Metamaterials are fast emerging from the research lab and turning up in real products. Claire Dancer and Alastair Hibbins tell Matin Durrani how the UK Metamaterials Network is helping to boost research into these fascinating structures and lower the barriers to commercialization
Metamaterials are artificial 3D structures that can provide all sorts of properties not available with “normal” materials. Pioneered around a quarter of a century ago by physicists such as John Pendry and David Smith, metamaterials can now be found in a growing number of commercial products.
Claire Dancer and Alastair Hibbins, who are joint leads of the UK Metamaterials Network, recently talked to Matin Durrani about the power and potential of these “meta-atom” structures. Dancer is an associate professor and a 125th anniversary fellow at the University of Birmingham, UK, while Hibbins is a professor and director of the Centre of Metamaterials Research and Innovation at the University of Exeter, UK.
Let’s start with the basics: what are metamaterials?
Alastair Hibbins (AH): If you want to describe a metamaterial in just one sentence, it’s all about adding functionality through structure. But it’s not a brand new concept. Take the stained-glass windows in cathedrals, which have essentially got plasmonic metal nanoparticles embedded in them. The colour of the glass is dictated by the size and the shape of those particles, which is what a metamaterial is all about. It’s a material where the properties we see or hear or feel depend on the structure of its building blocks.
Physicists have been at the forefront of much recent work on metamaterials, haven’t they?
AH: Yes, the work was reignited just before the turn of the century – in the late 1990s – when the theoretical physicist John Pendry kind of recrystallized this idea (see box “Metamaterials and John Pendry”). Based at Imperial College, London, he and others were was looking at artificial materials, such as metallic meshes, which had properties that were really different from the metal of which they were comprised.
In terms of applications, why are metamaterials so exciting?
Claire Dancer (CD): Materials can do lots of fantastic things, but metamaterials add a new functionality on top. That could be cloaking or it might be mechanically bending and flexing in a way that its constituent materials wouldn’t. You can, for example, have “auxetic metamaterials” with a honeycomb structure that gets wider – not thinner – when stretched. There are also nanoscale photonic metamaterials, which interact with light in unusual ways.
John Pendry: metamaterial pioneer
Metamaterials are fast becoming commercial reality, but they have their roots in physics –in particular, a landmark paper published in 2000 by theoretical physicist John Pendry at Imperial College, London (Phys. Rev. Lett. 85 3966). In the paper, Pendry described how a metamaterial could be created with a negative index of refraction for microwave radiation, calculating that it could be used to make a “perfect” lens that would focus an image with a resolution not restricted by the wavelength of light (Physics World September 2001 pp47–51).
A metamaterial using copper rings deposited on an electronic circuit board was built the following year by the US physicist David Smith and colleagues at the University of California, San Diego (Science 292 77). Pendry later teamed up with Smith and others to use negative-index metamaterials to create a blueprint for an invisibility cloak – the idea being that the metamaterial would guide light around an object to be hidden (Science 312 1780). While the mathematics describing how electromagnetic radiation interacts with metamaterials can be complicated, Pendry realized that it could be described elegantly by borrowing ideas from Einstein’s general theory of relativity.
Matin Durrani
What sorts of possible applications can metamaterials have?
CD: There are lots, including some exciting innovations in body armour and protective equipment for sport – imagine customized “auxetic helmets” and protective devices for contact sports like rugby. Metamaterials can also be used in communications, exploiting available frequencies in an efficient, discrete and distinct way. In the optical range, we can create “artificial colour”, which is leading to interesting work on different kinds of glitter and decorative substances. There are also loads of applications in acoustics, where metamaterials can absorb some of the incidental noise that plagues our world.
Have any metamaterials reached the commercial market yet?
AH: Yes. The UK firm Sonnobex won a Business Innovation Award from the Institute of Physics (IOP) in 2018 for its metamaterials that can reduce traffic noise or the annoying “buzz” from electrical power transformers. Another British firm – Metasonnix – won an IOP business award last year for its lightweight soundproofing metamaterial panels. They let air pass through so could be great as window blinds – cutting noise and providing ventilation at the same time.
High-end audio manufacturers, such as KEF, are using metamaterials as part of the baffle behind the main loudspeaker. There’s also Metahelios, which was spun out from the University of Glasgow in 2022. It’s making on-chip, multi-wavelength pixelated cameras that are also polarization-sensitive and could have applications in defence and aerospace.
The UK has a big presence in metamaterials but the US is strong too isn’t it?
AH: Perhaps the most famous metamaterial company is Metalenz, which makes flat conformal lenses for mobile phones – enabling amazing optical performance in a compact device. It was spun off in 2021 from the work of Federico Capasso at Harvard University. You can already find its products in Apple and Samsung phones and they’re coming to Google’s devices too.
