A smart curvy contact lens with built-in sensing and imaging functions.

Researchers inflated a balloon to fabricate the bowl-shaped electronic circuit in this ‘smart’ contact lens. Credit: C. Yu et al./Nat. Electron.

Materials science

The child’s toy that helps to make valuable electronic circuits

Balloon technique throws circuit manufacturers a curve.

A process that uses an ordinary balloon as a stamp for printing electronics can make all sorts of curved devices, from domed arrays of light sensors to ‘smart’ contact lenses.

Many electronic devices are 3D, but most methods of manufacturing circuits produce only flat, 2D arrays that don’t easily fit on curved surfaces. To build a millimetre-scale circuit that would hug a complex surface, Cunjiang Yu at the University of Houston, Texas, and his colleagues first manufactured a silicon circuit. The team then inflated a latex balloon, coated it with a commercially available urethane rubber and pressed it against the circuit, which stuck to the balloon. When the researchers then pressed the balloon to a dome made of silicone, the circuit transferred onto the dome.

To demonstrate the technique, the authors built a convex array of light sensors for a wide-angle camera, a hemispherical solar cell that can pick up more light than a flat model, and a prototype contact lens that measures levels of the bodily substance lactate in tears.