̽��ֱ�� of Cambridge - laser

Using lasers to ‘heat and beat’ 3D-printed steel could help reduce costs

sc604 — Mon, 30 Oct 2023 09:01:39 +0000

̽��ֱ��method, developed by a research team led by the ̽��ֱ�� of Cambridge, allows structural modifications to be ‘programmed’ into metal alloys during 3D printing, fine-tuning their properties without the ‘heating and beating’ process that’s been in use for thousands of years.

̽��ֱ��new 3D printing method combines the best qualities of both worlds: the complex shapes that 3D printing makes possible, and the ability to engineer the structure and properties of metals that traditional methods allow. ̽��ֱ��results are reported in the journal Nature Communications.

3D printing has several advantages over other manufacturing methods. For example, it’s far easier to produce intricate shapes using 3D printing, and it uses far less material than traditional metal manufacturing methods, making it a more efficient process. However, it also has significant drawbacks.

“There’s a lot of promise around 3D printing, but it’s still not in wide use in industry, mostly because of high production costs,” said Dr Matteo Seita from Cambridge’s Department of Engineering, who led the research. “One of the main drivers of these costs is the amount of tweaking that materials need after production.”

Since the Bronze Age, metal parts have been made through a process of heating and beating. This approach, where the material is hardened with a hammer and softened by fire, allows the maker to form the metal into the desired shape and at the same time impart physical properties such as flexibility or strength.

“ ̽��ֱ��reason why heating and beating is so effective is because it changes the internal structure of the material, allowing control over its properties,” said Seita. “That’s why it’s still in use after thousands of years.”

One of the major downsides of current 3D printing techniques is an inability to control the internal structure in the same way, which is why so much post-production alteration is required. “We’re trying to come up with ways to restore some of that structural engineering capability without the need for heating and beating, which would in turn help reduce costs,” said Seita. “If you can control the properties you want in metals, you can leverage the greener aspects of 3D printing.”

Working with colleagues in Singapore, Switzerland, Finland and Australia, Seita developed a new ‘recipe’ for 3D-printed metal that allows a high degree of control over the internal structure of the material as it is being melted by a laser.

By controlling the way that the material solidifies after melting, and the amount of heat that is generated during the process, the researchers can programme the properties of the end material. Normally, metals are designed to be strong and tough, so that they are safe to use in structural applications. 3D-printed metals are inherently strong, but also brittle.

̽��ֱ��strategy the researchers developed gives full control over both strength and toughness, by triggering a controlled reconfiguration of the microstructure when the 3D-printed metal part is placed in a furnace at relatively low temperature. Their method uses conventional laser-based 3D printing technologies, but with a small tweak to the process.

“We found that the laser can be used as a ‘microscopic hammer’ to harden the metal during 3D printing,” said Seita. “However, melting the metal a second time with the same laser relaxes the metal’s structure, allowing the structural reconfiguration to take place when the part is placed in the furnace.”

Their 3D printed steel, which was designed theoretically and validated experimentally, was made with alternating regions of strong and tough material, making its performance comparable to steel that’s been made through heating and beating.

“We think this method could help reduce the costs of metal 3D printing, which could in turn improve the sustainability of the metal manufacturing industry,” said Seita. “In the near future, we also hope to be able to bypass the low-temperature treatment in the furnace, further reducing the number of steps required before using 3D printed parts in engineering applications.”

̽��ֱ��team included researchers from Nanyang Technological ̽��ֱ��, the Agency for Science, Technology and Research (A*STAR), the Paul Scherrer Institute, VTT Technical Research Centre of Finland, and the Australian Nuclear Science & Technology Organisation. Matteo Seita is a Fellow of St John’s College, Cambridge.

Reference:
Shubo Gao et al. ‘Additive manufacturing of alloys with programmable microstructure and properties.’ Nature Communications (2023). DOI: 10.1038/s41467-023-42326-y

Researchers have developed a new method for 3D printing metal that could help reduce costs and make more efficient use of resources.