Other US companies include Kymeta, which makes metamaterial-based antennas, and Lumotive, which is involved in solid-state LIDAR systems for autonomous vehicles and drones. There’s also Echodyne and Pivotal Commware. Those US firms have all received a huge amount of start-up and venture funding, and are doing really well at showing how metamaterials can make money and sell products.
What are the aims of the UK Metamaterials Network?
CD: One important aim is to capitalize on all the work done in this country, supporting fundamental discovery science but driving commercialization too. We’ve been going since 2021 and have grown to a community of about 900 members – largely UK academics but with industry and overseas researchers too. We want to provide outsiders with a single source of access to the community and – as we move towards commercialization – develop ways to standardize and regulate metamaterials.
As well as providing an official definition of metamaterials (see box “Metamaterials: the official definition”), we also have a focus on talent and skills, trying to get the next generation into the field and show them it’s a good place to work.
How is the UK Metamaterials Network helping get products onto the market?
CD: The network wants to support the beginning of the commercialization process, namely working with start-ups and getting industry engaged, hopefully with government backing. We’ve also got various special-interest groups, focusing on the commercial potential of acoustic, microwave and photonics materials. And we’ve set up four key challenge areas that cut across different areas of metamaterials research: manufacturing; space and aviation; health; and sustainability.
Metamaterials: the official definition
One of the really big things the UK Metamaterials Network has done is to crowdsource the definition of a metamaterial, which has long been a topic of debate. A metamaterial, we have concluded, is “a 3D structure with a response or function due to collective effects of their building blocks (or meta-atoms) that is not possible to achieve conventionally with any individual constituent material”.
A huge amount of work went into this definition. We talked with the community and there was lots of debate about what should be in and what should be out. But I think we’ve emerged with a really nice definition there that’s going to stay in place for many years to come. It might seem a little trivial but it’s one of our great achievements.
Alastair Hibbins
What practical support can you give academics?
CD: The UK Metamaterials Network has been funded by the Engineering and Physical Sciences Research Council to set up a Metamaterials Network Plus programme. It aims to develop more research in these areas so that metamaterials can contribute to national and global priorities by, for example, being sustainable and ensuring we have the infrastructure for testing and manufacturing metamaterials on a large scale. In particular, we now have “pump prime” funding that we can distribute to academics who want to explore new applications of – and other reserach into – metamaterials.
What are the challenges of commercializing metamaterials?
CD: Commercializing any new scientific idea is difficult and metamaterials are no exception. But one issue with metamaterials is to ensure industry can manufacture them in big volumes. Currently, a lot of metamaterials are made in research labs by 3D printing or by manually sticking and gluing things together, which is fine if you just want to prove some interesting physics. But to make metamaterials in industry, we need techniques that are scalable – and that, in turn, requires resources, funding, infrastructure and a supply of talented, skilled workers. The intellectual property also needs to be carefully managed as much of the underlying work is done in collaborations with universities. If there are too many barriers, companies will give up and not bother trying.
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Looking ahead, where do you think metamaterials will be a decade from now?
AH: If we really want to fulfil their potential, we’d ideally fund metamaterials as a national UK programme, just as we do with quantum technology. Defence has been one of the leaders in funding metamaterials because of their use in communications, but we want industry more widely to adopt metamaterials, embedding them in everyday devices. They offer game-changing control and I can see metamaterials in healthcare, such as for artificial limbs or medical imaging. Metamaterials could also provide alternatives in the energy sector, where we want to reduce the use of rare-earth and other minerals. In space and aerospace, they could function as incredibly lightweight, but really strong, blast-resistant materials for satellites and satellite communications, developing more capacity to send information around the world.
How are you working with the IOP to promote metamaterials?
AH: The IOP has an ongoing programme of “impact projects”, informed by the physics community in the UK and Ireland. Having already covered semiconductors, quantum tech and the green economy through such projects, the IOP is now collaborating with the UK Metamaterials Network on a “pathfinder” impact project. It will examine the commercialization and exploitation of metamaterials in ICT, sustainability, health, defence and security.
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Have you been able to interact with the research community?
CD: We’ve so far run three annual industry events showcasing the applications of metamaterials. The first two were at the National Physical Laboratory in Teddington, and in Leeds, with last year’s held at the IOP in December. It included a panel discussion about how to overcome barriers to commercialization along with demonstrations of various technologies, and presentations from academics and industrialists about their innovations. We also discussed the pathfinder project with the IOP as we’ll need the community’s help to exploit the power of metamaterials.
What’s the future of the UK Metamaterials Network?
AH: It’s an exciting year ahead working with the IOP and we want to involve as many new sectors as possible. We’re also likely to hit a thousand members of our network: we’ll have a little celebration when we reach that milestone. We’ll be running a 2025 showcase event as well so there’s a lot to look forward to.
- This article is an edited version of an interview on the Physics World Weekly podcast of 5 December 2024
