METAFLEX - Metamaterials on Flexible optically transparent substrate

Lead Research Organisation: University of St Andrews
Department Name: Physics and Astronomy

Abstract

Metamaterials (MMs) are man made materials with unusual electromagnetic properties that are not typically found in Nature. They are the key to achieving such extraordinary properties as invisibility cloaks and perfect lenses. At present, they are bulky and confined to laboratories. If they were flexible, they could become much more versatile and practical. Here, I propose a novel concept for flexible MMs that will turn current cloaking devices from suits of armour into true cloaks.The concept of index of refraction underpins the physics of MMs, which can be illustrated with an example. The direction that light takes when it crosses the interface between two media depends on its initial direction with respect to the surface and on the refractive indices of the media. This is the reason why a pencil appears to kink when immersed in water. In nature, all transparent materials have a positive refractive index, like water. As a result, the image of the pencil always kinks in the same direction. Conversely, MM are manufactured with a negative refractive index, thus in a MM the kink of the pencil would appear in the opposite direction. This effect, which may seem to be a mere curiosity, drives the extraordinary behavior of MMs.The technological requirements of currently fabricated optical MMs impose a flat rigid geometry. This impedes the realistic implementations of an optical cloak made of soft fabric, for example. I aim to overcome such limits.The aim of this project is to fabricate MMs in flexible, extremely thin membranes (METAFLEX).Metaflex will retain all the power of material design typical of MMs and their ability to control light, in a more flexible framework. I have already achieved the first milestone of the project and printed MMs on polymer flexible membranes with thickness down to few nanometers.The physics of Metaflex is a rich and unexplored field of research. This ambitious project is structured around their most striking properties:-Metaflex can be wrapped around objects and stacked, a vital step to realistic cloaking applications.-Metaflex stacks can be easily fine tuned after fabrication, e.g. via deformation, hence light can be controlled with additional degrees of freedom. The flexibility of Metaflex permits the design and fabrication of a camouflaging system, as the material response can sense and adapt to the surrounding environment. This offers a remarkable example of smart fabrics and intelligent textiles, currently a thriving area of research in academia and industry.-Metaflex provide a new framework to study the interaction between optical and mechanical forces, as in Optical Trapping or the new field of Optomechanics. Potential applications include very small optical microphones.-Metaflex are very light. They could take advantage of the attractive and repulsive forces triggered by optical beams in order to levitate and behave as nano-flying carpets. This would be a breakthrough in biomedical nano-applications such as drug-delivery and single molecules manipulation.My interest in Metaflex arises from diverse theoretical and experimental projects in photonic structures and nanofabrication and from the knowledge gained throughout these projects, including the physics and applications of MMs. This project contains many exciting scientific challenges, which offer the possibility of developing the extraordinary properties of MMs for every-day life applications that were unimaginable only a few years ago.

