Printing Circuits with Electronic Ink

3D printers are becoming widely known for printing solid objects of just about any shape and size – from medical implants to automobiles – and are widely used for creating prototypes of custom enclosures for electronic devices. Now researchers are looking at using a similar technique to print the electronics that would go inside of them.

With transistors continuing to shrink (some of today’s chips contain transistors that are only 14 nanometers in size) it’s become possible to mix them with a liquid to produce “electronic ink.” Using the ink to print circuits is a logical next step, but getting the chips in the right place and in the proper orientation proved to be a challenge.

The solution turned out to be an “old” one – the same technology that was used as the basis for the first photocopiers. Known as xerography, it utilizes static electricity to attract toner particles to selective areas on a light-sensitive drum. The resulting image is fused to a substrate using heat and pressure. To orient the chips properly, a charge is induced on the surface of each chip so they can be steered into the proper position using an electrostatic field. The components are then “wired” together using inkjet printing or photolithography techniques.

Although it will be some time before the method is commercially viable, the implications for specialized, short-run, high performance products are vast because building the circuitry would no longer rely on economies of scale in order to be affordable. In fact, circuits could be as different as pages in a document, since the process is controlled by software. In addition, different electronic “inks” could be made containing different devices including optical, micromechanical and piezoelectric sensors.