History is filled with stories of the great being felled by the puny. Goliath and a pebble, Achilles and his heel, the ultra-fast 6G network and … walls. Researchers at Aalto University in Finland have now invented a cheap, 3D-printed solution that could help future wireless signals bend around the barriers that currently stop them in their tracks.
The device is a 3D-printed metacrystal panel that can passively redirect radio waves without the electronics or maintenance required by current active electronic solutions. In not-so-simple terms, it is a carefully shaped polymer-like dielectric structure that can change the direction of radio waves by geometry alone. The panels could be mounted on surfaces such as walls or ceilings to direct wireless signals into areas they would otherwise struggle to reach.
While 6G is currently still in the research and development phase, its potential is enormous. The technology is expected to reach a theoretical peak data rate of up to 1 Terabit per second (Tbps), which is 50 to 100 times faster than the theoretical maximum of 5G. For context, that translates to download speeds fast enough to download Michael Jackson’s entire catalog eight times over in one second, and that’s assuming you are downloading in ultra-high-fidelity, studio-quality audio.
The catch is that future networks will rely more heavily on millimeter-wave and sub-THz frequencies, which offer huge bandwidth but are far easier to block than lower-frequency signals. This is already a problem with 5G in some buildings and dense urban areas. With 6G, it gets worse.
The higher the frequency, the more the signal starts behaving like a fussy beam of light: great when it has a clear path, less useful when an obstacle, say a wall or a person, gets in the way. One answer is to install more base stations, routers, repeaters, relays, and powered antennas to densify the network or carry signals around obstacles. These work, but they also mean more hardware, more power consumption, more maintenance, and higher cost.
The researchers’ approach, published in Nature Communications, is a lower-tech but viable, possibly ingenious, solution. Instead of generating a new signal or amplifying the old one, the panel reshapes the path of radio waves already present in the environment.
“When a room is too dark, you can bring in more lamps – or use simple mirrors to guide the already available light,” says doctoral researcher Mahdi Asgari. “This is what these metacrystals do, but with radio waves.”
In practice, the panels could be placed on walls, ceilings, furniture, corridors, or other surfaces to steer a signal around a corner, into a shadowed area, or toward a particular user or device. They are not routers, and they are not signal boosters in the normal electronic sense. They are more like passive traffic directors for wireless energy.
The key is the metacrystal’s internal structure. Metamaterials are engineered materials whose useful behavior comes not just from what they are made of, but from how they are shaped at small scales. In this case, the team created an all-dielectric structure made from low-permittivity material and air gaps. The panel’s 3D geometry determines how incoming radio waves scatter, reflect, transmit, or get absorbed.
The researchers designed the structures using inverse topology optimization. Rather than manually sketching every internal feature, they defined the electromagnetic job they wanted the panel to perform, and the software generated a geometry capable of doing it. The resulting metacrystals were designed to handle multiple incoming waves, different angles, two polarizations, and multiple functions, including anomalous reflection, transmission, and absorption.
This last bit is important because it defines one of the “innovation” aspects of the project. Intelligent surfaces are not new. Passive metasurfaces exist, but they often work well for only one frequency band, polarization, or arrival angle. The researchers’ metacrystals aim to bridge that gap by using a modestly thick, volumetric 3D structure rather than a single patterned layer, giving the panel greater design freedom without adding electronics.
Reconfigurable intelligent surfaces have long been proposed as a means to improve future wireless coverage. However, many require electronic components and power, which leads us to another big advantage of the device: cost and simplicity.
Because the panels can be 3D-printed, the researchers estimate that the consumable material cost could be only a few tens of euros per piece. There’s also the benefit of customization: each panel could be tailored to a known environment rather than mass-produced as a universal box. A network and a space could have panels designed for their exact transceiver and obstacle layout, respectively.
“For industry, the most attractive use cases are static or slowly changing environments like factories, indoor 5G/6G networks, warehouses, and long corridors,” says Asgari. “In such places, a passive panel designed for a known layout could be much cheaper and simpler than an actively controlled surface that requires continuous maintenance.”
There are limits, of course. A passive panel cannot create power from nowhere, and every redirected path still faces real physics. Distance, absorption, scattering, reflection, and insertion losses all reduce signal strength. In theory, you could keep bouncing a beam with multiple panels toward a far-off destination, yet in practice, every bend and every extra meter eats into the link budget. At sub-THz frequencies, the atmosphere itself adds loss with distance.
The researchers now want to move from fixed panels to simpler, reconfigurable versions that adapt to changes in the wireless environment. They are also seeking commercialization and engagement from industrial collaborators.
Source: Aalto University