Planned Impact

My research project deals with Metamaterials (MMs), i.e. materials with properties that can be engineered and cannot be found in Nature, for optical applications. The impact that MMs promise to have on everyday life can be effectively compared to examples including the invention of plastic or the ubiquitous use of lasers. For example, it has been shown that MMs can be used to create lenses with unlimited resolution and materials that can conceal objects, realizing invisibility cloaks. With this project I aim at developing flexible metamaterials (Metaflex) exhibiting the extraordinary optical properties of MMs in a more supple and versatile framework. The ambitious outcome of my research is to facilitate realistic applications of MMs to everyday life, in different fields and timescales. -The immediate recipients of this research will be commercial and industrial subjects involved in the technological sector. The MMs technology is already finding its way to commercial exploitation (for example to fabricate cheaper and more efficient antennas for networking applications), and Metaflex promises to boost in the next five to ten years its range of applicability. Few examples include the fabrication of miniaturized frictionless actuators, chemical sensors and a range of optoelectronic devices, like optical microphones. Potential commercial application of the most promising results will be pursued trough collaborations with local and National based companies, fostering wealth and economic competitiveness of UK. - Nanotechnologies are already heavily pursued in bio-applications. It is likely that Metaflex will contribute in a short timescale (5-10 years) in this direction as well. Collaborations with the Schools of Medical Science and Biology will help developing tools and protocols relevant to the field of nano-toxicology, an EPSRC signposted activity. Examples include ways of sensing and trapping nano-toxins and nano-pollutants. The same collaboration could lead to the development of visual prosthesis for augmented vision applications. These activities will have impact in sectors like health and environment protection, also with short- and long-term public economical benefit. - One obvious way to exploit the remarkable properties of Metaflex is for intelligence purposes, for example to implement cloaking and camouflaging techniques. While it is not suggested that on a short time scale it will be possible to conceal to the eye a macroscopic object, it is definitely already possible to look for efficient ways to apply the MMs paradigm to obtain an enhanced stealth technology, with strong impact on warfare and security fields. With the involved staff, we will be actively pursuing the diffusion of the outcome of my research to maximise its impact over the intended recipients, through participation to dedicated and generic Conferences, like PECS, CLEO and Photonic West. Frequent meetings (4/year) will be organized with project partners to discuss the results of the common activities. My host institution has recently appointed a Knowledge-Transfer team. I will seek advice of this dedicated staff, to maximise the chances of successful exploitation and early recognition of potential commercial applications and spinout activities. I have recently filed an application for a patent for a biomedical tool for endoluminal surgery; I will exploit this experience both to deepen the collaboration with subjects in the field and to pursue protection of intellectual properties connected to Metaflex. Finally, some extraordinary aspects of my research, like invisibility and camouflaging, easily engage with the imagination of the general audience. This will be further fostered through participation to National and International Science Festivals and outreach activities, involving schools and pupils of every grade and level.

Publications


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Di Falco A (2012) Propagation Losses of Slotted Photonic Crystal Waveguides in IEEE Photonics Journal

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Di Falco A (2014) Chiral plasmonic nanostructures: Twisted by DNA. in Nature materials

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Di Falco A (2011) Luneburg lens in silicon photonics. in Optics express

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Di Falco A (2012) Lifetime statistics of quantum chaos studied by a multiscale analysis in Applied Physics Letters


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Falco A (2010) Flexible metamaterials at visible wavelengths in New Journal of Physics

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Gentilini S (2014) Optical shock waves in silica aerogel. in Optics express


 
Description With this research grant I have introduced the concept of flexible metamaterials (MMs) that operate at optical frequencies. Metaflex are extremely thin polymeric membranes hosting a plasmonic layer with optical properties not present in natural materials. - The main achievement of this reasearch has been establishing a generic platform for the fabrication of flexible structures with tailored electromagnetic response in the optical regime. I have developed a number of manufacture procedures, based on traditional top-down lithographic approaches and chemistry driven bottom up techniques. - Using the Metaflex technology we have demonstrated a number of different optical filters. Examples include photonics membranes able to screen a specific wavelength for every angle of incidence and polarization and optical filters that can be wrapped around objects with complicated shapes. This last features is highly desirable, as it permits to transfer a novel optical function on surfaces that are not planar, and that are otherwise difficult to pattern at the nanoscale. For example we have placed metaflex samples on the tip of optical fibers, for lab-on-fibers applications. This result permits to miniaturize large and bulky instruments like optical spectrum analysers. - I have managed to embed gain materials in Metaflex to compensate for the losses caused by the use of metallic layers. Using this approach I have shown that the permittivity of an optical metamaterials can be tuned using light itself. This result has been used to obtain material with refractive index close to zero, which can be used to transmit light very efficiently at the nanoscale and to harness the nonlinear response of optical materials at ultra low powers. - This research has made several significant contributions to the experimental demonstration of enhanced light-matter interactions using nanoplasmonics. These include the recent demonstration of a novel sensor for cancer biomarkers based on Surface Enhanced Raman Scattering that allows to analyze multimponent mixtures, and an efficient bi-directional optical sorting technique based on plasmonic resonances in gold nanoparticles. This approach promises improved resolution over standard sorting techniques. This work also contributed to demonstrate a method to address subwavelength plasmonic features with high precision.
Exploitation Route The possibility to coat virtually every object of any dimension and shape with a photonic layer is beneficial to a wide range of fields and applications, where advanced light manipulation is required. The applications that most readily can benefit of a tailored photonic layers are those where an enhanced and/or controlled absorption or emission of light is required. These include solar cells (absorption), organic and inorganic LED (emission) and filters (light management and sensing). These devices are heavily used in many sectors, including the discussed electronics, chemistry and energy but also aerospace and defence (camouflaging and stealth), healthcare (visual prostheses, miniaturised biopsy instruments, imaging), Environment, Food and Drink, Construction (biological and structural sensors). Mechanical flexibility offers the ideal technological platform to translate out of the lab the potentials of optical metamaterials. This is true for 3 main reasons: i) Leveraging on the manufacturing process of flexible electronic, it is possible to scale up the fabrication of flexible metamaterials, thus simplifying the pathway to their utilisation; ii) the mechanical flexibility offers a variety of tuning mechanisms of the optical response, by altering the topology of the material post-fabrication; iii) metaflex can be made compliant to any surface, thus augmenting the capability of existing devices and materials.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Construction,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections
URL https://synthopt.wp.st-andrews.ac.uk/
 
