The Fabrication And Applications Of Transparent Electrodes Based On Metal Nanowire Networks

Flexible and Transparent electrodes,a key component for many flexible electronic devices,have a wide range of applications in the fields of epidermal electronics,implantable electronics,wearable electronics,solar cells,touch screens,and soft robotics.However,traditional transparent conductive materials indium tin oxide(ITO)films cannot meet the growing demand of flexible,transparent conductive materials due to the brittleness.It is of great significance to develop materials with excellent flexibility,high optical transparency,and high electrical conductance to replace ITO films.In recent years,alternative materials including carbon-based conductive materials(e.g.,graphene,carbon nanotubes),conductive polymers,and metal nanowire-based transparent electrodes have been developed to be used as flexible transparent electrodes.Among those alternatives,the metalnanowire-based transparent electrodes is an ideal candidate because of its high conductivity and excellent mechanical properties of metals.This work is mainly focused on the fabrication and applications of stretchable and transparent electrodes based on Au nanotrough networks.The fabrication process consists of several steps:(1)ultra-thin and free-standing polyvinyl alcohol(PVA)nanofiber template fabricated by using electrospinning,(2)metal deposition,and(3)transferring to prestrained substrate and releasing the prestrains.Periodic spring-like stretchable structures are finally formed.The electrode exhibits excellent stretchability: it shows an increase of only 30% under 500% tensile strain,and keeps conducting until stretched to a huge strain of 950%.The electrode also exhibits high reliability: with the resistance increases by only 60% when it is subjected to cyclic tensile strains of 200% for 100,000 cycles.More importantly,the electrodes maintain good optoelectronic performances while the stretchability is greatly improved by prestretching.Regarding the application of this electrode,a sandwich structure of stretchable and transparent capacitive sensor with the Au nanotrough networks as the bottom and top electrodes and polydimethylsiloxane(PDMS)as the dielectric layer was prepared.Although the sensitivity is not high,but it can respond well to human skin deformation,showing good stability,high linearity,and high transparency.The stretchable transparent electrode based on Au nanotrough networks can also be use as epidermal electrodes on skin.The transfer of the spring-like Au nanotrough structure is critical.Here,a calcium-containing silk fibroin solution is used to transfer spring-like Au nanotrough networks from a PDMS or Ecoflex substrate to silk fibroin.Taking advantage of the good biocompatibility and excellent adhesion of silk fibroin to skin,we fabricated an epidermal electrode based on Au nanotrough networks on silk fibroin substrates and did electricity and biocompatibility tests on skin.Our work has shown that the electrode is an ideal candidate as epidermal electrodes.Flexible and transparent electrodes based on electrospun nanofibers template present many merits.The flexible and transparent electrodes prepared in this work not only exhibit excellent stretchability,but also can be easily transferred to other substrates.Such properties enable their wide application in the field of flexible electronics such as epidermal electronics and implantable electronics.