With the rapid development of smart wearable devices, flexible and biodegradable sensors are in urgent needs. In this study, ‘‘green" electrically conductive Ag nanowire (Ag NW)/cellulose nanofiber (CNF) hybrid...With the rapid development of smart wearable devices, flexible and biodegradable sensors are in urgent needs. In this study, ‘‘green" electrically conductive Ag nanowire (Ag NW)/cellulose nanofiber (CNF) hybrid nanopaper was fabricated to prepare flexible sensors using the facial solution blending and vacuum filtration technique. The amphiphilic property of cellulose is beneficial for the homogeneous dispersion of Ag NW to construct effective electrically conductive networks. Two different types of strain sensors were designed to study their applications in strain sensing. One was the tensile strain sensor where the hybrid nanopaper was sandwiched between two thermoplastic polyurethane (TPU) films through hot compression, and special micro-crack structure was constructed through the pre-strain process to enhance the sensitivity. Interestingly, typical pre-strain dependent strain sensing behavior was observed due to different crack densities constructed under different pre-strains. As a result, it exhibited an ultralow detection limit as low as 0.2%, good reproducibility under different strains and excellent stability and durability during 500 cycles (1% strain, 0.5 mm/min). The other was the bending strain sensor where the hybrid nanopaper was adhered onto TPU film, showing stable and recoverable linearly sensing behavior towards two different bending modes (tension and compression). Importantly, the bending sensor displayed great potential for human motion and physiological signal detection. Furthermore, the hybrid nanopaper also exhibited stable and reproducible negative temperature sensing behavior when it was served as a temperature sensor. This study provides a guideline for fabricating flexible and biodegradable sensors.展开更多
文摘碳纤维混杂增强复合材料由于具有重量轻、可设计性强等诸多优点,广泛用于汽车、海洋、航空航天等行业.根据固化剂与环氧树脂的配比化学原理,计算出石墨烯-碳纤维混杂增强树脂基(GO-CF/EP)复合材料的最佳配比为1∶5,并采用真空浸渗热压成型工艺(VIHPS)制备1∶2~1∶7共六个配比的试样,结合形状记忆性能测试及微观形貌的观察,得到固化剂与环氧树脂实际最佳配比.实验结果表明,GO-CF/EP复合材料性能主要取决于体系中交联度的大小,交联度越大,复合材料的形状记忆性能越好,微观组织形貌也较理想.当基体配比为1∶5时,GO-CF/EP复合材料体系中交联度最大,微观形貌呈现均匀致密的状态,形状固定率最大,为95.90%;形状回复率最大,为95.40%;形状回复时间最短,为80.30 s;形状回复力最大,为9.48 N.当基体配比为1∶2或1∶7时,固化剂过量或不足,交联度较小,微观组织形貌中有大量的基体聚集区,其形状记忆性能下降,形状固定率及回复率也相应减小,分别为82.99%,81.66%,81.91%,78.75%;形状回复力分别只有5.20 N和5.50 N.
基金supported by the National Natural Science Foundation of China(51803191)the China Postdoctoral Science Foundation(2018M642782)the 111 project(D18023)
文摘With the rapid development of smart wearable devices, flexible and biodegradable sensors are in urgent needs. In this study, ‘‘green" electrically conductive Ag nanowire (Ag NW)/cellulose nanofiber (CNF) hybrid nanopaper was fabricated to prepare flexible sensors using the facial solution blending and vacuum filtration technique. The amphiphilic property of cellulose is beneficial for the homogeneous dispersion of Ag NW to construct effective electrically conductive networks. Two different types of strain sensors were designed to study their applications in strain sensing. One was the tensile strain sensor where the hybrid nanopaper was sandwiched between two thermoplastic polyurethane (TPU) films through hot compression, and special micro-crack structure was constructed through the pre-strain process to enhance the sensitivity. Interestingly, typical pre-strain dependent strain sensing behavior was observed due to different crack densities constructed under different pre-strains. As a result, it exhibited an ultralow detection limit as low as 0.2%, good reproducibility under different strains and excellent stability and durability during 500 cycles (1% strain, 0.5 mm/min). The other was the bending strain sensor where the hybrid nanopaper was adhered onto TPU film, showing stable and recoverable linearly sensing behavior towards two different bending modes (tension and compression). Importantly, the bending sensor displayed great potential for human motion and physiological signal detection. Furthermore, the hybrid nanopaper also exhibited stable and reproducible negative temperature sensing behavior when it was served as a temperature sensor. This study provides a guideline for fabricating flexible and biodegradable sensors.
