Qioptiq Ltd

Invisibility cloaks are fantastic devices in popular culture from Harry Potter to Star Trek. But even in the real world so-called metamaterials (synthetic composite materials with emergent new properties) can act as (partial) cloaks both against light (vision) and sound (acoustics). We recently discovered that the 65MY old arms race with their echolocating bat predators has equipped moths with remarkable acoustic metamaterials on their wings and bodies (e.g. Shen et al. 2018 PNAS). The strength of a moth's echo determines the distance over which bats can detect it. Fur on bodies and scales on wings of moths have broadband absorptive properties that each outperform current sound absorber technology. While moth fur is a fibrous porous absorber almost twice as efficient as comparable technical solutions, the scales on moth wings have an even more exciting functional principle: Each scale resonates and together they create efficient broadband absorption of bat ultrasound. In contrast to technical solutions, these scales best absorb low frequencies, and show an unparalleled deep-subwavelength (<1% of wavelength) functionality. Their structure and (postulated) functionality make moth wings the first documented biological acoustic metamaterial - a discovery as transformative as nanoscale photonic crystals creating structural colour in butterfly scales. Our objective is to reveal the, as yet unknown, biophysics behind these evolved metamaterial absorbers and translate them into the human hearing range. In collaboration with our industry partner we will then develop prototypes for the next generation of more efficient bio-inspired noise control devices (biology-push). In return, understanding the biophysics will cross-inspire biology, as it allows us to look for and identify further acoustic metamaterials with different adaptiveness (i.e. tuneable metasurfaces; technology-pull). Unlocking the potential of evolved deeply subwavelength sound absorber metamaterials requires a coordinated, multidisciplinary, world-leading team of researchers; it is not possible to disassociate the biology from the mechanical modelling and treat the problem piecemeal. The assembled team of researchers has complementary expertise ranging from structural analysis of scales created by epidermal cells, acoustomechanical characterisation, and absorptive index assessment (lead Biology, Holderied, Robert), to theoretical biophysics of metamaterial properties (lead Applied Mathematics, Craster), to computational biophysics, modelling, and prototyping (lead Ultrasonics Engineering, Drinkwater with industry partner) and product development and commercialisation (industry partner). A range of cutting-edge technologies and methodologies (some of which pioneered in the applicants' labs exclusively) are required for this research including Dynamic Acoustic 3D imaging, Scanning Laser Doppler Vibrometry and Refractometry, X-ray nanoCT (successful Diamond synchrotron light source bid 2018), COMSOL multiphysics modelling, 3D lithography and nanoScribe 3D fabrication. Promisingly, our first lithographically produced scale replicas indeed resonate at the most important frequency for human communication (4 kHz). The outcome of our iterative effort will be novel broadband sound absorbers, that are much thinner and lighter than existing systems. These bioinspired absorbers not only have substantial economic potential (as evidenced by the commitment of our industry partner), their lower space and weight footprint promises more flexible and acceptable noise control solutions for our offices and homes. They will help in our fight against acoustic pollution (e.g. cost to the NHS of hearing loss is estimated to be 450M per year), which is the 2nd largest environmental health risk in Western Europe leading to over 10000 premature deaths every year (EEA, 2014; WHO, 2011).

