DGIST Scholar는 학술문화팀에서 운영하는 기관 리포지터리로, 학술정보 공유와 글로벌 확산을 위해 DGIST에서 생산되는 학술성과물(논문, 프로시딩, 학위논문, 특허, 연구보고서 등)을 수집, 관리하는 Open Access 디지털 저장소입니다.
A Proof of Concept: Optimized Jawbone-Reduction Model for Mandibular Fracture Surgery
2024-06Journal of Imaging Informatics in Medicine, v.37, no.3, pp.1151 - 1159
Previous research on computer-assisted jawbone reduction for mandibular fracture surgery has only focused on the relationship between fractured sections disregarding proper dental occlusion with the maxilla. To overcome malocclusion caused by overlooking dental articulation, this study aims to provide a model for jawbone reduction based on dental occlusion. After dental landmarks and fracture sectional features are extracted, the maxilla and two mandible segments are aligned first using the extracted dental landmarks. A swarm-based optimization is subsequently performed by simultaneously observing the fracture section fitting and the dental occlusion condition. The proposed method was evaluated using jawbone data of 12 subjects with simulated and real mandibular fractures. Results showed that the optimized model achieved both accurate jawbone reduction and desired dental occlusion, which may not be possible by existing methods.
Intelligent Bladder Volume Monitoring for Wearable Ultrasound Devices: Enhancing Accuracy through Deep Learning-based Coarse-to-Fine Shape Estimation
2024-07IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, v.71, no.7, pp.775 - 785
Accurate and continuous bladder volume monitoring is crucial for managing urinary dysfunctions. Wearable ultrasound devices offer a solution by enabling non-invasive and real-time monitoring. Previous studies have limitations in power consumption and computation cost or quantitative volume estimation capability. To alleviate this, we present a novel pipeline that effectively integrates conventional feature extraction and deep learning to achieve continuous quantitative bladder volume monitoring efficiently. Particularly, in the proposed pipeline, bladder shape is coarsely estimated by a simple bladder wall detection algorithm in wearable devices, and the bladder wall coordinates are wirelessly transferred to an external server. Subsequently, a roughly estimated bladder shape from the wall coordinates is refined in an external server with a diffusion-based model. With this approach, power consumption and computation costs on wearable devices remained low, while fully harnessing the potential of deep learning for accurate shape estimation. To evaluate the proposed pipeline, we collected a dataset of bladder ultrasound images and RF signals from 250 patients. By simulating data acquisition from wearable devices using the dataset, we replicated real-world scenarios and validated the proposed method within these scenarios. Experimental results exhibit superior improvements, including +9.32% of IoU value in 2D segmentation and -22.06 of RMSE in bladder volume regression compared to state-of-the-art performance from alternative methods, emphasizing the potential of this approach in continuous bladder volume monitoring in clinical settings. Therefore, this study effectively bridges the gap between accurate bladder volume estimation and the practical deployment of wearable ultrasound devices, promising improved patient care and quality of life. © 2024 IEEE.
