A thin gel layer that mimics camel fur could help insulate objects, potentially keeping them cool for days, without electricity.
Researchers have long been interested in hydrogels, which can absorb water and then release it through evaporation to produce a passive cooling effect without power. But a key challenge has been in finding ways to make this effect last longer.
Jeffrey Grossman at the Massachusetts Institute of Technology and his colleagues looked to camels for inspiration by combining hydrogel with a thin layer of another gel – aerogel – which is a light, porous insulating material.
“Our evaporation-insulation bilayer mimics the camels,” says Grossman.
The hydrogel layer is like the camel’s sweat gland, allowing water to evaporate and provide a cooling effect, whereas the aerogel layer plays the same role as the camel’s fur, he says, providing crucial insulation to keep out heat from the surroundings, while still allowing water from the hydrogel to escape through it.
“We achieve evaporation and insulation at the same time, extending the cooling period significantly,” says Grossman. Altogether, the gel bilayer is about 10 millimetres thick.
The researchers tested their double-layered gel in a temperature and humidity controlled chamber in the laboratory. It was able to cool an object to 7°C below the surrounding temperature, while also keeping it cool for longer compared with a single hydrogel layer.
The team found that, compared with the hydrogel layer alone, the addition of the aerogel layer resulted in an effective cooling time five times as long. “This translates to over 250 hours of cooling,” says Grossman – equivalent to about 10 days.
“We are working on making the materials more scalable to pave the way for wider adoption of this technology,” says Grossman. He says the gel bilayer could have applications in keeping food or medical supplies cool, as well as helping cool buildings to reduce their energy consumption.
A result of millions of years of successive improvement through natural selection, nature seems to have a solution for everything – find out how we’re using them to solve modern, human problems.
The Pyramids, skyscrapers, supersonic flight – despite the incredible ingenuity and engineering ability humans have demonstrated over past millennia, we are continually looking for new inspiration and ways to improve our designs. Given evolution has the benefit of millions of years of trial and error to perfect its designs in nature, it is logical that human construction can benefit in drawing from its influence.
This approach to human innovation, via emulating nature, is called biomimetic design and has inspired many of our greatest creations – from buildings to bionic cars, here are some of the favourite examples.
The humpback whale weighs an astonishing 36 tonnes, yet it is one of the most elegant swimmers, divers and jumpers in the sea. As first researched by Frank Fish, a biomechanic, these aerodynamic abilities are greatly attributed to the bumpy protrusions on the front of its fins, called tubercles.
Similar to the processes of aircraft wings, whales use their fins at different steepening angles to increase their lift. Too much tilt though, and the opposite will occur and they’ll stall – a loss of lift due to current turbulence and the formation of eddies in the water.
By comparing bumpy blades to smooth-edged ones, Fish and colleagues found that stalling occurs at a much higher angle with tubercles – an increase by nearly 40 per cent, in fact. They deduced this higher angle proficiency was beneficial for the whale in allowing it to manoeuvre in tight circles, hence how they circle and entrap their prey in a ‘net’ of bubbles.
Further testing by Fish also revealed that serrated-edge wind turbines proved to be more efficient and quieter than the typical smooth blades. This led to the formation of WhalePower tubercle technology, a company developing a range of tubercle technology products, with a range of blade applications, including wind turbines, hydroelectric turbines, irrigation pumps, ventilation pumps.
Despite the cumbersome appearance of the boxfish, it has a low flow resistance and a drag coefficient of an astounding 0.06. In comparison, penguins swimming through water have a coefficient of 0.19.
In 2005, inspired by the great structural strength and low mass of the boxfish, Mercedes Benz developed the Bionic Car, which reported to reduce drag, have great rigidity, low weight and a significantly lower fuel consumption than traditional cars.
Of course just because something seems like the perfect design in the natural world, doesn’t necessarily mean it works out that way in industrial design. You might have noticed the distinct lack of Bionic Car-shaped vehicles on the road, which is probably because a 2015 study found that the shape of the boxfish didn’t reduce drag at all and actually made it more unstable – great for a box fish with 50 million years of evolution to perfect the art of being a boxfish, less good for a people carrier.
Kingfisher and the Shinkansen
Japan is renowned for the incredible speed and efficiency of their trains. However, with speeds in excess of 300km/h, bullet trains presented a problem in creating huge sonic boom every time they emerged from a tunnel. An unfortunate result of changing air pressures, this source of noise pollution greatly disturbed local residents and placed pressure on engineers to address the problem.
This they did, and drew inspiration from a rather unlikely source: the Kingfisher. Kingfishers are masters in travelling between the mediums of air water, with very little splash. Just like the Kingfisher, the Shinkansen bullet train is equipped with a long beak-shaped nose. This significantly reduces the amount of noise the train makes, but also uses 15 per cent less electricity, and travels 10 per cent faster
