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Doping and alloying are fundamental strategies to improve the thermoelectric performance of bare materials. However, identifying outstanding elements and compositions for the development of high-performance thermoelectric materials is challenging. In this study, we present a data-driven approach to improve the thermoelectric performance of SnSe compounds with various doping. Based on the newly generated experimental and computational dataset, we built highly accurate predictive models of thermoelectric properties of doped SnSe compounds. A well-designed feature vector consisting of the chemical properties of a single atom and the electronic structures of a solid plays a key role in achieving accurate predictions for unknown doping elements. Using the machine learning predictive models and calculated map of the solubility limit for each dopant, we rapidly screened high-dimensional material spaces of doped SnSe and evaluated their thermoelectric properties. This data-driven search provided overall strategies to optimize and improve the thermoelectric properties of doped SnSe compounds. In particular, we identified five dopant candidate elements (Ge, Pb, Y, Cd, and As) that provided a high ZT exceeding 2.0 and proposed a design principle for improving the ZT by Sn vacancies depending on the doping elements. Based on the search, we proposed yttrium as a new high-ZT dopant for SnSe with experimental confirmations. Our research is expected to lead to novel high-ZT thermoelectric material candidates and provide cutting-edge research strategies for materials design and extraction of design principles through data-driven research.

Leveraging three-dimensional (3D) bioprinting in the fields of tissue engineering and regenerative medicine has rapidly accelerated progress toward the development of living tissue constructs and biomedical devices. Ongoing vigorous research has pursued the development of 3D in vitro tissue models to replicate the key aspects of human physiology by incorporating relevant cell populations and adequate environmental cues. Given their advantages of being able to intimately mimic the heterogeneity and complexity of their native counterparts, 3D in vitro models hold promise as alternatives to conventional cell cultures or animal models for translational application to model human physiology/pathology and drug screening. Research has highlighted the importance of in vitro models, and a sophisticated biomanufacturing strategy is vitally required. In particular, vascularization is critical for the prolonged survival and functional maturation of the engineered tissues, which has remained one of the major challenges in the establishment of physiologically relevant 3D in vitro models. To this end, 3D bioprinting can efficiently generate solid and reproducible vascularized tissue models with high architectural and compositional similarity to the native tissues, leading to improve the structural maturation and tissue-specific functionality. Multiple bioprinting strategies have been developed to vascularize in vitro tissues by spatially controlled patterning of vascular precursors or generating readily perfusable vascular structures. This review presents an overview of the advanced 3D bioprinting strategies for vascularized tissue model development. We present the key elements for rebuilding functional vasculature in 3D-bioprinted tissue models and discuss the recent achievements in the engineering of 3D vascularized in vitro models using 3D bioprinting. Finally, we delineate the current challenges and future outlooks of 3D bioprinting-based vascularized tissue models.

In the last two decades, there have been significant advancements in the development of more physiologically relevant organ-on-a-chip (OOC) systems that can mimic the tissue microenvironment. Despite the advantages of these microphysiological systems, such as portability, the ability to mimic physiological flow conditions, and the reduction of reagents required for preparation and detection, they lack real-time detection of analytes with high accuracy. To address this, biosensor technologies have been integrated with OOC systems to enable simultaneous analysis of different analytes in a single device. However, integrating biosensors with OOC systems is challenging due to the competing demands for low-cost, simple fabrication processes, and speed. This study presents the fabrication of a glucose sensing device integrated with a liver-on-a-chip (LOC) platform. The conductive PLA-based three-electrode system was printed using FDM 3D printing technology to simplify the fabrication process. The sensitivity of the glucose biosensing device was enhanced by adding multi-walled carbon nanotubes on the electrodes. The biosensing integration study using a perfusion-based LOC showed the stability, biocompatibility, and sensitivity of the glucose sensing devices. Furthermore, drug toxicity studies on the LOC platform demonstrated the device’s ability to detect a broad range of glucose concentrations and its enhanced sensitivity.

In the last decade, organoids have gained popularity for developing mini-organs to support advancements in the study of organogenesis, disease modeling, and drug screening and, subsequently, in the development of new therapies. To date, such cultures have been used to replicate the composition and functionality of organs such as the kidney, liver, brain, and pancreas. However, depending on the experimenter, the culture environment and cell conditions may slightly vary, resulting in different organoids; this factor significantly affects their application in new drug development, especially during quantification. Standardization in this context can be achieved using bioprinting technology—an advanced technology that can print various cells and biomaterials at desired locations. This technology offers numerous advantages, including the manufacturing of complex three-dimensional biological structures. Therefore, in addition to the standardization of organoids, bioprinting technology in organoid engineering can facilitate automation in the fabrication process as well as a closer mimicry of native organs. Further, artificial intelligence (AI) has currently emerged as an effective tool to monitor and control the quality of final developed objects. Thus, organoids, bioprinting technology, and AI can be combined to obtain high-quality in vitro models for multiple applications.

