Multifunctional Polymer Light-Emitting Diodes with Visible Light Communications (MARVEL)

Lead Research Organisation: University College London
Department Name: Electronic and Electrical Engineering

Abstract

With the dramatic increase in traffic carried by telecommunication networks, the demand for wireless resources (spectrum) is quickly outstripping its limited supply. Serious deterioration of service quality due to spectral congestion is becoming evident in high-density user scenarios, where users demand leads to a limited access. This problem is even worse in indoor applications where a lack of spectrum and a large number of users causes significant network slowdown. It is estimated that more than 70% of wireless traffic takes place in an indoor environment (home/office etc.). Thus, there is the need for reliable low-cost, high-capacity wireless technologies to ensure seamless indoor wireless connectivity at all times. Visible light communications (VLC) offers wireless connectivity using the visible band (~400 THz), which is a license free spectrum with high security and where its sources are used to provide lighting. VLC utilises semiconductor light emitting diodes (LED), which can be modulated at high speeds while providing a constant level of illumination. Traditionally, VLCs use inorganic LEDs as their transmitters' light sources. Such devices introduce significant drawbacks that have yet to be addressed, such as the inability to produce large panels due to the brittle and complex epitaxial processing methods that are expensive. Furthermore, to provide proper illumination, matrices of devices are required, thus introducing a significant circuit complexity. Other drawbacks include the inability to use flexible substrates that are attractive for mobile devices and the difficulties in producing devices with inherent different wavelengths. All of these disadvantages can be dealt with by replacing the commonly used inorganic metals by organic polymers as the semiconductor material of the LEDs. Polymer LEDs (PLEDs) can be manufactured using inexpensive wet processing methods at room temperature (such as inkjet printing) to produce single panel devices with large photoactive areas, at extremely low cost. Further, PLEDs can be deposited on a wide variety of substrate materials and with different shapes, allowing the development of a new generation of devices. Using a simple manufacturing process (one step deposition of different organic polymers) PLEDs may be designed to produce red, green and blue (RGB) light and then combined to allow the dual function of lighting and signal transmission.

Over the past decade, the teams applying for this grant have collectively demonstrated major successes in using organic (polymer) LEDs in VLC systems, with manufacturing, cost and operational advantages. Our previous work has led to several "world firsts" in terms of transmitted signal quality and bit rates, and our results were published at leading international journals and conferences.

In this proposal we will build on the existing strengths and varied expertise of our three team consortium. Specifically our research in inorganic semiconductors, optical component design and fabrication, electronic circuit design and communication systems integration, will be used to construct and demonstrate a new PLED based VLC proof of concept system, which includes novel device, circuit and system designs. We expect to achieve unprecedented VLC transmission speeds in realistic indoor environments. The project will study new methods of designing PLEDs and new optical techniques to maximise their light efficiency. New circuits and communication engineering techniques will be investigated to allow optimised coupling of electronic circuitry to PLEDs, overcoming some of PLEDs inherent data carrying limitations. We aim to assemble a complete system and test in in a specially designed test chambers of VLC.

In summary, we believe this work to be highly timely as it addresses the two key challenges; the design of systems operating in license free spectral bands and the provision of easy to manufacture and low cost organic optoelectronic devices.

Planned Impact

We hope that the leading work on inorganic devices in the UK will be strongly complemented by this work, to the benefit of the UK's leading standing in this fast developing area.

the scope and impact of MARVEL is broad. The research will not only develop the required technologies to reach its multiple goals but also it will look into creating new business opportunities based on VLC in an important number of practical scenarios. In fact, home, office and public places, are basic scenarios where the technology developed in MARVEL can be applied. As people spend most of their time in such places, the impact of this work on users is potentially high. The impact of of this research on operators, equipment manufacturers (mobile devices and infrastructure), standardization bodies and regulators is expected to be high.

Academically, the knowledge attained in modelling, design, simulations, implementation and processing of PLED based VLC networks will be invaluable in extending the interdisciplinary expertise of the research associates. The EPSRC and UK government has listed conductive polymer technologies as an area for significant growth and this proposal directly supports these claims and enables improved UK competitiveness in the display technology sector with a unique interdisciplinary project. Furthermore the European Union Horizon 2020 programme has identified organic technologies as an area for growth, and allocated at least 30m Euros for research funding.

