̽��ֱ�� of Cambridge - Oren Scherman

Soft, stretchy ‘jelly batteries’ inspired by electric eels

sc604 — Wed, 17 Jul 2024 18:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, took their inspiration from electric eels, which stun their prey with modified muscle cells called electrocytes.

Like electrocytes, the jelly-like materials developed by the Cambridge researchers have a layered structure, like sticky Lego, that makes them capable of delivering an electric current.

̽��ֱ��self-healing jelly batteries can stretch to over ten times their original length without affecting their conductivity – the first time that such stretchability and conductivity has been combined in a single material. ̽��ֱ��results are reported in the journal Science Advances.

̽��ֱ��jelly batteries are made from hydrogels: 3D networks of polymers that contain over 60% water. ̽��ֱ��polymers are held together by reversible on/off interactions that control the jelly’s mechanical properties.

̽��ֱ��ability to precisely control mechanical properties and mimic the characteristics of human tissue makes hydrogels ideal candidates for soft robotics and bioelectronics; however, they need to be both conductive and stretchy for such applications.

“It’s difficult to design a material that is both highly stretchable and highly conductive, since those two properties are normally at odds with one another,” said first author Stephen O’Neill, from Cambridge’s Yusuf Hamied Department of Chemistry. “Typically, conductivity decreases when a material is stretched.”

“Normally, hydrogels are made of polymers that have a neutral charge, but if we charge them, they can become conductive,” said co-author Dr Jade McCune, also from the Department of Chemistry. “And by changing the salt component of each gel, we can make them sticky and squish them together in multiple layers, so we can build up a larger energy potential.”

Conventional electronics use rigid metallic materials with electrons as charge carriers, while the jelly batteries use ions to carry charge, like electric eels.

̽��ֱ��hydrogels stick strongly to each other because of reversible bonds that can form between the different layers, using barrel-shaped molecules called cucurbiturils that are like molecular handcuffs. ̽��ֱ��strong adhesion between layers provided by the molecular handcuffs allows for the jelly batteries to be stretched, without the layers coming apart and crucially, without any loss of conductivity.

̽��ֱ��properties of the jelly batteries make them promising for future use in biomedical implants, since they are soft and mould to human tissue. “We can customise the mechanical properties of the hydrogels so they match human tissue,” said Professor Oren Scherman, Director of the Melville Laboratory for Polymer Synthesis, who led the research in collaboration with Professor George Malliaras from the Department of Engineering. “Since they contain no rigid components such as metal, a hydrogel implant would be much less likely to be rejected by the body or cause the build-up of scar tissue.”

In addition to their softness, the hydrogels are also surprisingly tough. They can withstand being squashed without permanently losing their original shape, and can self-heal when damaged.

̽��ֱ��researchers are planning future experiments to test the hydrogels in living organisms to assess their suitability for a range of medical applications.

̽��ֱ��research was funded by the European Research Council and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Oren Scherman is a Fellow of Jesus College, Cambridge.

Reference:
Stephen J.K. O’Neill et al. ‘Highly Stretchable Dynamic Hydrogels for Soft Multilayer Electronics.’ Science Advances (2024). DOI: 10.1126/sciadv.adn5142

Researchers have developed soft, stretchable ‘jelly batteries’ that could be used for wearable devices or soft robotics, or even implanted in the brain to deliver drugs or treat conditions such as epilepsy.

Scherman Lab

Jelly batteries

̽��ֱ��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 – 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.

Yes

‘Super jelly’ can survive being run over by a car

sc604 — Thu, 25 Nov 2021 16:02:38 +0000

̽��ֱ��soft-yet-strong material, developed by a team at the ̽��ֱ�� of Cambridge, looks and feels like a squishy jelly, but acts like an ultra-hard, shatterproof glass when compressed, despite its high water content.

̽��ֱ��non-water portion of the material is a network of polymers held together by reversible on/off interactions that control the material’s mechanical properties. This is the first time that such significant resistance to compression has been incorporated into a soft material.