This method could help reduce the costs of metal 3D printing, which could in turn improve the sustainability of the metal manufacturing industry

Matteo Seita

Jude E. Fronda

Retrieval of a stainless steel part made by 3D printing

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Little ANTs: researchers build the world’s tiniest engine

sc604 — Mon, 02 May 2016 19:01:00 +0000

Researchers have developed the world’s tiniest engine – just a few billionths of a metre in size – which uses light to power itself. ̽��ֱ��nanoscale engine, developed by researchers at the ̽��ֱ�� of Cambridge, could form the basis of future nano-machines that can navigate in water, sense the environment around them, or even enter living cells to fight disease.

̽��ֱ��prototype device is made of tiny charged particles of gold, bound together with temperature-responsive polymers in the form of a gel. When the ‘nano-engine’ is heated to a certain temperature with a laser, it stores large amounts of elastic energy in a fraction of a second, as the polymer coatings expel all the water from the gel and collapse. This has the effect of forcing the gold nanoparticles to bind together into tight clusters. But when the device is cooled, the polymers take on water and expand, and the gold nanoparticles are strongly and quickly pushed apart, like a spring. ̽��ֱ��results are reported in the journal PNAS.

“It’s like an explosion,” said Dr Tao Ding from Cambridge’s Cavendish Laboratory, and the paper’s first author. “We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them.”

“We know that light can heat up water to power steam engines,” said study co-author Dr Ventsislav Valev, now based at the ̽��ֱ�� of Bath. “But now we can use light to power a piston engine at the nanoscale.”

Nano-machines have long been a dream of scientists and public alike, but since ways to actually make them move have yet to be developed, they have remained in the realm of science fiction. ̽��ֱ��new method developed by the Cambridge researchers is incredibly simple, but can be extremely fast and exert large forces.

̽��ֱ��forces exerted by these tiny devices are several orders of magnitude larger than those for any other previously produced device, with a force per unit weight nearly a hundred times better than any motor or muscle. According to the researchers, the devices are also bio-compatible, cost-effective to manufacture, fast to respond, and energy efficient.

Professor Jeremy Baumberg from the Cavendish Laboratory, who led the research, has named the devices ‘ANTs’, or actuating nano-transducers. “Like real ants, they produce large forces for their weight. ̽��ֱ��challenge we now face is how to control that force for nano-machinery applications.”

̽��ֱ��research suggests how to turn Van de Waals energy – the attraction between atoms and molecules – into elastic energy of polymers and release it very quickly. “ ̽��ֱ��whole process is like a nano-spring,” said Baumberg. “ ̽��ֱ��smart part here is we make use of Van de Waals attraction of heavy metal particles to set the springs (polymers) and water molecules to release them, which is very reversible and reproducible.”

̽��ֱ��team is currently working with Cambridge Enterprise, the ̽��ֱ��’s commercialisation arm, and several other companies with the aim of commercialising this technology for microfluidics bio-applications.

̽��ֱ��research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC).

Reference:
Tao Ding et al. ‘Light-induced actuating nanotransducers.’ PNAS (2016). DOI: 10.1073/pnas.1524209113

Researchers have built a nano-engine that could form the basis for future applications in nano-robotics, including robots small enough to enter living cells.

Like real ants, they produce large forces for their weight.

Jeremy Baumberg

Yu Ji/ ̽��ֱ�� of Cambridge NanoPhotonics

Expanding polymer-coated gold nanoparticles

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Yes

Mirage maker

lw355 — Fri, 30 Oct 2015 11:30:54 +0000

This is a photothermal deflection spectrometer (PDS) and the mirage – only the width of a human hair in distance from the glass – is helping researchers to measure the quality of materials that turn light energy into electricity.

“We can see one defect in a million molecules,” explains Sadhanala, who built the machine while working on his PhD in the lab of Professor Sir Richard Friend. “ ̽��ֱ��PDS technique measures the amount of light absorbed by a material with up to five orders of magnitude more sensitivity than conventional techniques, making it one of the most sensitive absorption spectrometers in the world.”

A mirage is formed as light is bent when it passes through a medium with varying refractive index – a puddle of water seems to appear on the road ahead, for instance, when light meets hotter air radiating from the ground on a sunny day.

