Fabrication of bagel-like graphene aerogels and its application in pressure sensors

In this study, a new bagel-like graphene aerogel composed of graphene sheets is reported. This bagel-like graphene aerogel was fabricated by a droplet containing graphene oxide sheets, which had an impact on the coagulation bath of the mixed ethanol and hydrochloric acid. During the impact process, the graphene oxide droplet locked the ripple of the coagulation bath while forming a special structure with the stagnating ripple, which was gradually transformed into a bagel-like graphene oxide hydrogel. Then, this graphene oxide hydrogel was processed by reduction and freeze drying to obtain a small and light-weight bagel-like graphene aerogel. As characterized by Raman spectrum, XRD and XPS, we confirmed that graphene oxide sheets were effectively reduced. The excellent electrical conductivity and stable mechanical properties of this bagel-like graphene aerogel were experimentally measured. We found that it could be applied as piezoresistive pressure sensors with high sensitivity at low pressure, wide measurement range and good stability. As confirmed by SEM, this outstanding sensing property was attributed to the aerogel's special lamellar multi-layered microstructure, which played a key role in the piezoresistive working mechanism.