̽��ֱ��‘super jelly’ could be used for a wide range of potential applications, including soft robotics, bioelectronics or even as a cartilage replacement for biomedical use. ̽��ֱ��results are reported in the journal Nature Materials.

̽��ֱ��way materials behave – whether they’re soft or firm, brittle or strong – is dependent upon their molecular structure. Stretchy, rubber-like hydrogels have lots of interesting properties that make them a popular subject of research – such as their toughness and self-healing capabilities – but making hydrogels that can withstand being compressed without getting crushed is a challenge.

“In order to make materials with the mechanical properties we want, we use crosslinkers, where two molecules are joined through a chemical bond,” said Dr Zehuan Huang from the Yusuf Hamied Department of Chemistry, the study’s first author. “We use reversible crosslinkers to make soft and stretchy hydrogels, but making a hard and compressible hydrogel is difficult and designing a material with these properties is completely counterintuitive.”

Working in the lab of Professor Oren A Scherman, who led the research, the team used barrel-shaped molecules called cucurbiturils to make a hydrogel that can withstand compression. ̽��ֱ��cucurbituril is the crosslinking molecule that holds two guest molecules in its cavity – like a molecular handcuff. ̽��ֱ��researchers designed guest molecules that prefer to stay inside the cavity for longer than normal, which keeps the polymer network tightly linked, allowing for it to withstand compression.

“At 80% water content, you’d think it would burst apart like a water balloon, but it doesn’t: it stays intact and withstands huge compressive forces,” said Scherman, Director of the ̽��ֱ��’s Melville Laboratory for Polymer Synthesis. “ ̽��ֱ��properties of the hydrogel are seemingly at odds with each other.”

“ ̽��ֱ��way the hydrogel can withstand compression was surprising, it wasn’t like anything we’ve seen in hydrogels,” said co-author Dr Jade McCune, also from the Department of Chemistry. “We also found that the compressive strength could be easily controlled through simply changing the chemical structure of the guest molecule inside the handcuff.”

To make their glass-like hydrogels, the team chose specific guest molecules for the handcuff. Altering the molecular structure of guest molecules within the handcuff allowed the dynamics of the material to ‘slow down’ considerably, with the mechanical performance of the final hydrogel ranging from rubber-like to glass-like states.

“People have spent years making rubber-like hydrogels, but that’s just half of the picture,” said Scherman. “We’ve revisited traditional polymer physics and created a new class of materials that span the whole range of material properties from rubber-like to glass-like, completing the full picture.”

̽��ֱ��researchers used the material to make a hydrogel pressure sensor for real-time monitoring of human motions, including standing, walking and jumping.

“To the best of our knowledge, this is the first time that glass-like hydrogels have been made. We’re not just writing something new into the textbooks, which is really exciting, but we’re opening a new chapter in the area of high-performance soft materials,” said Huang.

Researchers from the Scherman lab are currently working to further develop these glass-like materials towards biomedical and bioelectronic applications in collaboration with experts from engineering and materials science. ̽��ֱ��research was funded in part by the Leverhulme Trust and a Marie Skłodowska-Curie Fellowship. Oren Scherman is a Fellow of Jesus College.

Reference:
Zehuan Huang et al. ‘Highly compressible glass-like supramolecular polymer networks.’ Nature Materials (2021). DOI: 10.1038/s41563-021-01124-x

Researchers have developed a jelly-like material that can withstand the equivalent of an elephant standing on it, and completely recover to its original shape, even though it’s 80% water.

At 80% water content, you’d think it would burst apart like a water balloon, but it doesn’t: it stays intact and withstands huge compressive forces

Oren Scherman

‘Super jelly’ can survive being run over by a car

Zehuan Huang

Super jelly

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 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.

Yes

Nano ‘camera’ made using molecular glue allows real-time monitoring of chemical reactions

sc604 — Thu, 02 Sep 2021 14:59:34 +0000

̽��ֱ��device, made by a team from the ̽��ֱ�� of Cambridge, combines tiny semiconductor nanocrystals called quantum dots and gold nanoparticles using molecular glue called cucurbituril (CB). When added to water with the molecule to be studied, the components self-assemble in seconds into a stable, powerful tool that allows the real-time monitoring of chemical reactions.