Description Metaflex has generated impact at many different levels. Worldwide media coverage is the clearest measure of impact. The press release that went along with the publication of the first demonstration of the Metaflex concept in the optical domain was picked up by BBC and a number of other international news agencies. In the following two weeks, newspapers, TV, Radio, magazines and countless Internet sites on all five continents published articles about this research and interviews. This directly promoted the cultural and economical competitiveness of UK. This project has fostered the creation of a skilled workforce promoting UK science with national and international students. Two postdoc, three PhD students and more than 15 undergraduate project students have been directly involved and trained in the framework of this project. These also include international students who have been attracted to UK by the media coverage of the research. The work has also contributed to several outreach activities. Seminars on the results of the research have been presented at national and international schools, like the Merchiston Castle Lecture (Edinburgh) that ADF held in 2013 on invisibility and advanced uses of light. I have been invited to give seminars and expose samples of my work to representatives of the textile industry in Spain. I have been invited to a forthcoming round table discussion about new material research in Spain, supported by the Spanish research councils. This researched has been showcased in one of the events at the Science Festival of Edinburgh. Samples of Metaflex are part of a permanent exhibition in a museum in Amsterdam, hosted by a private company (Materia). Several aspects of my research have the potential to generate further impact through patenting and licensing. In less than 16 months, I have filed 2 patent applications for enhanced visual prostheses based on Metaflex technology.
First Year Of Impact 2010
Sector Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal
 
Description A light touch for flexible metamaterials
Amount £15,000 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 10/2011 
End 10/2012
 
Description An electrochemical approach to loss management in plasmonic nanostructures - Institutional Sponsorship
Amount £20,000 (GBP)
Funding ID EP/J501542/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 07/2011 
End 06/2012
 
Description Institutional Sponsorship 2012
Amount £60,000 (GBP)
Funding ID EP/K503587/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 04/2012 
End 03/2013
 
Description Plasmonic nanostructures for light emission engineering
Amount £12,000 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 03/2015 
End 03/2017
 
Description Shaped Light at the Interface
Amount £1,479,536 (GBP)
Funding ID EP/M000869/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 07/2014 
End 06/2019
 
Description Unexpected uses of synthetic optics: harnessing the beauty within - Impact Acceleration Account
Amount £20,000 (GBP)
Funding ID EP/K503940/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 06/2014 
End 09/2014
 
Description ANU 
Organisation Australian National University (ANU)
Country Australia, Commonwealth of 
Sector Academic/University 
PI Contribution Expertise in nanoplasmonics based sensors. Design, fabrication and characterisation of devices.
Collaborator Contribution Plasmonic-Activation of Selective Surface Redox Reaction for Non-Invasive Medical Diagnostics by Breath Analysis
Impact No results yet. The project will start in Dec 2014
Start Year 2014
 
Description KAUST 
Organisation King Abdullah University of Science and Technology (KAUST)
Country Saudi Arabia, Kingdom of 
Sector Academic/University 
PI Contribution My research team has fabricated and characterised a few photonic crystal samples, object of several papers on chaotic resonators
Collaborator Contribution The collaborators at KAUST have developed the theory associated to the research.
Impact The collaboration has produced 4 papers in International journals (2 Nature group, PRX and APL) and 5 contributions to international conferences and workshops.
Start Year 2011