The idea of printing a light bulb may seem bizarre, but US engineers are now developing an ink-jet printing technology to do just that. The research at the University of California in Berkeley will allow fully assembled electric and electronic gadgets to be printed in one go.

The idea was revealed at a December workshop on robotic algorithms in Nice. Instead of creating a casing and then laboriously filling it with electronic circuit boards, components and switches, the plan is to print a complete and fully assembled device.

The trick is to print layer upon layer of conducting and semiconducting polymers in such a way that the circuitry the device requires is built up as part of the bodywork.

When the technique is perfected, devices such as light bulbs, radios, remote controls, mobile phones and toys will be spat out as individual fully functional systems without expensive and labour-intensive production on an assembly line.

Three-dimensional printers are already valuable tools for making prototypes of newly designed products. They deposit layers made from droplets of smart polymers, which gradually build up into 3D shapes. Such printing techniques have become so sophisticated it is now possible to print working prototypes with mechanical parts that move as they would in the final product.

But Berkeley's crucial addition to this art is to allow the electronics to be included in the printed device, rather than being added at great cost later on.

Electroactive polymers

Already, the Berkeley team has worked out how to print electronic components such as transistors, capacitors, inductive coils and other semiconductor components. "These may be connected to form complete circuits for actuation and control," says John Canny, who heads the team.

Once they have developed ink-jet cartridges that can handle all the polymers needed for casing and circuit printing, Canny predicts they could make, say, a remote control for a TV.

Printed as a single continuous component, it would contain the buttons, a polymer-based infrared emitter and polymer-based electronics. Everything, in fact, except the batteries. They could use transparent polymers and plastic light emitters to print light bulbs.

By printing with "electroactive" polymers, which produce voltages across them when compressed, or bunch up tight when a voltage is applied to them, the printed devices can be made to respond to pressure or flex in certain directions. So buttons can be created that produce voltages, for example, or artificial muscles for robots that flex when a voltage is applied.

"Flexonics"

This merging of flexible materials with electronics has been dubbed "flexonics" and could do away with the conventional printed circuit board. These are normally multilayered flat plastic plates on which electronic components are soldered. Copper strips running between the layers connect the components.

But flexonics makes this unnecessary. It is this ability to embed the electronics in the device that has the potential to revolutionise industrial design. Rather than a casing housing the circuitry, the casing is the circuitry.

But there is a downside. When a flexonic device breaks, it will be irreparable, because none of the embedded components can be replaced. So the technology will fuel the throwaway society.

Flexonics faces considerable challenges. Polymer-based electronic devices may be cheaper to make than silicon, but their performance is considerably poorer. Polymer transistors, for example, still have switching speeds 100 times slower than silicon transistors.

But Jordan Pollack at Brandeis University in Waltham, Massachusetts, who is interested in using 3D printing to make robots, says speed is not everything. The appeal of being able to print electronic devices means the new technology will inevitably find its niche. "Ultimately such 'Santa Claus' machines will begin to eat into lower-performance circuitry, like light bulbs, toys and transistor radios," he predicts.

--Duncan Graham-Rowe
New Scientist Print Edition