Economic and societal: VLC in networking is well suited for a number of applications including a replacement for standard Wi-Fi deployment in local area networks in indoor environments; in areas where Wi-Fi networks are not practical or may cause harm due to electromagnetic interference from the Wi-Fi system or it causing issues with in-room equipment, such as a hospital setting; in home area networks to communicate with appliances and automatic home systems; car-to-car communications; underwater communications systems between various manned and unmanned platforms; for communication between handheld devices; as an enabler for local positioning systems. This introduces a huge market opportunity for the VLC in addition to posing a technical challenge, since the current RF based mobile systems cannot support all these requirements. Therefore, the adoption of VLC technologies can give rise to new business ecosystems, characterised by new actors and value chains. This research will assist in making this to become a reality, since our results would demonstrate white LED cab be used in a wide scale allowing communications as well as illumination with minimum energy usage, high performance and high data rates. Therefore, this research will provide economic and societal benefits within a few years in the UK as well as worldwide,

Knowledge and training: We plan to disseminate our findings to a much wider community including the lighting industries, telecommunication network service provider, in the UK and the rest of the world.
The proposed research will offer personal development for the research team. researchers will be mentored by the PIs and CoIs, who between them have proven track records in of nurturing close 50 early-career researchers to reach their full potential. Furthermore, RAs will be able to draw upon the investigators considerable technical expertise and experience. Furthermore, PhD students (funded by the universities) will work in this area and related areas and will be trained in optoelectronic and VLC systems design as well as in practical techniques. We believe such training will provide the necessary skills for furthering the UK's standing in this area in industry and academia.

Publications

10 25 50
 
Description 1- New methods of modulating (superimposing) data on devices used for lighting (red, green and blue LEDs) have been developed and tested in the laboratory. We have also been developing circuits for visible light transmitters and receivers that are optimised for the specialist types of devices to be developed in this project, which are organic based devices.
2- Adjustments to modulation formats have been proposed that introduce substantially lower computational complexity in VLC systems. This is important because it saves hardware resources and battery life, based on simple-yet-elegant tweaks to well known systems.
3- A new modulation format called super-Nyquist carrier-less amplitude and phase modulation was developed that saves bandwidth by compressing sub-bands. This has shown spectral efficiency improvements of over 40% and has been published in the prestigious Optics Express journal.
4- work has been developed that investigates the performance of organic LEDs in the context of high speed VLC systems and tests the performance of different operating points and materials to obtain optimal performance.
5- the optoelectronic characteristics of organic LEDs have been investigated from a communications systems point of view for the first time, and published in several articles. a model has been developed that is expected to be adopted by the research community.
6- a real time system has been developed based on field programmable gate arrays that transmits high data rates over visible wavelengths using organic LEDs. this has developed into a demonstration at the prestigious IEEE flagship event, INFOCOM, one of the most important conferences in the field of communications.
7- a new method of doubling the data rate (to be published) has been developed through this project, leveraging on wavelength division multiplexing and the natural non-linear response of photodetectors. Diversity between signals carried on different wavelengths is introduced and exploited to recover the original data. This means, the same frequency spectrum can be used to send 2 (or more) parallel data streams and decoded using simple subtractions. to be published.
8- new photodetector circuits have been developed that tolerate large equivalent capacitances. this means that large area devices can be utilised, thus increasing link distances; this has been a significant challenge in the research community for the proposal of visible light communications, and as such, this work was accepted at the most prestigious electronics and circuits conference in the world, IEEE ISCAS.
9- circuits have also been proposed that show the effective LED capacitance being absorbed into artificial transmission lines, improving the bandwidth through simple circuit techniques.
10- results have been proved through transmission over other relevant wavelengths including several radio-based applications, showing the generality of the work, which is important, because 5G access will be made up of many technologies.
11- New circuits for transmitters and receivers developed, manufactured and verified.
Exploitation Route we anticipate that the adoption of circuit models and equivalent circuits proposed in this project will result in significant recognition both by academic contemporaries and industrialists, alike. we will also lobby that modulation techniques and digital signal processing methods developed through this project will directly be adopted in the next set of standards for visible light communications systems (IEEE802.15.7), which are under development. our work has been adopted by large industrial companies (i.e. National Instruments) and developed in conjunction with others (i.e. Huawei and Siemens AG).
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Healthcare

