When it comes to certain minerals, bigger is not always better. In some cases, scaling down to the nanoscale can transform an unassuming lump of rock into a highly functional material.
For Conor Boland, a researcher in the School of Mathematical and Physical Sciences at The University of Sussex, his work on nanomaterials and their application in sustainable technologies on Earth led him down an unexpected road: producing clean energy for a future society on Mars.
A core philosophy of Boland’s work is to conduct eco-friendly research that can benefit society. For this reason, he wanted to take something we already use and make something new.
Gypsum is a mineral that fit the bill as it is a commonly used in everything from building materials to textiles to food supplements. It is also different from other minerals used to make nanomaterials and Boland was curious about it’s potential.
A sustainable challenge
For Boland, any new production method would need to be sustainable, which means putting constraints on what types of processes, chemicals, and techniques can be used. For example, forbidding the use of harsh solvents. As a result, his group focuses on using water-based chemistry and low energy processes — and he happens to enjoy these constraints.
“I think the restraints actually make it fun because it means you have to think constantly,” he said. After some initial testing, Boland was confident that gypsum nanomaterials could have interesting and potentially useful electrical properties.
“I think the worst-case scenario that I assumed is that it would be a nanobelt that was an insulator,” Boland said. A nanobelt refers to a specific size and shape of nanomaterial, where the pieces produced are longer than they are wide and thinner than the length or width. As a result of their shape and structure, they possess some unique properties and have potential applications in functional devices such as sensors and transistors.
As Boland dug deeper, he soon found an opportunity that would present an “out of this world” challenge.
Martian nanomaterial production
When searching for the most cutting-edge uses of gypsum, he stumbled upon a method NASA had developed for extracting water from gypsum found on the surface of Mars. This method produces a waste product called anhydrite — a dehydrated form of gypsum. This got Boland and his team thinking about the possibility of future Mars colonists using this anhydrite to make nanobelts for different technological applications, such as increasing the durability or stiffness of building materials.
If they could develop a method that required little expert training, used only the resources available on Mars, and technology that could realistically be transported there, a future Martian colony could potentially produce valuable nanomaterials for themselves.
“Essentially we started with the rock,” said Boland, describing the piece of gypsum the lab bought from a geology store. After cleaning off the dirt and mud, they set to work breaking the mineral down to the nanobelt sizes.
According to Boland, the team believed they would first need to break the gypsum down to nanoscales and then further dehydrate them to produce anhydrite, the form which would be produced as waste on Mars. To keep things simple, water and either mechanical energy or sound energy, a process known as sonication, was used to break up the rock. Surprisingly, this turned out to be enough.
“Through our processing, it created the nanobelts and created the byproducts that NASA was already working with,” said Boland.
Serendipitously, they now had a simple way for the Martian colony to produce nanobelts. “You could just take the anhydrite that NASA was already making, mix it in water at a high level, add the sonic energy and then break the anhydrite up into the nanobelts,” he explained. This nanobelt-water solution could then be poured out, allowing the water to evaporate, and leaving the nanobelts ready for use. Furthermore, at each step, water could be continuously collected and recycled.
When testing the functionality of this new material, the team received another surprise. Using a simple centrifuge to size select the anhydrite nanobelts, they found a larger than expected range of bandgaps, which dictate how well a current can travel through a material and is the foundation for things like transistors and circuits.
Given that a centrifuge is already in use on the International Space Station, Boland feels that they truly have a method that could be deployed on a Martian colony where there is unlikely to be a nanoscience expert. “Anyone could get this dust that they created, this mineral, put it into water, put it into something that, mixes it up, and then put it into a centrifuge,” explained Boland. “It’s just clicking buttons.”
Full scale electronics production requires clean rooms and sterile conditions, which likely wouldn’t be available on a Mars colony, but anhydrite nanobelts may inspire electronics here on Earth. For the Mars colony however, they could still have a profound effect — the production of clean energy.
Mars: The first sustainable society
A goal for Boland was to give the Martian colony the chance to be a sustainable society from the start. “That’s why we’re interested in the hydrogen evolution reaction,” Boland said. This reaction is a way to produce hydrogen for use as a clean burning fuel. The technique requires an acid diluted in water to serve as an electrolyte and some electrodes to pass a current through.
The anhydrite nanobelts were tested as possible electrodes and the results were positive. “They’re on par with most other kinds of nano sheets and nanotubes that were used previously for similar reactions,” he said. Importantly too, the team carefully assessed the feasibility of the process on Mars.
“We then critically assessed: Could we do this exact same experiment on Mars? And essentially, our setup requires an acid that forms naturally on Mars and water,” said Boland. Once again, all the materials are in place and the setup so simple that anyone could operate it.
This proof of concept stirs the imagination and shows that useful materials may one day be produced using native Martian resources. But it also demonstrates how clever thinking and problem solving could lead to more sustainable technology like anhydrite-based electronics here on our planet.
“As a group, we’re really trying to be more eco friendly and look at the real impact that research can have,” said Boland.
Reference: Cencen Wei, et al., Quasi–1D Anhydrite Nanobelts from the Sustainable Liquid Exfoliation of Terrestrial Gypsum for Future Martian-based Electronics, Advanced Functional Materials (2023) DOI: 10.1002/adfm.202310600
Feature image credit: NASA