Honeycomb-Inspired Metal Gives Gas-Free Cooling a 100-Million-Cycle Lifespan
A fridge that cools without gas, without a compressor, and without wearing out could be one step closer to your home. Scientists in Hong Kong have built a cooling part inspired by honeycombs that survived more than 100 million rounds of squeezing and releasing in laboratory tests — the equivalent of over 10 years of use — and they say it can be made quickly and cheaply. The work, published in the journal Science, tackles the biggest problem holding back a cleaner way to keep things cold: making a material that is strong, cheap and long-lasting all at the same time.
The technology is called elastocaloric cooling. Instead of compressing a gas the way an ordinary fridge does, it squeezes a special metal. The metal heats up when it is squeezed and cools down when the pressure is released. That heating and cooling cycle can be used to move heat out of a fridge or an air conditioner — with no refrigerant gas at all.
It is an elegant idea, and researchers have known about it for years. The trouble has always been practical. The metal parts cracked, wore out or cost too much to make. The new study, led by Professor Sun Qingping at the Hong Kong University of Science and Technology (HKUST), reports a design that solves all three problems at once.
Why cooling needs a new idea
Almost every fridge, freezer and air conditioner in the world today works the same way. A gas called a refrigerant is compressed until it gets hot, the heat is dumped outside, and then the gas expands and gets cold, chilling the inside of the appliance. The system works well, but it has two costs. It uses a lot of electricity, and the refrigerant gases themselves can add to the greenhouse effect if they leak into the atmosphere.
As the world gets hotter, demand for cooling keeps growing. More homes, offices, hospitals and food stores need air conditioning and refrigeration, and that means more energy use and more refrigerant gas in circulation. Scientists and engineers have been searching for a solid-state alternative — a way to cool things using a solid material instead of a gas — for years. Elastocaloric cooling is one of the most promising candidates, because it uses no gas, has no compressor, and the metal itself does the work.
The HKUST team puts it plainly: “As global demand for cooling continues to grow, the urgent need for sustainable refrigeration technologies is becoming increasingly evident.”
The timing is hard to miss. World leaders are gathering in Antalya, Türkiye, for the COP31 climate talks, where the future of energy use — including cooling — is on the agenda. For countries with long, hot summers, including Pakistan, cooling is not a luxury. It keeps food fresh, medicines safe and people alive during heatwaves. A cheaper, cleaner way to cool could matter a great deal.
What is elastocaloric cooling?
The key ingredient is a shape-memory alloy — a metal that can change its internal structure when it is squeezed and then spring back to its original shape when the pressure is released. The alloy used here is nickel-titanium, usually shortened to NiTi.
Here is the simple version of how it works:
- Squeeze the metal. When the alloy is compressed, its crystal structure changes and it gives off heat — it gets warmer.
- Dump the heat. That extra heat is carried away, for example into the air outside a fridge.
- Release the pressure. When the squeeze is released, the metal’s structure snaps back, and it absorbs heat from its surroundings — it gets colder.
- Repeat. Run the cycle again and again, and you steadily move heat from one place to another.
It is the same basic idea as a normal fridge, but the working material is a solid piece of metal rather than a gas that must be pumped around pipes. There is nothing to leak, and there is no compressor to break down.
The catch is that the metal has to survive being squeezed and released millions of times without cracking. In a working fridge, the cooling part might be squeezed several times every second, day after day, for years. Most designs so far failed that test. They were made from tubes, plates or wires, or from thin-walled structures cut with an expensive technique called wire-cut electrical discharge machining. Those shapes were slow and costly to produce, and they tended to split or buckle after repeated loading.
The honeycomb idea
The HKUST team’s answer came from nature. Honeycombs and bamboo are light, yet remarkably strong. A honeycomb is made of thin walls arranged in hexagons, and it can take a heavy load without collapsing. Bamboo grows in hollow, layered segments that resist splitting. The researchers copied that layered, porous design.
