A passive 3D-printed panel could redirect wireless signals around corners without electronics or power. The metacrystal design can handle multiple incoming waves and different frequency bands, offering a lower-cost option for hard-to-reach indoor spaces.

Basements, tunnels, large buildings—a weak Wi-Fi or mobile signal in these hard-to-reach places is frustrating. The usual solution is to add more electronics like routers, repeaters and base stations. Yet, as we move towards a 6G mobile network, this kind of complex infrastructure can be unsustainable and prohibitively expensive. Higher-frequency channels of 6G communications aim to provide vastly more data bandwidth than the current 5G, but those channels are more easily blocked by walls, people and other obstacles.

To tackle this, researchers at Aalto University have developed a new solution in the form of metacrystals: passive, 3D-printed smart panels that can shape wireless signals without electronics, a power supply or active tuning. The paper, “Metacrystals: Inversely-designed 3D-printed intelligent panels for 6G communications” is published in Nature Communications.

“When a room is too dark, you can bring in more lamps—or use simple mirrors to guide the already available light. This is what these metacrystals do, but with radio waves,” explains doctoral researcher Mahdi Asgari. “Unlike previously proposed single-layer intelligent surfaces, these volumetric metacrystals can be designed to control multiple incoming signals or frequency bands independently—a key requirement for realistic wireless communication.”