Softening of thermoelectric generators facilitates conformal contact with arbitrary-shaped heat sources, which offers an opportunity to realize self-powered wearable applications. However, existing ...wearable thermoelectric devices inevitably exhibit reduced thermoelectric conversion efficiency due to the parasitic heat loss in high-thermal-impedance polymer substrates and poor thermal contact arising from rigid interconnects. Here, we propose compliant thermoelectric generators with intrinsically stretchable interconnects and soft heat conductors that achieve high thermoelectric performance and unprecedented conformability simultaneously. The silver-nanowire-based soft electrodes interconnect bismuth-telluride-based thermoelectric legs, effectively absorbing strain energy, which allows our thermoelectric generators to conform perfectly to curved surfaces. Metal particles magnetically self-assembled in elastomeric substrates form soft heat conductors that significantly enhance the heat transfer to the thermoelectric legs, thereby maximizing energy conversion efficiency on three-dimensional heat sources. Moreover, automated additive manufacturing paves the way for realizing self-powered wearable applications comprising hundreds of thermoelectric legs with high customizability under ambient conditions.
Although three-dimensional (3D) bioprinting technology has gained much attention in the field of tissue engineering, there are still several significant engineering challenges to overcome, including ...lack of bioink with biocompatibility and printability. Here, we show a bioink created from silk fibroin (SF) for digital light processing (DLP) 3D bioprinting in tissue engineering applications. The SF-based bioink (Sil-MA) was produced by a methacrylation process using glycidyl methacrylate (GMA) during the fabrication of SF solution. The mechanical and rheological properties of Sil-MA hydrogel proved to be outstanding in experimental testing and can be modulated by varying the Sil-MA contents. This Sil-MA bioink allowed us to build highly complex organ structures, including the heart, vessel, brain, trachea and ear with excellent structural stability and reliable biocompatibility. Sil-MA bioink is well-suited for use in DLP printing process and could be applied to tissue and organ engineering depending on the specific biological requirements.
Bioprinting researchers agree that “printability” is a key characteristic for bioink development, but neither the meaning of the term nor the best way to experimentally measure it has been ...established. Furthermore, little is known with respect to the underlying mechanisms which determine a bioink’s printability. A thorough understanding of these mechanisms is key to the intentional design of new bioinks. For the purposes of this review, the domain of printability is defined as the bioink requirements which are unique to bioprinting and occur during the printing process. Within this domain, the different aspects of printability and the factors which influence them are reviewed. The extrudability, filament classification, shape fidelity, and printing accuracy of bioinks are examined in detail with respect to their rheological properties, chemical structure, and printing parameters. These relationships are discussed and areas where further research is needed, are identified. This review serves to aid the bioink development process, which will continue to play a major role in the successes and failures of bioprinting, tissue engineering, and regenerative medicine going forward.
Nonalcoholic fatty liver disease (NAFLD) has been associated with relative skeletal muscle mass in several cross‐sectional studies. We explored the effects of relative skeletal muscle mass and ...changes in relative muscle mass over time on the development of incident NAFLD or the resolution of baseline NAFLD in a large, longitudinal, population‐based 7‐year cohort study. We included 12,624 subjects without baseline NAFLD and 2943 subjects with baseline NAFLD who underwent health check‐up examinations. A total of 10,534 subjects without baseline NAFLD and 2631 subjects with baseline NAFLD were included in analysis of changes in relative skeletal muscle mass over a year. Subjects were defined as having NAFLD by the hepatic steatosis index, a previously validated NAFLD prediction model. Relative skeletal muscle mass was presented using the skeletal muscle mass index (SMI), a measure of body weight–adjusted appendicular skeletal muscle mass, which was estimated by bioelectrical impedance analysis. Of the 12,624 subjects without baseline NAFLD, 1864 (14.8%) developed NAFLD during the 7‐year follow‐up period. Using Cox proportional hazard analysis, compared with the lowest sex‐specific SMI tertile at baseline, the highest tertile was inversely associated with incident NAFLD (adjusted hazard ratio AHR = 0.44, 95% confidence interval CI = 0.38‐0.51) and positively associated with the resolution of baseline NAFLD (AHR = 2.09, 95% CI = 1.02‐4.28). Furthermore, compared with the lowest tertile of change in SMI over a year, the highest tertile exhibited a significant beneficial association with incident NAFLD (AHR = 0.69, 95% CI = 0.59‐0.82) and resolution of baseline NAFLD (AHR = 4.17, 95% CI = 1.90‐6.17) even after adjustment for baseline SMI. Conclusion: Increases in relative skeletal muscle mass over time may lead to benefits either in the development of NAFLD or the resolution of existing NAFLD.