URL https://www.ucl.ac.uk/iccs/research-projects/2018/feb/marvel-multi-functional-polymer-light-emitting-diodes-visible-light
 
Description Results developed through this project have been used by a major industrial company, namely National Instruments (with revenues over $1.2B), who have used a case study based on new modulation schemes and signal processing techniques as a demonstrator for 5G (http://sine.ni.com/cs/app/doc/p/id/cs-17492#). Two of the project investigators are the senior authors of the case study. These results have been directly extrapolated from work developed in this project.
First Year Of Impact 2018
Sector Digital/Communication/Information Technologies (including Software),Electronics
Impact Types Economic,Policy & public services

 
Description Academic collaboration with CNR Bologna (Dr E Lunedei) - Pulsed characterisation of OLEDs 
Organisation National Research Council
Country Italy 
Sector Public 
PI Contribution Design, fabrication and preliminary characterisation of OLEDs. Results interpretation and modelling. Manuscript writing and handling
Collaborator Contribution Spectroscopic, time-resolved characterisation of the OLEDs fabricated at UCL.
Impact Manuscript draft
Start Year 2017
 
Description Academic collaboration with Czech Technical University 
Organisation Czech Technical University in Prague
Department Department of Electromagnetic Field
Country Czech Republic 
Sector Academic/University 
PI Contribution Exchange of intellectual input and dissemination of information. Training of staff including visits and free-of-charge access to state-of-the-art laboratories at UCL. Knowledge and expertise exchange in the areas of advanced modulation formats and signal processing, directly corresponding to input required for work packages 2 and 3, whilst enabling the Czech Technical University to increase their knowledge and begin their own research into polymer based visible light communications systems.
Collaborator Contribution Same as previous, including visits to CTU and free-of-charge access to their laboratories and facilities. Access to expertise and development of ideas that correspond directly to the tasks and work packages of this project.
Impact Several papers have been produced and published (10.1109/ICCW.2017.7962624, 10.1109/JPHOT.2017.2749203), refer to dissemination section of the submission. A number of successive papers are in preparation for submission based on collaborations between our laboratories.
Start Year 2017
 
Description Academic collaboration with Dr Vrigilio Mattoli at IIT (Pontedera) 
Organisation Italian Institute of Technology (Istituto Italiano di Tecnologia IIT)
Country Italy 
Sector Academic/University 
PI Contribution Hosted collaborator from IIT (Pontedera, near Pisa, Italy) to work on OLEDs on tattoo paper. Contribute know how, materials and appropriate facilities for fabrication of the devices, and for their testing. Data interpretation, manuscript drafting.
Collaborator Contribution Know how on fabrication of electronic and optoelectronic devices on tattoo paper.
Impact - Results collected -Manuscript draft written but data quality is not yet sufficient. Further experiments needed.
Start Year 2017
 
Description Academic collaboration with Prof Gryko (Polish Academy of Sciences) 
Organisation Polish Academy of Sciences
Country Poland 
Sector Public 
PI Contribution Fabrication and characterisation of OLEDs incorporating materials provided by collaborator.
Collaborator Contribution New materials for organic electroluminescence.
Impact Manuscript in preparation.
Start Year 2017
 
Description Academic collaboration with University of Oxford (HL Anderson - Chemistry) 
Organisation University of Oxford
Country United Kingdom 
Sector Academic/University 
PI Contribution Design, fabrication and characterisation of OLEDs incorporating materials provided by the partner Data analysis, interpretation, manuscripts writing and interpretation.
Collaborator Contribution Provision of materials (in particular porphyrin derivatives) for OLEDs emissive layers.
Impact Manuscript drafts in final stages of preparation
Start Year 2017
 
Description Academic collaboration with University of Pisa 
Organisation University of Pisa
Country Italy 
Sector Academic/University 
PI Contribution OLEDs design and related issues identification.
Collaborator Contribution Help with solving problems with OLEDs characterisation and interpretation.
Impact No output yet
Start Year 2017
 