Sadhanala’s machine creates a mirage effect when light absorbed by the solar material is released as heat, which passes to a liquid that surrounds the sample. When a laser beam is directed to pass parallel to it, the mirage deflects the beam; the amount of deflection corresponds to the amount of heat absorbed, which in turn corresponds to the amount of light absorbed.

“Before, we would have had to make a whole solar device and spend months and months testing it to find out how efficient the material is,” explains Sadhanala. “Now you can measure a new material in half a day, and you don’t even need to make the whole device – you just need to be able to coat the material onto glass and make a mirage.”

A few weeks ago, Tushita Mukhopadhyay – a chemist at the Indian Institute of Science, Bangalore – carefully packaged up five new materials and flew to the UK to test them on the ‘mirage machine’ in Cambridge, and analyse other properties with researchers at Imperial College London. She had spent months making and characterising the materials – all of them belonging to a group of organic solar cells (OSCs) that can be printed as thin-film sheets.

What connects the two researchers, and indeed many other chemists, physicists and engineers, is the APEX project – an ambitious Anglo-Indian initiative to turn fundamental advances in solar materials into commercial reality.

APEX involves research institutes in Bangalore, Delhi, Hyderabad, Kanpur and Pune in India, and Brunel (which leads the partnership), Cambridge, Edinburgh, Imperial, Swansea and Oxford in the UK, plus solar industries in both countries. It has received almost £6 million funding since 2010 from the Indian Department of Science and Technology and Research Councils UK.

“Solar has always been the eventual solution to our energy problems but it’s always been the day after tomorrow,” explains Friend, who leads the Cambridge component. “Each of the partners in this project has an extensive research programme aimed at developing highly efficient photovoltaic devices, but there is a disconnect between what you can do in the lab and what can be rolled out at huge scale. This project is aimed at moving from established science to a viable technology.”

First though, there is the matter of achieving a major cost reduction and efficiency increase in solar power. ̽��ֱ��APEX team started by focusing on developing a new class of ‘excitonic’ solar cell (which produces electricity from the sun’s energy through the creation of an ‘exciton’ – essentially a free electron). Instead of using the conventional solar material, silicon, the researchers used solar materials made from organic dyes – dye-sensitised solar cells (DSSCs) – which are easy to make, easy to process and cost less.

However, one of the main issues surrounding the search for alternative solar materials to silicon has been their power conversion efficiencies (PCEs) – the amount of the sun’s energy that can be trapped and turned into electricity.

̽��ֱ��PCE for silicon is around 25%, whereas the current state-of-the-art PCE figures for DSSCs and OSCs are a little over 10%. To achieve incremental boosts in these figures, researchers like those in Friend’s group have been analysing what happens at the nanoscale when light hits the material. For instance, they now know that manipulating the ‘spin’ of electrons in solar cells can dramatically improve their performance.

Mukhopadhyay, who travelled to the UK thanks to funding through the UK–India Education and Research Initiative, explains: “My materials have a fast charge transport rate – as we’ve now proved at Cambridge and Imperial – but they have a low PCE. We think that a process called singlet fission, in which one exciton splits into two, is happening. This makes them interesting to look at because if more than one charge carrier is generated then this can increase the PCE.”

Another family of materials the team has high hopes for is a set of perovskite-structure lead halides. Work at the ̽��ֱ�� of Oxford has already achieved a PCE of above 17% for such materials, and Sadhanala has begun using his machine to see the effect of different processing methods on their properties.

As well as developing cheap, high-performing solar materials, the team will scale up towards prototypes that replicate the performance achieved in the research phase.

Although the aim is to provide a technology that can reduce the carbon footprint of electricity generation anywhere in the world, solar energy could fulfil a massive demand for energy in India. India is the fifth largest producer and consumer of electricity, around 70% of which is based on coal, yet around 200 million people are without access to electricity. With a rapidly growing economy and more than 1 billion people, India faces a huge energy challenge to meet the current government’s mission of ‘Power for all, 24x7, by 2019’.

