Autonomous Underwater 3D Printing Robot Swarm CoralPrint Deep Dive: Printing Artificial Reef Substrates In Situ on the Seabed

Autonomous Underwater 3D Printing Robot Swarm CoralPrint Deep Dive: Printing Artificial Reef Substrates In Situ on the Seabed

Global coral reefs are degrading at a rate of 1% to 2% per year. Traditional artificial reef restoration methods involve sinking prefabricated concrete or ceramic structures to the seabed, but the shapes and sizes of these structures are difficult to precisely match the water flow, lighting, and biological community conditions of specific sites. The CoralPrint underwater 3D printing robot swarm developed by the Technion – Israel Institute of Technology (Technion) is offering an entirely new solution.

CoralPrint consists of 2 to 4 autonomous underwater robots, each carrying a micro concrete 3D print head and hopper. The robot swarm can print customized artificial reef substrate structures directly on the seabed — generating optimal three-dimensional structural designs based on the water depth, current direction, substrate type, and target coral species at each restoration site.

"Every coral reef is unique," said Technion Professor Tali Treibitz. "CoralPrint allows restoration plans to precisely match the natural conditions of each site, rather than forcing standardized prefabricated structures to fit."

In Red Sea trials in Eilat Bay, Israel, CoralPrint printed a set of 1.2-meter-high reef substrate structures at a depth of 8 meters, achieving millimeter-level printing precision. The structure surfaces were designed with complex micropores and grooves to provide ideal attachment surfaces for coral larvae. Six months later, manual inspection found that coral larval attachment density on CoralPrint-printed structures was 3.5 times higher than on traditional prefabricated structures.

The printing material uses a special marine-grade microporous concrete with pH adjusted to match the seawater environment, and surface roughness precisely controlled through aggregate particle size. The material also includes trace amounts of iron and phosphorus to provide nutrients for the coral's calcification process.

CoralPrint's printing speed is 0.3 cubic meters per hour — not fast, but one robot swarm can print a 50-square-meter artificial reef substrate within a week. The team is developing multi-robot collaborative printing technology, with the goal of increasing printing speed by fivefold.

However, the long-term ecological effects of artificial reefs still require years of monitoring. Excessive artificial intervention may interfere with natural recovery processes, and a balance must be struck between artificial restoration and natural recovery.