Advanced soft ion-conducting hydrogels have been developed rapidly in the integrated portable health monitoring equipment due to their higher sensitivity, sensory traits, tunable conductivity, and stretchability for physiological activities and personal healthcare detection. However, traditional hydrogel conductors are normally susceptible to large deformation and strong mechanical stress, which leads to inferior electro-mechanical stability for real application scenarios. Herein, a strong ionically conductive hydrogel (poly(vinyl alcohol)-boric acid-glycerol/sodium alginate-calcium chloride/electrolyte ions (PBG/SC/EI)) was designed by engineering the covalently and ionically crosslinked networks followed by the salting-out effect to further enhance the mechanical strength and ionic conductivity of the hydrogel. Owing to the collective effects of the energy-dissipation mechanism and salting-out effect, the designed PBG/SC/EI with excellent structural integrity and robustness exhibits exceptional mechanical properties (elongation at break for 559.1% and tensile strength of 869.4 kPa) and high ionic conductivity (1.618 S·m⁻¹). As such, the PBG/SC/EI strain sensor features high sensitivity (gauge factor = 2.29), which can effectively monitor various kinds of human motions (joint motions, facial micro-expression, faint respiration, and voice recognition). Meanwhile, the hydrogel-based Zn||MnO₂ battery delivers a high capacity of 267.2 mAh·g⁻¹ and a maximal energy density of 356.8 Wh·kg⁻¹ associated with good cycle performance of 71.8% capacity retention after 8000 cycles. Additionally, an integrated bio-monitoring system with the sensor and Zn||MnO₂ battery can accurately identify diverse physiological activities in a real-time and non-invasive way. This work presents a feasible strategy for designing high-performance conductive hydrogels for highly-reliable integrated bio-monitoring systems with excellent practicability.

When a laser beam writes on a metallic film, it usually coarsens and deuniformizes grains because of Ostwald ripening, similar to the case of annealing. Here we show an anomalous refinement effect of metal grains: A metallic silver film with large grains melts and breaks into uniform, close-packed, and ultrafine (~ 10 nm) grains by laser direct writing with a nanoscale laser spot size and nanosecond pulse that causes localized heating and adaptive shock-cooling. This method exhibits high controllability in both grain size and uniformity, which lies in a linear relationship between the film thickness (h) and grain size (D), D ∝ h. The linear relationship is significantly different from the classical spinodal dewetting theory obeying a nonlinear relationship (D ∝ h^5/3) in common laser heating. We also demonstrate the application of such a silver film with a grain size of ~ 10.9 nm as a surface-enhanced Raman scattering chip, exhibiting superhigh spatial-uniformity and low detection limit down to 10⁻¹⁵ M. This anomalous refinement effect is general and can be extended to many other metallic films.

Growth of high-quality large-sized crystals using the traditional chemical vapor transport (CVT) or vertical Bridgman (VB) technique is costly and time-consuming, limiting its practical industrial application. Here, we propose an ultrafast crystal growth process with low energy consumption and capability of producing crystals of excellent quality, and demonstrate that large-sized GaSe crystals with a lateral size of 0.5 to 1 cm can be obtained within a short period of 5 min. X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) studies clearly indicate that the as-grown crystals have a good crystallinity. To further show the potential application of the resulting GaSe crystals, we fabricate the few-layer GaSe-based photodetector, which exhibits low dark current of 21 pA and fast response of 34 ms under 405 nm illumination. Our proposed technique for rapid crystal growth could be further extended to other metallenes with low-melting point, such as Bi-, Sn-, In-, Pb-based crystals, opening up a new avenue in fulfilling diverse potential optoelectronics applications of two-dimensional (2D) crystals.