Many efforts have been expended in the emulations of the kidney’s glomerular unit because of its limitless potential in the field of drug screening industry and nephrotoxicity testing in the clinics. Herein, we have fabricated a functional bilayer glomerular microvessel-on-a-chip that recapitulates the specific arrangement of glomerular endothelial cell (GE), podocyte layers, and the intervening glomerular basement membrane (GBM) in a single step. Our perfusable chip allows for the coculture of the monolayer glomerular endothelium and podocyte epithelium that display mature functional markers of glomerular cells, and their proper interactions produce GBM proteins, which are the major components of the GBM in vivo. Furthermore, we tested the selective permeability capacity, a representative hallmark function of the glomerular filtration barrier. Lastly, we evaluated the response of our glomerular model to Adriamycin- and hyperglycemia-induced injury to evaluate its applicability for drug screening and glomerular disease modeling.

Extraordinary properties of traditional hyperbolic metamaterials, not found in nature, arise from their man-made subwavelength structures causing unique light-matter interactions. However, their preparation requiring nanofabrication processes is highly challenging and merely provides nanoscale two-dimensional structures. Stabilizing their bulk forms via scalable procedures has been a sought-goal for broad applications of this technology. Herein, we report a new strategy of designing and realizing bulk metamaterials with finely tunable hyperbolic responses. We develop a facile two-step process: (1) self-assembly to obtain heterostructured nanohybrids of building blocks and (2) consolidation to convert nanohybrid powders to dense bulk pellets. Our samples have centimeter-scale dimensions typically, readily further scalable. Importantly, the thickness of building blocks and their relative concentration in bulk materials serve as a delicate means of controlling hyperbolic responses. The resulting new bulk heterostructured material system consists of the alternating h-BN and graphite/graphene nanolayers and exhibits significant modulation in both type-I and type-II hyperbolic resonance modes. It is the first example of real bulk hyperbolic metamaterials, consequently displaying the capability of tuning their responses along both in-plane and out-of-plane directions of the materials for the first time. It also distinctly interacts with unpolarized and polarized transverse magnetic and electronic beams to give unique hyperbolic responses. Our achievement can be a new platform to create various bulk metamaterials without complicated nanofabrication techniques. Our facile synthesis method using common laboratory techniques can open doors to broad-range researchers for active interdisciplinary studies for this otherwise hardly accessible technology.

Nature materials (2021). doi:10.1038/s41563-021-01064-6, Published by Nature Publishing Group, Basingstoke

Liver fibrosis is a critical liver disease which can lead to liver cirrhosis, cancer, and liver failure. Among various etiological factors, activated stellate cells are a major factor that can induce liver fibrosis. Several studies have presented in vitro models to identify drugs for liver fibrosis; however, there are still limitations in terms of the 2D culture conditions, random co-culture of liver cells, and lack of extracellular matrix components. Therefore, a 3D liver fibrosis-on-a-chip was developed with three liver cell types (hepatocytes, activated stellate cells, and endothelial cells) using a novel cell-printing technique with gelatin bioinks, which were used to deliver each nonparenchymal liver cell type as a multilayer construct. Liver fibrosis-specific gene expression, collagen accumulation, cell apoptosis, and reduced liver functions caused by activated stellate cells were also evaluated. Furthermore, previously reported chemicals were added to the 3D liver fibrosis-on-a-chip to examine the downregulation of activated hepatic stellate cells. In conclusion, the developed 3D liver fibrosis-on-a-chip could be used as a potential in vitro model in the research field.

Scientific databases offer remarkable potential for solving complex questions in materials science, such as global optimization of materials and designing unknown materials for novel properties. ThermoElectric materials eXplorer (TEXplorer) is a web-based platform designed to collect and share all types of thermoelectric materials data, including synthesis information, materials characterization, transport measurements, and electronic structures obtained from experiments and computations. TEXplorer also provides valuable tools, such as an easy upload and download system, retrieval, automatic post-processing calculations, visualization of datasets, and toolkits for predicting thermoelectric properties through machine learning models. Using the platform, we collected and managed the thermoelectric dataset of SnSe and Bi2Te3 with various doping/alloying elements in this study in order to investigate the complex relationship between doping/alloying elements and the thermoelectric properties of host materials. The web-based interactive data platform enables efficient management and utilization of experimental and computational datasets, supporting the acceleration of data-driven materials research and autonomous material synthesis.

This perspective discusses the surprising discovery and development of SnSe thermoelectrics. Undoped, hole-doped, and electron-doped SnSe single crystals have successively represented an extraordinarily high thermoelectric figure of merit (ZT) ranging from 2.6 to 2.9, revitalizing efforts on finding new high-performance thermoelectric systems. Their unprecedented performance is mainly attributed to ultralow thermal conductivity arising from the uniquely anisotropic and anharmonic crystal chemistry of SnSe. Soon after the publications on SnSe single crystals, substantial debates were raised on their thermoelectric performance, especially on truth in ultralow thermal conductivity. Very recently, polycrystalline SnSe samples were synthesized, exhibiting lower lattice thermal conductivity and higher ZT than the single crystal samples. This work clearly addressed many questions that have arisen on the intrinsic thermal and charge transport properties of SnSe-based materials. It shows a peak ZT of ~3.1 at 783 K and an average ZT of ~2.0 from 400 to 783 K, which are the record-breaking performances of all bulk thermoelectric materials in any form ever reported.