Their method is called “stamping and stacking”, and it is deliberately simple. Thin sheets of the nickel-titanium alloy — the kind already sold commercially — are stamped into small porous chips, like a machine stamping out shapes from a sheet of metal. The chips are then stacked on top of each other to form a tube-shaped cooling part.
The design has three advantages, according to the team:
It is fast and cheap to make. The stamping process can produce 100 alloy chips per minute. That makes it more than 100 times faster and 95 per cent cheaper than the existing wire-cut machining method.
It lasts an extremely long time. Because the cooling part is built from separate stacked chips rather than one long tube, the boundaries between the chips stop cracks from spreading. A crack that starts in one chip runs into the edge of the next chip and stops, instead of splitting the whole structure lengthways. In tests, the structure survived more than 100 million operating cycles — an estimated service life of more than 10 years under the tested conditions.
It cools well. Using a cooling unit just 30 millimetres long — about the length of a matchbox — containing 200 stacked chips, the team built a prototype that achieved a maximum temperature span of 11.7 kelvin and a specific cooling power of 3.85 watts per gram. A kelvin is the same size as a degree Celsius when you are measuring a difference in temperature, so the prototype could create a temperature gap of 11.7 degrees between its hot and cold ends. The cooling power figure means each gram of the metal can shift 3.85 watts of heat.
Professor Sun said the manufacturing question was just as important as the cooling itself. “The cost-effective manufacturing of refrigerant structure is a key factor in determining whether elastocaloric cooling can move from the laboratory prototypes to mass-produced products,” he said. “These structures must deliver fast heat transfer, extremely high mechanical reliability and at the same time low manufacturing cost. Achieving all three has been a longstanding challenge for the field.”
What the numbers mean in plain English
Big numbers in a science paper can be hard to picture, so here is what the key figures actually mean.
100 million cycles. Every squeeze-and-release is one cycle. A fridge cooling part might run through several cycles a second, which adds up to millions of cycles a year. Surviving 100 million cycles in testing is the laboratory equivalent of more than a decade of daily use — and the structure was still working at the end of the test.
100 chips per minute. The stamping machine turns out chips fast enough for factory production. Older methods cut each piece slowly, one at a time. Stamping is the kind of process already used to make coins, bottle caps and car parts, which is why the team says it can scale up.
95 per cent cheaper. The new method costs about one-twentieth as much as the wire-cutting method it replaces. Cost has been one of the main reasons elastocaloric cooling stayed in the laboratory. A technology that works beautifully but costs too much to build will never reach a shop shelf.
11.7 degrees of temperature span. The prototype could hold one end 11.7 degrees Celsius colder than the other. That is not yet enough to freeze food on its own, but it shows the cooling effect is strong. Real appliances would combine several units or stages to reach the temperatures a fridge needs.
Three breakthroughs in one year
The new paper is the HKUST team’s third cooling breakthrough in less than a year, and the three results build on each other.
In January, the same group built what they describe as the world’s first sub-zero elastocaloric green freezer, a device that could reach minus 12 degrees Celsius. Those findings were published in the journal Nature.
In August, they developed a fatigue-resistant nickel-titanium-copper-cobalt alloy and built what they call the world’s first zero-degradation elastocaloric cooling device — a machine whose cooling performance did not fade over a million operating cycles. That work was published in the energy science journal Joule.
Now, in November, they have reported the cheap, durable structure that could make the whole approach practical to manufacture, published in Science. The paper is titled “Stacked porous NiTi structure with low cost and ultrahigh fatigue life for elastocaloric cooling”. Its first author is Su Changfeng, a PhD student, and the corresponding authors are Professor Sun Qingping, Professor Li Qiao and Dr Li Xueshi. The work was supported by the Research Grants Council of Hong Kong and the Innovation and Technology Commission of Hong Kong, and the team has filed multiple international patents for the technology.
Taken together, the three papers tell a clear story: the cooling effect works, the device can run without degrading, and now the parts can be made cheaply and last for years. The next step, the team says, is to improve heat transfer, build more energy-efficient systems to squeeze the metal, and develop even better alloys.
