title: Shape-memory polymer nanocomposites with a 3D conductive network for bidirectional actuation and locomotion application.
abstract: Electrical stimulation of shape-memory polymers (SMPs) has many advantages over thermal methods; creating an efficient conductive path through the bulk polymers is essential for developing high performance electroactive systems. Here, we show that a three-dimensional (3D) porous carbon nanotube sponge can serve as a built-in integral conductive network to provide internal, homogeneous, in situ Joule heating for shape-memory polymers, thus significantly improving the mechanical and thermal behavior of SMPs. As a result, the 3D nanocomposites show a fast response and produce large exerting forces (with a maximum flexural stress of 14.6 MPa) during shape recovery. We further studied the construction of a double-layer composite structure for bidirectional actuation, in which the shape change is dominated by the temperature-dependent exerting force from the top and bottom layer, alternately. An inchworm-type robot is demonstrated whose locomotion is realized by such bidirectional shape memory. Our large stroke shape-memory nanocomposites have promising applications in many areas including artificial muscles and bionic robots.
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Peng
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Hongqiu
authors.initials: H
authors.lastname: Wei
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Qin
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Zaishan
authors.initials: Z
authors.lastname: Lin
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Xu
authors.initials: X
authors.lastname: Zhao
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Fan
authors.initials: F
authors.lastname: Xu
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Leng
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China. anyuan@pku.edu.cn.
authors.forename: Anyuan
authors.initials: A
authors.lastname: Cao
authors.affiliation: National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P. R. China. liyibin@hit.edu.cn hexd@hit.edu.cn lengjs@hit.edu.cn.
authors.forename: Yibin
authors.initials: Y
authors.lastname: Li