The superiority of in vitro 3D cultures over conventional 2D cell cultures is well recognized by the scientific community for its relevance in mimicking the native tissue architecture and functionality. The recent paradigm shift in the field of tissue engineering toward the development of 3D in vitro models can be realized with its myriad of applications, including drug screening, developing alternative diagnostics, and regenerative medicine. Hydrogels are considered the most suitable biomaterial for developing an in vitro model owing to their similarity in features to the extracellular microenvironment of native tissue. In this review article, recent progress in the use of hydrogel-based biomaterial for the development of 3D in vitro biomimetic tissue models is highlighted. Discussions of hydrogel sources and the latest hybrid system with different combinations of biopolymers are also presented. The hydrogel crosslinking mechanism and design consideration are summarized, followed by different types of available hydrogel module systems along with recent microfabrication technologies. We also present the latest developments in engineering hydrogel-based 3D in vitro models targeting specific tissues. Finally, we discuss the challenges surrounding current in vitro platforms and 3D models in the light of future perspectives for an improved biomimetic in vitro organ system.

Due to the excellent biocompatibility of natural polymers, a variety of natural polymers have been widely used as biomaterials for manufacturing tissue engineered scaffolds. Despite the excellent biological activity of natural polymers, there have been obstacles in using them on their own to prepare 3D scaffolds with sufficient mechanical strength. Although multiple 3D-bioprinting technologies have recently emerged as effective manufacturing tools for scaffold preparation, scaffold preparation using only natural polymers with tunable mechanical properties is still difficult. Herein, we introduce novel scaffold fabrication methods using the natural polymer silk fibroin via indirect 3D-bioprinting technology. The developed silk fibroin scaffolds showed biocompatibility and tunable mechanical strength by changing the concentration of the silk fibroin. Furthermore, controlling the flexibility of the silk fibroin scaffolds was made possible by changing the solvent for the silk fibroin solution used to fabricate the scaffold. Consequently, silk fibroin scaffolds fabricated via our method can be considered for various applications in the bioengineering of either soft or musculoskeletal tissues.

Lee, H.; Kim, J.; Chang, S., and Kim, I., 2021. Analysis of beach changes after construction of submerged breakwaters. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 300–304. Coconut Creek (Florida), ISSN 0749-0208. This study presents seasonal investigations of submerged breakwaters constructed from 2013 to 2014 as part of a government erosion prevention project in the region of Samcheok-si, South Korea. Parameters, including wave-induced currents, wave heights, beach profiles, and shoreline changes, were investigated to monitor and analyze sand transport trends in the study area. The construction of Gungchon Harbor in 2006 led to the transport of sand from southern Wonpyeong Beach to northern Gungchon Beach, which resulted in an average shoreline retreat of greater than 50 m. However, despite the subsequent construction of the submerged breakwaters, beach erosion continued to occur in adjacent areas. Specifically, a tombolo was generated behind the submerged breakwaters, which led to beach erosion. Rip currents were also typically generated near submerged breakwaters, which play a role in the offshore transportation of sand. Wonpyeong Beach experienced erosion following the construction of Gungchon Harbor, whereas Gungchon Beach exhibited accretion. Moreover, evidence of further erosion was observed near the breakwater construction area. Therefore, this study indicates that detailed monitoring during and after the construction of breakwaters is required to predict potential secondary erosion and understand the erosion mechanism for an optimal breakwater design.

Realizing high average thermoelectric figure of merit (ZT

Retinal pigment epithelium (RPE) is a monolayer of the pigmented cells that lies on the thin extracellular matrix called Bruch&rsquo, s membrane. This monolayer is the main component of the outer blood&ndash, retinal barrier (BRB), which plays a multifunctional role. Due to their crucial roles, the damage of this epithelium causes a wide range of diseases related to retinal degeneration including age-related macular degeneration, retinitis pigmentosa, and Stargardt disease. Unfortunately, there is presently no cure for these diseases. Clinically implantable RPE for humans is under development, and there is no practical examination platform for drug development. Here, we developed porcine Bruch&rsquo, s membrane-derived bioink (BM-ECM). Compared to conventional laminin, the RPE cells on BM-ECM showed enhanced functionality of RPE. Furthermore, we developed the Bruch&rsquo, s membrane-mimetic substrate (BMS) via the integration of BM-ECM and 3D printing technology, which revealed structure and extracellular matrix components similar to those of natural Bruch&rsquo, s membrane. The developed BMS facilitated the appropriate functions of RPE, including barrier and clearance functions, the secretion of anti-angiogenic growth factors, and enzyme formation for phototransduction. Moreover, it could be used as a basement frame for RPE transplantation. We established BMS using 3D printing technology to grow RPE cells with functions that could be used for an in vitro model and RPE transplantation.

Coronavirus disease 2019 (COVID-19), which has recently emerged as a global pandemic, has caused a serious economic crisis due to the social disconnection and physical distancing in human society. To rapidly respond to the emergence of new diseases, a reliable in vitro model needs to be established expeditiously for the identification of appropriate therapeutic agents. Such models can be of great help in validating the pathological behavior of pathogens and therapeutic agents. Recently, in vitro models representing human organs and tissues and biological functions have been developed based on high-precision 3D bioprinting. In this paper, we delineate an in-depth assessment of the recently developed 3D bioprinting technology and bioinks. In particular, we discuss the latest achievements and future aspects of the use of 3D bioprinting for in vitro modeling.