̽��ֱ��camera harvests light within the semiconductors, inducing electron transfer processes like those that occur in photosynthesis, which can be monitored using incorporated gold nanoparticle sensors and spectroscopic techniques. They were able to use the camera to observe chemical species which had been previously theorised but not directly observed.

̽��ֱ��platform could be used to study a wide range of molecules for a variety of potential applications, such as the improvement of photocatalysis and photovoltaics for renewable energy. ̽��ֱ��results are reported in the journal Nature Nanotechnology.

Nature controls the assemblies of complex structures at the molecular scale through self-limiting processes. However, mimicking these processes in the lab is usually time-consuming, expensive and reliant on complex procedures.

“In order to develop new materials with superior properties, we often combine different chemical species together to come up with a hybrid material that has the properties we want,” said Professor Oren Scherman from Cambridge’s Yusuf Hamied Department of Chemistry, who led the research. “But making these hybrid nanostructures is difficult, and you often end up with uncontrolled growth or materials that are unstable.”

̽��ֱ��new method that Scherman and his colleagues from Cambridge’s Cavendish Laboratory and ̽��ֱ�� College London developed uses cucurbituril – a molecular glue which interacts strongly with both semiconductor quantum dots and gold nanoparticles. ̽��ֱ��researchers used small semiconductor nanocrystals to control the assembly of larger nanoparticles through a process they coined interfacial self-limiting aggregation. ̽��ֱ��process leads to permeable and stable hybrid materials that interact with light. ̽��ֱ��camera was used to observe photocatalysis and track light-induced electron transfer.

“We were surprised how powerful this new tool is, considering how straightforward it is to assemble,” said first author Dr Kamil Sokołowski, also from the Department of Chemistry.

To make their nano camera, the team added the individual components, along with the molecule they wanted to observe, to water at room temperature. Previously, when gold nanoparticles were mixed with the molecular glue in the absence of quantum dots, the components underwent unlimited aggregation and fell out of solution. However, with the strategy developed by the researchers, quantum dots mediate the assembly of these nanostructures so that the semiconductor-metal hybrids control and limit their own size and shape. In addition, these structures stay stable for weeks.

“This self-limiting property was surprising, it wasn’t anything we expected to see,” said co-author Dr Jade McCune, also from the Department of Chemistry. “We found that the aggregation of one nanoparticulate component could be controlled through the addition of another nanoparticle component.”

When the researchers mixed the components together, the team used spectroscopy to observe chemical reactions in real time. Using the camera, they were able to observe the formation of radical species – a molecule with an unpaired electron – and products of their assembly such as sigma dimeric viologen species, where two radicals form a reversible carbon-carbon bond. ̽��ֱ��latter species had been theorised but never observed.

“People have spent their whole careers getting pieces of matter to come together in a controlled way,” said Scherman, who is also Director of the Melville Laboratory. “This platform will unlock a wide range of processes, including many materials and chemistries that are important for sustainable technologies. ̽��ֱ��full potential of semiconductor and plasmonic nanocrystals can now be explored, providing an opportunity to simultaneously induce and observe photochemical reactions.”

“This platform is a really big toolbox considering the number of metal and semiconductor building blocks that can be now coupled together using this chemistry– it opens up lots of new possibilities for imaging chemical reactions and sensing through taking snapshots of monitored chemical systems,” said Sokołowski. “ ̽��ֱ��simplicity of the setup means that researchers no longer need complex, expensive methods to get the same results.”

Researchers from the Scherman lab are currently working to further develop these hybrids towards artificial photosynthetic systems and (photo)catalysis where electron-transfer processes can be observed directly in real time. ̽��ֱ��team is also looking at mechanisms of carbon-carbon bond formation as well as electrode interfaces for battery applications.

̽��ֱ��research was carried out in collaboration with Professor Jeremy Baumberg at Cambridge’s Cavendish Laboratory and Dr Edina Rosta at ̽��ֱ�� College London. It was funded in part by the Engineering and Physical Sciences Research Council (EPSRC).

