Conductive ‘felt’ promises flexible wires for wearables

Conductive ‘felt’ promises flexible wires for wearables

Technology News |
By Rich Pell

The conductive, stretchable composite reported in the ACS Nano journal under the paper title “Stretchable Conductive Composites from Cu–Ag Nanowire Felt” consists of a copper-silver (Cu–Ag) core–shell nanowire felt infiltrated with a silicone elastomer.

The nanowires were filtrated from a solution through a stencil, leaving a dry felt of millions of nanowires randomly interwoven, similar to the interwoven fibers that comprise fabric felt. An annealing step melts the contacts together before silicone rubber is added to fill in the gaps between the wires, turning the felt into a conductive elastomer compound.

What the researchers demonstrated is that the new composite retained its high conductivity (greater than 1000 S cm–1) even under strain, trying out several meandering patterns that could then be stretched up to 300% their initial length without losing their conductivity. This compares favorably over other stretchable wires reported in literature, reads the paper.

Interestingly, the mechanical and conductive properties of this new flexible conductor can easily be tuned based on the stiffness of the chosen silicone matrix. Not surprisingly, increasing the matrix’ Young’s modulus decreased the retention of conductivity under strain, which was attributed to void formation as a result of debonding between the nanowire felt and the elastomer.

The conductive felt is made of stacks of interwoven silver-coated copper nanotubes filled with a stretchable silicone rubber (left). When stretched, felt made from more pliable rubber is more resilient to small tears and holes than felts made of stiffer rubber (middle). These tears can be seen in small cavities in the felt (right). Credit: Matthew Catenacci.

The researchers anticipate that such felt could be patterned on fabrics using a combination of stencils and vacuum filter before adding the silicone to make it stretchable.

Duke University –

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