Highly conductive, stretchable and biocompatible Ag–Au core–sheath nanowire composite for wearable and implantable bioelectronics

Abstract

Wearable and implantable devices require conductive, stretchable and biocompatible materials. However, obtaining composites that simultaneously fulfil these requirements is challenging due to a trade-off between conductivity and stretchability. Here, we report on Ag-Au nanocomposites composed of ultralong gold-coated silver nanowires in an elastomeric block-copolymer matrix. Owing to the high aspect ratio and percolation network of the Ag-Au nanowires, the nanocomposites exhibit an optimized conductivity of 41,850 S cm (maximum of 72,600 S cm). Phase separation in the Ag-Au nanocomposite during the solvent-drying process generates a microstructure that yields an optimized stretchability of 266% (maximum of 840%). The thick gold sheath deposited on the silver nanowire surface prevents oxidation and silver ion leaching, making the composite biocompatible and highly conductive. Using the nanocomposite, we successfully fabricate wearable and implantable soft bioelectronic devices that can be conformally integrated with human skin and swine heart for continuous electrophysiological recording, and electrical and thermal stimulation.

Physical sensors for skin‐inspired electronics

“…In addition to the supporting materials, the development of biocompatible active materials is also essential. For example, Choi et al reported a highly conductive and biocompatible Ag‐Au NW composite for implantable electrophysiological sensors (Figure A) …”

Compositional and structural engineering of inorganic nanowires toward advanced properties and applications

“…G, Conductivity evolution of the two types of composites at the same weight ratio of nanowire:SBS of 80:20. Reproduced with permission . Copyright 2018, Nature Publishing Group.…”

“…From another viewpoint, hybrid nanowires can be treated as a simple integration of the advantages of the different components. For example, Au and CuNi have been wrapped around AgNWs and CuNWs, respectively, to realize high conductivity nanowire interconnects with better stability . As a structural protection layer and electrical shielding, SiO 2 and Al 2 O 3 have been frequently applied as nanowire shells .…”

“…For example, Au and CuNi have been wrapped around AgNWs and CuNWs, respectively, to realize high conductivity nanowire interconnects with better stability. [40][41][42] As a structural protection layer and electrical shielding, SiO 2 and Al 2 O 3 have been frequently applied as nanowire shells. 43,44 Additionally, all of these operations result in changed mechanical performance, that is, modified Young's modulus, fracture strength, maximum strain, nonlinear elasticity, viscoelasticity, and so on, which has stimulated fundamental research and largely expanded their application in fields such as nano electro mechanical system (NEMS) and flexible (wearable) devices.…”

Adhesion‐Free Thin‐Film‐Like Curvature Sensors Integrated on Flexible and Wearable Electronics for Monitoring Bending of Joints and Various Body Gestures

“…[17] Also, fully rubber conductive materials that show quite good van der waals adhesion to the human skin have been used for wearable sensing/actuating applications. [18] However, in comparison with the prosperity of research on strain sensors, there have been rare reports on the curvature sensors that can measure bending deformation, although accurate dynamic measurement of curvature is of great interest: it is especially useful for detection of activities of some special body parts such as spines and finger/elbow/knee/ankle joints.…”