From Shrimp to Steel: An Introduction to Nature-Inspired Metalworking

Humans have long looked to nature for solutions, from deciphering the mysteries of flight to creating more resilient materials. For Javier Fernandez, an associate professor at the Singapore University of Technology and Design (SUTD), nature is a model for sustainability. “Unlike our society’s energy-intensive engineering, nature operates in a scarcity paradigm and finds solutions without access to intense energy sources or means of transporting materials,” he observed.

Chitin, found everywhere in nature, from shrimp to shellfish to fungi, is an organic material that deserves closer study. In addition to being the second most abundant organic material on Earth, it is strong and lightweight, making it an ideal material for many engineering applications.

“Chitin also has a strong affinity for metals,” said Associate Professor Fernandez. “We decided to evaluate whether this affinity, combined with the processes that shape the cuticle, could be used to produce functional metal structures in a ‘biological’ way.”

In nature, metals, although rarely used, can be found in some chitinous structures, such as the cuticles and exoskeletons of insects and crustaceans. By digging deeper into the affinity that chitins and their derivatives have for metals, Fernandez and his team have devised a new approach to metalworking, which they published in their paper, “A Biological Approach to Metalworking Based on Chitinous Colloids and Composites,” in the journal Advanced functional materials.

Using design and technology inspired by these chitinous compounds, the research team demonstrated a new way to produce functional metal structures without the usual energy costs.

In traditional metalworking, high temperatures and pressures are essential to melt and shape metals. This is in stark contrast to how metals are incorporated into chitinous materials in nature, which occurs under ambient conditions.

Consider the example of metal compounds found in the cuticles of arthropods, such as crab shells. Typically, metals only enter the crab shell in the late stages of chitin development. The chitin first hardens into a shell through tanning and dehydration before metals from the environment are added.

The researchers found that this phenomenon is similar to what they observed in their experiments with chitosan, a derivative of chitin. They were able to form strong metal composites at standard temperature and pressure by simply introducing very small amounts of chitosan and water between particles of different metals.

When the water evaporates, the chitosan molecules replicate the consolidation process in the cuticles, holding the particles together with such force that they become a continuous solid composed of 99.5% metal.

Fernandez compares the manufacturing process to forming concrete, explaining: “By pouring metal particles into dissolved chitosan and letting them ‘dry,’ we can form massive metal parts without the constraints of fusion.”

Although these chitometallic composites are not physically strong, the researchers found that the material acquired good electrical conductivity and could be 3D printed. At the same time, the material continued to show compatibility with other biomaterials despite its low chitosan content. This opens up the possibility of introducing these chitometallic properties into other biomaterials, such as wood and cellulose.

Fernandez believes that this technology creates a new paradigm for metalworking. Despite its lack of mechanical strength, the manufactured biomaterial is suitable for non-load-bearing metal components, such as electrical components or battery electrodes. Metalworking for some components can now be done without requiring many resources.

“This technology does not replace traditional methods but allows new complementary production methods,” he stressed.

Since then, Fernandez’s team has successfully filed a patent for the innovative manufacturing method and is now looking to design new technology to develop biodegradable 3D electronic components, which can pave the way for more efficient and sustainable production methods.