Flex-to-Stretch Hybrid Electronics–Bonding-Free Robust Interface for Wearable Wireless Physiological Monitoring
2024-05IEEE Internet of Things Journal, v.11, no.9, pp.15656 - 15666
Hybrid electronics require a robust mechanical interface between externally fabricated stretchable sensors and flexible printed circuit boards (FPCBs) to obtain stable electrophysiological information. The most advanced technique for the integration of FPCBs with stretchable sensors is anisotropic conductive film bonding. Fabricating high-performance sensors requires microfabrication techniques, such as photolithography and etching, which are cumbersome and expensive. Therefore, a sensor fabrication process that supports FPCB manufacturing with lower complexity and cost is required. Herein, we propose a bonding-free approach for fabricating FPCBs and stretchable sensors on a single substrate. This approach utilizes in-and out-of-plane mechanical gradients to obtain a robust and durable mechanical interface for a smooth transition of the internal mechanical stress compliance, as confirmed by experiments and simulations. The gradient mesh patterns, without ACF bonding, can withstand tensile strains of over 30% before experiencing electrical breakdown. Additionally, Kirigami-inspired mesh patterns can extend stretchability by over 100%. The electrical performance of temperature sensors (linear response to temperature changes) and ECG sensors (clear visibility of PQRST peaks) remains stable under various physical activities. User-accessible, facile laser ablation and cutting techniques compatible with the FPCB manufacturing process were employed to fabricate stretchable sensors. This approach enables the development of FPCB-compatible on-skin stretchable sensors with robust mechanical properties. Authors
Exploration of superconductivity in LK-99 synthesized under different cooling conditions
2024-06Current Applied Physics, v.62, pp.22 - 28
The claim of superconductivity above room temperature at ambient pressure in Cu-doped lead apatite (LK-99, Pb10-xCux(PO4)6O) has attracted considerable attention. In this paper, we present the results of synthesized LK-99 using a systematic approach based on quenching method variations. A slower cooling rate resulted in an increased LK-99 phase and a decreased Cu2S phase, with the slowest cooling method achieving the highest concentration of the LK-99 phase. Magnetic levitation was observed in certain specimens, with one end adhering to the magnet and the other end floating, which was distinguished from the Meissner effect. The majority of samples synthesized under different conditions exhibited no response to the magnet. The slowest cooled sample exhibited mostly insulating behavior. The samples synthesized in the other conditions had metallic behaviors, which contained a significant amount of Cu2S. No evidence of superconductivity was observed within the temperature range of 4 K–300 K in our samples. © 2024 Korean Physical Society
Computational insights and phase transition of ruthenium alloy by classical molecular dynamics simulations
2024-06AIP Advances, v.14, no.6
Understanding the mechanism of metal solidification holds both theoretical significance and practical importance. In this study, we conducted molecular dynamics simulations to investigate the impact of cooling rates on the solidification of a melted ruthenium alloy using the embedded atom method (EAM) potential. The EAM potential is a widely employed interatomic potential for describing the metallic system, which can capture numerous crucial properties, including mechanical properties, the energy of competing crystal structure dynamics, defects, and liquid structures. Our simulations showed that upon quenching with different cooling rates, the system transformed into a supercooled liquid state at 1200K, and a hexagonal close-packed cluster emerged as a dominant structure that remained stable even in the supercooled state. A critical cooling rate (1011 K/s) marked the transition from crystal to amorphous phase; this transition exhibited an upward trend as the superheating temperature increased until it reached the maximum achievable cooling rate. Our simulations also revealed that the optimal conditions for undercooling and superheating occur at ∼0.4396 and 1.2893 Tm, respectively, where Tm is the melting temperature. Our results provide comprehensive insights into the evolution of melt structures with changing temperatures during deep undercooling, the formation of homogeneous melt-free crystal regions, and the effect of the molten state on solidification phenomena.
Ultrasound-Assisted Photothermal Therapy (ULTRA-PTT) for the Treatment of Deep-Seated Tumors
ACCEPTAdvanced Optical Materials
Photothermal therapy (PTT) has garnered considerable attention as an attractive treatment tool for cancer due to precisely selective treatment and minimal side effects. The primary challenge of PTT, which hinders its widespread application, is the limited therapeutic depth. This limitation arises from optical scattering in biological tissues, causing inadequate heat distribution within the deep tissue. To overcome this challenge, ultrasound-assisted PTT (ULTRA-PTT) is proposed that leverages the temporary formation of gas bubbles induced by ultrasound within the light propagation path. These bubbles act as optical clearing agents, effectively reducing optical scattering in biological tissues. To facilitate ULTRA-PTT, a dedicated handpiece consisting of a ring-shaped ultrasound transducer and a laser delivery module is developed. In-vivo experiments show that ULTRA-PTT statistically outperforms conventional PTT in melanoma treatment, mostly due to its ability to deliver sufficient laser energy to deep-seated cancer cells. These findings underscore the potential of ULTRA-PTT to expand the clinical applications of PTT beyond local tumors occurring in superficial tissue. © 2024 Wiley-VCH GmbH.
Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches
2024-02Journal of Extracellular Vesicles, v.13, no.2
Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its ‘Minimal Information for Studies of Extracellular Vesicles’, which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly. © 2024 The Authors. Journal of Extracellular Vesicles published by Wiley Periodicals, LLC on behalf of the International Society for Extracellular Vesicles. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Ethyl 2-(2-fluoroethoxy)ethyl carbonate as a new electrolyte additive for high-voltage Li-metal batteries
2023-01Battery Energy, v.2, no.1
The combination of a high-Ni LiNixMnyCo1-x-yO2 (NMC) cathode and Li metal anode is currently considered the most promising candidate for high-energy-density Li-metal batteries. However, undesired parasitic reactions in LiPF6-based carbonate electrolytes hinder their further application. Herein, we report a new fluorinated linear carbonate additive, ethyl 2-(2-fluoroethoxy)ethyl carbonate) (EFEEC), to a lithium bis(trifluoromethanesulfonyl) imide-lithium bis(oxalate)borate-based dual-salt electrolyte system which is compatible with high-Ni NMC and Li metal electrodes. We showed that in our electrolyte with well-controlled lowest unoccupied molecular orbital/highest unoccupied molecular orbital levels, robust and stable solid electrolyte interphases are formed on both the cathode and anode synergistically, which enables neat and dense lithium metal deposition as well as the structural stability of NMC622 operated under a 4.5V cut-off voltage. The use of the dual-salt-based electrolyte with the EFEEC additive improved cycle performance with high-capacity retention (76.0% at 200 cycles) even when operated under high voltage. © 2023 The Authors. Battery Energy published by Xijing University and John Wiley & Sons Australia, Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
카보네이트 전해질 기반 리튬 전착/용출 사이클과 계면 진화 메커니즘에 대한 연구 동향
2023-07한국전지학회지, v.3, no.1, pp.78 - 87
리튬 금속은 리튬이차전지의 에너지밀도 한계를 뛰어넘을 수 있는 궁극의 음극 소재이다. 허나, 본연의 높은 반응성으로 인해 전해액과의 부반응이 극심하고 불균일한 리튬 전착 및 덴드라이트 성장은 리튬 음극의 가역성을 현저히 저하시킨다. 리튬음극의 가역성을 평가하는 플랫폼인 리튬/구리 반쪽 전지의 충방전 거동은 전기화학적 특성 예측이 어렵고 셀 내에서 기공성의 전극/전해질 계면의 성장으로 인해 정확한 효율 측정이 어려운 한계점이 있다. 본 연구에서는 리튬/구리 반쪽 전지의 전기화학적 특성에 영향을 미치는 주요인자에 대해서 밝히고 기공성 전극/전해질 계면의 성장 메커니즘을 다룬다. 반복되는 충방전 과정 중에 형성되는 기 공성 SEI의 표면 부도체화와 성장 속도가 늦춰지는 상이한 성장거동을 확인하였고, 사이클 후반의 극심한 전 해액 부반응에 대해서 다룬다. Lithium (Li) metal is the ultimate anode material that can overcome the energy density limit of today'sLi-ion batteries. However, Li metal anodes (LMAs) have suffered from significant deterioration due to severeside reactions against electrolytes and non-uniform Li electrodeposition triggered by dendrite formation andgrowth of Li plating. The charging/discharging behavior of Li||Cu half-cell, a platform for evaluating thereversibility of lithium cathodes, is not fully understood to predict electrochemical properties and accurate efficiencymeasurements due to the growth of the porous electrode/electrolyte interface (SEI) within the cell. Inthis study, the main factors affecting the electrochemical properties of Li||Cu half-cells are redefined, revealingthe mechanism of porous SEI growth. Two different SEI growth modes include fast growth during the initialstage of cycling and slow-down development over later cycles due to high compression within the cell. Through the quantification of the porous layer, the extreme side reaction of the electrolyte solution mainlyoccurs during later cycling. It is suggested that the porous Li layer grew outward towards the electrolyte phaseby generating underneath Li deposition and pushing up the former layer due to its insulating nature.