Bi2Te3-based materials are a representative thermoelectric system operating near ambient temperature. Their n-type family is very limited and underperforms the p-type counterpart, which is a major concern in the thermoelectric community. Here we report that alkali earth metals (AE = Mg, Ca, Sr, Ba) in Group 2 unusually induce n-type thermoelectric properties in Bi2Te3. Mg is the most efficient electron donor among them. The x = 0.01 sample of MgxBi2-xTe3 (x = 0.005, 0.01, 0.015) system exhibits remarkably enhanced power factor and ZT of ~0.8 at 350 K in comparison with pristine Bi2Te3. The improved performance is attributed to simultaneously enhanced electrical conductivity and reduced lattice thermal conductivity. Remarkably, MgxBi2-xTe3 materials show larger Seebeck coefficients than those expected by the theoretical Pisarenko relation.

3D cell-printing technique has been under spotlight as an appealing biofabrication platform due to its ability to precisely pattern living cells in pre-defined spatial locations . In skin tissue engineering , a major remaining challenge is to seek for a suitable source of bioink capable of supporting and stimulating printed cells for tissue development. However, current bioinks for skin printing rely on homogeneous biomaterials , which has several shortcomings such as insufficient mechanical properties and recapitulation of microenvironment . In this study, we investigated the capability of skin-derived extracellular matrix (S-dECM) bioink for 3D cell printing-based skin tissue engineering. S-dECM was for the first time formulated as a printable material and retained the major ECM compositions of skin as well as favorable growth factors and cytokines. This bioink was used to print a full thickness 3D human skin model. The matured 3D cell-printed skin tissue using S-dECM bioink was stabilized with minimal shrinkage, whereas the collagen-based skin tissue was significantly contracted during in vitro tissue culture. This physical stabilization and the tissue-specific microenvironment from our bioink improved epidermal organization, dermal ECM secretion, and barrier function. We further used this bioink to print 3D pre-vascularized skin patch able to promote in vivo wound healing. In vivo results revealed that endothelial progenitor cells (EPCs)-laden 3D-printed skin patch together with adipose-derived stem cells (ASCs) accelerates wound closure, re-epithelization, and neovascularization as well as blood flow. We envision that the results of this paper can provide an insightful step towards the next generation source for bioink manufacturing.

The generation of physiologically aligned multinucleated myotubes is critical in the fabrication of functional engineered skeletal muscle. Although micro-/nano-topographical contact guidance, such as groove/ridge structures, has induced the alignment of muscle fibers by providing cells with extracellular matrix (ECM) topography, the complex biochemical microenvironment of the ECM cannot be recapitulated. Here, we report the enhancement of myogenic differentiation and maturation using muscle decellularized ECM (mdECM) and sinusoidal wavy surfaces, which provided a biochemical microenvironment and microscale contact guidance, respectively. Sinusoidal wavy polystyrene surfaces with wavelengths of 20, 40, and 80 μm were fabricated by a deep X-ray lithography-based process. The mdECM was prepared by decellularization of porcine tibialis anterior skeletal muscle. An mdECM coating significantly improved the surface wettability of polystyrene substrates and exhibited higher seeding efficiency, cell viability, and proliferation compared with collagen- and non-coating cases. The sinusoidal wavy surfaces induced well-aligned myotubes and showed significantly enhanced formation of myotubes and myogenic differentiation when the surface was coated with mdECM. Particularly, there was an approximately 1.5-2 fold improvement in morphological analysis and gene expression for mdECM-compared to non-coated sinusoidal wavy surfaces. These results suggest that the consideration of both topographical and biochemical environmental cues can generate a highly mimicked ECM environment, thereby providing cells with a synergistic effect on myogenic differentiation and maturation. The outcome of this study will be useful in developing of functional engineered muscle for application in tissue regeneration or a high-throughput in vitro model for drug screening.

Polybenzimidazole containing graphitic carbon nitride moiety (PBICN) is prepared by in situ polymerization of 3,3′-diaminobenzidine (DAB), isophthalic acid (IPA), and graphitic carbon nitride (g-CN) for the application in high-temperature fuel cell membrane. Since g-CN has a nanosheet structure and lots of amine end groups, it can be involved in the polymerization process producing PBI-grafted g-CN. The PBICN membrane shows much improved thermal property, oxidative stability, mechanical strength, and proton conductivity compared to pristine PBI membrane and the PBI composite membrane prepared simply by mixing PBI and g-CN. In addition, it is confirmed that the PBI-grafted g-CN structure formed during the in situ polymerization can contribute to the increase of the dimensional stability for the PBICN membrane. Especially, PBICN membrane prepared by the in situ polymerization using g-CN exhibits much improved fuel cell performance. For example, the power density value of the membrane electrode assembly (MEA) fabricated using PBICN membrane prepared using 0.5 wt% of g-CN is 400 mW cm−2, which is much larger than those of MEA fabricated using PBI membrane (241 mW cm−2) and the PBI composite membrane containing 0.5 wt% of g-CN (326 mW cm−2) membrane during the fuel cell performance test performed at 160 °C without humidification.

