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Design and fabrication of metal-organic-framework based coatings for high fire safety and UV protection, reinforcement and electrical conductivity properties of textile fabrics
No full textRational design and fabrication of multifunctional textile fabrics coatings were developed. The green coatings were facilely prepared from metal-organic-framework UiO-66 as porous crystalline framework which was easily decorated with green spherical polypyrrole nanoparticles of an average size of 165 nm and then wrapped with chitosan chains. The nanocomposites were synthesized in one-step method with the aid of cost-effective ultrasonication method to facilitate the individualization of polypyrrole nanoparticles and their decoration on UiO-66 surface. The as developed coating was then coated on cotton fabrics. The structure and crystalline structure of UiO-66 were elucidated, also the structure and morphological properties of polypyrrole nanoparticles were studied using FT-IR, XRD and SEM. The mass loadings of UiO-66 and polypyrrole nanoparticles were varied and their influence was studied. The flammability, thermal stability, mechanical properties, UV protection and electrical conductivity of coated textiles were studied. The newly developed multifunctional coating affords high flame retardancy to coated cotton fabrics achieving reduction in rate of burning by 54 % compared to uncoated sample. Significant thermal stability was attained recording 23 degrees C increase in temperature of maximum mass loss. Besides, the tensile strength of coated sample achieved 29 % improvement compared to uncoated one. Moreover, outstanding UV protection feature for coated cotton fabrics was obtained recording more than twofold enhancement in ultraviolet protection factor compared to pristine sample. Interestingly, the smart coating layer fabricated on cotton fabrics impregnated the fabrics with electrical conductivity property recording electrical resistance of 2 M omega compared to 45 M omega for pristine fabrics. Additionally, the flame retardancy action was fully studied and elucidated
A Review on Robust Control of Robot Manipulators for Future Manufacturing
No full textRobots are used for many manufacturing tasks, and its prevalence in manufacturing is ever-increasing. Robots in future manufacturing are expected to be valuable and essential tools. It is difficult to control a robot to achieve assigned tasks because of the nonlinear time-varying coupled multi-input multi-output dynamics, nonlinear joint friction being difficult to estimate and compensate for, and variations in payload and in environmental dynamics. Further, from the manufacturing engineers' point of view, the controller needs to be simple and intuitive to understand and implement in practice. One such controller is Time Delay Control, which has been used for more than three decades with many advances. The time-delay estimation allows us to estimate the unknown/uncertain robot dynamics and disturbances by just using the most recent past control torque and acceleration, alleviating the need to identify robot dynamics and/or its parameters for the design of the controller. Time Delay Control can be implemented in industrial controllers allowing only proportional-integral-derivative control thanks to the gain relationship between Time Delay Control and proportional-integral-derivative control; has built-in first-order low-pass filter reducing noise; can be equipped with a simple anti-windup scheme for increasing its stability. A brief comparison of Time Delay Control and Disturbance Observer is also provided for readers who are interested in various robust control. With the introduction and review of the Time Delay Control for a robot, it is expected that the readers' understanding of this robust control is increased and the use of the Time Delay Control in manufacturing becomes prevalent
Folding the Energy Storage: Beyond the Limit of Areal Energy Density of Micro-Supercapacitors
No full textDespite the ever-growing interest in micro-supercapacitors (MSCs) as a promising power source for microelectronics, their low areal energy density has plagued practical applications. Herein, accordion foldable MSCs (af-MSCs) are presented as a cell architectural strategy in contrast to traditional material-driven approaches. The constituent unit cells of an in-plane MSC array are compactly stacked in a confined device footprint via accordion folding. Decoupling the energy storage (MSC cells) and folding section (electrical interconnection between the cells) in the MSC array, in combination with neutral plane-controlled flexible hydrophobic cellulose nanofiber (CNF) substrates, enables the realization of the af-MSCs. The af-MSCs achieve high areal integration density with a fill factor of 81.1% and on-demand (in-series/in-parallel) cell configurations owing to the microscale direct-ink-writing of rheology-tuned MSC cell components on the CNF substrates. The af-MSC with a miniaturized footprint (22.75 mm(2)) achieves exceptional areal electrochemical performances (areal energy density of 89.2 mu Wh cm(-2)), which exceed those of previously reported in-plane MSCs
Bioadhesives based on multifunctional biopolymers for biomedical applications
No full textWith the recent advancement in emerging biomedical engineering fields, such as tissue engineering, regenerative medicine, and wearable medical devices, there is a growing need to develop adhesives that can function not only as tissue sealants for surgery and wound closure, but also attach various biomaterials and devices. These "bioadhesives" should allow refined control of cohesive and adhesive properties, while significantly improving the biocompatibility and biodegradability. For this reason, bioadhesives are being developed using a wide range of natural biopolymers with proven biocompatibility that can also impart multifunctionality either using their innate properties and/ or obtained via various chemical modifications. In this review, state-of-the-art bioadhesives made from multifunctional biopolymers are introduced. [GRAPHICS]
Electrical Transport Properties Driven by Unique Bonding Configuration in ?-GeSe