수계 아연 금속 전지용 아연 분말 기반 복합음극 안정화 기술 개발
2023-07한국전지학회지, v.3, no.1, pp.57 - 65
아연 분말 기반 음극 소재의 도입을 통한 비발화, 유효 전류 밀도 감소, 높은 가공 특성의 차세대 전지 를 구현할 수 있으나, 전극 제조법 및 소재에서의 최적화 연구가 전무하다. 본 연구에서는 다양한 도전재와 바 인더를 도입하여 수계 아연 전지용 아연 분말 기반의 복합 음극 안정화 및 최적 효율과 구조적 안정성을 가 진 아연 분말 기반 음극 제조법을 확립하였다. Aqueous zinc (Zn) ion batteries (AZIB) has various advantages compared to other metal-based batteriessuch as high gravimetric capacity, low reduction potential, and intrinsic safety. Furthermore, Zn powdershows more flexible processing technology and lower current density due to its large surface area. However,because Zn powder has problems with uncontrolled dendrite growth, corrosion, and hydrogen evolution reaction(HER), indicating that improvements of the performance and the stability are still limited. To solve theproblem, this study searches the best method for stabilizing aqueous Zn powder battery anode by adjusting conductiveagents and binders, which have appropriate hydrophilicity and hydrophobicity to maintain the stabilityof electrode. Therefore, the possibility of Zn powder composite electrode as anode was confirmed for the nextgenerationenergy storage systems (ESSs) batteries.
Multi-Scale Self-Attention Network for Denoising Medical Images
2024-01APSIPA Transactions on Signal and Information Processing, v.12, no.5, pp.1 - 26
Deep learning-based image denoising plays a critical role in medical imaging, especially when dealing with rapid fluorescence and ultrasound captures where traditional noise mitigation strategies are limited, such as increasing pixel dwell time or frame averaging. Although numerous denoising techniques based on deep learning have exhibited commendable results across biomedical domains, further optimization is pivotal, particularly for precise real-time tracking of molecular kinetics in cellular settings. This is vital for decoding the intricate dynamics of biological processes. In this context, we propose the Multi-Scale Self-Attention Network (MSAN), an innovative architecture tailored for optimal denoising of fluorescence and ultrasound images. MSAN integrates three main modules: a feature extraction layer adept at discerning high and low-frequency attributes, a multi-scale self-attention mechanism that predicts residuals using original and downsampled feature maps, and a decoder that produces a residual image. When offset from the original image, the residual output yields the denoised result. Benchmarking shows MSAN outperforms state-of-the-art models such as RIDNet and DnCNN, achieving peak signal-to-noise ratio improvements of 0.17 dB, 0.23 dB, and 1.77dB on the FMD, W2S datasets, and ultrasound dataset, respectively, thus showcasing its superior denoising capability for fluorescence and ultrasound imagery. © 2024 K. Lee et al. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http:// creativecommons.org/ licenses/ by-nc/ 4.0/ ), which permits unrestricted re-use, distribution, and reproduction in any medium, for non-commercial use, provided the original work is properly cited.
Low-Cost and Easy-to-Build Soft Robotic Skin for Safe and Contact-Rich Human - Robot Collaboration
2024-03IEEE Transactions on Robotics, v.40, pp.2327 - 2338
Although many soft robotic skins have been introduced, their use has been hindered due to practical limitations, such as difficulties in manufacturing, poor accessibility, and cost inefficiency. To solve this, we present a low-cost, easy-to-build soft robotic skin utilizing air-pressure sensors and 3D-printed pads. In our approach, we utilized digital fabrication and robot operating system (ROS) to facilitate the creation and use of the robotic skin. The skin pad was fabricated by printing thermoplastic urethane (TPU) and postprocessed with an organic solvent to secure air-tightness. Each pad consists of a TPU shell and infill, so the internal air-pressure changes in response to tactile stimuli, such as force and vibration. The internal pressure is measured and processed by a microcontroller and transmitted to the host computer via a serial bus. We conducted experiments to investigate the characteristics of the skin pads, and the results showed that the developed robotic skins are capable of perceiving interaction force and dynamic stimuli. Finally, we developed the dedicated soft robotic skins for our custom robot designed in-house, and demonstrated safe and intuitive physical human-robot interaction. © 2024 The Authors. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/