The liver is an important organ and plays major roles in the human body. Because of the lack of liver donors after liver failure and drug-induced liver injury, much research has focused on developing liver alternatives and liver in vitro models for transplantation and drug screening. Although numerous studies have been conducted, these systems cannot faithfully mimic the complexity of the liver. Recently, three-dimensional (3D) cell printing technology has emerged as one of a number of innovative technologies that may help to overcome this limitation. However, a great deal of work in developing biomaterials optimized for 3D cell printing-based liver tissue engineering remains. Therefore, in this work, we developed a liver decellularized extracellular matrix (dECM) bioink for 3D cell printing applications and evaluated its characteristics. The liver dECM bioink retained the major ECM components of the liver while cellular components were effectively removed and further exhibited suitable and adjustable properties for 3D cell printing. We further studied printing parameters with the liver dECM bioink to verify the versatility and fidelity of the printing process. Stem cell differentiation and HepG2 cell functions in the liver dECM bioink in comparison to those of commercial collagen bioink were also evaluated, and the liver dECM bioink was found to induce stem cell differentiation and enhance HepG2 cell function. Consequently, the results demonstrate that the proposed liver dECM bioink is a promising bioink candidate for 3D cell printing-based liver tissue engineering.

Emulation of diverse electronic devices on textile platform is considered as a promising approach for implementing wearable smart electronics. Of particular, the development of multifunctional polymeric fibers and their integration in common fabrics have been extensively researched for human friendly wearable platforms. Here we report a successful emulation of multifunctional body-motion sensors and user-interface (UI) devices in textile platform by using in situ polymerized poly(3,4-ethylenedioxythiophene) (PEDOT)-coated fibers. With the integration of PEDOT fibers in a fabric, via an optimization of the fiber pattern design, multifunctional textile sensors such as highly sensitive and reliable strain sensors (with maximum gauge factor of ∼1), body-motion monitoring sensors, touch sensors, and multilevel strain recognition UI devices were successfully emulated. We demonstrate the facile utilization of the textile-based multifunctional sensors and UI devices by implementing in a wireless system that is capable of expressing American Sign Language through predefined hand gestures.

Sooner Trend Anadarko Canadian Kingfisher, also known as STACK, is a booming unconventional oil play in North America. As one of the main features that makes the asset profitable, multiple targeting benches raise a challenge of optimization. Well-developed natural fracture system brings in another level of complexity to estimate well spacing. This study introduces an integrated workflow to better understand the fluid flow mechanism in the reservoir and optimize development strategy. From borehole image log, natural fracture orientation and density was interpreted and statistically populated into geologic model along with petrophysical properties. To account for productivity enhancement due to natural fractures, enhanced permeability was embedded into the simulation model according to the distribution of discrete fracture network. After being history matched, the reservoir model was used to test the sensitivity on well spacing, landing zone and hydraulic fracturing pump schedule. Both infill drilling program and green field development scenarios were tested and compared to optimize our field development study. Production history match indicates that natural fractures serve as fluid flow conduit and contribute significantly to the production in Osage. Pressure transient observation shows a similar reservoir behavior in the Osage as opposed to the Woodford. Multiple wells experience productivity reduction over longer production history, indicating near-field damage (such as scaling) and/or far-field damage (such as fracture closure). Introduction of skin factor and pressure dependent permeability captured the trend on productivity behavior in the history match. In addition, the simulation study shed light on the hydraulic fracture geometry that provides direct insight on well spacing and landing zone analyses. Results from the infill drilling program show that staggered design with 3 Osage and 4 Woodford wells per section yields the higher oil recovery. However, using the greenfield sensitivities, and depending on the pumping schedule, hydraulic fractures from Woodford wells show upward growth, draining both formations effectively even without Osage wells. This study provides valuable information about the development strategy in STACK unconventional resources, particularly for scenarios with natural fracture system and multiple targeting zones. The simulation workflow considers well interference in both horizontal and vertical directions simultaneously to optimize oil recovery and reduce operational cost.

3D cell printing technology is in the spotlight for producing 3D tissue or organ constructs useful for various medical applications. In printing of neuromuscular tissue, a bioink satisfying all the requirements is a challenging issue. Gel integrity and motor neuron activity are two major characters because a harmonious combination of extracellular materials essential to motor neuron activity consists of disadvantages in mechanical properties. Here, a method for fabrication of 3D neuromuscular tissue is presented using a porcine central nervous system tissue decellularized extracellular matrix (CNSdECM) bioink. CNSdECM retains CNS tissue-specific extracellular molecules, provides rheological properties crucial for extrusion-based 3D cell printing, and reveals positive effects on the growth and maturity of axons of motor neurons compared with Matrigel. It also allows long-term cultivation of human-induced-pluripotent-stem-cell-derived lower motor neurons and sufficiently supports their cellular behavior to carry motor signals to muscle fibers. CNSdECM bioink holds great promise for producing a tissue-engineered motor system using 3D cell printing.

Lee, H.S.; Kim, I.H., and Kim, H.G., 2016. Application of terrestrial 3D laser scanning to monitor changes of beach landforms. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 173–177. Coconut Creek (Florida), ISSN 0749-0208. Monitoring changes in the beach morphology of coastal landforms is important when considering coastal management measures. In this paper, to create a changing beach surface, point cloud data of the beach are obtained using three-dimensional (3D) terrestrial laser scanning (TLS), and a beach surface model is analysed based on 3D point data. The 3D point cloud is generated from the scanned beach, including breakwaters, and these points are registered and merged through a reference point (scan origin and ball target) surveyed by RTK-GPS. Noise elements and unnecessary points are eliminated to yield better surface modelli...

