Inspired by Coral, Scientists Turn CO2 Into Strong, Self-Healing Materials

By Nidhi DhullReviewed by Bethan DaviesApr 3 2025

Researchers have developed an innovative method to capture and convert atmospheric CO₂ into solid, high-performance materials—drawing inspiration from the way corals build their skeletons.

As detailed in a recent npj Advanced Manufacturing article, the team engineered an electrochemical process that deposits calcium carbonate minerals onto 3D-printed polymer scaffolds. The end result is composite materials that not only trap carbon but also offer exceptional strength, fracture resistance, fire retardancy, and even self-healing properties.

This approach doesn’t just reduce carbon emissions—it uses CO₂ as a building block for durable, load-bearing structures. It stands out from most current carbon capture strategies, which focus on storage or conversion into less-robust forms like liquids. The coral-inspired method opens new possibilities for creating functional, sustainable materials that meet the demands of real-world engineering.

Background

Coral reefs are known for their resilience against environmental stressors like strong ocean currents and biological erosion. This strength comes from their aragonite skeletal structure, formed within a semi-enclosed extracellular compartment.

Within this compartment, corals use CO₂ captured from the atmosphere—via photosynthesis—and calcium ions from seawater to build a micro-structured skeleton around organic templates. This natural process doesn’t just lock away CO₂; it converts it into durable mineralized structures. Translating this mechanism into an engineered solution, however, poses a challenge.

This study builds on that biological model, proposing a new way to capture and immobilize CO₂ to produce solid composites with outstanding mechanical properties.

Methods

To replicate coral’s natural mineralization in an engineered setting, the researchers developed a controlled electrochemical process. At the heart of the method was a custom-designed polymer scaffold, created using high-resolution 3D printing to allow precise control over the structure’s geometry and internal surfaces.

They used a stereolithography-based 3D printer with Clear V4 resin to build the scaffolds layer by layer—each just 25 µm thick, cured in 83 seconds per layer. Once printed, the scaffolds were cleaned with acetone, air-dried at room temperature, and coated with a thin palladium layer to make the surfaces conductive—an essential step for the electrochemical reaction to take place.

The mineralization phase took place in a calcium chloride solution. The coated polymer scaffold acted as the cathode, while a platinum electrode served as the anode. Over the course of six days, calcium carbonate gradually precipitated onto the internal surfaces of the scaffold, forming a tightly bonded mineral layer that mimicked coral’s aragonite skeleton.

To understand the material’s structure and properties, the team used a range of imaging techniques—including optical microscopy, scanning electron microscopy (SEM), and micro-computed tomography (µCT). They also carried out mechanical tests: compression tests measured the stiffness (Young’s modulus), and three-point bending tests assessed flexural strength. Additional evaluations looked at shear strength, fracture toughness, fire resistance, and the material’s ability to self-heal after damage.

One particularly innovative aspect of the process was its reversibility. After mineralization, the composite could be fully demineralized by soaking it in hydrochloric acid, which dissolved the calcium carbonate without damaging the polymer scaffold. The same electrochemical process could then be used to re-mineralize the structure, without the need to reapply the conductive layer—showing potential for circular material use.

Results and Discussion

The resulting mineralized composites demonstrated a compelling combination of mechanical performance and functional versatility. In terms of strength, the materials matched—or outperformed—other leading carbon-reducing building materials, including lightweight concrete, carbon-negative concrete, and CO₂-absorbing engineered wood. Notably, their specific shear strength and fracture toughness were among the highest in this category, and their CO₂ uptake rate exceeded that of carbon-negative concrete.

But what set these composites apart wasn’t just their strength—it was how tunable and multifunctional they were.

By selectively coating only certain regions of the 3D-printed polymer with a conductive layer before mineralization, the researchers could control exactly where the calcium carbonate formed. In one test, a rectangular lattice was coated only at its two ends, resulting in mineralization confined to those regions. When compressed, the structure showed a clear difference in deformation between the mineralized and unmineralized zones—demonstrating that stiffness could be programmed into the material’s architecture.

The composites also performed well under thermal stress. While the original polymer scaffold lacked fire resistance, the mineralized versions showed significant fire retardancy, making them more suitable for real-world structural applications.

Perhaps most striking was the material’s ability to self-repair. When a composite was fractured, initiating mineral growth at the broken interface allowed the structure to fuse back together. The repaired sample regained approximately 60.5 % of its original flexural strength—a significant recovery, and one that highlights the potential for extending material lifespan in practical applications.

Finally, the process proved to be fully reversible. Immersing a mineralized sample in hydrochloric acid dissolved the calcium carbonate layer in about 10 minutes. The exposed polymer scaffold could then be directly re-mineralized using the same electrochemical method—no need to reapply a conductive coating. This reusability suggests a promising route toward more sustainable, circular material systems.

Conclusion

This coral-inspired process offers more than just a new method for carbon capture—it turns CO₂ into useful, durable structures. Unlike most approaches that trap or convert CO₂ into short-lived products, this method locks it into materials that could directly serve in construction, product design, and other engineering applications.

In fact, the carbon sequestration efficiency was shown to be 25 times greater than some current low-carbon concrete production methods. On top of that, the materials created are tough, fire-retardant, and even repairable—qualities that could be useful in designing complex, modular structures with low environmental impact.

These composites also open the door to new hybrid materials, such as bouligand and nacre-like architectures, that balance strength, resilience, and sustainability.

Journal Reference

Deng, H. et al. (2025). Towards negative carbon footprint: carbon sequestration enabled manufacturing of coral-inspired tough structural composites. npj Advanced Manufacturing, 2(1). DOI: 10.1038/s44334-024-00012-x, https://www.nature.com/articles/s44334-024-00012-x

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