In fact, India could be an ideal place to adopt new solar technologies on a large scale, says Friend: “India is already currently running the largest renewable capacity expansion programme in the world, and there is a sense that the next technology revolutions may well happen in an emerging country like India that hasn’t already built its future renewables-heavy electricity system.”

“India may well leapfrog the UK in taking up radical new approaches to power generation,” he adds. “We want APEX to contribute to the search for such approaches now and in the future. This is a journey, not a day’s outing.”

Aditya Sadhanala wanders over to the wall, turns a pulley, and a wooden box about a metre squared swings up and away. Below it gleams an array of carefully positioned lasers, deflectors and sensors surrounding a piece of glass no bigger than a contact lens. He flips a switch and creates a ‘mirage’.

India may well leapfrog the UK in taking up radical new approaches to power generation

Richard Friend

H. Raab

Venus transits the rising Sun

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Licence type:

Attribution-Noncommerical

Building ‘invisible’ materials with light

sc604 — Mon, 28 Jul 2014 09:00:00 +0000

A new method of building materials using light, developed by researchers at the ̽��ֱ�� of Cambridge, could one day enable technologies that are often considered the realm of science fiction, such as invisibility cloaks and cloaking devices.

Although cloaked starships won’t be a reality for quite some time, the technique which researchers have developed for constructing materials with building blocks a few billionths of a metre across can be used to control the way that light flies through them, and works on large chunks all at once. Details are published today (28 July) in the journal Nature Communications.

̽��ֱ��key to any sort of ‘invisibility’ effect lies in the way light interacts with a material. When light hits a surface, it is either absorbed or reflected, which is what enables us to see objects. However, by engineering materials at the nanoscale, it is possible to produce ‘metamaterials’: materials which can control the way in which light interacts with them. Light reflected by a metamaterial is refracted in the ‘wrong’ way, potentially rendering objects invisible, or making them appear as something else.

Metamaterials have a wide range of potential applications, including sensing and improving military stealth technology. However, before cloaking devices can become reality on a larger scale, researchers must determine how to make the right materials at the nanoscale, and using light is now shown to be an enormous help in such nano-construction.

̽��ֱ��technique developed by the Cambridge team involves using unfocused laser light as billions of needles, stitching gold nanoparticles together into long strings, directly in water for the first time. These strings can then be stacked into layers one on top of the other, similar to Lego bricks. ̽��ֱ��method makes it possible to produce materials in much higher quantities than can be made through current techniques.

In order to make the strings, the researchers first used barrel-shaped molecules called cucurbiturils (CBs). ̽��ֱ��CBs act like miniature spacers, enabling a very high degree of control over the spacing between the nanoparticles, locking them in place.

In order to connect them electrically, the researchers needed to build a bridge between the nanoparticles. Conventional welding techniques would not be effective, as they cause the particles to melt. “It’s about finding a way to control that bridge between the nanoparticles,” said Dr Ventsislav Valev of the ̽��ֱ��’s Cavendish Laboratory, one of the authors of the paper. “Joining a few nanoparticles together is fine, but scaling that up is challenging.”

̽��ֱ��key to controlling the bridges lies in the cucurbiturils: the precise spacing between the nanoparticles allows much more control over the process. When the laser is focused on the strings of particles in their CB scaffolds, it produces plasmons: ripples of electrons at the surfaces of conducting metals. These skipping electrons concentrate the light energy on atoms at the surface and join them to form bridges between the nanoparticles. Using ultrafast lasers results in billions of these bridges forming in rapid succession, threading the nanoparticles into long strings, which can be monitored in real time.

“We have controlled the dimensions in a way that hasn’t been possible before,” said Dr Valev, who worked with researchers from the Department of Chemistry, the Department of Materials Science & Metallurgy, and the Donostia International Physics Center in Spain on the project. “This level of control opens up a wide range of potential practical applications.”

A new technique which uses light like a needle to thread long chains of particles could help bring sci-fi concepts such as cloaking devices one step closer to reality.