Reference:
Kamil Sokołowski et al. ‘Nanoparticle surfactants for kinetically arrested photoactive assemblies to track light-induced electron transfer.’ Nature Nanotechnology (2021). DOI: 10.1038/s41565-021-00949-6

Researchers have made a tiny camera, held together with ‘molecular glue’ that allows them to observe chemical reactions in real time.

This platform is a really big toolbox – it opens up lots of new possibilities for imaging chemical reactions

Kamil Sokołowski

Scherman Group

Nano camera

Yes

Green method developed for making artificial spider silk

sc604 — Mon, 10 Jul 2017 19:00:00 +0000

A team of architects and chemists from the ̽��ֱ�� of Cambridge has designed super-stretchy and strong fibres which are almost entirely composed of water, and could be used to make textiles, sensors and other materials. ̽��ֱ��fibres, which resemble miniature bungee cords as they can absorb large amounts of energy, are sustainable, non-toxic and can be made at room temperature.

This new method not only improves upon earlier methods of making synthetic spider silk, since it does not require high energy procedures or extensive use of harmful solvents, but it could substantially improve methods of making synthetic fibres of all kinds, since other types of synthetic fibres also rely on high-energy, toxic methods. ̽��ֱ��results are reported in the journal Proceedings of the National Academy of Sciences.

Spider silk is one of nature’s strongest materials, and scientists have been attempting to mimic its properties for a range of applications, with varying degrees of success. “We have yet to fully recreate the elegance with which spiders spin silk,” said co-author Dr Darshil Shah from Cambridge’s Department of Architecture.

̽��ֱ��fibres designed by the Cambridge team are “spun” from a soupy material called a hydrogel, which is 98% water. ̽��ֱ��remaining 2% of the hydrogel is made of silica and cellulose, both naturally available materials, held together in a network by barrel-shaped molecular “handcuffs” known as cucurbiturils. ̽��ֱ��chemical interactions between the different components enable long fibres to be pulled from the gel.

̽��ֱ��fibres are pulled from the hydrogel, forming long, extremely thin threads – a few millionths of a metre in diameter. After roughly 30 seconds, the water evaporates, leaving a fibre which is both strong and stretchy.

“Although our fibres are not as strong as the strongest spider silks, they can support stresses in the range of 100 to 150 megapascals, which is similar to other synthetic and natural silks,” said Shah. “However, our fibres are non-toxic and far less energy-intensive to make.”

̽��ֱ��fibres are capable of self-assembly at room temperature, and are held together by supramolecular host-guest chemistry, which relies on forces other than covalent bonds, where atoms share electrons.

“When you look at these fibres, you can see a range of different forces holding them together at different scales,” said Yuchao Wu, a PhD student in Cambridge’s Department of Chemistry, and the paper’s lead author. “It’s like a hierarchy that results in a complex combination of properties.”

̽��ֱ��strength of the fibres exceeds that of other synthetic fibres, such as cellulose-based viscose and artificial silks, as well as natural fibres such as human or animal hair.

In addition to its strength, the fibres also show very high damping capacity, meaning that they can absorb large amounts of energy, similar to a bungee cord. There are very few synthetic fibres which have this capacity, but high damping is one of the special characteristics of spider silk. ̽��ֱ��researchers found that the damping capacity in some cases even exceeded that of natural silks.

“We think that this method of making fibres could be a sustainable alternative to current manufacturing methods,” said Shah. ̽��ֱ��researchers plan to explore the chemistry of the fibres further, including making yarns and braided fibres.

This research is the result of a collaboration between the Melville Laboratory for Polymer Synthesis in the Department of Chemistry, led by Professor Oren Scherman; and the Centre for Natural Material Innovation in the Department of Architecture, led by Dr Michael Ramage. ̽��ֱ��two groups have a mutual interest in natural and nature-inspired materials, processes and their applications across different scales and disciplines.

̽��ֱ��research is supported by the UK Engineering and Physical Sciences Research Council (EPSRC) and the Leverhulme Trust.

