Bioinspired controlled crystallisation: Towards sustainable artificial coral reefs and more

Artificial coral reefs are often made of concrete or steel to provide stable structures for a marine habitat. However, they can also foster biofilm formation, promoting bacterial growth that may influence water chemistry.

Now a team led by Boaz Pokroy at Technion Israel Institute of Technology is working on artificial coral reefs that are as close to their natural counterparts as possible by reproducing the biomineralisation process typical of coral reefs and other marine organisms.

“For many years, we’ve extensively studied many marine organisms, such as the coralline alga Jania sp., sea urchins, starfish or brittle stars, and have unveiled the steps these organisms take to create a super hard skeleton through the process of biomineralisation”, explains Pokroy.

The natural process of biomineralisation starts as an amorphous phase before transforming into crystalline stable structures.

A key player in in this process is amorphous calcium carbonate (ACC), a precursor that can crystallise into different forms of calcium carbonate, including calcite, aragonite, and vaterite. The stability of ACC is influenced, among other factors, by impurities like magnesium, which affects the final crystal structure and properties. Traditionally, controlling this transformation required chemical additives and environmental adjustments.

Pokroy and his team used lasers to selectively transform ACC into different mineral phases. Laser power, scanning speed and the composition of the substrate are factors that affect the process of formation of distinct crystalline phases.

As the next step, the powders were analysed using synchrotron high-resolution powder X-ray diffraction (HR-PXRD) to identify the phases formed. “The experiments on beamline ID22 at the ESRF were crucial to characterise the different phases and track the impurities in the sample”, explains Hadar Shaked, scientist at Technion and first author of the publication. “With EBS providing higher flux, we were able to scan hundreds of samples in a very short time”, adds Pokroy.

Engineering bio-inspired materials

This method represents a significant advancement in bio-inspired material science, offering a way to engineer complex mineral structures with the same spatial accuracy seen in biological systems. “Whilst crystallisation from an amorphous phase was already possible through heating, it is the first time that we have full control of the process, which is key in engineering new structures as we wish”, says Shaked.

Dubbed ‘writing crystallography’, this approach opens exciting possibilities not only for artificial coral reefs but also for advanced additive manufacturing, semiconductors or single-layer patterning, where precise phase control is essential.

Reference:

H. Shaked, et al,  Adv. Funct. Mater. 2025, 2502691. https://doi.org/10.1002/adfm.202502691

Text by Montserrat Capellas Espuny

Video by Olivia Moncorgé and Montserrat Capellas Espuny

Top image: School in great numbers at Rapture Reef, French Frigate Shoals, Papahānaumokuākea National Marine Monument (Image credit: James Watt)