A team of scientists has developed silicon-based circuits that can be stretched or bent to a radius of curvature as small as 85µm without compromising their electronic properties.

John A. Rodgers, a materials science professor at the University of Illinois, first developed wavy silicon nanoribbons that could stretch and flex in 2005. Since then Rodgers and his team have taken the idea and applied it to an entire circuit.

Rogers explained: “The core underlying concept is similar, but the implementation is orders of magnitude beyond what we did previously. I think the way that we’re doing things now is applicable to electronic systems of arbitrary levels of complexity.”

The circuits are created by applying a sacrificial layer of poly(methyl methacrylate) to a rigid substrate. This creates a base on which traditional circuit fabrication tools can be used, despite the fact that the circuits assembled on the base are around 1.5 ?m thick. On top of the poly(methyl methacrylate), a layer of polyimide is cast, then conventional fabrication techniques are used to lay down the device’s components. Silicon nanoribbons are also printed onto the substrate.

Finally, the sacrificial layer is dissolved and the remaining circuit bonded onto a piece of stretched silicone rubber. When the rubber snaps back to its original shape, it carries the circuit along with it, creating wrinkles in the material. These wrinkles allow the circuit to bend and stretch like accordion bellows. The circuit is designed so that the most fragile components experience the least strain.

Rogers continued: “One thing I like about this work is that it doesn’t involve new materials. It presents new fabrication techniques and a new packaging strategy, he says, but the materials are familiar to electronics makers and don’t face the uncertainties that new materials might.”

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