In this paper we discuss the transformation of a sheet of material into a wide range of desired shapes and patterns by introducing a set of simple cuts in a multilevel hierarchy with different ...motifs. Each choice of hierarchical cut motif and cut level allows the material to expand into a unique structure with a unique set of properties. We can reverse-engineer the desired expanded geometries to find the requisite cut pattern to produce it without changing the physical properties of the initial material. The concept was experimentally realized and applied to create an electrode that expands to >800% the original area with only very minor stretching of the underlying material. The generality of our approach greatly expands the design space for materials so that they can be tuned for diverse applications.
Sensory neurons generate spike patterns upon receiving external stimuli and encode key information to the spike patterns, enabling energy-efficient external information processing. Herein, we report ...an epifluidic electronic patch with spiking sweat clearance using a sensor containing a vertical sweat-collecting channel for event-driven, energy-efficient, long-term wireless monitoring of epidermal perspiration dynamics. Our sweat sensor contains nanomesh electrodes on its inner wall of the channel and unique sweat-clearing structures. During perspiration, repeated filling and abrupt emptying of the vertical sweat-collecting channel generate electrical spike patterns with the sweat rate and ionic conductivity proportional to the spike frequency and amplitude over a wide dynamic range and long time (> 8 h). With such 'spiking' sweat clearance and corresponding electronic spike patterns, the epifluidic wireless patch successfully decodes epidermal perspiration dynamics in an event-driven manner at different skin locations during exercise, consuming less than 0.6% of the energy required for continuous data transmission. Our patch could integrate various on-skin sensors and emerging edge computing technologies for energy-efficient, intelligent digital healthcare.
The tensile deformation behavior of Al-Mg-Si alloy under a pulsed electric current has been investigated. Specimens subjected to three types of heat treatment, solution treatment, natural aging, and ...artificial aging, are prepared. In solution treated specimens, elongation and flow stress increase when pulsed electric current is applied during plastic deformation; also, the Portevin–Le Chatelier (PLC) phenomenon, which is observed in the tensile test without electric current, nearly disappears when the pulsed electric current is applied. In naturally aged specimens, the flow stress decreases and the elongation significantly increases when pulsed electric current is applied during the tensile test. In artificially aged specimens, both elongation and flow stress decrease under pulsed electric current. The result of XRD analysis shows that thermal and electric current–induced annealing occurs in all specimens subjected to the electric current. Especially in the solution treated specimen, the formation of early stage precipitates from a supersaturated state might be accelerated by the electric current, in an effect distinct from Joule heating; this effect would explain the observed increase in flow stress and the disappearance of the PLC phenomenon. Microstructural observation shows that electric current accelerates the formation of microvoids around the precipitates at the grain boundary, resulting in earlier fracture in the artificially aged specimen. A constitutive model based on dislocation density model and precipitation hardening model is proposed to describe the uniaxial tensile behavior for the age hardening alloys. Based on the experimental findings, the proposed constitutive model is modified to describe the upper boundary of the ratchet shape stress-strain curve under a pulsed electric current. Thermal and electric current-induced annealing with precipitation hardening is considered simultaneously in the modified constitutive model. Phenomenological descriptions of each parameter are demonstrated considering the microstructural features observed in experiments. The modified model is capable of predicting the experimental results very well.
•A tensile deformation behavior of Al-Mg-Si alloy under an electric current is investigated.•Electric current can assist the annealing, aging and void formation during tension.•Constitutive model to describe the non-pulsed and pulsed tensile behavior is proposed.•Constitutive model is able to describe annealing and aging during pulsed tension.
By prescribing asymmetric ligaments with different arrangements in elastomeric porous membranes of pre‐twisted kagome lattices, the buckling instability is avoided, allowing for smooth and homogenous ...structural reconfiguration in a deterministic fashion. The stress–strain behaviors and negative Poisson's ratios can be tuned by the pre‐twisting angles.
With the growing demand for wearable electronics, developing new compatible energy systems is a prominent topic of research. Energy systems mounted on wearable electronics should exhibit high cost ...efficiency, mechanical robustness, and high electrochemical activity. Herein, all‐carbon‐based large‐area nanocomposites for freely deformable electrochemical capacitors are suggested to address these requirements. The three‐dimensionally integrated, self‐supported nanocomposites consist of activated carbons (ACs) distributed in direct spinning‐derived carbon nanotube (DS‐CNT) sheets without any additives, including conducting agents or binders. Owing to synergetic effects of the highly porous AC particles, high electron transport kinetics of CNTs, and facile ion accessibility resulting from acid treatment, the nanocomposites show a greatly improved specific capacitance of 128 F g−1, compared to that of pristine ACs (62 F g−1), based on the total mass of the electrodes. The exceptional mechanical stability of the nanocomposites, which are attached on prestretched elastomer substrates, is confirmed; only a ≈15% increase in the electrical resistance is observed under a tensile strain of 100%, and the initial resistance is fully recovered after releasing. Finally, the outstanding durability and electrochemical performance of the deformable all‐carbon‐based symmetric capacitors under various mechanical deformations of bending, folding, twisting, and stretching are successfully demonstrated.
A new type of mechanically robust electrochemical capacitor for wearable electronics based on all‐carbon‐based self‐supported nanocomposites is suggested. By optimizing the architecture of the 3D nanocomposite structure with activated carbons uniformly embedded in carbon nanotube sheets, outstanding durability and electrochemical performances are demonstrated under extreme mechanical deformations of bending, folding, twisting, and stretching.