No full textGroup IV monochalcogenides have recently shown great potential for their thermoelectric, ferroelectric, and other intriguing properties. The electrical properties of group IV monochalcogenides exhibit a strong dependence on the chalcogen type. For example, GeTe exhibits high doping concentration, whereas S/Se-based chalcogenides are semiconduc-tors with sizable bandgaps. Here, we investigate the electrical and thermoelectric properties of gamma-GeSe, a recently identified polymorph of GeSe. gamma-GeSe exhibits high electrical conductivity (similar to 106 S/m) and a relatively low Seebeck coefficient (9.4 mu V/K at room temperature) owing to its high p-doping level (5 x 1021 cm-3), which is in stark contrast to other known GeSe polymorphs. Elemental analysis and first-principles calculations confirm that the abundant formation of Ge vacancies leads to the high p -doping concentration. The magnetoresistance measurements also reveal weak antilocalization because of spin-orbit coupling in the crystal. Our results demonstrate that gamma-GeSe is a unique polymorph in which the modified local bonding configuration leads to substantially different physical properties
A machine learning approach to discover migration modes and transition dynamics of heterogeneous dendritic cells
No full textDendritic cell (DC) migration is crucial for mounting immune responses. Immature DCs (imDCs) reportedly sense infections, while mature DCs (mDCs) move quickly to lymph nodes to deliver antigens to T cells. However, their highly heterogeneous and complex innate motility remains elusive. Here, we used an unsupervised machine learning (ML) approach to analyze long-term, two-dimensional migration trajectories of Granulocyte-macrophage colony-stimulating factor (GMCSF)-derived bone marrow-derived DCs (BMDCs). We discovered three migratory modes independent of the cell state: slow-diffusive (SD), slow-persistent (SP), and fast-persistent (FP). Remarkably, imDCs more frequently changed their modes, predominantly following a unicyclic SD -> FP -> SP -> SD transition, whereas mDCs showed no transition directionality. We report that DC migration exhibits a history-dependent mode transition and maturation-dependent motility changes are emergent properties of the dynamic switching of the three migratory modes. Our ML-based investigation provides new insights into studying complex cellular migratory behavior
Buried Guanidinium Passivator with Favorable Binding Energy for Perovskite Solar Cells
No full textRational design and modification of the buried interface toward high performance perovskite solar cells (PSCs) are highly desired and challenging. Here, we demonstrate a series of guanidinium passivators with multiamine substitutions to shed light on the effective passivation geometry at the SnO2/perovskite heterojunction interface. Comparative theoretical and experimental studies reveal that the binding geometry of the highly polarized imine moiety in guanidinium passivators dominates its energeti-cally favorable passivation on the SnO2 surface, which decreases the trap density to 1.11 x 1016 cm-3 with reduced interior/interface nonradiative recombination in the unsymmetrical aminoguanidine hydrochloride (Agu) platform. Consequently, the PSCs with buried Agu passivator deliver a champion power conversion efficiency (PCE) of 24.4% with an advanced open-circuit voltage (VOC) of 1.197 V and prolonged lifetime over 90% of the initial PCE after 900 h in ambient conditions
Human atlastins are sufficient to drive the fusion of liposomes with a physiological lipid composition
No full textThe dynamin-like GTPase atlastin is believed to be the minimal machinery required for homotypic endoplasmic reticulum (ER) membrane fusion, mainly because Drosophila atlastin is sufficient to drive liposome fusion. However, it remains unclear whether mammalian atlastins, including the three human atlastins, are sufficient to induce liposome fusion, raising doubts about their major roles in mammalian cells. Here, we show that all human atlastins are sufficient to induce fusion when reconstituted into liposomes with a lipid composition mimicking that of the ER. Although the fusogenic activity of ATL1, which is predominantly expressed in neuronal cells, was weaker than that of ATL2 or ATL3, the addition of M1-spastin, a neuron-specific factor, markedly increased ATL1-mediated liposome fusion. Although we observed efficient fusion between ER microsomes isolated from cultured, non-neuronal cells that predominantly express ATL2-1, an autoinhibited isoform of ATL2, ATL2-1 failed to support liposome fusion by itself as reported previously, indicating that cellular factors enable ATL2-1 to mediate ER fusion in vivo. Atlastins regulate the structure and function of the endoplasmic reticulum (ER). In this study, using reconstituted proteoliposomes with a lipid composition mimicking that of the ER, Jang et al. show that all human atlastins are sufficient to drive membrane fusion
All-natural water-resistant paper coated by chitosan nanowhiskers through hydrophilic-to-hydrophobic self-assembly
No full textAlthough chitosan-coated hydrostable papers are promising alternatives to non-degradable plastic-coated papers, an acidic chitosan solution is not eco-friendly. Therefore, we developed a non-acidic aqueous coating technique for preparing all-natural water-resistant papers using chitosan nanowhiskers (CSWs). As the CSWs disperse in water after synthesis, they form a hydrophobic layer on the paper after the coating process owing to the hydrophilic-to-hydrophobic self-assembly. Quantum simulations reveal that the repulsion between protonated amine groups contributes to water dispersibility; however, their interfibrillar interaction after coating is hardly dissociated by water. Together with soybean oil, the CSW- and oil-coated papers (C/O-papers) exhibit significantly higher water contact angles (95.8??) and absorption (6.0%) than control paper (21.9?? and 91.9%, respectively). Moreover, the C/O-papers had a 16.0- and 9.1-fold higher mechanical modulus and strength (1498.5 and 31.0 MPa, respectively) than control paper (93.8 and 3.4 MPa, respectively) under wet conditions. Therefore, bio-renewable water-resistant paper has great potential for preparing disposable materials