Description Academic collaborations with a group of synthetic chemists originally from Chalmers University 
Organisation Chalmers University of Technology
Country Sweden 
Sector Academic/University 
PI Contribution Design, fabrication, characterisation and data interpretation of a range of OLEDs. Writing and handling of the manuscript.
Collaborator Contribution Provision of materials for OLEDs fabrication. Input to manuscript writing.
Impact - 1 paper published so far within hte remit of this award: A. Minotto, P. Murto, Z. Genene, A. Zampetti, G. Carnicella, W. Mammo, M.R. Andersson, E. Wang, F. Cacialli. "Efficient Near-Infrared Electroluminescence at 840 nm with "Metal-free" Small-molecule:Polymer Blends". Advanced Materials 30, 1706584 (2018). - 1 additional paper currently submitted: P. Chvojka, P.A. Haigh, A. Burton, I. Darwazeh, A. Minotto, F. Cacialli, P. Murto, Z. Genene, W. Mammo, M. R. Andersson, E. Wang, A. Burton, Z. Ghassemlooy and S. Zvanovec. "Expanded Multi-Band Super-Nyquist CAP Modulation for Highly Bandlimited Organic Visible Light Communications". IEEE Systems Journal - 1 conference proceeding currently submitted: Burton, A. Minotto, P.A. Haigh, Z. Ghassemlooy, P. Murto, Z. Genene, W. Mammo, M.R. Andersson, E. Wang, F. Cacialli, I. Darwazeh. "Experimental Demonstration of Staggered CAP Modulation for Low Bandwidth red-emitting Polymer-LED based Visible Light". Proceedings of IEEE ICC conference (https://icc2019.ieee-icc.org/workshop/w23-5th-workshop-optical-wireless-communications).
Start Year 2017
 
Description Collaboration with Newcastle University 
Organisation Newcastle University
Country United Kingdom 
Sector Academic/University 
PI Contribution Dr Paul Anthony Haigh has been appointed as lecturer at Newcastle University through activities based on this project. He will continue to collaborate with UCL and Northumbria University on this project.
Collaborator Contribution Paul has directly contributed to many of the papers published in this project, and will continue to do so after he moves to Newcastle University.
Impact see papers
Start Year 2019
 
Description Industrial collaboration with Huawei 
Organisation Huawei Technologies
Country China 
Sector Private 
PI Contribution UCL experts have provided intellectual input and expertise into demonstrating mobile-to-mobile visible light communications using the in-built features of mobile phones, and also high speed optical fibre access based on advanced modulation formats developed at UCL.
Collaborator Contribution Provided mobile devices and optical fibre topologies and performed the experimental testing, resulting in several upcoming publications.
Impact Two papers published (https://doi.org/10.1364/ACPC.2017.M2G.4, https://doi.org/10.1364/ACPC.2017.S4B.6) and several papers under submission and in preparation in the area of mobile visible light communications specifically relating to WP2 and WP3.
Start Year 2017
 
Description Industrial collaboration with Siemens Healthineers 
Organisation Siemens Healthcare
Country Germany 
Sector Private 
PI Contribution Knowledge exchange with UCL experts from various fields, new applications for devices and new areas for innovation for Siemens Healthineers devices.
Collaborator Contribution Provisioning of bespoke-in-the-world organic polymer photodetectors, specifically adapted from their original purpose as X-ray detectors for use in this project.
Impact Cash-in-kind transfer of organic polymer photodetectors. Bespoke devices adapted specifically for our use based on our specifications and requests. multi-disciplinary covering materials science, organic electronics, circuit design, information theory and communications systems. Papers in preparation for submission specifically related to WP1.
Start Year 2017
 
Description IET e-academy lecture series 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Study participants or study members
Results and Impact A lecture series was developed and delivered for the IET e-academy for their career professional development (CPD) courses. It is expected that thousands of participants based in the UK and beyond will use the course towards gaining their chartered engineering status. The course was developed in 2017 and made accessible to users in early 2018.
Year(s) Of Engagement Activity 2017,2018
URL https://ietacademy.eu.crossknowledge.com/site/path/328#tab/path/activity/28954
 
Description Interview of Dr Paul Haigh-UCL 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Interview by UCL media for a Podcast that has a wide reach and appears on UCL web.
Suzie McCarthy: Understanding how science works is really crucial, especially in an age where there is a growing awareness of scientific uncertainty and where experts are often dismissed. And, as Ruth says, that includes being honest about what forensic science can and can't tell us.

