Cheng Han,Huan Zhang,Quan Chen,Tao Li,Lingjian Kong,Hui Zhao,Lirong He
Directional sensors endowed by inherent anisotropic structure have drawn great attention in intelligent sensing systems. Unidirectional lyophilization is the mainstream technique to architect anisotropic structure particularly for water dispersible systems as the ice template can be readily removed at the melting point of water (0 °C). However, it is impractical for water insoluble polymers such as piezoelectric polymer systems as it features extremely low lyophilization temperature (for instance, −61 °C). So far, no piezoelectric polymer derived anisotropic devices has been realized. In this work, for the first time, we succeeded the constructing of anisotropic PVDF/Mxene device with directionally oriented micropores through delicate formulation design which enables the maintaining of oriented template even at temperature above 0 °C. As a result, the as-fabricated PVDF/Mxene composite foam exhibits distinct anisotropic behavior, featuring compressive modulus along the direction of penetrating microchannels being approximately 1.7 times of that in the orthogonal direction. The anisotropic foam is applied as directional sensor with piezo-current as the output signal, which displays a 3.93-fold higher sensitivity difference in the direction perpendicular to the microchannel than in its orthogonal direction. Moreover, the foam exhibits the highest sensitivity of 41.3nA/kPa over pressure range of 2.5–20 kPa, which outperforms state-of-the-art polymer piezoelectric sensors. This novel strategy provides a practical avenue for architecting water-insoluble polymer-derived devices with anisotropic structure in a green and energy-saving manner, which could spur innovations from the fields of electromagnetic interference shielding, energy storage, piezoresistive, thermal insulation and so on wherever anisotropic characteristic is desired.
Hydrogel-based interfacial evaporators have demonstrated effective solar evaporation performance for supplying clean water. However, balancing a high evaporation rate, salt-resistant performance, and enhanced mechanical properties remains challenging. Herein, through structural design and chemical modification, a robust and salt-resistant hydrogel evaporator comprising interconnected directional micropores with excellent desalination performance is fabricated by the strategy of sacrificial template-assisted solvent exchange and directional vertical freezing. The hydrogels can withstand cyclic compression and stabilize shape in 3.5–20 % salt solutions. Due to the pores' high porosity and low tortuosity, the evaporator possesses an evaporation rate of 3.12 kg m −2 h −1 under one sun illumination. In addition, since a zwitterionic polymer is used to improve the salt-resistant performance, no salt deposition was observed on the surface of hydrogel evaporators after 8 h irradiation in a 20 wt% salt solution. The durability and practicability of the evaporators are also evaluated through purification experiments among various contaminants and outdoor evaluations. It is anticipated that the zwitterionic polymer-modified directional porous hydrogel evaporators will provide a viable solution to the shortage of freshwater resources and play a significant role in promoting the development of seawater desalination.
危险品化学品经营许可证（带存储）