Free-standing nanocomposites with high conductivity and extensibility

Abstract

The prospect of electronic circuits that are stretchable and bendable promises tantalizing applications such as skin-like electronics, roll-up displays, conformable sensors and actuators, and lightweight solar cells. The preparation of highly conductive and highly extensible materials remains a challenge for mass production applications, such as free-standing films or printable composite inks. Here we present a nanocomposite material consisting of carbon nanotubes, ionic liquid, silver nanoparticles, and polystyrene-polyisoprenepolystyrene having a high electrical conductivity of 3700 S cm -1 that can be stretched to 288% without permanent damage. The material is prepared as a concentrated dispersion suitable for simple processing into free-standing films. For the unstrained state, the measured thermal conductivity for the electronically conducting elastomeric nanoparticle film is relatively high and shows a non-metallic temperature dependence consistent with phonon transport, while the temperature dependence of electrical resistivity is metallic. We connect an electric fan to a DC power supply using the films to demonstrate their utility as an elastomeric electronic interconnect. The huge strain sensitivity and the very low temperature coefficient of resistivity suggest their applicability as strain sensors, including those that operate directly to control motors and other devices. © 2013 IOP Publishing Ltd. AbstractThe prospect of electronic circuits that are stretchable and bendable promises tantalizing applications such as skin-like electronics, roll-up displays, conformable sensors and actuators, and lightweight solar cells. The preparation of highly conductive and highly extensible materials is still a remaining challenge amenable to mass production such as free-standing film or printable composite ink. Here we present a nanocomposite material consisting of carbon nanotubes, ionic liquid, silver nanoparticles, and polystyrene-polyisoprene-polystyrene having a high electrical conductivity of 3700 S cm -1 that can be stretched to 288% without permanent damage. The material is prepared as a concentrated dispersion suitable for simple processing into free-standing films. For the unstrained 2 state, the measured thermal conductivity for the electronically conducting elastomeric nanoparticle film is relatively high and shows a non-metallic temperature dependence consistent with phonon transport, while the temperature dependence of electrical resistivity is metallic. We connect an electric fan to a DC power supply using the films to demonstrate their utility as an elastomeric electronic interconnect. The giant strain sensitivity and the very low temperature coefficient of resistivity suggest applicability for strain sensors, including those that operate directly to control motors and other devices.

Three-dimensionally deformable, highly stretchable, permeable, durable and washable fabric circuit boards

“…The stretchability has been increased by either structural conversion or using organic materials from approximately 3% (SiNW on PDMS substrate [110]) to more than approximately 400% (wrinkled graphene on PDMS substrate [71]). The relative change in electrical resistance varies from approximately 2.1% (horseshoe pattern on PDMS substrate [108]) to approximately 7300% (Ag-MWNT-SIS nanocomposite film [73]), which may hinder the use as conductive tracks in stretchable circuit boards, in particular, for low-impedance electronic components or high-precision measurements [96,97]. By contrast, the knitted FCB has exhibited an extraordinarily electrical stability with almost no change in electrical resistance up to strain of 300% in unidirectional tensile deformation.…”

“…Organic materials such as (well-controlled) graphene particles [19,70,71], CNT composites [72][73][74]95], polyaniline-conducting polymer [75] as well as PEDOT-PSS composites [76] yield different stretching levels (ranging from several per cent to more than 100%) through blending with silicone rubbers (e.g. PDMS).…”

“…PDMS). The conductivity for those organic elastic conductors, except MWNT/Ag composite (conductivity: 3700 S cm −1 ) [73], is too low (conductivity: less than 1000 S cm −1 ) to perform as electrical wirings, particularly for integrated circuits [96][97][98]. More crucially, most of such organic conductors, except polymeric ionic conductors [99], drop their conductivity by at least several orders of magnitude even within 10% strain [75].…”

Review of Flexible Temperature Sensing Networks for Wearable Physiological Monitoring

“…A large number of stretchable interconnects have been created through three approaches . The first method relies on novel organic materials with inherent stretchability, such as (well controlled) graphene/PDMS composites, single‐walled carbon nanotube (SWNT) conductor or MWNT/Ag composites or over‐twisting CNT ropes, polyaniline conductive polymer, and PEDOT:PSS/PDMS composite . Such new material‐based interconnects, except MWNT/Ag composites, are not sufficiently conductive to perform as electrical wires in integrated circuits .…”

“…The stretchable capacity ranges from 3% to 400% . The relative resistance change, whereas, varies from 2.1% to 7300% with applied strain, which is much larger than that of knitted interconnects . Hence, the efforts to develop knitted stretchable interconnects could open doors to new applications in areas where new organic materials and thin film‐based electronics are not effective, such as next‐to‐skin electronics or intimately wearable devices.…”