Reference
Yuchao Wu et al. ‘Bioinspired supramolecular fibers drawn from a multiphase self-assembled hydrogel.’ Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1705380114

Researchers have designed a super stretchy, strong and sustainable material that mimics the qualities of spider silk, and is ‘spun’ from a material that is 98% water.

This method of making fibres could be a sustainable alternative to current manufacturing methods.

Darshil Shah

William Waterway

Spider web necklace with pearls of dew

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

Yes

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Attribution-ShareAlike

Nano ‘hall of mirrors’ causes molecules to mix with light

sc604 — Mon, 13 Jun 2016 15:00:00 +0000

When a molecule emits a blink of light, it doesn’t expect it to ever come back. However researchers have now managed to place single molecules in such a tiny optical cavity that emitted photons, or particles of light, return to the molecule before they have properly left. ̽��ֱ��energy oscillates back and forth between light and molecule, resulting in a complete mixing of the two.

Previous attempts to mix molecules with light have been complex to produce and only achievable at very low temperatures, but the researchers, led by the ̽��ֱ�� of Cambridge, have developed a method to produce these ‘half-light’ molecules at room temperature.

These unusual interactions of molecules with light provide new ways to manipulate the physical and chemical properties of matter, and could be used to process quantum information, aid in the understanding of complex processes at work in photosynthesis, or even manipulate the chemical bonds between atoms. ̽��ֱ��results are reported in the journal Nature.

To use single molecules in this way, the researchers had to reliably construct cavities only a billionth of a metre (one nanometre) across in order to trap light. They used the tiny gap between a gold nanoparticle and a mirror, and placed a coloured dye molecule inside.

“It’s like a hall of mirrors for a molecule, only spaced a hundred thousand times thinner than a human hair,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.

In order to achieve the molecule-light mixing, the dye molecules needed to be correctly positioned in the tiny gap. “Our molecules like to lie down flat on the gold, and it was really hard to persuade them to stand up straight,” said Rohit Chikkaraddy, lead author of the study.

To solve this, the team joined with a team of chemists at Cambridge led by Professor Oren Scherman to encapsulate the dyes in hollow barrel-shaped molecular cages called cucurbiturils, which are able to hold the dye molecules in the desired upright position.

When assembled together correctly, the molecule scattering spectrum splits into two separated quantum states which is the signature of this ‘mixing’. This spacing in colour corresponds to photons taking less than a trillionth of a second to come back to the molecule.

A key advance was to show strong mixing of light and matter was possible for single molecules even with large absorption of light in the metal and at room temperature. “Finding single-molecule signatures took months of data collection,” said Chikkaraddy.

̽��ֱ��researchers were also able to observe steps in the colour spacing of the states corresponding to whether one, two, or three molecules were in the gap.

̽��ֱ��Cambridge team collaborated with theorists Professor Ortwin Hess at the Blackett Laboratory, Imperial College London and Dr Edina Rosta at Kings College London to understand the confinement and interaction of light in such tiny gaps, matching experiments amazingly well.

̽��ֱ��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), the Winton Programme for the Physics of Sustainability and St John’s College.

Reference:
Rohit Chikkaraddy et al. ‘Single-molecule strong coupling at room temperature in plasmonic nanocavities.’ Nature (2016). DOI: 10.1038/nature17974

Researchers have successfully used quantum states to mix a molecule with light at room temperature, which will aid in the exploration of quantum technologies and provide new ways to manipulate the physical and chemical properties of matter.

It’s like a hall of mirrors for a molecule, only spaced a hundred thousand times thinner than a human hair.

Jeremy Baumberg

Yu Ji/ ̽��ֱ�� of Cambridge NanoPhotonics

Mixing light with dye molecules, trapped in golden gaps

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

Yes

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

Trapping the light fantastic

lw355 — Mon, 16 Jun 2014 08:13:42 +0000

Jeremy Baumberg and his 30-strong team of researchers are master manipulators of light. They are specialists in nanophotonics – the control of how light interacts with tiny chunks of matter, at scales as small as a billionth of a metre. It’s a field of physics that 20 years ago was unknown.

