▎ 摘　　要

Graphene fibers attract tremendous interest due to their huge potentials in energy devices, pressure sensors, and electro-heaters. However, there still remain some challenges to prepare robust ultralight graphene fibers by a dry spinning strategy due to the low aspect ratio, poor entanglements and high surface tension of graphene sheets. Here, we present a facile and green dry twist-spinning assembly strategy to prepare ultralight graphene fibers with hierarchical structure. Because of hierarchical assembly, stronger entanglements of graphene nanoscrolls endow ultralight graphene fibers high mechanical strength of similar to 3.9 +/- 0.5 MPa. Such light graphene fibers show high specific electrical conductivity of 0.95-1.67 S m(2) g(-1) and specific thermal conductivity of 42.3-100 W cm(2) K-1 g(-1), which are comparative to that of copper and silver. Therefore, they exhibit ultrafast electro-thermal response (5943 K s(-1)), which exceeds the record value of carbon nanotube (CNT) film ever reported (3500 K s(-1)). Such facile and green dry spinning strategy offers new opportunity to prepare and apply the ultralight graphene fibers. (C) 2019 Elsevier Ltd. All rights reserved.