional neuro-muscular connections. Consequently, further research is imperative to deepen our understanding of the intricate interactions between neurons and myocardial cells.

Optical mapping techniques assessed transmembrane voltage, mitochondrial activity, and calcium signals during electric pacing. These comprehensive assessments aim to advance our understanding of cardiac electrophysiology under drug exposure, providing crucial insights into the intricate responses of cardiac cells to chemotherapy. This research has significant implications for enhancing our understanding of cardiac safety in the context of chemotherapy.
(Invited) 3D Printing-Assisted Casting of Conducting Polymers for Bioelectronics
Authors: Wang Yue
Published: August 2024

3D structured conducting polymers, known for their high conductivity, low impedance, and tunable form factor, are promising candidates for various bioelectronics applications. However, achieving a balance between structural complexity, electrical conductance, and processing generality has been challenging in these materials. In this talk, I will discuss our efforts to address this trade-off through 3D printing-assisted casting. Light-based 3D printing is used to create hollow molds, providing structural complexity and design freedom, whereas the casting nature imparts material versatility. The casting molds are made of superabsorbent polymers and printed in a partially hydrated state. Their dehydration provides significant enhancement in feature resolution and excellent thermal and mechanical properties, making them versatile for casting. After casting, over-hydration of the molds facilitate their energy-efficient removal. Using poly(3,4-ethylenedioxythiophene) (PEDOT) as a model system, complex architectures such as octet and truncated octahedron can be achieved. Compositing silver flakes with PEDOT through a thermal injection process leads to prints with conductivity over 6000 S/cm and high environmental stability. This method can potentially be applied to other hard-to-print soft materials and composites.
Estimation of Onset Potential for Oxygen Evolution Reaction at Platinum Surface Via Discharge of the Adsorption Capacitance of Intermediate Species
Authors: Gyanprakash Maurya , Srinivasan Ramanathan , Pala Raj Ganesh
Published: August 2024

Developments in onset potential estimation for oxygen evolution reaction seeks to overcome several disadvantages in existing methods. For example, in the current tangent intersection method from the Nonfaradaic to Faradaic region, the electrocatalyst with large pseudocapacitance shows a negative slope near the onset potential in the Nonfaradaic zone. In such systems, the intersection of tangents from the Nonfaradaic to Faradaic region fails to give the onset potential. Similarly, onset potential determination from the fixed current density (10 mA/cm2) can be inaccurate for electrocatalysts having a large pseudocapacitive current. In addition, the commonly utilized methods do not provide insight into the underlying physicochemical properties that modulate reactivity around the onset potential. We propose an approach based on reaction mechanism analysis integrated with electrochemical impedance to detect the onset potential via the capacitance variation generated from the intermediate species of OER. We demonstrate our proposed method via experiments on oxygen evolution reaction in the acidic medium on platinum as the model system. The impedance analysis of such a system from the Nonfaradaic to Faradaic region shows the capacitance generated from the intermediate species (S-OH) shows the maxima at the onset potential. Further, the Tafel analysis showed the S-OH step as the rate-determining step (RDS) in a low overpotential region. Additionally, the onset potential obtained from the tangent intersection from the Nonfaradaic to Faradaic region matches that obtained from the impedance analysis. We are in the process of extending the proposed approach to more complex systems with multiple product evolutions.
Distinguishing Electrochemical Processes in PEM Electrolysis By Impedance Modeling – Distribution of Relaxation Times
Authors: Chan Ai-Lin , Yu Haoran , Alia Shaun M
Published: August 2024

Proton exchange membrane (PEM) water electrolysis is a key technology in hydrogen production to provide capacity and flexibility for renewable energy power sources. Various research topics for electrolyzer development focus on cost reduction, performance optimization and lifetime extension with minimum platinum group metal (PGM) loading required [1]. Understanding degradation mechanisms in PEM electrolysis cells becomes necessary for developing mitigation strategies in dynamic durability tests, which facilitates the importance of advanced electrochemical characterization methods.

Electrochemical impedance spectroscopy (EIS) is a commonly used diagnostic technique in electrochemical systems. For impedance interpretation, equivalent circuit model (ECM) can be an option with prior knowledge about the system and appropriate circuit elements to prevent overfitting. Alternatively, distribution of relaxation times (DRT) provides a model-free pathway to address electrochemical mechanisms with different time constants and it has been applied to fuel cells, batteries and capacitors in the past years [2, 3]. Impedance deconvolution by DRT, however, has not been well adapted for PEMECs. In this study, electrochemical processes are successfully identified from the DRT profile by varying membrane electrode assembly (MEA) compositions and different operational conditions. In a single cell testing, four main peaks in DRT results associated with (1) mass transport losses (2) reaction kinetic (3) ionic conductivity within the catalyst layer and (4) ohmic properties at the interface of membrane and catalyst layers can be separated and quantified. Examination of electron microscopy provides further explanation of different MEA characteristics in performance analysis. This study verifies DRT is a promising tool to better understand PEM electrolysis processes and will be applied to degradation mitigation in the future.

