The speed of a wave moving through a material is set by the refractive index; something immutable we might look up in a table and perhaps promptly forget. But imagine having the power to change it at will. What could we do? It would allow a single object to have different functions: a chassis that becomes transparent at the flick of a switch, or a room that can be made instantly private, turning thin walls into sound absorbers. Yet these ideas are just the beginning of the story. If we can rapidly switch the wave speed, then completely new effects emerge. For example, changing the refractive index abruptly causes a wave to "reflect in time" - a paradoxical temporal analogue of the ordinary reflection we see and hear every day (e.g. the echo from a wall), but one that can cause the wave to gain energy. Other new effects arise if we can also change the refractive index differently at each point in space. With this control it becomes possible - for instance - to make a stationary object look like it is moving. Unlike true motion there is no restriction on this speed, and we can even mimic objects moving faster than light! Our research will develop new materials where the refractive index can be changed in time, exploring switchable functionality and the plethora of new wave effects that emerge when the material properties are varied rapidly. This is not always an easy thing to do and to avoid potential obstacles to our research we take a "wave agnostic" view, where we - in parallel - explore the effects of a time varying wave speed for airborne acoustic waves, mechanical vibrations, radio frequency waves, terahertz waves, and in optics. To illustrate the huge advantage of this approach, consider the time scales involved: "rapid" means the change must be imposed more quickly than the wave oscillates. For audible sound this is milliseconds, for visible light femtoseconds. We should use very different techniques in these two cases! In optics, special materials are subject to ultra-fast, high-intensity fields, while in acoustics we use electronically controlled transducers. Through considering different wave regimes we can implement a time varying wave speed by the most promising means, avoiding the limitations of any individual technique. Our program of research is split into four, first developing experiments to demonstrate rapid switching of acoustic, elastic, and electromagnetic wave speeds in time, and the theory required to design them. The second part pushes this work to the next stage, developing materials where the wave speed varies in both space and time, allowing us to e.g. mimic motion. Having developed these experimental and theoretical capabilities, the final two parts of the project explore new wave effects in these materials, specifically wave amplification and unusual materials where the wave can only propagate in one direction. While our research is a fundamental study into wave physics in time-varying materials, we predict multiple applications of this technology. Future communications (6G) is perhaps the simplest. This will need an enormous number of separately powered antennas to precisely direct beams of electromagnetic waves. But if we can rapidly change the reflective properties of a surface next to a single antenna, we can make it alone perform the function of these many different antennas, reducing energy requirements and complexity! Wave-based computing is a second example: like every physical process, the scattering of a wave from a material is equivalent to a computation. Although electromagnetic waves perform this computation very quickly - at the speed of light! - to use it as a "computer" we need to program it. The material properties are fixed, so the wave always scatters in the same way. If we can switch the material properties, we can program it and create a new class of high-speed computational devices based on wave-scattering.

The project aims to create a new Hub that will act as a national gateway for Advanced Metrology, engaging with UK industry to co-create and co-deliver frontier and innovative research and technologies, and with policy makers and scientific leaders, to drive future UK manufacturing excellence with a clear emphasis on sustainability. The Hub will have environmental and economic sustainability embedded throughout its programme, both in terms of prioritising industry challenges that the research will address, and within the operational delivery. One of the largest challenges in improving sustainability in manufacturing is the availability of the actionable information that is essential to both improve existing processes to reduce waste, and to enable new processes and methods that significantly enhance resource efficiency through reduced energy usage, material reuse and recycling, and reduced transportation (as a result of supply-chain efficiency). By delivering a future where pervasive metrology systems sense, monitor and control manufacturing systems to self-optimise, we will realise the connected and autonomous systems critical for achieving net zero. Delivering these advances requires the development of manufacturing systems that cannot be realised without a new integrated paradigm in metrology, embracing ultra-fast and compact sensors, distributed artificial intelligence (AI) technologies, and autonomous prognostics control systems far beyond the current state-of-the-art. Hence, the Hub's research programme will be structured around three underpinning research themes to address three Key Research Objectives: Create and apply new sensor technologies incorporating nanophotonics/quantum sensing principles combined with photonic edge computing to realise high-precision ultra-fast, ultra-compact, and low-cost sensors/instruments within smart manufacturing processes and systems. Create and apply new resilient and interpretable metrology aimed at capturing actionable information for sustainable manufacturing. Unify whole system autonomous control for sustainability in manufacturing machinery systems, which optimises process, energy use and resource efficiency in complex systems at the design state and through life. When combined, these objectives will deliver universal 'measurement/analysis/control' solutions for early adoption to address sustainable manufacturing challenges. Five priority areas have been identified to demonstrate new metrology technologies and methods; sustainable and connected machinery, zero carbon transport, clean energy systems, semiconductors, and manufacturing reuse. The programme will develop and demonstrate new metrology technologies and methods with clear applications in these sectors. This will be achieved working closely with metrology equipment/software/service providers, manufacturing systems providers, and with manufacturing end-users, supported closely by partners across the UK Catapult network and national and international standardisation bodies. The Hub comprises a substantial consortium, led by the Centre for Precision Technologies at Huddersfield. Initial research spokes will be based at Heriot-Watt, Oxford, Queens (Belfast) and Southampton universities, with Innovation Spokes at The Manufacturing Technologies Centre (MTC) and the Advanced Manufacturing Research Centre (AMRC), and a hybrid Research/Innovation Spoke at the National Physical Laboratory (NPL). Over 25 industrial partners were involved in co-creating the Hub and will be working with the research team to support, delivery and accelerate commercialisation of research outcomes via sponsored research projects, knowledge exchange, technology transfer (IP licensing and spin-out), and training/skills development.