Ultrastretchable Hybrid Electrodes of Silver Nanowires and Multiwalled Carbon Nanotubes Realized by Capillary‐Force‐Induced Welding

Abstract

The paucity of soft materials with both high electrical conductivity and the capability to maintain their superior conductance under large and complex mechanical deformations is a crucial barrier hindering the development of stretchable electronics toward practical applications. A type of ultrastretchable hybrid electrodes composed of silver nanowires (AgNWs) and multiwalled carbon nanotubes (CNTs) are reported, which show sheet resistance as low as 7.1 Ω sq.−1 and a small resistance increase of only 42% when uniaxially stretched to a strain of 580%. The hybrid electrodes can also withstand equibiaxial stretching, showing a resistance increase of 100% at a strain of 200%, and survive at least 1500 stretching/releasing cycles with negligible resistance change. The key to such performance is welding the loosely stacked AgNWs and CNTs into one integrated network with the aid of capillary force. When coated onto both sides of a polyacrylate‐based elastomer, VHB, the AgNW/CNT hybrid films can serve as excellent compliant electrodes of a dielectric elastomer actuator, causing a maximum actuated areal strain of 190% with a relatively low starting electric field of 11.6 V µm−1. These ultrastretchable AgNW/CNT electrodes will pave the way for the rapid development of high‐end stretchable electronics.

Hybrid‐Filler Stretchable Conductive Composites: From Fabrication to Application

“…Hot welding uses light or Joule heat to fuse the junctions of hybrid metal fillers such as AgNWs and AgNPs to reduce the junction resistance. [ 35,94 ] Cold welding sinters nanofiber (NF) fillers through capillary forces generated by solvent evaporation, which is suitable for carbon fillers like CNTs [11a,95] . Incorporating secondary fillers into conductive sponges or fabrics can also significantly enhance the electrical conductivity.…”

“…This strategy has been widely used in the fabrication of stretchable conductor films in recent years. [ 95,116 ] A recent study prepared an ultrastretchable hybrid‐filler electrode composed of AgNWs and MWCNTs through prestretching. [ 95 ] The wrinkled surface resulted in an increase in resistance as low as 42% at a uniaxial strain of 580%.…”

“…[ 95,116 ] A recent study prepared an ultrastretchable hybrid‐filler electrode composed of AgNWs and MWCNTs through prestretching. [ 95 ] The wrinkled surface resulted in an increase in resistance as low as 42% at a uniaxial strain of 580%. Unlike other prestrained composite films that can only keep stable resistance under uniaxial stretching, this hybrid electrode can withstand biaxial stretching and show an increase in resistance of only 100% at a 200% equibiaxial strain.…”

“…For example, using prestretching, methanol etching, and water vapor cold‐welding techniques can greatly enhance the stretchability of the SCC film filled with CNTs−AgNWs hybrid fillers and reduce its strain sensitivity. [ 95 ] The composite film formed this way had a stable resistance stretched by 580%. Similar work also obtained a strain‐insensitive conductive film by transferring metal‐coated CNT tapes to a prestretched PDMS substrate.…”

“…The electrode filled with CNT−AgNW hybrid fillers had a low sheet resistance of 10 Ω sq −1 at a 580% strain, which was used as the stretchable electrode of a dielectric elastomer actuator (DEA). [ 95 ] Using a hybrid network of long AgNFs and short AgNWs, it is possible to reduce the sheet resistance of a PDMS‐based conductive film to only 1 Ω sq −1 . The electrode not only had low piezoresistivity (GF = 0.3) but also could be stretched to a 70% strain by 15 000 times and therefore was used as the electrode of a capacitive fingerprint sensor (Figure 12C,D).…”