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This Pen Can Draw Electrical Circuits

A silver salt based ink lets users draw any circuit they can dream

(2/Dylan Ellis/Ocean/Corbis)
smithsonian.com

From the processors in phones to the motherboards of computers, silver tracings of electronic circuitry underlie many common devices. But scientists are now putting circuit design in the hands of the public with pens that can draw with conductive ink.

This new ink can be loaded into a regular ballpoint pen and lets users sketch out electrical circuits on paper, reports Prachi Patel for Chemical & Engineering News. The ink itself is a mixture of silver salt and adhesive rubber that can stick to various surfaces. The rubber helps the circuits stretch and bend without losing their conductivity, the researchers report in ACS Nano.

That stretchiness is one of the distinguishing qualities of this new ink, according to the researchers, led by Jun Yang, a professor of mechanical and materials engineering at the University of Western Ontario. Other conductive silver inks don’t produce flexible wiring and the commonly used silver nanoparticles clump too much for use with a ball point pen, Patel reports.

When the ink dries, the team paints the lines with a solution of formaldehyde and sodium hydroxide. This cocktail reduces the silver salt in the ink to metallic silver nanoparticles, 'activating' it or making it conductive. The team’s ink can stick to paper, plastic and other materials, Patel writes. If a link breaks or requires greater conductance, just trace over it again.

To demonstrate the success of their ink, the researchers drew a heart-shaped circuit that lights up 14 LEDs.

Devices that make it easier to manufacture circuits could lead to new applications and allows non-experts to experiment with the power of creating circuitry. While recent years have seen the release of several pens—such as the Circuit Scribe from Electroninks—the new group is launching a startup called Nectro to sell pens with the ink and a specially formulated eraser tip.

"It’s a very simple method," Yang tells C&EN. "You can easily make wearable electronics. Just hand draw a circuit to make a personalized T-shirt." The circuits the pen can draw may only be limited by what the person holding it can imagine.

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