References:

[1] S. M. Alia, S. Stariha and R. L. Borup, J. Electrochem. Soc., 166, F1164 (2019).

[2] A. Kulikovsky, J. Phys. Chem. C 126 (5), 2424-2429 (2022).

[3] Y. Li, et al., Chemical Engineering Journal 451: 138327 (2023).

Figure 1
Two-Dimensional Modeling of Proton Exchange Membrane Water Electrolyzer
Authors: Neerob Foysal Ahmed , Pasaogullari Ugur , Uddin Aman
Published: August 2024

Proton exchange membrane water electrolyzers (PEMWEs) are a central focus in the quest for clean fuel production from water. A comprehensive computational modeling of PEMWE is essential for predicting and optimizing the performance of PEMWE, enabling efficient design and advancement in clean energy technologies. In this study, a 2-D, transient, multiphysics, and multiphase model is developed to study the performance of PEMWE with a focus on morphological and geometrical features of porous transport layer (PTL), liquid saturation, gas pressure, and operating temperature. User Defined Function (UDF), an add-on of Ansys Fluent® is used to solve the transport equations in different layers of the PEMWE model. The model is first validated against experimental data (figure 1) from the literature. Mass transfer of each species (hydrogen, oxygen, vapor, and dissolved water) and heat transfer are analyzed in each layer of PEMWE, including PTL, anode catalyst layer, membrane, cathode catalyst layer, and gas diffusion layer. Besides, the electronic and ionic potential in all domains, along with the liquid water saturation distribution in porous layers, are investigated. Different governing parameters such as cell voltage, and operating temperature are varied to get the performance of the electrolyzer cell. The findings will provide new insights into electrolyzer cell performance under various operating conditions, offering valuable information for adjusting parameters and optimizing the design of electrolyzer cells.

Figure 1
(Invited) Affordable Green Hydrogen from Alkaline Water Electrolysis: An Industrial Perspective
Authors: Therkildsen Kasper T.
Published: August 2024

Electrolysers is a novel component in the energy system and is expected to play a key role in the transition to a fossil free energy system and supply Green Hydrogen to a number of small- and large-scale applications within a number of industries e.g. transportation, industry etc. with several hundreds of GW is projected to be installed towards 2030.

Modularity and mass production are key factors for the large scale deployment of electrolysis as envisioned in Hydrogen Strategies across the World. However, a number of different design strategies and modularities can be chosen in order to achieve this.

This talk focuses on fundamental aspects of alkaline electrolysis including industrial requirements for catalysts and diaphragms, how to develop an electrolyser product and the development of multi-MW alkaline electrolysers plants with factory assembled modules allowing rapid on-site installation in order to keep up with the pace needed to reach deployment targets.
Understanding Degradation Mechanisms in PEM Water Electrolysis Under Dynamic and Static Operating Conditions
Authors: Padgett Elliot , Yu Haoran , Blair Sarah J. , Pivovar Bryan S. , Myers Deborah J. , Cullen David A. , Alia Shaun M
Published: August 2024

Hydrogen production by electrolysis has great potential to enable a decarbonized economy, although further effort is needed to decrease its cost to meet ambitious targets, such as the US Department of Energy Hydrogen Earthshot goal of $1/kgH2.1 Achieving such low hydrogen production costs using polymer electrolyte membrane water electrolysis (PEMWE) will require decreasing the cost of input electricity while lowering capital costs through thrifting of iridium and other measures. An important opportunity to lower costs is the use of inexpensive intermittent electricity, either directly sourced from renewables or from grid leveling. However, previous studies have shown that dynamic cycling can accelerate degradation, especially when combined with low iridium catalyst loadings.2 It is therefore necessary to further understand the relevant degradation mechanisms, mitigation strategies, and implications for water electrolysis deployment.

Here we present the results of investigations to understand the degradation mechanisms in PEMWEs under dynamic and static operating conditions. This presentation will discuss the attribution of voltage degradation observed during long-term, constant-current operation as well as comparison of the degradation observed under cycled and static test conditions, with select results illustrated in Figure 1. This includes experiments designed to understand the transition between static and dynamic degradation behavior, differences in the degradation mechanisms, and opportunities for mitigation of dynamic degradation. We will further present investigations into the impacts of porous transport layer-catalyst layer interactions on anode catalyst degradation. Finally, we will discuss the implications of these results for guiding research priorities in PEMWE and developing operational and materials-based mitigation strategies.

Citations:

Energy.gov https://www.energy.gov/eere/fuelcells/hydrogen-shot.

S. M. Alia, S. Stariha, and R. L. Borup, J. Electrochem. Soc., 166, F1164–F1172 (2019).

Figure 1: Voltage over time profiles for durability tests comparing different current densities and cycle/hold protocols. All tests use anode/cathode catalyst loadings of 0.4 mgIrcm-2/0.1 mgPtcm-2 and a Nafion N115 membrane, operating at 80°C.

Figure 1