Hydrogels are soft–wet materials with a hydrophilic three-dimensional network structure offering controllable stretchability, conductivity, and biocompatibility. However, traditional conductive hydrogels only operate in mild environments and exhibit poor environmental tolerance due to their high water content and hydrophilic network, which result in undesirable swelling, susceptibility to freezing at sub-zero temperatures, and structural dehydration through evaporation. The application range of conductive hydrogels is significantly restricted by these limitations. Therefore, developing environmentally tolerant conductive hydrogels (ETCHs) is crucial to increasing the application scope of these materials. In this review, we summarize recent strategies for designing multifunctional conductive hydrogels that possess anti-freezing, anti-drying, and anti-swelling properties. Furthermore, we briefly introduce some of the applications of ETCHs, including wearable sensors, bioelectrodes, soft robots, and wound dressings. The current development status of different types of ETCHs and their limitations are analyzed to further discuss future research directions and development prospects.

To address the growing need for high-frequency tunable surface acoustic wave (SAW) devices in power ultrasound applications, this study uses finite element method (FEM) for designing and simulation of an AlN/GaN composite heterogeneous piezoelectric thin film structure fabricated on a sapphire substrate. The configuration employs a double piezoelectric layer approach to significantly improve electromechanical conversion efficiency, achieving an electromechanical coupling coefficient of 0.42%. The thickness of AlN/GaN is optimized to enable a systematic investigation of the dispersion characteristics and acoustic field distribution of Rayleigh and Sezawa waves within multilayer heterostructures. This optimization aims to facilitate the precision of ultrasonic fields, enhancing the high-frequency ultrasonic power density and the local acoustic field intensity. Simultaneously, the incorporation of SiO₂ compensation layer into the AlN/GaN heterostructure results in the formation of periodic structure that exploits disparities in sound velocity and acoustic impedance. This facilitates enhanced acoustic energy, which significantly improves both the cavitation efficiency and the intensity of acoustic flow within the liquid-phase medium. The structured surface acoustic wave (SAW) devices exhibit high-frequency characteristics coupled with low insertion loss, rendering them highly suitable for deployment in high-power SAW microfluidic platforms aimed at achieving efficient liquid-phase microfluidic material transport and manipulation. These findings hold substantial value for the advancement of novel high-frequency power ultrasound devices, providing critical insights and implications for expanding the applications within the domains of microfluidics and biomedical acoustic manipulation.

用固相反应法制备了B位空位补偿型钐掺杂非准同型相界组分PZT (54/46)陶瓷。通过正电子湮没寿命谱（PALS）和符合多普勒展宽能谱（CDBS）对陶瓷中的缺陷结构进行综合表征，结合常规表征手段如XRD、SEM、介电、铁电和压电性能测量，研究缺陷对陶瓷压电性能的影响。XRD结果显示所有陶瓷均为纯钙钛矿相，掺杂诱导了菱方-四方（R-T）相变，准同型相界位于Sm掺杂量x=0.01-0.02。电学测量结果反映：介电、铁电和压电性能均先增强后减弱，MPB附近两个样品都有优异的介电和铁电性能，但其压电性能差别很大。x=0.01给出最优压电性能d₃₃=572pC/N，较未掺杂样品增强了一倍。PALS结果表明掺杂使陶瓷中缺陷类型发生变化，x≤0.01，样品中同时含有A位空位与B位空位； x≥0.02，样品中以A位相关缺陷为主，B位空位浓度很低。CDBS结果进一步证实x=0.01和0.02中B位空位浓度分别是该体系中最高和最低的。由以上结果推断出x=0.01获得的最优压电性能与其中较高浓度的B位空位有关，B位空位可稀释A位空位浓度，降低氧空位浓度，从而降低A位空位与氧空位形成缺陷偶极子的几率，促进畴壁运动，使压电性能增强。