Coastal areas have been affected by hazards such as floods and storms due to the impact of climate change. As coastal systems continue to become more socially and environmentally complex, the damage ...these hazards cause is expected to increase and intensify. To reduce such negative impacts, vulnerable coastal areas and their associated risks must be identified and assessed. In this study, we assessed the flooding risk to coastal areas of South Korea using multiple machine learning algorithms. We predicted coastal areas with high flooding risks, as this aspect has not been adequately addressed in previous studies. We forecasted hazards under different representative concentration pathway climate change scenarios and regional climate models while considering ratios of sea level rise. Based on the results, a risk probability map was developed using a probability ranging from 0 to 1, where higher values of probability indicate areas at higher risk of compound events such as high tides and heavy rainfall. The accuracy of the average receiver operating characteristic curves was 0.946 using a k-Nearest Neighbor algorithm. The predicted risk probability in 10 year increments from the 2030s to the 2080s showed that the risk probability for southern coastal areas is higher than those of the eastern and western coastal areas. From this study, we determined that a probabilistic approach to analyzing the future risk of coastal flooding would be effective to support decision-making for integrated coastal zone management.
Forthcoming smart energy era is in strong pursuit of full‐fledged rechargeable power sources with reliable electrochemical performances and shape versatility. Here, as a naturally ...abundant/environmentally friendly cellulose‐mediated cell architecture strategy to address this challenging issue, a new class of hetero‐nanonet (HN) paper batteries based on 1D building blocks of cellulose nanofibrils (CNFs)/multiwall carbon nanotubes (MWNTs) is demonstrated. The HN paper batteries consist of CNF/MWNT‐intermingled heteronets embracing electrode active powders (CM electrodes) and microporous CNF separator membranes. The CNF/MWNT heteronet‐mediated material/structural uniqueness enables the construction of 3D bicontinuous electron/ion transport pathways in the CM electrodes, thus facilitating electrochemical reaction kinetics. Furthermore, the metallic current collectors‐free, CNF/MWNT heteronet architecture allows multiple stacking of CM electrodes in series, eventually leading to user‐tailored, ultrathick (i.e., high‐mass loading) electrodes far beyond those accessible with conventional battery technologies. Notably, the HN battery (multistacked LiNi0.5Mn1.5O4 (cathode)/multistacked graphite (anode)) provides exceptionally high‐energy density (=226 Wh kg−1 per cell at 400 W kg−1 per cell), which surpasses the target value (=200 Wh kg−1 at 400 W kg−1) of long‐range (=300 miles) electric vehicle batteries. In addition, the heteronet‐enabled mechanical compliance of CM electrodes, in combination with readily deformable CNF separators, allows the fabrication of paper crane batteries via origami folding technique.
CNFs/CNTs‐based hetero‐nanonet paper batteries are presented as a 1D material‐mediated cell architecture strategy to enable ultrahigh energy density and shape versatility far beyond those achievable with conventional battery technologies. Owing to the 3D bicontinuous electron/ion transport pathways and exceptional mechanical compliance, the hetero‐nanonet paper batteries provide unprecedented improvements in the electrochemical reaction kinetics, energy density, and origami foldability.