Song, D.S; Kim, I.H.; Choi, J.S., and Lee, H.S., 2016. Evaluating of Coastal Erosion Status from CEMP results in Eastern Coast, South Korea. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1407 - 1411. Coconut Creek (Florida), ISSN 0749-0208. The Gangwon province, which is located in the mid-eastern part of the Korean Peninsula, started the Coastal Erosion Monitoring Program (CEMP) on 2006 and has been currently progressing. The CEMP in the eastern coast of Gangwon province is carried out in all the 41 littoral drift cells. In this study, we compared and evaluated a level of beach erosion based on the four years CEMP results. The indicators for coastal erosion evaluation in South Korea are consists of the beach width change (40 points), the beach area change (30 pts), the hinterland risk vulnerability (20 pts), the population (5 pts) and ...

The items of investigation include wave induced current, wave height, beach profile, shoreline change, etc. The investigation has been performed seasonally. After the construction of submerged breakwaters, a tombolo was generated behind the submerged breakwaters. This caused beach erosion in the nearby areas. Rip currents are mainly generated near submerged breakwaters, which plays a role in the transportation of sand in the offshore direction. In order to analyze the sand movement, numerical analysis was conducted. The analysis indicated that a strong rip current is generated near submerged breakwaters.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5p2wiNSMKlM

Kim, I.H.; Kim, J.H.; Nam, J.M.; Chang, S.Y.; Cho, W.C.; Do, K.D.; Kim, Y.J.; Song, D.S., and Lee, H.S., 2020. Changes in sand budget for littoral cell after coastal improvement project. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 242–246. Coconut Creek (Florida), ISSN 0749-0208.The Munam2 harbor was constructed in 1989 and the direction of Munam river mouth was changed from the Gyoam beach to the Backdo beach in order to prevent sediment deposit within the harbor inside. In order to reduce erosion damage at the Gyoam beach, the CIP started in March 2014, and three submerged breakwaters were constructed in September 2016, as well as the beach nourishment. Therefore, the characteristics of shoreline change and bathymetric change were analyzed due to wave transmission after the implementation of submerged breakwaters in littoral drift cell. The beach monitoring was performed twice annually from 2014 to 2018, that the surveying items were shoreline change, beach profile and bathymetric change, including two times wave field observation during the monitoring period. As a result, the wave transmission rate between the W-2 and W-3 shows that the function of submerged breakwater is working effectively only when a significant wave, height over 1.3 m, occurs. However, it was analyzed that there was no wave energy reduction effect as a submerged breakwater when the significant wave height is below 0.3 m. After the submerged breakwaters were constructed to solve the erosion problem, the stable coastal line was formed on the Gyoam beach.

Recently, researches have been actively conducted according to the government's policy direction on authentication methods that comply with web standards, such as the abolition of accredited certification systems. The problem was that the data stored in the existing web repository could be tampered with, resulting in a vulnerability. In this paper, we applied a mutual verification technique and API (Application Programming Interface) forgery/forgery blocking and obfuscation to solve the authentication weakness in web browsers that comply with the FIDO (Fast IDentity Online) standard. In addition, user convenience is improved by implementing the No-Plugin, which does not require the installation of a separate program. Performance tests show that most browsers perform at about 0.1ms based on the RSA key generation rate. In addition, this study proved that this service can be used for commercialization as it showed a performance of less than 0.1 second, even in the digital signature verification speed of the server. The service is expected to be useful as an alternative to browser authentication and to establish a secure web repository that does not require a public certificate.

To overcome the drawbacks of in vitro liver testing during drug development, numerous liver-on-a-chip models have been developed. However, current liver-on-a-chip technologies are labor-intensive, lack extracellular matrix (ECM) essential for liver cells, and lack a biliary system essential for excreting bile acids, which contribute to intestinal digestion but are known to be toxic to hepatocytes. Therefore, fabrication methods for development of liver-on-a-chip models that overcome the above limitations are required. Cell-printing technology enables construction of complex 3D structures with multiple cell types and biomaterials. We used cell-printing to develop a 3D liver-on-a-chip with multiple cell types for co-culture of liver cells, liver decellularized ECM bioink for a 3D microenvironment, and vascular/biliary fluidic channels for creating vascular and biliary systems. A chip with a biliary fluidic channel induced better biliary system creation and liver-specific gene expression and functions compared to a chip without a biliary system. Further, the 3D liver-on-a-chip showed better functionalities than 2D or 3D cultures. The chip was evaluated using acetaminophen and it showed an effective drug response. In summary, our results demonstrate that the 3D liver-on-a-chip we developed is promising in vitro liver test platform for drug discovery.

Supplemental Digital Content is available in the text., Summary: Reconstruction of maxilla defects has remained one of the most challenging problems in craniomaxillofacial reconstruction because it typically requires harvesting and grafting of autologous bone, which poses limitations related to the difficulties in accurately reconstructing the defected bone and the highly prolonged duration of surgery. We employed tissue-engineered, patient-specific, 3-dimensional (3D)-printed biodegradable scaffolds for maxillofacial bone reconstruction in patients with complex maxillary defects after surgical removal of cancer. A customized polycaprolactone (PCL) scaffold was designed and fabricated for each patient. For this purpose, we used computer-aided design and manufacturing combined with 3D printing technology. The patients implanted with the PCL scaffolds were followed up for up to 2 years with careful evaluation of morphological changes in the face. We confirmed that the patient-specific 3D-printed PCL scaffold effectively filled the maxillary defect and promoted regeneration of the deficient tissue while remaining stable in the body for a relatively long period. Employing customized tissue-engineered scaffolds built using the patient’s computed tomography data and an extrusion-based 3D printing system is safe and clinically feasible, helping create and maintain improved morphological features of the face, which represents the most important aspect from the perspective of the patients.