Why it matters for Pakistan
Pakistan is one of the countries where cooling matters most. Summers are long and fiercely hot, and air conditioning and refrigeration are essential for health, food and work. At the same time, electricity is expensive, power cuts are common, and many households cannot afford the running cost of a conventional air conditioner.
A cooling technology that uses less energy, has no gas to leak or top up, and has fewer moving parts to break could be especially useful in such conditions — if it ever reaches the market at an affordable price. That is still a big “if”. The HKUST prototype is a laboratory device, not a product. It would need years of engineering, safety testing and factory investment before it appeared in a shop.
But the direction of travel is encouraging. The researchers themselves say the stamping method is not limited to one type of metal sheet. Similar structures could be made from sheets cut by laser or etching, and the team is already working on the next steps towards commercialisation. The patents they have filed are a sign they intend to take the technology out of the university and into industry.
For now, the honest summary is this: scientists have shown that gas-free cooling can be made to last. The fridge of the future may be built not around a gas and a compressor, but around a piece of metal that learned its shape from a honeycomb.
Frequently asked questions
What is elastocaloric cooling?
Elastocaloric cooling is a way of moving heat using a solid metal instead of a gas. When a shape-memory alloy such as nickel-titanium is squeezed, it heats up. When the pressure is released, it cools down. Repeating that cycle moves heat from one place to another, which is how a fridge or air conditioner works — without any refrigerant gas.
Why is honeycomb the inspiration?
Honeycombs are light but very strong. Their hexagonal walls spread force evenly and resist collapsing. The HKUST team copied that layered, porous structure, stamping thin metal sheets into chips and stacking them. The boundaries between the stacked chips stop cracks from spreading, which is why the structure survives so many cycles.
How long did the new cooling part last in tests?
More than 100 million operating cycles, which the researchers estimate is equal to more than 10 years of use under the tested conditions. The structure was still working when the test ended.
How much cheaper is the new manufacturing method?
The stamping process can make 100 metal chips per minute, and the team says it is more than 100 times faster and 95 per cent cheaper than the wire-cutting method used before. Cost and durability have been the two biggest obstacles for elastocaloric cooling.
Can I buy a fridge with this technology yet?
No. This is laboratory research, not a product. The prototype is a small cooling unit that proves the idea works and can be made cheaply. Real appliances would need further engineering, safety testing and factory investment. The research team has filed international patents and says it is working towards commercialisation.
Where was the research published?
The study, titled “Stacked porous NiTi structure with low cost and ultrahigh fatigue life for elastocaloric cooling”, was published in the journal Science. Its DOI is 10.1126/science.aeh7074. The lead research team is at the Hong Kong University of Science and Technology.
Conclusion
Cooling is one of the quiet giants of modern life — invisible when it works, and a crisis when it does not. The search for a cleaner way to do it has run into the same wall for years: materials that worked in a laboratory cracked, wore out or cost too much once they were asked to run day after day.
The honeycomb-inspired design reported this week attacks that wall directly. It borrows nature’s strongest shape, stamps it out of ordinary metal sheets at factory speed, and survives a decade’s worth of squeezing in the laboratory. It is not a fridge you can buy, and it would be wrong to pretend otherwise. But it is the clearest sign yet that gas-free cooling can be practical — and for the world’s hottest countries, that is a result worth watching.
Sources
- HKUST: https://hkust.edu.hk/news/hkust-researchers-develop-low-cost-elastocaloric-refrigerant-structure-over-100-million-cycle
- Tech Xplore: https://techxplore.com/news/2026-11-honeycombs-cooling-million.html
- Science: https://www.science.org/doi/10.1126/science.aeh7074
- Interesting Engineering: https://interestingengineering.com/energy/honeycomb-inspired-cooling-structure
- Knowridge Science Report: https://knowridge.com/2026/11/honeycomb-inspired-metal-could-make-cleaner-cooling-last-much-longer/
This article is for general information and education only. It is not legal or financial advice.
