Printable Superelastic Conductors with Extreme Stretchability and Robust Cycling Endurance Enabled by Liquid‐Metal Particles

Abstract

Stretchable conductors are vital and indispensable components in soft electronic systems. The development for stretchable conductors has been highly motivated with different approaches established to address the dilemma in the conductivity and stretchability trade-offs to some extent. Here, a new strategy to achieve superelastic conductors with high conductivity and stable electrical performance under stretching is reported. It is demonstrated that by electrically anchoring conductive fillers with eutectic gallium indium particles (EGaInPs), significant improvement in stretchability and durability can be achieved in stretchable conductors. Different from the strategy of modulating the chemical interactions between the conductive fillers and host polymers, the EGaInPs provide dynamic and robust electrical anchors between the conductive fillers. A superelastic conductor which can achieve a high stretchability with 1000% strain at initial conductivity of 8331 S cm and excellent cycling durability with about eight times resistance change (compared to the initial resistance at 0% strain before stretching) after reversibly stretching to 800% strain for 10 000 times is demonstrated. Applications of the superelastic conductor in an interactive soft touch device and a stretchable light-emitting system are also demonstrated, featuring its promising applications in soft robotics or soft and interactive human-machine interfaces.

Liquid Metal–Based Soft Microfluidics

“…f) Electrical response of the 3D vial integrated with the touch sensor. Reproduced with permission . Copyright 2018, John Wiley and Sons.…”

“…Further, Lee et al reported a stretchable conductor filled with conductive fillers (such as Ag flakes) and EGaIn particles with superelasticity. The composite can be patterned on an arbitrary substrate and even on 3D curved surfaces (such as glass vial) (Figure d).…”

“…g) Photograph showing a stripe of 198 LEDs connected by the prepared LM‐filled elastic conductor with a strain of ≈700%. Reproduced with permission . Copyright 2018, John Wiley and Sons.…”

“…Compared with the soft elastomers with high elastic strains but low level of stress, and metals with larger modulus but low stains, the core–shell composite fibers possess both excellent toughness and large strains by dissipating energy in the form of successive fracture of the high modulus core. The mechanical adaptive electronics can be also developed without significant loss of the electrical conductivity of the LM‐filled elastomers (Ag particles doped), as illustrated in Figure e–g . After assembly of the LM‐filled elastomers with LED array/stripe, the LEDs can be powered and lightened with repeatedly stretched up to 300% strain for the arrays of five LEDs (Figure e,f) and 700% strain for the stripe of 198 LEDs (Figure g).…”

Tuning the Electromechanical Properties of PEDOT:PSS Films for Stretchable Transistors And Pressure Sensors

“…An additional challenge for fabricating fully stretchable OECTs is that they require stretchable metal contacts. Stretchable conductors such as liquid metals, although increasingly used in stretchable electronics, are not suitable as electrodes for OECTs due to their limited electrochemical stability and biocompatibility.…”