Our next story takes us from the transfer of gun residue to the transfer of information. And it starts with a light.

Paul Haig: So, imagine that you have a light, like an LED, and you switch it on and off, but you switch it on and off really, really quickly, much faster than you can notice with your eyes. So it looks like the lights on all the time but in actual fact, it's switching on and off. And then suppose that we switch it on and off in a pattern that corresponds to some information that we want to send. So, for example, if we want to stream a video on YouTube, in essence, that dilutes to a binary sequence of ones and zeros data. So you can impress that series of ones and zeros onto the LED, onto the light. So it flickers with that pattern. And then on your laptop, or phone or computer or whatever, you can sense that series of information, the ones and zeros, which translates to a video that you might want to watch or internet or a game that you might want to play or or so on.

Suzie McCarthy (in room with Paul): So you turn the light on and off.

Paul Haig: Yeah

Suzie McCarthy (in room with Paul): Really fast? And that can send a video to a computer?

Paul Haig: Exactly. That's right.

Suzie McCarthy: This is Dr. Paul Haigh, an expert and visible light communications. Which is basically Wi Fi but on light. It's a new technology in development and UCL is one of the places that Paul and his colleagues have been working to make it a reality. What it means is that in the near future, the light bulbs in our ceilings won't just be lighting up our rooms, but sending signals to computers and other devices. We will be getting the internet not through broadband routers, but through LED light bulbs.

Paul Haig: If that makes any sense whatsoever.

Suzie McCarthy (in room with Paul): I mean, it doesn't make any sense.

Suzie McCarthy: Whether it makes sense to you, or whether like me, it only half makes sense and the rest seems like magic, Lifi technology is going to make big changes within the next 5 to 10 years. Firstly, it can send a lot of data much faster than traditional Wi Fi. Because light cycles at a frequency which is much faster than radio waves. Each little LED lamp will each be turning on and off really fast and sending loads of information out into the world. And let's be honest, we all appreciate fast internet.

Paul Haig: The current speed record in VLC (in visible light communications) is about 17 gigabits per second, which is... or maybe more, I'm not sure... I think it's about 17 gigabits per second, which is 17 billion pieces of information every second. Which is something like three Blu-ray discs every one second. Which is rapid. It's really fast. And if anybody can watch three Blu-ray discs in one second, it's even more impressive. [laughs]

Suzie McCarthy: It's true. I've never watched three movies at the same time before, let alone in one second! But more than just fast internet, Paul told me about some applications that could even be life saving.

Paul Haig: One really important and interesting aspect for me is not data communications inside your house or your office or anywhere you want to stream videos because Wi Fi does quite a good job of that. But it's actually in cars and transport systems, where you might use the brake lights of the car in front of you as an early warning system for your car. So you could put a small set of photo detectors that sense the light and convert it into electricity on your bonnet. And then if the car in front of you suddenly breaks, the red lights come on, and instead of you having to react to that car suddenly breaking, and potentially having an accident, actually, the photo detector will read that warning sign and, and slowly automatically break your car to avoid kind of traffic collisions and so on. So I think that's one super cool application of the technology. I think that's really exciting and has a big future.

And the other one is cancer research. So we have this new thread of development where we're looking at how the light signals can measure oxygen inside tissue. And that translates to tumour growth. And I'm completely ignorant in this area, so I can't tell you any more than that! That's what I've understood. So what we're doing what we're starting to do now is develop plastic foils with lights and detectors on that you can actually place on the tissue and pulse light through it. So that's light with the signal on top of it. And then at the receiver, measure the signal and see how it's changed from what we transmitted. And that corresponds to, somehow by some magic, the oxygen level inside the tumour. And therefore we can gain a lot of information about whether or not somebody does or doesn't have cancer and what stage is and how it's, you know, kind of developing and so on

Suzie McCarthy (in room with Paul): It does seem a bit like magic

Paul Haig: It is a little bit like magic. But there's a lot of clever people that do a lot of clever things. And I'm not one of them, I'm afraid.

Suzie McCarthy (in room with Paul): Well you must be a little bit,

Paul Haig: It's a massive team, you'd be surprised, you'd be surprised.

