He Xiaowei, Liu Qiongzhen, Zhong Weibing, Chen Jiahui, Sun Dengming, Jiang Haiqing, Liu Ke, Wang Wenwen, Wang Yuedan, Lu Zhentan, Li Mufang, Liu Xue, Wang Xiaojun, Sun Gang, Wang Dong
Hubei Key Laboratory of Advanced Textile Materials & Application , Wuhan Textile University , Wuhan 430200 , China.
Division of Textiles and Clothing , University of California , Davis , California 95616 , United States.
ACS Appl Mater Interfaces. 2019 May 29;11(21):19350-19362. doi: 10.1021/acsami.9b02591. Epub 2019 May 14.
Three-dimensional (3D) graphene aerogels (GAs) have attracted huge attention from researchers due to their great potential in vast applications. The hydrothermal reaction combined with freeze-drying using graphene oxide (GO) as a precursor has proven to be an effective method for obtaining relatively well-structured pure GAs. However, insufficient mechanical strength and low compressibility of the materials still limit their practical applications. Here, we report the microstructure-induced strong mechanical anisotropy of these monolithic GAs in transverse direction (TD) and longitudinal direction (LD), which has never been considered to be related to structural vulnerability. To overcome this anisotropy and enhance the structure, we hereby introduce our self-made poly(vinyl alcohol)- co-polyethylene (PVA- co-PE) nanofibers and low-molecular weight PVA as structural enhancers into the original 3D network to form a novel nanofiber-graphene composite aerogel. Intriguingly, a unique configuration is formed in the GA, in which the highly aligned stacked reduced GO sheets serve as the framework (cellular walls) and the nanofibers act as cross-linking columns anchored between the walls to support the structure along the TD, whereas the micro/nanosized PVA lamellae serve as binders. The resulting aerogel (referred to as graphene-PVA- co-PE nanofibers-PVA aerogel (GNPA)) has excellent compressive resilience along the TD and exhibits an ultrahigh gauge factor (14387%) at a very subtle strain (0.23%) in piezoresistive properties. The GNPA-TD has also been assembled into a variety of wearable sensors and demonstrates great potential for wireless human pressure sensing. In short, this study offers an extremely simple and effective method for developing graphene aerogels with a strong mechanical structure and paves the way for the application of 3D graphene in wearable sensors.
三维（3D）石墨烯气凝胶（GAs）因其在众多应用中的巨大潜力而备受研究人员关注。以氧化石墨烯（GO）为前驱体，通过水热反应结合冷冻干燥已被证明是获得结构相对良好的纯GAs的有效方法。然而，材料的机械强度不足和压缩性低仍然限制了它们的实际应用。在此，我们报道了这些整体式GAs在横向（TD）和纵向（LD）上由微观结构引起的强机械各向异性，而这种各向异性从未被认为与结构脆弱性有关。为了克服这种各向异性并增强结构，我们在此将自制的聚乙烯醇 - 共聚乙烯（PVA - co - PE）纳米纤维和低分子量PVA作为结构增强剂引入原始的3D网络中，以形成一种新型的纳米纤维 - 石墨烯复合气凝胶。有趣的是，在GA中形成了一种独特的结构，其中高度排列堆叠的还原GO片层作为框架（细胞壁），纳米纤维作为交联柱锚固在壁之间以沿TD方向支撑结构，而微米/纳米尺寸的PVA薄片作为粘合剂。所得气凝胶（称为石墨烯 - PVA - co - PE纳米纤维 - PVA气凝胶（GNPA））在TD方向上具有出色的压缩弹性，并且在压阻特性中，在非常微小的应变（0.23％）下表现出超高的应变系数（14387％）。GNPA - TD还被组装成各种可穿戴传感器，并在无线人体压力传感方面显示出巨大潜力。简而言之，本研究提供了一种极其简单有效的方法来开发具有强大机械结构的石墨烯气凝胶，并为3D石墨烯在可穿戴传感器中的应用铺平了道路。