Increase in incident light and surface modification of the charge transport layer are powerful routes to achieve high‐performance efficiency of perovskite solar cells (PSCs) by improving the ...short‐circuit current density (JSC) and charge transport characteristics, respectively. However, few techniques are studied to reduce reflection loss and simultaneously improve the electrical performance of the electron transport layer (ETL). Herein, an inclined fluorine (F) sputtering process to fabricate high‐performance PSCs is proposed. The proposed process simultaneously implements the antireflection effect of F coating and the effect of F doping on a TiO2 ETL, which increases the amount of light transmitted into the PSC due to the extremely low refractive index (≈1.39) and drastically improves the electrical properties of TiO2. Consequently, the JSC of the F coating and doping perovskite solar cell (F‐PSC) increased from 25.05 to 26.01 mA cm−2, and the power conversion efficiency increased from 24.17% to 25.30%. The unencapsulated F‐PSC exhibits enhanced air stability after 900 h of exposure to ambient environment atmosphere (30% relative humidity, 25 °C under dark condition). The inclined F sputtering process in this study can become a universal method for PSCs from the development stage to commercialization in the future.
The inclined fluorine (F) sputtering process can simultaneously implement an antireflection effect of F coating and the F doping effect on TiO2 electron transport layer. Consequently, the short‐circuit current density of F coating and doping perovskite solar cell is improved from 25.05 to 26.01 mA cm−2, and the power conversion efficiency increases from 24.17% to 25.30%.
A bioengineered skeletal muscle tissue as an alternative for autologous tissue flaps, which mimics the structural and functional characteristics of the native tissue, is needed for reconstructive ...surgery. Rapid progress in the cell-based tissue engineering principle has enabled in vitro creation of cellularized muscle-like constructs; however, the current fabrication methods are still limited to build a three-dimensional (3D) muscle construct with a highly viable, organized cellular structure with the potential for a future human trial. Here, we applied 3D bioprinting strategy to fabricate an implantable, bioengineered skeletal muscle tissue composed of human primary muscle progenitor cells (hMPCs). The bioprinted skeletal muscle tissue showed a highly organized multi-layered muscle bundle made by viable, densely packed, and aligned myofiber-like structures. Our in vivo study presented that the bioprinted muscle constructs reached 82% of functional recovery in a rodent model of tibialis anterior (TA) muscle defect at 8 weeks of post-implantation. In addition, histological and immunohistological examinations indicated that the bioprinted muscle constructs were well integrated with host vascular and neural networks. We demonstrated the potential of the use of the 3D bioprinted skeletal muscle with a spatially organized structure that can reconstruct the extensive muscle defects.
Polymer-based pressure sensors play a key role in realizing lightweight and inexpensive wearable devices for healthcare and environmental monitoring systems. Here, conductive core/shell polymer ...nanofibers composed of poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP)/poly(3,4-ethylenedioxythiophene) (PEDOT) are fabricated using three-dimensional (3D) electrospinning and vapor deposition polymerization methods, and the resulting sponge-like 3D membranes are used to create piezoresistive-type pressure sensors. Interestingly, the PEDOT shell consists of well-dispersed spherical bumps, leading to the formation of a hierarchical conductive surface that enhances the sensitivity to external pressure. The sponge-like 3D mats exhibit a much higher pressure sensitivity than the conventional electrospun 2D mats due to their enhanced porosity and pressure-tunable contact area. Furthermore, large-area, wireless, 16 × 10 multiarray pressure sensors for the spatiotemporal mapping of multiple pressure points and wearable bands for monitoring blood pressure have been fabricated from these 3D mats. To the best of our knowledge, this is the first report of the fabrication of electrospun 3D membranes with nanoscopically engineered fibers that can detect changes in external pressure with high sensitivity. The developed method opens a new route to the mass production of polymer-based pressure sensors with high mechanical durability, which creates additional possibilities for the development of human–machine interfaces.
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