title: Growth of a Large-Area, Free-Standing, Highly Conductive and Fully Foldable Silver Film with Inverted Pyramids for Wearable Electronics Applications.
abstract: A promising new concept is the application of flexible and foldable conductive film or paper for wearable electronics, in which silver nanowires, carbon nanotubes, and graphene are primarily used as conductive materials. However, their insufficient nanostructure contacts lead to poor electrical conductivity and mechanical fracture. Here, we demonstrate a simple and innovative strategy for fabricating a free-standing silver film with inverted pyramids by replicating pyramids on a textured silicon wafer under a hydrothermal reaction. In this unique structure, the inverted pyramids on the film surface can provide sufficient buffer space for a mechanically foldable and unfoldable cushion, and the continuous film ensures an uninterrupted electron transport pathway. As a result, the silver film with inverted pyramids can exhibit extremely high conductivity, with a sheet resistance as low as 2.55 × 10-3Ω/sq, corresponding to an electrical conductivity of 4.2 × 105S cm-1for a 9.2-μm-thick film (67.7% of bulk silver's conductivity). Surprisingly, this film has outstanding mechanical folding stability, with less than a 0.5% deviation from the initial resistance after 35,000 repetitive folding and unfolding cycles when tested at the folding site. The film is free-standing, thin, flexible, foldable, and suitable for cutting and patterned growth, which makes it suitable for wearable electronics, showing a much wider range of applications than substrate-based ones.
authors.affiliation: School of Materials Science and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, ‡Instrumental Analysis & Research Center, and §Institute for Solar Energy System, Sun Yat-sen University , Guangzhou 510275, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yu
authors.affiliation: School of Materials Science and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, ‡Instrumental Analysis & Research Center, and §Institute for Solar Energy System, Sun Yat-sen University , Guangzhou 510275, China.
authors.forename: Zihua
authors.initials: Z
authors.lastname: Li
authors.affiliation: School of Materials Science and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, ‡Instrumental Analysis & Research Center, and §Institute for Solar Energy System, Sun Yat-sen University , Guangzhou 510275, China.
authors.forename: Yong
authors.identifier: http://orcid.org/0000-0002-0357-9906
authors.initials: Y
authors.lastname: Liu
authors.affiliation: School of Materials Science and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, ‡Instrumental Analysis & Research Center, and §Institute for Solar Energy System, Sun Yat-sen University , Guangzhou 510275, China.
authors.forename: Wenxia
authors.initials: W
authors.lastname: Zhao
authors.affiliation: School of Materials Science and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, ‡Instrumental Analysis & Research Center, and §Institute for Solar Energy System, Sun Yat-sen University , Guangzhou 510275, China.
authors.forename: Ruimei
authors.initials: R
authors.lastname: Xu
authors.affiliation: School of Materials Science and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, ‡Instrumental Analysis & Research Center, and §Institute for Solar Energy System, Sun Yat-sen University , Guangzhou 510275, China.
authors.forename: Donghai
authors.initials: D
authors.lastname: Wang
authors.affiliation: School of Materials Science and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, ‡Instrumental Analysis & Research Center, and §Institute for Solar Energy System, Sun Yat-sen University , Guangzhou 510275, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
keywords: hydrothermal reaction; shape conformability; silver film; smart electronic textile; wearable electronics