This level of control opens up a wide range of potential practical applications

Ventsislav Valev

An efficient route to manufacturing nanomaterials with light through plasmon-induced laser-threading of gold nanoparticle strings

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Yes

Exposing ‘evil twins’

sc604 — Fri, 16 May 2014 07:23:08 +0000

A direct relationship between the way in which light is twisted by nanoscale structures and the nonlinear way in which it interacts with matter could be used to ensure greater purity for pharmaceuticals, allowing for ‘evil twins’ of drugs to be identified with much greater sensitivity.

Researchers from the ̽��ֱ�� of Cambridge have used this relationship, in combination with powerful lasers and nanopatterned gold surfaces, to propose a sensing mechanism that could be used to identify the right-handed and left-handed versions of molecules.

Some molecules are symmetrical, so their mirror image is an exact copy. However, most molecules in nature have a mirror image that differs - try putting a left-handed glove on to your right hand and you’ll see that your hands are not transposable one onto the other. Molecules whose mirror-images display this sort of “handedness” are known as chiral.

̽��ֱ��chirality of a molecule affects how it interacts with its surroundings, and different chiral forms of the same molecule can have completely different effects. Perhaps the best-known instance of this is Thalidomide, which was prescribed to pregnant women in the 1950s and 1960s. One chiral form of Thalidomide worked as an effective treatment for morning sickness in early pregnancy, while the other form, like an ‘evil twin’, prevented proper growth of the foetus. ̽��ֱ��drug that was prescribed to patients however, was a mix of both forms, resulting in more than 10,000 children worldwide being born with serious birth defects, such as shortened or missing limbs.

When developing new pharmaceuticals, identifying the correct chiral form is crucial. Specific molecules bind to specific receptors, so ensuring the correct chiral form is present determines the purity and effectiveness of the end product. However, the difficulty with achieving chiral purity is that usually both forms are synthesised in equal quantities.

Researchers from the ̽��ֱ�� of Cambridge have designed a new type of sensing mechanism, combining a unique twisting property of light with frequency doubling to identify different chiral forms of molecules with extremely high sensitivity, which could be useful in the development of new drugs. ̽��ֱ��results are published in the journal Advanced Materials.

̽��ֱ��sensing mechanism, designed by Dr Ventsislav Valev and Professor Jeremy Baumberg from the Cavendish Laboratory, in collaboration with colleagues from the UK and abroad, uses a nanopatterned gold surface in combination with powerful lasers.

Currently, differing chiral forms of molecules are detected by using beams of polarised light. ̽��ֱ��way in which the light is twisted by the molecules results in chiroptical effects, which are typically very weak. By using powerful lasers however, second harmonic generation (SHG) chiroptical effects emerge, which are typically three orders of magnitude stronger. SHG is a quantum mechanical process whereby two red photons can be annihilated to create a blue photon, creating blue light from red.

Recently, another major step towards increasing chiroptical effects came from the development of superchiral light – a super twisty form of light.

̽��ֱ��researchers identified a direct link between the fundamental equations for superchiral light and SHG, which would make even stronger chiroptical effects possible. Combining superchiral light and SHG could yield record-breaking effects, which would result in very high sensitivity for measuring the chiral purity of drugs.

̽��ֱ��researchers also used tiny gold structures, known as plasmonic nanostructures, to focus the beams of light. Just as a glass lens can be used to focus sunlight to a certain spot, these plasmonic nanostructures concentrate incoming light into hotspots on their surface, where the optical fields become huge. Due to the presence of optical field variations, it is in these hotspots that superchiral light and SHG combine their effects.

“By using nanostructures, lasers and this unique twisting property of light, we could selectively destroy the unwanted form of the molecule, while leaving the desired form unaffected,” said Dr Valev. “Together, these technologies could help ensure that new drugs are safe and pure.”

A combination of nanotechnology and a unique twisting property of light could lead to new methods for ensuring the purity and safety of pharmaceuticals.

Together, these technologies could help ensure that new drugs are safe and pure

Ventsislav Valev

When twisted light matches the twist of nanostructures, strong interactions with chiral molecules could arise

Yes