At the heart of nanophotonics is the idea that changing the structure of materials at the scale of a few atoms can be used to alter not only the way light interacts with the material, but also its functional properties.

“ ̽��ֱ��goal is to design materials with really intricate architecture on a really small scale, so small it’s smaller than the wavelength of light,” said Baumberg, Professor of Nanophotonics in the Department of Physics. “Whether the starting material is polystyrene or gold, changing the shape of its nanostructure can give us extraordinary control over how light energy is absorbed by the electrons locked inside. We’re learning how to use this to develop new functionality.”

One of their recent achievements is to develop synthetic materials that mimic some of nature’s most striking colours, among them the iridescent hue of opals. Naturally occurring opals are formed

‘Polymer opals’, however, are plastic – like the polystyrene in drinking cups – and formed within a matter of minutes. With some clever chemistry, the researchers have found a way of making polysterene spheres coated in a soft chewing-gum-like outer shell.

As these polymer opals are twisted and stretched, ‘metallic’ blue–green colours ripple across their surface. Their flexibility and the permanence of their intense colour make them ideal materials for security cards and banknotes or to replace toxic dyes in the textile industry.

“ ̽��ֱ��crucial thing is that by assembling things in the right way you get the function you want,” said Baumberg, who developed the polymer opals with collaborators in Germany (at the DKI, now the Fraunhofer Institute for Structural Durability and System Reliability). “If the spheres are random, the material looks white or colourless, but if stacked perfectly regularly you get colour. We’ve found that smearing the spheres against each other magically makes them fall into regular lines and, because of the chewing gum layer, when you stretch it the colour changes too.

“It’s such a good example of nanotechnology – we take a transparent material, we cut it up in the right form, we stack it in the right way and we get completely new function.”

Although nanophotonics is a comparatively new area of materials research, Baumberg believes that within two decades we will start to see nanophotonic materials in anything from smart textiles to buildings and food colouring to solar cells.

Now, one of the team’s latest discoveries looks set to open up applications in medical diagnostics.

“We’re starting to learn how we can make materials that respond optically to the presence of individual molecules in biological fluids,” he explained. “There’s a large demand for this. GPs would like to be able to test the patient while they wait, rather than sending samples away for clinical testing. And cheap and reliable tests would benefit developing countries that lack expensive diagnostic equipment.”

A commonly used technique in medical diagnostics is Raman spectroscopy, which detects the presence of a molecule by its ‘optical signature’. It measures how light is changed when it bounces off a molecule, which in turn depends on the bonds within the molecule. However, the machines need to be very powerful to detect what can be quite weak effects.

Baumberg has been working with Dr Oren Scherman, Director of the Melville Laboratory for Polymer Synthesis in the Department of Chemistry, on a completely new way to sense molecules they have developed using a barrel-shaped molecular container called cucurbituril (CB). Acting like a tiny test tube, CB enables single molecules to enter its barrel shape, effectively isolating them from a mixture of molecules.

In collaboration with researchers in Spain and France, and with funding from the European Union, Baumberg and Scherman have found a way to detect what’s in each barrel using light, by combining the barrels with particles of gold only a few thousand atoms across.

“Shining light onto this gold–barrel mixture focuses and enhances the light waves into tiny volumes of space exactly where the molecules are located,” Baumberg explained. “By looking at the colours of the scattered light, we can work out which molecules are present and what they are doing, and with very high sensitivity.”

Whereas most sensing equipment requires precise conditions that can only really be achieved in the laboratory, this new technology has the potential to be a low-cost, reliable and rapid sensor for mass markets. ̽��ֱ��amount of gold required for the test is extremely small, and the gold particles self-assemble with CB at room temperature.

Now, with funding from the Engineering and Physical Sciences Research Council, and working with companies and potential end users (including the NHS), Baumberg and Scherman have begun the process of developing their ‘plasmonic sensors’ to test biological fluids such as urine and tears, for uses such as detecting neurotransmitters in the brain and protein incompatibilities between mother and fetus.