In this project we shall investigate the potential for spintronics of the quantum spin Hall (QSH) regime in hybrid nanostructures made by attaching ferromagnetic metal contacts to the edge states of two-dimensional topological insulators. These 2D materials will be formed from semiconducting InAs/GaSb coupled quantum wells. Being able to harness the spin-momentum-locked helical edge states in the QSH regime will have the potential for realising dramatic reductions in the power consumption of classical ICT hardware, and in the longer term offer the prospect of being useful for topological quantum computing. To build such spintronic devices, we need to know the conditions under which current flows through their edge states. We need to know the spin polarisation of a current injected from a ferromagnet into the QSH edge state, and which ferromagnetic contact material provides the largest spin-polarisation. We need to know how efficiently spins can be injected and detected in these QSH edge channels using ferromagnetic metal contacts. We also need to know over what distance spin information can propagate in the QSH edge states, and in what circumstances this distance is the longest. The project is a collaboration between the School of Physics and Astronomy, who have expertise in spintronics and the study of devices incorporating ferromagnetic materials, as well as topological materials, and the School of Electronic and Electrical Engineering, who are capable of growing ultra-high quality InAs/GaSb coupled quantum wells in their III-V semiconductor molecular beam epitaxy system. We will begin by constructing contacted InAs/GaSb mesas with top and bottom gates that allow them to be tuned into a charge-neutral and non-trivial regime, which are the correct conditions for current to flow only in the edge states. We will attach normal drain contacts on either side of a ferromagnetic source contact on a InAs/GaSb mesa and measure the drain currents from left- and right-flowing edge states in the non-trivial edge state regime; the spin-momentum locking in the QSH edge states will mean that these spatially separated currents directly correspond to the spin-resolved currents, allowing a direct measurement of the spin-polarisation of the current injected from the ferromagnet. We shall try different ferromagnetic metals to determine which one works best. We will then study the flow of a current in a QSH edge state between two closely-spaced ferromagnetic contacts, which is expected to be larger when the current flow direction is spin-momentum locked to the majority spin direction of the contacts; reversing the magnetisation direction in the contacts will invert this diode-like behaviour. The difference between forward and reverse currents will tell us the efficiency of the spin injection and detection. Moving the contacts apart will allow us to determine the length over which spins can flow coherently within the edge states by measuring the decline in difference between forward and reverse currents with spacing; we shall study this as a function of temperature in order to determine the physical mechanisms causing the loss of spin coherence. The results we shall obtain will not only lead to high impact publications and conference presentations by shedding light on the possibilities offered by this novel combination of materials, but also develop valuable know-how in the field of quantum spin Hall spintronics for technological applications.

The portable electronics boom has been driven by advances made in Li ion battery technology, following the initial work on the lithium cobalt oxide cathode material by Goodenough and co-workers. Other notable advances in terms of phosphate containing cathodes have extended the applications of lithium ion batteries to higher charge/discharge rate applications such as power tools and transport. Applications in terms of the latter have intensified the already substantial interest in lithium ion batteries, as a result of the environmental benefits of hybrid and all electric cars. Further applications as energy storage for renewable sources have also been proposed to overcome the intermittency of supply problems of renewable energy sources such as solar or wind power. While research on new lithium ion battery electrode materials has been intensive, the development of new electrolyte materials has received comparatively less attention. In a typical Li ion battery, the electrolyte is usually a Li salt in an organic solvent, as a result of the high Li ion conductivity of such systems. The flammable, toxic and volatile nature of such electrolytes, the instability in conjunction with higher voltage electrode materials, and the desire for miniaturisation are placing distinct limitations on further advances with conventional liquid electrolyte batteries. The use of a solid state electrolyte allows the potential to overcome these problems along with supplying a range of other advances including the simplified production of high voltage battery packs. A further unique advantage of solid state batteries is their low leakage currents, which delivers other potential applications in terms of use in energy harvesting devices. Furthermore the desire for shape-flexible, wearable electronic devices offers another avenue for the exploitation of all solid state battery systems. This interdisciplinary project involving researchers from chemistry, materials science, chemical engineering and industry aims therefore to develop new Solid State Li ion batteries. Such all solid state cells have been identified as one of the most important future targets in battery research, as illustrated by their inclusion as one of the fast-track projects in the Faraday challenge (industry strategy challenge objective 2). The importance of these batteries lies in their potential to deliver improved safety, reduced size, and higher capacity, as well as to open up new applications such as energy harvesting devices. In particular, the demonstration of a commercially viable scaleable ceramic-based electrolyte with higher safety will offer large benefits in terms of UK wealth generation/investment opportunities (Industry strategy challenge objective 1). In terms of potential commercialisation, the optimisation of garnet Li ion conducting electrolytes, their scale-up synthesis and demonstration in all solid state batteries offers significant potential in terms of Li ion battery technology, with applications ranging from portable consumer devices to transport. In terms of helping to ensure the delivery of impact in this area, a strong link has already been set up with industry, to provide key input into the project from an industrial viewpoint, along with industrial validation of the full cell tests on the most promising systems (industrial strategy challenge objective 3). This will allow UK industry to capitalise on the developments made during this work and offer an early route to exploitation (Industry strategy challenge objective 1).

