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As an alternative to thermionic X‐ray generators, cold‐cathode X‐ray tubes are being developed for portable and multichannel tomography. Field emission propagating from needle structures such as carbon nanotubes or Si tips currently dominates related research and development, but various obstacles prevent the widespread of this technology. An old but simple electron emission design is the planar tunnelling cathode using a metal–oxide–semiconductor (MOS) structure, which achieves narrow beam dispersion and low supplying voltage. Directly grown vertical graphene (VG) is employed as the gate electrode of MOS and tests its potential as a new emission source. The emission efficiency of the device is initially ≈1% because of unavoidable fabrication damage during the patterning processes; it drastically improves to >40% after ozone treatment. The resulting emission current obeys the Fowler–Nordheim tunnelling model, and the enhanced emission is attributed to the effective gate thickness reduction by ozone treatment. As a proof‐of‐concept experiment, a clustered array of 2140 cells is integrated into a system that provides mA‐class emission current for X‐ray generation. With pulsed digital excitations, X‐ray imaging of a chest phantom, demonstrating the feasibility of using a VG MOS electron emission source as a new and innovative X‐ray generator is realized. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are utilized as essential biomarkers for plant health and the surrounding environmental conditions in light of global imperatives surrounding food security and sustainable agriculture. However, conventional VOC detection methods have inherent limitations related to operational costs, portability, in situ monitoring, and accessibility. Wearable electronic systems have garnered significant attention as an alternative method because of their capability to detect, identify, and quantify VOCs quickly and cost‐effectively. This article presents a comprehensive perspective of recently developed wearable VOC monitoring sensors. It highlights various detection methods for VOCs related to plant metabolism, hormones, and environmental conditions and then multi‐VOC sensing based on data‐driven analysis. Emerging wearable sensor devices are comprehensively examined from the perspectives of material, structural, sensing mechanisms, and plant monitoring demonstration. The principal issues inherent in recently developed VOC monitoring techniques are discussed, and potential avenues for future research and development are identified. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have emerged as promising portable and sustainable energy sources in daily life, harvesting energy from human motion, water, and wind. However, they still face limitations in aspects such as contact area, deformability, wettability, and manufacturing method. Here, a wearable TENG incorporating an anisotropic domino structure based on a fluorinated elastomer blend is presented. Because of its thin, elongated structure with broad sides, the TENG achieves substantially larger contact areas and high bendability. Introducing a fluorinated elastomer into the polydimethylsiloxane matrix via a simple blending process not only enhances the triboelectric performance but also reduces surface energy and improves the stretchability of elastomers. The anisotropic arrangement of dominoes, in synergy with the fluorinated elastomer, mimics the surface physicochemical properties of natural rice leaves, resulting in anisotropic superhydrophobic wetting behavior with a self‐cleaning effect and controlled directional water flow for efficient water energy harvesting. Therefore, the TENG functions as an energy‐harvesting leaf that captures energy from wind and water droplets, as well as a wearable energy‐harvesting wristband that generates power from human motions such as touching, shaking, and hand washing. [ABSTRACT FROM AUTHOR]

Biosensors are analytical tools for monitoring various parameters related to living organisms, such as humans and plants. Liquid metals (LMs) have emerged as a promising new material for biosensing applications in recent years. LMs have attractive physical and chemical properties such as deformability, high thermal and electrical conductivity, low volatility, and low viscosity. LM‐based biosensors represent a new strategy in biosensing particularly for wearable and real‐time sensing. While early demonstrations of LM biosensors focus on monitoring physical parameters such as strain, motion, and temperature, recent examples show LM can be an excellent sensing material for biochemical and biomolecular detection as well. In this review, the recent progress of LM‐based biosensors for personalized healthcare and disease monitoring via both physical and biochemical signaling is survey. It is started with a brief introduction of the fundamentals of biosensors and LMs, followed by a discussion of different mechanisms by which LM can transduce biological or physiological signals. Next, it is reviewed example LM‐based biosensors that have been used in real biological systems, ranging from real‐time on‐skin physiological monitoring to target‐specific biochemical detection. Finally, the challenges and future directions of LM‐integrated biosensor platforms is discussed. [ABSTRACT FROM AUTHOR]

Rubbing‐induced alignment of conjugated polymers is systematically investigated in terms of intra‐ and inter‐molecular interaction. Various polymer films with a broad range of polymer chain rigidity are rubbed, and the degree of polymer chain alignment is quantitatively characterized. The rubbing technique effectively aligns crystalline domains in conjugated polymer films when the temperature approaches the critical rubbing temperature (Trc$T_{\mathrm{r}}^{\mathrm{c}}$), at which the rearrangement and the slip of polymer chains are possible. A polymer with significant intra‐/inter‐molecular interactions exhibits higher Trc$T_{\mathrm{r}}^{\mathrm{c}}$, though quantitative analysis reveals an intermediately aligned state at temperature Tr′ lower than Trc$T_{\mathrm{r}}^{\mathrm{c}}$. This state originates from polymer chain aggregation in an amorphous domain. The intermediately aligned state can be controlled by plasticizer, which enables low‐temperature alignment of high‐mobility polymer film by reducing Tr′ to near 100 °C, increases the crystallinity, and improves the alignment effect at this state comparable to that of the completely aligned state obtained at extremely high temperatures. [ABSTRACT FROM AUTHOR]