“At the same time, we want to understand how we can go further with the technology, from controlling chemical reactions happening inside the barrel, to making captured molecules inside ‘flex’ themselves, and detecting each of these modifications through colour change,” added Baumberg.

“ ̽��ֱ��ability to look at small numbers of molecules in a sea of others has appealed to scientists for years. Soon we will be able to do this on an unprecedented scale: watching in real time how molecules come together and undergo chemical reactions, and even how they form a bond. This has huge implications for optimising catalysis in industrially relevant processes and is therefore at the heart of almost every product in our lives.”

Baumberg views nanophotonics technology as a whole new toolbox. “ ̽��ֱ��excitement for me is the challenge of how difficult the task is combined with the fact that you can see that, if only you could do it, you can get things out that are incredible.

“At the moment we are capable of assembling new structures with different optical properties in a highly controlled way. Eventually, though, we will be able to build things with light itself.”

̽��ֱ��development of a ‘nanobarrel’ that traps and concentrates light onto single molecules could be used as a low-cost and reliable diagnostic test.

Eventually... we will be able to build things with light itself

Jeremy Baumberg

Gen Kamita and Jeremy Baumberg

Light can be manipulated at the nanoscale, as in this elastic material which has been folded like nano-origami

Yes

‘Smart’ microcapsules in a single step

ns480 — Fri, 10 Feb 2012 15:22:25 +0000

̽��ֱ��ability to enclose materials in capsules between 10 and 100 micrometres in diameter, while accurately controlling both the capsule structure and the core contents, is a key concern in biology, chemistry, nanotechnology and materials science.

Currently, producing microcapsules is labour-intensive and difficult to scale up without sacrificing functionality and efficiency. Microcapsules are often made using a mould covered with layers of polymers, similar to papier-mâché. ̽��ֱ��challenge with this method is dissolving the mould while keeping the polymers intact.

Now, a collaboration between the research groups of Professor Chris Abell and Dr Oren Scherman in the Department of Chemistry has developed a new technique for manufacturing ‘smart’ microcapsules in large quantities in a single step, using tiny droplets of water. Additionally, the release of the contents of the microcapsules can be highly controlled through the use of various stimuli.

̽��ֱ��microdroplets, dispersed in oil, are used as templates for building supramolecular assemblies, which form highly uniform microcapsules with porous shells.

̽��ֱ��technique uses copolymers, gold nanoparticles and small barrel-shaped molecules called cucurbiturils (CBs), to form the microcapsules. ̽��ֱ��CBs act as miniature ‘handcuffs’, bringing the materials together at the oil-water interface.

“This method provides several advantages over current methods as all of the components for the microcapsules are added at once and assemble instantaneously at room temperature,” said lead author Jing Zhang, a PhD student in Professor Abell’s research group. “A variety of ‘cargos’ can be efficiently loaded simultaneously during the formation of the microcapsules. ̽��ֱ��dynamic supramolecular interactions allow control over the porosity of the capsules and the timed release of their contents using stimuli such as light, pH and temperature.”

̽��ֱ��capsules can also be used as a substrate for surface-enhanced Raman spectroscopy (SERS), an ultra-sensitive, non-destructive spectroscopic technique that enables the characterisation and identification of molecules for a wide variety of applications, including environmental sensing, forensic analysis and medical diagnosis.

This research has been funded by the Engineering and Physical Sciences Research Council (EPSRC), the European Union and the European Research Council (ERC). ̽��ֱ��commercialisation of this research is supported by an ERC Proof of Concept grant, awarded to Dr Scherman.

A new, single-step method of fabricating microcapsules, which have potential commercial applications in industries including medicine, agriculture and diagnostics, has been developed by researchers at the ̽��ֱ�� of Cambridge. ̽��ֱ��findings are published Friday (10 February) in the journal Science.

This method provides several advantages over current methods as all of the components for the microcapsules are added at once and assemble instantaneously at room temperature.

Jing Zhang

̽��ֱ�� of Cambridge

Microcapsules

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