For nearly 100 years, scientists have dreamed of turning the lightest of all the elements, hydrogen, into a metal.
Now, in a stunning act of modern-day alchemy, scientists at Harvard University have finally succeeded in creating a tiny amount of what is the rarest, and possibly most valuable, material on the planet, they reported in the journal Science.
For metallic hydrogen could theoretically revolutionise technology, enabling the creation of super-fast computers, high-speed levitating trains and ultra-efficient vehicles and dramatically improving almost anything involving electricity.
And it could also allow humanity to explore outer space as never before.
But the prospect of this bright future could be at risk if the scientists’ next step – to establish whether the metal is stable at normal pressures and temperatures – fails to go as hoped.
Professor Isaac Silvera, who made the breakthrough with Dr Ranga Dias, said: “This is the holy grail of high-pressure physics.
“It's the first-ever sample of metallic hydrogen on Earth, so when you're looking at it, you're looking at something that’s never existed before.”
At the moment the tiny piece of metal can only be seen through two diamonds that were used to crush liquid hydrogen at a temperature far below freezing.
The amount of pressure needed was immense – more than is found at the centre of the Earth.
Nanotechnology: The search for micro miracles
Nanotechnology: The search for micro miracles
1/5 Doctors inside your body
Wearable fitness technology means we can monitor our health by strapping gadgets to ourselves. There are even prototype electronic tattoos that can sense our vital signs. But by scaling down this technology, we could go further by implanting or injecting tiny sensors inside our bodies. This would capture much more detailed information with less hassle to the patient, enabling doctors to personalise their treatment.
The possibilities are endless, ranging from monitoring inflammation and post-surgery recovery to more exotic applications whereby electronic devices actually interfere with our body's signals for controlling organ function. Although these technologies might sound like a thing of the far future, multi-billion healthcare firms such as GlaxoSmithKline are already working on ways to develop so-called "electroceuticals".
2/5 Sensors, sensors, everywhere
These sensors rely on newly-invented nanomaterials and manufacturing techniques to make them smaller, more complex and more energy efficient. For example, sensors with very fine features can now be printed in large quantities on flexible rolls of plastic at low cost. This opens up the possibility of placing sensors at lots of points over critical infrastructure to constantly check that everything is running correctly. Bridges, aircraft and even nuclear power plants could benefit.
3/5 Self-healing structures
If cracks do appear then nanotechnology could play a further role. Changing the structure of materials at the nanoscale can give them some amazing properties – by giving them a texture that repels water, for example. In the future, nanotechnology coatings or additives will even have the potential to allow materials to "heal" when damaged or worn. For example, dispersing nanoparticles throughout a material means that they can migrate to fill in any cracks that appear. This could produce self-healing materials for everything from aircraft cockpits to microelectronics, preventing small fractures from turning into large, more problematic cracks.
4/5 Making big data possible
All these sensors will produce more information than we've ever had to deal with before – so we'll need the technology to process it and spot the patterns that will alert us to problems. The same will be true if we want to use the "big data" from traffic sensors to help manage congestion and prevent accidents, or prevent crime by using statistics to more effectively allocate police resources.
Here, nanotechnology is helping to create ultra-dense memory that will allow us to store this wealth of data. But it's also providing the inspiration for ultra-efficient algorithms for processing, encrypting and communicating data without compromising its reliability. Nature has several examples of big-data processes efficiently being performed in real-time by tiny structures, such as the parts of the eye and ear that turn external signals into information for the brain.
5/5 Tackling climate change
The fight against climate change means we need new ways to generate and use electricity, and nanotechnology is already playing a role. It has helped create batteries that can store more energy for electric cars and has enabled solar panels to convert more sunlight into electricity.
The common trick in both applications is to use nanotexturing or nanomaterials (for example nanowires or carbon nanotubes) that turn a flat surface into a three-dimensional one with a much greater surface area. This means that there is more space for the reactions that enable energy storage or generation to take place, so the devices operate more efficiently.
In the future, nanotechnology could also enable objects to harvest energy from their environment. New nano-materials and concepts are currently being developed that show potential for producing energy from movement, light, variations in temperature, glucose and other sources with high conversion efficiency.
The sample has remained trapped in this astonishing grip, but sometime in the next few weeks, the researchers plan to carefully ease the pressure.
According to one theory, metallic hydrogen will be stable at room temperature – a prediction that Professor Silvera said was “very important”.
“That means if you take the pressure off, it will stay metallic, similar to the way diamonds form from graphite under intense heat and pressure, but remains a diamond when that pressure and heat is removed,” he said.
If this is true, then its properties as a super-conductor could dramatically improve anything that uses electricity.
“As much as 15 per cent of energy is lost to dissipation during transmission, so if you could make wires from this material and use them in the electrical grid, it could change that story,” the scientist said.
And metallic hydrogen could also transform humanity’s efforts to explore our solar system by providing a form of rocket fuel nearly four times more powerful than the best available today.
“It takes a tremendous amount of energy to make metallic hydrogen,” Professor Silvera said.
“And if you convert it back to molecular hydrogen, all that energy is released, so it would make it the most powerful rocket propellant known to man, and could revolutionize rocketry.
“That would easily allow you to explore the outer planets.
“We would be able to put rockets into orbit with only one stage, versus two, and could send up larger payloads, so it could be very important.”
However some scientists have theorised that metallic hydrogen will be unstable on its surface and so would gradually decay.
Asked what he thought would happen, Professor Silvera said: “I don’t want to guess, I want to do the experiment.”
But it could be a moment almost as exciting as the time the researchers first realised what they had created.
“Ranga was running the experiment, and we thought we might get there, but when he called me and said, ‘The sample is shining’, I went running down there, and it was metallic hydrogen.
“I immediately said we have to make the measurements to confirm it, so we rearranged the lab ... and that's what we did.
“It's a tremendous achievement, and even if it only exists in this diamond anvil cell at high pressure, it's a very fundamental and transformative discovery.”