Suzie McCarthy: So here's the thing. Paul's own expertise is in something called digital signal processing, which essentially boils down to finding ways to filter out interference in the signals that these devices send, to make them as fast as possible.

Paul Haig: That's where my expertise lie. And that's what I like to kind of mess around doing.

Suzie McCarthy: Now, he's got to be pretty clever to be able to do this, but he couldn't do it alone. And more than that, he couldn't come up with the idea of how to apply this technology to cancer diagnosis without a whole team of experts, each with their own specialisms.

Paul Haig: So there's a big collaboration there's a collaboration that includes UCL engineering - Ioannis Papakonstantinou and Manish Tiwari - the Great Ormond Street Hospital - which is Paolo De Coppi - and also myself in Newcastle. And this is a collaboration that includes proper doctors, if you want, the people that do the surgeries and so on and save people's lives, and us who like to play engineering games. And these we have kind of complementary skills together. So we're mechanical engineers, electrical engineers, a little bit of biomedical engineering in the middle. And all of those skills together make a solution that we can then give to the doctors, and maybe they can apply to their patients down the line somewhere.

Suzie McCarthy: Now, forgive me for this analogy, because it's very much on the nose. But I can't help thinking of all those experts, as though they were all the little lights turning on and off, sending and receiving information themselves. I've sometimes heard people being critical of academics and of the amount of money that goes into research funding. I've heard people say that researchers ought to 'get a real job'. Paul's own dad doesn't really understand what he does...

Paul Haig: Five years working in a university and [I've] told him a million times that I'm working . But he still always tells me when you're gonna finish school. So...

Suzie McCarthy: And sure, a lot of what goes on at universities is about learning and experimenting. And sometimes it hits dead ends. Or it might find something that is only useful in a very, very small way. But sometimes, when a number of people come together and swap ideas and share information, they can find solutions to much, much bigger problem. A lot of this is based on chance. But that sort of chance can only come about when funding allows open cooperative environments to be created. And transfers of information can take place from one human to another. It's for this reason that research councils are keen to fund something called interdisciplinary research.

Paul Haig: So that means that you organize a group with people who have completely different expertise than you, you have an idea and you say: "This might work. This might be really cool." So you get together with some people in a different department that might know about those things. And you say:

"Well, what can we do together? How can we solve these problems?"

And then, you know, over a coffee or a beer or whatever, you might have a conversation where somebody has a piece of expertise, for example, in healthcare, ( [in] which I have no experience, I have experience in signal processing and optics) and say:

"Well, actually, we have this problem in connected health. And I can see a solution to that based on my expertise."

And I can say to my colleague: "Well, actually, why don't we try this?" And because of the fact that we've had a conversation, because we've had the funding and the opportunity, that might lead to a thread of research that significantly improves society and maybe solves one specific problem.

The cancer detection came about kind of in the same way. So it's really cool when those type of things happen and it's so natural. And also then when you start doing those projects, you're really excited about it and, you know, you know the potential of what you're doing and you can see that there could be an outcome and it's all very exciting.

Suzie McCarthy: When we decided to cover this story, I was really determined to pin down exactly how this magical light communication works. But I realised that what's more important is how this technology came to be, and how it continues to be developed: through specialists working collectively, transferring their knowledge from one person to another.

Suzie McCarthy (in room with Paul): And you know, when you like, think about the universe as a whole?

Paul Haig: Yeah.

Suzie McCarthy (in room with Paul): And you get like a bit teary, because it's just like, woah?

Paul Haig: Okay, yeah,

Suzie McCarthy (in room with Paul): Does that... do you... is that just me or?

Paul Haig: I can't relate personally. But go ahead.

Suzie McCarthy (in room with Paul): Okay. [laughs] Well, that's how I get. And then I used to get like that about computers, because it just seems, and the same with internet like, it does seem like magic. And it does seem like, you know, how did humans make that happen?

Paul Haig: It's just clever people doing stuff.

Suzie McCarthy (in room with Paul): Yeah.

Paul Haig: When people have some interest in what they do, and they really like, you know, like spending their time on that and they're given the opportunity and the resources, people can do magic.

***
Year(s) Of Engagement Activity 2019
URL https://www.ucl.ac.uk/made-at-ucl/madeatucl-podcasts/podcast-2-transcript#light%20wave