Skin injury to the face remains one of the greatest challenges in wound care due to the varied contours and complex movement of the face. Current treatment strategies for extensive facial burns are limited to the use of autografts, allografts, and skin substitutes, and these often result in scarring, infection, and graft failure. Development of an effective treatment modality will greatly improve the quality of life and social integration of the affected individuals. In this proof of concept study, we developed a novel strategy, called "BioMask", which is a customized bioengineered skin substitute combined with a wound dressing layer that snugly fits onto the facial wounds. To achieve this goal, three-dimensional (3D) bioprinting principle was used to fabricate the BioMask that could be customized by patients' clinical images such as computed tomography (CT) data. Based on a face CT image, a wound dressing material and cell-laden hydrogels were precisely dispensed and placed in a layer-by-layer fashion by the control of air pressure and 3-axis stage. The resulted miniature BioMask consisted of three layers; a porous polyurethane (PU) layer, a keratinocyte-laden hydrogel layer, and a fibroblast-laden hydrogel layer. To validate this novel concept, the bioprinted BioMask was applied to a skin wound on a pre-fabricated face-shaped structure in mice. Through this in vivo study using the 3D BioMask, skin contraction and histological examination showed the regeneration of skin tissue, consisting of epidermis and dermis layers, on the complex facial wounds. Consequently, effective and rapid restoration of aesthetic and functional facial skin would be a significant improvement to the current issues a facial wound patient experience.

© 2015 American Chemical Society. Near-infrared (NIR) dye-sensitized upconversion nanoparticles (UCNPs) can broaden the absorption range and boost upconversion efficiency of UCNPs. Here, we achieved significantly enhanced upconversion luminescence in dye-sensitized core/active shell UCNPs via the doping of ytterbium ions (Yb3+) in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. As a result, we synergized the two most practical upconversion booster effectors (dye-sensitizing and core/shell enhancement) to amplify upconversion efficiency. We demonstrated two biomedical applications using these UCNPs. By using dye-sensitized core/active shell UCNP embedded poly(methyl methacrylate) polymer implantable systems, we successfully shifted the optogenetic neuron excitation window to a biocompatible and deep tissue penetrable 800 nm wavelength. Furthermore, UCNPs were water-solubilized with Pluronic F127 with high upconversion efficiency and can be imaged in a mouse model.

Rapid functional epithelial regeneration on the luminal surface is essential when using artificial tracheal grafts to repair tracheal defects. In this study, we imposed human turbinate mesenchymal stromal cell (hTMSC) sheets for tracheal epithelial regeneration, and then assessed their potential as a new clinical cell source. In vitro, hTMSCs sheets showed high capacity to differentiate into tracheal epithelium. We fabricated a poly(ε-caprolactone) (PCL) tracheal graft by indirect three-dimensional (3D) printing technique and created a composite construct by transplanting the hTMSC sheets to its luminal surface of the tracheal graft, then applied this tissue-engineered tracheal graft to non-circumferential tracheal reconstruction in a rabbit model. 4 weeks after implantation, the luminal surface of tissue-engineered tracheal graft was covered by a mature and highly-ciliated epithelium, whereas tracheal grafts without hTMSC sheets were covered by only a thin, immature epithelium. Therefore, hTMSC sheets on the luminal surface of a tissue-engineered tracheal graft can accelerate the tracheal epithelial regeneration, and the tissue-engineered tracheal graft with hTMSC sheets provides a useful clinical alternative for tracheal epithelial regeneration.

Kim, I.H.; Lee, H.S.; Kim, J.H.; Yoon, J.S., and Hur, D.S., 2014. Shoreline change due to construction of the artificial headland with submerged breakwaters. The littoral drift cell of Bongpyeong Beach in Gyeongsangbuk-do ranges from Jukbyeon harbor to Goljang harbor. The beach erosion has largely occurred due to the expansion construction of Jukbyeon harbor. Headlands were installed as a countermeasure, however, the effectiveness of headland was not good as expected because of complicated coastal hydraulic phenomena. Furthermore, the headlands spoil the coastal landscape. Therefore, in this study, the field investigation of the shoreline and beach profile was conducted to analyze the characteristics around Bongpyeong Beach from 2013 through 2014. The causes of the beach erosion were identified by physical oceanographic investigation and numerical analysis. As a result, the complicated flow characteristics due to the construction of headlands and submerged breakwaters appear. The results also sho...

