Researchers at Caltech came up with a technique to coat flexible electronic circuits with graphene to enhance their durability on folding, as well as to improve their resistance to sweat (in the case of graphene-coated gold) and their conductivity. The method could enhance the flexible electronics that are employed in many medical wearables. The approach avoids the need for high temperatures and harsh chemicals that are typically used to grow graphene sheets, making it suitable for use with delicate electronic components and polymer materials. This technique can lay down a graphene coating onto a surface in as little as 15 minutes.
Medical wearables are often flexible to conform to the undulating surface of our bodies and maintain maximal contact with the skin. However, making electronic circuitry flexible means that is prone to strain and repeated bending can cause stress on delicate electrical circuitry that eventually results in device failure. Graphene, which is essentially a honeycomb lattice of carbon atoms that is just one atom thick, offers a way to strengthen and reinforce flexible components, but creating a layer of the material over these tiny components is challenging.
Typically, very high levels of heat are required to achieve this, but this would destroy many of the polymer components of flexible wearables. “Flexible and wearable electronics can be made of soft materials like polymers that can’t sustain high temperatures,” said Chen-Hsuan Lu, a researcher involved in the study. “Our method allows us to grow graphene directly on the substrates at a low temperature, preventing any damage to sensitive materials.”
To address this, these researchers have developed a new method to grow graphene layers on electronics. This involves using a plasma ray that glows a pleasing pink color and methane gas as a carbon source. The plasma causes the methane to dissociate into reactive species and then the carbon can be deposited onto the surface of the electrical components.
The graphene significantly enhances the durability of the flexible circuitry. The researchers tested this by folding the components repeatedly. Impressively, the graphene-coated components were folded 200,000 times without failure, whereas unmodified components failed after about 20,000 cycles. When the graphene coating was applied to gold components it also enhanced their ability to resist deterioration caused by human sweat.
See a video about the technique below.
Study in ACS Applied Materials & Interfaces: Single-Step Direct Growth of Graphene on Cu Ink toward Flexible Hybrid Electronic Applications by Plasma-Enhanced Chemical Vapor Deposition