Wearable electronics are attracting increasing attention as recent developments in materials, mechanics, and manufacturing techniques create new opportunities for the integration of high-quality electronic systems into a single miniaturized Continuous monitoring of human physiological signals is critical to managing personal healthcare by early detection of health disorders. Wearable and implantable devices are attracting growing attention as they show great potential for real-time recording of physiological conditions and body motions. Conventional piezoelectric sensors have the advantage of potentially being self-powered, but have limitations due to their intrinsic lack of stretchability. Herein, a kirigami approach to realize a novel stretchable strain sensor is introduced through a network of cut patterns in a piezoelectric thin film, exploiting the anisotropic and local bending that the patterns induce. The resulting pattern simultaneously enhances the electrical performance of the film and its stretchability while retaining the mechanical integrity of the underlying materials. The power output is enhanced from the mechanoelectric piezoelectric sensing effect by introducing an intersegment, through-plane, electrode pattern. By additionally integrating wireless electronics, this sensing network could work in an entirely battery-free mode. The kirigami stretchable piezoelectric sensor is demonstrated in cardiac monitoring and wearable body tracking applications. The integrated soft, stretchable, and biocompatible sensor demonstrates excellent in vitro and ex vivo performances and provides insights for the potential use in myriad biomedical and wearable health monitoring applications.
Graphite‐derived carbon materials have been widely used in metal‐ion batteries due to their good mechanical and electrical properties, cost effectiveness, light weight, and environmental friendliness. Though natural graphite has been commercially used in lithium‐ion batteries, the small interlayer spacing hinders its application in other metal‐ion batteries. As such, numerous works have been done to enhance the metal‐ion storage capability of graphite and its derivatives. In this review, structural engineering on graphite including expanded graphite, graphite intercalation compounds and porous graphite, and the corresponding electrolyte engineering for lithium‐ion batteries, sodium ion batteries, potassium ion batteries, and dual ion batteries are summarized, aiming to make a comparison between various strategies and give a suggestion on future work in this area.
This paper presents a three-dimensional micro-mechanical finite element (FE) modelling strategy for predicting the mixed-mode response of single Z-pins inserted in a composite laminate. The modelling approach is based upon a versatile ply-level mesh, which takes into account the significant micromechanical features of Z-pinned laminates. The effect of post-cure cool down is also considered in the approach. The Z-pin/laminate interface is modelled by cohesive elements and frictional contact. The progressive failure of the Z-pin is simulated considering shear-driven internal splitting, accounted for using cohesive elements, and tensile fibre failure, modelled using the Weibull's criterion. The simulation strategy is calibrated and validated via experimental tests performed on single carbon/BMI Z-pins inserted in quasi-isotropic laminate. The effects of the bonding and friction at the Z-pin/laminate interface and the consequences of the internal Z-pin splitting are discussed in detail. The primary aim is to develop a robust numerical tool, as well as guidelines for designing Z-pins with optimal bridging behaviour. .
3D chiral color printing displays a color image under left-handed circular-polarized light, while revealing a different appearance under right-handed light.
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