A class of biocompatible upconverting nanoparticles (UCNPs) with largely amplified red-emissions was developed. The optimal UCNP shows a high absolute upconversion quantum yield of 3.2% in red-emission, which is 15-fold stronger than the known optimal β-phase core/shell UCNPs. When conjugated to aminolevulinic acid, a clinically used photodynamic therapy (PDT) prodrug, significant PDT effect in tumor was demonstrated in a deep-tissue (>1.2 cm) setting in vivo at a biocompatible laser power density. Furthermore, we show that our UCNP–PDT system with NIR irradiation outperforms clinically used red light irradiation in a deep tumor setting in vivo. This study marks a major step forward in photodynamic therapy utilizing UCNPs to effectively access deep-set tumors. It also provides an opportunity for the wide application of upconverting red radiation in photonics and biophotonics.

Kim, I.H.; Kim, J.H.; Nam, J.M.; Lee, H.S., and Song, D.S., 2019. Monitoring of coastal geomorphological changes in Wolchun Beach after LNG base construction. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 366-370. Coconut Creek (Florida), ISSN 0749-0208.Constructions of industrial facilities nearby coastal region often break a natural equilibrium between sediment budget and littoral current condition. The Wolchun beach, which is facing East Sea of South Korea, had a longshore stretch of 1.9 km before the LNG storing base was constructed. In this study, we analyzed the change patterns of the Wolchun beach topography caused by the installation of artificial structures, as well as coastal geomorphological changes. The control points in the study area were divided into 8 sections, each spaced 50 m pitch apart, for the trend analysis of the beach profiles. Also, the sea zone with 1.35 km2 area was divided into 6 sections with 300 m × 750 m per section, for the monitoring of water depth variation. The surveying results show that the area of the northern side of the Wolchun beach near the LNG storage base was continuously increased due to the accumulation of sediment after the construction of LNG base. On the contrary, the continuous erosion occurred on the south side of Wolchun beach, and it was observed that the water depth near the surf zone is deepened. Also, the bathymetric change of the test area was occurred actively, and the significantly unstable change of water depth in the region of about -10 m ∼ -15 m was confirmed to be generated by the breakwater with the disrupting of operable wave condition. It is found that the natural equilibrium has been collapsed along the unexpectedly formed shielding zone after the construction of the LNG base and the breakwater on the outside of the base.

Kim, J.; Kim, I.; Nam, J.; Song D., and Lee, H., 2019. Changes in the behavioral characteristics of the Gangmun and Anmok beaches following the construction of artificial reefs. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 26-30. Coconut Creek (Florida), ISSN 0749-0208.On the East coast of South Korea, there is only a small significant difference between low and high tides, meaning that seasonal wave directions appear clearly in recorded data. During summer, southeasterly waves dominate, and northward longshore drift occurs. In addition, the southward transport of littoral sediment occurs under the northeasterly waves that are dominant during winter. However, recent changes in the coastal environment, due to the development of coastal flooding prevention facilities, harbor development projects, and unusual weather conditions, have shown a tendency to increase the erosion of coastal areas. In other words, there is a repeating cycle of positive feedback, in which structures introduced to prevent a certain kind of coastal erosion cause different kinds of coastal erosion. In this study, we used field survey data to analyze the behavioral characteristics of the Gangmun and Anmok beaches for a period of seven years. The results show that the Gangmun and the Anmok beaches are very vulnerable to the effects of artificial constructs. Coastal erosion on Gangmun beach occurred through northward sediment transportation, caused by a dike that was built to avoid the closure of the mouth of Gyungpo stream. After an artificial reef and the groin were constructed to solve this erosion problem, the coastline stabilized. In the case of the Anmok beach, an imbalance in the sand budget supplied from the Namdae stream was brought about by the expansion of the Gangneung harbor, leading to significant beach erosion. After artificial reefs were installed on both beaches to prevent erosion, the area of each beach was increased and each beach's status was stabilized, as a salient beach.

The tactile display is an important tool to help the human interact with machines by using feels of touch. In this paper, we present a multiply arrayed tactile display device with Dielectric Elastomer Actuator (DEA). The device employs the liquid coupling between the touch spot and the actuator as the transmission of force. It is designed to ensure the comfort of touch and the safety of operation for the users while contacting with the human skin. The operating principle is explained in details, and a systematic design analysis is given. The displacements of tactile display is about 240–120 μm at 3–10 Hz, which satisfies the frequency requirements for simulating the Merkel cells as well as the Meissner corpuscles and the force is over 40 mN to simulate the finger tip. In addition, a dedicated fabrication method and performance measurements are explained.

Organ-on-a-chip engineering aims to create artificial living organs that mimic the complex and physiological responses of real organs, in order to test drugs by precisely manipulating the cells and their microenvironments. To achieve this, the artificial organs should to be microfabricated with an extracellular matrix (ECM) and various types of cells, and should recapitulate morphogenesis, cell differentiation, and functions according to the native organ. A promising strategy is 3D printing, which precisely controls the spatial distribution and layer-by-layer assembly of cells, ECMs, and other biomaterials. Owing to this unique advantage, integration of 3D printing into organ-on-a-chip engineering can facilitate the creation of micro-organs with heterogeneity, a desired 3D cellular arrangement, tissue-specific functions, or even cyclic movement within a microfluidic device. Moreover, fully 3D-printed organs-on-chips more easily incorporate other mechanical and electrical components with the chips, and can be commercialized via automated massive production. Herein, we discuss the recent advances and the potential of 3D cell-printing technology in engineering organs-on-chips, and provides the future perspectives of this technology to establish the highly reliable and useful drug-screening platforms.