Stretchable gold conductors on elastomeric substrates

Abstract

Stripes of thin gold films are made on an elastomeric substrate with built-in compressive stress to form surface waves. Because these waves can be stretched flat they function as elastic electrical conductors. Surprisingly, we observe electrical continuity not only up to an external strain of ϳ2% reached by stretching the films first flat (ϳ0.4%) and then to the fracture strain of free-standing gold films (ϳ1%), but up to ϳ22%. Such large strains will permit making stretchable electric conductors that will be essential to three-dimensional electronic circuits.

Localization of Folds and Cracks in Thin Metal Films Coated on Flexible Elastomer Foams

“…They arise from a mechanical mismatch between a stiff sheet bonded to a compliant substrate. The sheet forms wrinkles under compressive stress [1][2][3][4] and forms cracks under tensile stress. [5][6][7] Self-organized patterns of folds and cracks have been exploited in a number of applications, including nano/microfabrication, [ 8 ] surface and interface science, [ 9 , 10 ] biotechnology, [ 11 ] photonics [ 12 ] and stretchable electronics.…”

“…A variety of two-component systems are available to produce PU foams, allowing for a wide range of foam densities and morphologies. To study the infl uence of the substrate cellular structure, foams are prepared with two distinct densities, 0.1 and 0.4 g/cm 3 , corresponding to tensile moduli of 80 kPa and 500 kPa, respectively (Figure 2 b). The plain PU membrane ( ρ = 1.2 g/cm 3 ) has a modulus of 6 MPa.…”

“…To study the infl uence of the substrate cellular structure, foams are prepared with two distinct densities, 0.1 and 0.4 g/cm 3 , corresponding to tensile moduli of 80 kPa and 500 kPa, respectively (Figure 2 b). The plain PU membrane ( ρ = 1.2 g/cm 3 ) has a modulus of 6 MPa. To quantify the strain levels at the surface of the foam further, we simulate the deformation of the structure as in Figure 3 d under elongation using the fi nite element method.…”

3D Printing of Transparent and Conductive Heterogeneous Hydrogel–Elastomer Systems

“…[5][6][7][8] Although many stretchable conductors exist, including liquid metals, [9,10] nanowires, [11,12] nanoribbons [13] , pre-stretched elastomer fibers with conductive coatings, [14] and micro-cracked metals, [15,16] these materials have generally been unable to achieve high levels of optical transparency while maintaining high conductivities and stretchability; a feature that would enable their use in optogenetics [17] or allow optical imaging of the underlying substrate. Conventional strategies of incorporating metallic components with elastomers to attain stretchability also yield non-trivial failure modes such as liquid metal leakage [8] and hard-soft material interfacial failure [18] .…”

Interface Integrity in Stretchable Electronics

“…These interconnects are often very stretchable but the conductivity is low which limits frequency of the electronic signals. Designs following the second path mostly use metals for the interconnects adding stretchability by structuring the interconnects in mechanistic patterns which locally reduce the deformation, when they are stretched globally, similar to a helical telephone cord [5][6][7]. Although, both design paths have reliability issues, this paper focuses mainly on issues related to the second design path.…”