Using 3D printing to create 3D circuits: Researchers unlock self-healing circuit boards

Traditional printed circuit boards are almost always flat and two-dimensional. But a research team at the National University of Singapore has taken circuit printing into the third dimension using a smart new technology called CHARM3D. Not only are they three-dimensional, these printed circuits are also self-healing.

By being stacked vertically rather than flatly, components can be stacked, which means our electronics have a much smaller footprint - and these days we all want our devices to be smaller and sleeker. But to realize three-dimensional circuits, existing methods such as direct ink writing (DIW) are a challenge. These technologies use special composite inks, require auxiliary materials, are highly viscous and slow.

CHARM3D takes a completely different approach, taking advantage of some clever material properties. It uses a metal alloy called Field's metal made of indium, bismuth and tin. This alloy has a very low melting point of approximately 62°C, flows smoothly, and self-solidifies quickly.

The unique combination of these properties helps CHARM 3D print ultra-smooth, uniform three-dimensional metal microstructures ranging in width from 100 to 300 microns, which is about as thin as a few hairs. The structures also include cubic frames, vertical letters and retractable spirals.

The printed structure can also self-heal damage. If circuits become scratched or deformed, simply heat them past their low melting point and they will resolidify back into their original shape. This makes the circuit more durable and even recyclable.

The possibilities here are huge. As the researchers mentioned, the high resolution, fast printing (up to 100 millimeters per second), and ability to create complex 3D shapes make it useful for all kinds of cool stuff.

Perhaps the biggest application noted by researchers is healthcare. Imagine wearing smart clothes with 3D printed sensors that can monitor your vital signs without touching your skin. It could also lead to more precise medical imaging, such as the early detection of breast cancer tumors using microwaves. The team has used the technology to create wearable, battery-free temperature sensors, antennas for wireless vital signs monitoring, and metamaterials for manipulating electromagnetic waves.