“I like pondering unconventional ideas and imagining a world that is yet to come,” said Eleni Chatzi, professor of structural mechanics at ETH Zurich. One such vision is bridges that grow out of a handful of seeds and consist entirely of organic material.
Similar issues are also being addressed by ETH researchers in other fields such as biomedical applications, says an article in the latest issue of ETH's magazine, Globe. As a result, materials scientists, chemical, civil and electrical engineers, biologists and computer scientists have all joined in to develop materials with the goal of working at different scales right from the start instead of scaling them at a later stage.
An initial workshop and a symposium are scheduled to take place in spring 2020. The idea is to define research questions and then launch the first transdisciplinary projects.
Chatzi specialises in structural health monitoring. Currently, engineers have to either externally install the sensors needed to measure tension, deformation, acceleration, wind and strain, or incorporate these devices into the initial structural design, she pointed out. “However, this is usually an extra expense and a disruptive factor, especially on building sites,” she said. Crews have to install countless cables to transmit the measured data to a central computer for analysis. “That’s why we’d like to develop infrastructures and machines with intrinsic intelligence that are aware of their condition even without externally mounted sensors,” she said.
One example is intrinsic self-sensing concrete, mixed using carbon fibres, carbon nanotubes and nickel powder. The material monitors its condition autonomously to provide information about cracks, moisture or unusually heavy loads. The data is coaxed from the structure by applying voltage and constantly measuring the electrical resistance.
A second line of research is into materials with self-healing properties. Last year, in a project inspired by plant photosynthesis, US researchers presented a polymer that can repair itself by reacting with carbon dioxide in the surrounding air.
Other groups are working with bacteria that form lime when exposed to rainwater and other moisture. Added to concrete, they can seal small cracks on their own. Experiments are under way with microvascular networks that release “healing” fluids when an injury occurs. Responding much like the human organism to a skin wound, they polymerise to fill the fractures.
“We’re seeing a fusion of materials science and biology,” said Mark Tibbitt, professor at the Macromolecular Engineering Laboratory at ETH Zurich. He noted that in the past, chemical and other engineers had looked to nature primarily for inspiration for mimicking properties such as the lotus blossom’s ability to repel water. “Today, we’re trying to incorporate biological functions into materials,” he said.
These efforts are fuelled by breakthroughs in materials science and biotechnology. DNA engineering and new molecular biological methods such as gene editing can now serve to introduce new biological functions into cells for very specific purposes. Additive manufacturing using 3D printers enables high-resolution, data-based material design.
Tibbitt’s work combines concepts from a number of fields – chemical engineering, polymer chemistry, materials science and systems biology - with the aim of developing soft, tissue-like polymers for biomedical applications. He met Chatzi a year ago at an event for exploring radically new avenues of research. They found that, although the two work on very different scales, they often talk about the same concepts.
Recurring topics include materials that can ‘heal’ themselves. Recently, they began to foster dialogue among researchers at ETH about living, self-sensing and self-healing materials and infrastructure.
The researchers said that one big question is how to assure safety and stability when structures develop a life of their own. Another is how humans and animals will react to an engineered environment consisting of living organisms. And what happens if a synthetic organism leaches from a new building material into surrounding waters? “We have to think about bioethical questions and safety concerns from day one,” says Tibbitt.