On June 8, a research team from Aalto University in Finland developed a 3D-printed metamaterial crystal panel for 6G communications. The findings have been published in *Nature Communications*. The panel can passively guide radio waves around obstacles without requiring power, active tuning, or complex control circuits, improving wireless connection quality in weak coverage areas such as basements, tunnels, large buildings, factories, and corridors.

This technology addresses the more pronounced propagation challenges of high-frequency communication as it enters the 6G era. Future 6G networks will increasingly use high-frequency bands to achieve greater bandwidth and higher data capacity than 5G. However, as frequencies rise, signals become more susceptible to obstruction by walls, human bodies, furniture, equipment, and building structures. Traditional approaches often involve adding more routers, repeaters, small cells, or reconfigurable intelligent surfaces in weak coverage areas, but these solutions typically require power, wiring, control chips, RF modules, and ongoing maintenance, with deployment costs increasing alongside scenario complexity. The metamaterial crystal panel proposed by the Aalto team adopts a volumetric structural design that redistributes radio waves through geometric shapes, enabling signals to bypass corners, enter shadowed areas, or be concentrated toward specific users and devices. Researchers liken this principle to using a mirror to guide light, except that here, the guided medium is radio waves.

The panel can be installed on walls, ceilings, furniture, or other surfaces, with material costs estimated at just tens of euros per unit.

In terms of technical mechanism, the metamaterial crystal panel differs from many single-layer intelligent surfaces that can only handle a single incident direction or function. The Aalto team states that this type of volumetric metamaterial crystal can simultaneously process multiple incident waves, operate synchronously across different frequency bands, and achieve reflection, transmission, or even absorption of unwanted signals based on design objectives. Its manufacturing relies on 3D printing, allowing researchers to customize the panel structure according to the specific layout of buildings, factories, warehouses, or corridors, enabling the "geometry" to continuously perform signal control after installation. For static or slowly changing environments, such as factories, indoor 5G/6G networks, storage spaces, and long corridors, this solution offers advantages in low cost, low maintenance, and ease of large-scale replication, without requiring additional electronic devices at every point or continuous adjustment of numerous active units.

The application prospects of this achievement focus on building intelligent wireless environments. Future factories, logistics warehouses, hospitals, underground spaces, transportation hubs, and large public buildings will host more robots, sensors, industrial cameras, AR terminals, unmanned transport equipment, and low-latency control services. Relying solely on increasing base station power or adding relay equipment will bring pressure in terms of energy consumption, wiring, and operation and maintenance. If the 3D-printed metamaterial crystal panel enters engineering applications, it can serve as a "passive communication component" within buildings, improving coverage blind spots without altering the main network architecture and enhancing the accessibility of 6G high-frequency signals in complex spaces. The research team is currently exploring commercialization pathways and seeking industrial collaboration in areas such as programmable metasurfaces, intelligent wireless infrastructure, and low-cost passive signal control technologies.

Subsequent research and development will progress from static panels to reconfigurable panels, enabling them to adapt to changes in the wireless environment. If this path can maintain the advantages of low cost and ease of deployment, 6G network construction will gain a new tool between traditional base station expansion and complex active intelligent surfaces, providing more flexible engineering solutions for high-frequency communication entering indoor spaces, factories, and urban environments.