This research project is a psychologically-inspired investigation of an analogy of infant play as the central mechanism for autonomous, self-motivated robots that learn the local physics of their world. We note that infants and children at play exhibit exactly the kind of autonomous learning that would be very desirable in robotics. Infant play has a major role in the acquisition of new skills and cognitive growth. Noticing that early infants spend hours in play, we have designed a computer analogy of infant play and this project is an in-depth investigation into the use of play as a means of building subjective understanding of the physics of the local world. The project will implement a play generator algorithm on an iCub humanoid robot and perform experiments with a wide range of scenarios involving varieties of objects. This includes playing solitarily with objects to learn their properties, and interactive play with a human participant. We also include experiments with tool use (using one object as a tool for acting on another) to investigate how objects may become extensions of self. A panel of selected scientific experts on infants and play will provide their psychological expertise throughout the project and will also assist with the design of a series of matching experiments that will compare results from the robot model with those from selected psychological experiments on infants. The data from the experiments will be analysed and interpreted to shed light on a set of scientific issues. When we report on the results we will also extract some general principles for robot learning through play. We will examine the applicability of these principles in new robotic and intelligent systems developments. For example, we anticipate particular applications in areas such as assistive technology and home care where the re-programming of mass-produced systems is not feasible. We believe technology with a developmental approach will have wide implications and provide an alternative to "building robots" by establishing the idea of "developing robots" for applications.

Energy plays a vital role in our lives, and during last 150 years civilization has increasing used fossil fuels / gas, coal and oil. As a result more and more difficult operating conditions, such as that in deviated or horizontal long-reach wells, become a norm within the drilling industry, and this requires better effectiveness and controllability of the downhole drilling processes. The latest research in this area confirmed that a basis for novel downhole drilling techniques of hard formations is founded upon imposing dynamic loading at the bit-rock interface. One way of practically realising this is a superposition of adjustable percussive loading on conventional rotary drilling. This method will allow adaptive operation across a wide range of drilled formations, so enhancing cutting rates while reducing tool wear and lending itself ideally to extended-reach horizontal drilling. A robust mathematical model of the dynamic interactions occurring in the borehole is the first and most important step in understanding how this philosophy can be applied. Apart from the dynamics of the percussive drilling module, which can be described as a system of non-smooth nonlinear ordinary differential equations, the model has to account for the damage zone in the borehole having a major influence on the dynamics of the drilling module. A significant research programme in this area comprising experimental and theoretical studies has been carried out at Aberdeen since 1998. These studies have been focussed to assess the practicality of a novel drilling method named as the resonance enhanced drilling, where the drill-bit operates in resonance conditions to increase the efficiency of generating controllable impact loading and consequently to create a sustainable damage zone in the borehole. Mathematical modelling of resonance enhanced drilling has been also part of these studies, and the latest work has been concentrated on the fracture dynamics of drilled formations, which is crucial for an accurate prediction of the system behaviour. It is proposed to take the current work a step further by developing a suite of robust models of the dynamic fracture. These models will be coupled with the dynamic model of the drill-bit in order to analyse the nonlinear interactions in the borehole. The development of such models will be the first major task of the project. Construction of the iterative maps for the percussive drilling will be the second major task. It has been understood that dimension reduction, and in particular construction of analytical iterative maps, would be especially beneficial for understanding and designing of the system described by non-linear piece-wise smooth equations as there are no well developed mathematical techniques for obtaining solutions for these systems and often there are difficulties even in proving the solution existence. The main advantage of iterative maps is that the computation of dynamic responses using the maps takes a fraction of time when compared to the techniques based on direct numerical integration. Also it is important that the dimension reduction achieved by constructing iterative maps means that the amount of data required for the system analysis is significantly decreased. The fast prediction of the system behaviour and reduced amount of data are both very useful for developing efficient control systems. Analysis of the system dynamics using the constructed iterative maps aims at formulation of optimal patterns of the external excitation, and in particular it will be focused on obtaining the frequencies and amplitudes of the percussive motion maximising drilling rates as functions of the drilled formation properties.