Despite many efforts to advance the understanding of nanowire mechanics, a precise characterization of the mechanical behavior and properties of nanowires is still far from standardization. The ...primary objective of this work is to suggest the most appropriate testing method for accurately determining the mechanical performance of silicon nanowires. To accomplish this goal, the mechanical properties of silicon nanowires with a radius between 15 and 70 nm (this may be the widest range ever reported in this research field) are systematically explored by performing the two most popular nanomechanical tests, atomic force microscopy (AFM) bending and nanoindentation, on the basis of different analytical models and testing conditions. A variety of nanomechanical experiments lead to the suggestion that AFM bending based on the line tension model is the most appropriate and reliable testing method for mechanical characterization of silicon nanowires. This recommendation is also guided by systematic investigations of the testing environments through finite element simulations. Results are then discussed in terms of the size‐dependency of the mechanical properties; in the examined range of nanowire radius, the elastic modulus is about 185 GPa without showing significant size dependency, whereas the nanowire strength dramatically increases from 2 to 10 GPa as the radius is reduced.
Nanomechanical
tests are performed on silicon nanowires with radii between 15 and 70 nm based on different analytical models and testing conditions in order to suggest the most appropriate method for determining mechanical performance of nanowires. The investigations also extensively explore size‐dependent mechanical properties.
Heat shock protein 27 (HSP27), induced by heat shock, environmental, and pathophysiological stressors, is a multi-functional protein that acts as a protein chaperone and an antioxidant. HSP27 plays a ...significant role in the inhibition of apoptosis and actin cytoskeletal remodeling. HSP27 is upregulated in many cancers and is associated with a poor prognosis, as well as treatment resistance, whereby cells are protected from therapeutic agents that normally induce apoptosis. This review highlights the most recent findings and role of HSP27 in cancer, as well as the strategies for using HSP27 inhibitors for therapeutic purposes.
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•▪ ZrO2-N bears Lewis acidic Zr4+, Brönsted acidic -OH, and mono-dentate NO3− (NO3-SUP).•▪ NO3-SUP elevates acidic strengths of Zr4+/-OH to lower energy barrier of OH desorption for ...OH → NO3SUP.•▪ ZrO2 and ZrO2-N primarily use OH and NO3SUP in degrading pollutants, respectively.•▪ ZrO2-N enhances efficiency/recyclability over ZrO2 in aromatic degradation with poison accumulation evaded.•▪ ZrO2-N outperforms α-MnO2-N in recycling textile wastewater mineralization with minute Zr leaching.
To advance aqueous pollutant degradation using OH, H2O2 (OH carrier) should be cleaved homolytically on a non-reducible metal oxide (ZrO2) rather than heterolytically on a reducible counterpart (MnO2), given the merits of H2O2 homolysis such as improved OH productivity, unnecessity to recover H2O2 activators (Lewis acidic metals; LA) via electron reduction, and minute LA leaching. This paper presents a methodology to exploit H2O2 homolysis with the rate-determining step of endothermic OH desorption, thereby proposing the coupling of H2O2 homolysis and exothermic radical inter-conversion of OH → NO3SUP (supported NO3) to create the overall OH → NO3SUP route. ZrO2 was modified with NO3− functionalities (NO3SUP precursors) to form ZrO2-N, where NO3-SUP species were located close to Zr4+ (LA) and Brönsted acidic -OH (BA) sites, whose acidic strengths must be elevated to facilitate OH desorption for reducing the energy barrier (EBARRIER) of the overall OH → NO3SUP route. NO3-SUP species were bound to the ZrO2 surface via mono-dentate configuration only, thereby avoiding LA loss (rate in a per-gram↑), escalating LA/BA strengths (EBARRIER↓), and imparting two free oxygens available to OH → NO3SUP (rate in a per-site↑). Moreover, NO3SUP species extract electrons from contaminants via electron transfer to recover NO3-SUP species used for recurring OH → NO3SUP, while sustaining pollutant fragmentation efficiency by circumventing surface poison accumulation. Hence, NO3SUP on ZrO2-N revealed higher efficiencies in fragmenting bisphenol A or recycling phenol degradation than OH evolved from ZrO2. In addition, ZrO2 outperformed MnO2 in exploiting NO3SUP species, thus showing greater recyclability in mineralizing textile wastewater, while leaching a negligible amount of Zr.
Materials that can expand and collapse, fold, and transform into a variety of shapes have attracted significant interest and have applications in the design of flexible electronics, color displays, ...smart windows, actuators, sensors, and both photonic and phononic devices. But how can we render a rigid device super-flexible so that it can wrap around a sphere without bending and stretching? How can flat surfaces be transformed into any desired three-dimensional (3D) structure without disruptive or catastrophic deformation? The key lies in cuts. Here, we review recent research progress in the design of super-conformable and foldable materials by employing fractal cutting and lattice-based kirigami elements that combine cutting and folding. By prescribing cuts with different motifs, identifying edges in the right geometry, and by programming the folding directions, we show that a single flat sheet can be transformed into a variety of targeted 2D and 3D structures—a pluripotent platform for new technologies.
The mechanical behavior of an aluminum alloy under a pulsed electric current was investigated by uniaxial tension and subsequent microstructural observations. The elongation increased drastically ...with softening of the flow stress under the electric current. Microstructural observations confirmed that the effect of Joule heating on this softening is not dominant and the recovery of dislocation occurs at a given current density. This study proves that the electric current itself could play a distinct role in inducing annealing apart from Joule heating.
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