̽��ֱ�� of Cambridge - Jong min Kim

Smart lighting system based on quantum dots more accurately reproduces daylight

sc604 — Wed, 03 Aug 2022 09:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, designed the next-generation smart lighting system using a combination of nanotechnology, colour science, advanced computational methods, electronics and a unique fabrication process.

̽��ֱ��team found that by using more than the three primary lighting colours used in typical LEDs, they were able to reproduce daylight more accurately. Early tests of the new design showed excellent colour rendering, a wider operating range than current smart lighting technology, and wider spectrum of white light customisation. ̽��ֱ��results are reported in the journal Nature Communications.

As the availability and characteristics of ambient light are connected with wellbeing, the widespread availability of smart lighting systems can have a positive effect on human health since these systems can respond to individual mood. Smart lighting can also respond to circadian rhythms, which regulate the daily sleep-wake cycle, so that light is reddish-white in the morning and evening, and bluish-white during the day.

When a room has sufficient natural or artificial light, good glare control, and views of the outdoors, it is said to have good levels of visual comfort. In indoor environments under artificial light, visual comfort depends on how accurately colours are rendered. Since the colour of objects is determined by illumination, smart white lighting needs to be able to accurately express the colour of surrounding objects. Current technology achieves this by using three different colours of light simultaneously.

Quantum dots have been studied and developed as light sources since the 1990s, due to their high colour tunability and colour purity. Due their unique optoelectronic properties, they show excellent colour performance in both wide colour controllability and high colour rendering capability.

̽��ֱ��Cambridge researchers developed an architecture for quantum-dot light-emitting diodes (QD-LED) based next-generation smart white lighting. They combined system-level colour optimisation, device-level optoelectronic simulation, and material-level parameter extraction.

̽��ֱ��researchers produced a computational design framework from a colour optimisation algorithm used for neural networks in machine learning, together with a new method for charge transport and light emission modelling.

̽��ֱ��QD-LED system uses multiple primary colours – beyond the commonly used red, green and blue – to more accurately mimic white light. By choosing quantum dots of a specific size – between three and 30 nanometres in diameter – the researchers were able to overcome some of the practical limitations of LEDs and achieve the emission wavelengths they needed to test their predictions.

̽��ֱ��team then validated their design by creating a new device architecture of QD-LED based white lighting. ̽��ֱ��test showed excellent colour rendering, a wider operating range than current technology, and a wide spectrum of white light shade customisation.

̽��ֱ��Cambridge-developed QD-LED system showed a correlated colour temperature (CCT) range from 2243K (reddish) to 9207K (bright midday sun), compared with current LED-based smart lights which have a CCT between 2200K and 6500K. ̽��ֱ��colour rendering index (CRI) – a measure of colours illuminated by the light in comparison to daylight (CRI=100) – of the QD-LED system was 97, compared to current smart bulb ranges, which are between 80 and 91.

̽��ֱ��design could pave the way to more efficient, more accurate smart lighting. In an LED smart bulb, the three LEDs must be controlled individually to achieve a given colour. In the QD-LED system, all the quantum dots are driven by a single common control voltage to achieve the full colour temperature range.

“This is a world-first: a fully optimised, high-performance quantum-dot-based smart white lighting system,” said Professor Jong Min Kim from Cambridge’s Department of Engineering, who co-led the research. “This is the first milestone toward the full exploitation of quantum-dot-based smart white lighting for daily applications.”

“ ̽��ֱ��ability to better reproduce daylight through its varying colour spectrum dynamically in a single light is what we aimed for,” said Professor Gehan Amaratunga, who co-led the research. “We achieved it in a new way through using quantum dots. This research opens the way for a wide variety of new human responsive lighting environments.”

̽��ֱ��structure of the QD-LED white lighting developed by the Cambridge team is scalable to large area lighting surfaces, as it is made with a printing process and its control and drive is similar to that in a display. With standard point source LEDs requiring individual control this is a more complex task.

̽��ֱ��research was supported in part by the European Union and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
Chatura Samarakoon et al. ‘Optoelectronic System and Device Integration for Quantum-Dot Light-Emitting Diode White Lighting with Computational Design Framework.’ Nature Communications (2022). DOI: 10.1038/s41467-022-31853-9

Researchers have designed smart, colour-controllable white light devices from quantum dots – tiny semiconductors just a few billionths of a metre in size – which are more efficient and have better colour saturation than standard LEDs, and can dynamically reproduce daylight conditions in a single light.

This research opens the way for a wide variety of new human-responsive lighting environments

Gehan Amaratunga

Yaorusheng via Getty Images

Long exposure light painting

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Scientists develop fully woven, smart display

sc604 — Thu, 10 Feb 2022 13:17:14 +0000

An international team of scientists have produced a fully woven smart textile display that integrates active electronic, sensing, energy and photonic functions. ̽��ֱ��functions are embedded directly into the fibres and yarns, which are manufactured using textile-based industrial processes.

̽��ֱ��researchers, led by the ̽��ֱ�� of Cambridge, say their approach could lead to applications that sound like sci-fi: curtains that are also TVs, energy-harvesting carpets, and interactive, self-powered clothing and fabrics.

This is the first time that a scalable large-area complex system has been integrated into textiles using an entirely fibre-based manufacturing approach. Their results are reported in the journal Nature Communications.

Despite recent progress in the development of smart textiles, their functionality, dimensions and shapes are limited by current manufacturing processes.

Integrating specialised fibres into textiles through conventional weaving or knitting processes means they could be incorporated into everyday objects, which opens up a huge range of potential applications. However, to date, the manufacturing of these fibres has been size limited, or the technology has not been compatible with textiles and the weaving process.

To make the technology compatible with weaving, the researchers coated each fibre component with materials that can withstand enough stretching so they can be used on textile manufacturing equipment. ̽��ֱ��team also braided some of the fibre-based components to improve their reliability and durability. Finally, they connected multiple fibre components together using conductive adhesives and laser welding techniques.

Using these techniques together, they were able to incorporate multiple functionalities into a large piece of woven fabric with standard, scalable textile manufacturing processes.

̽��ֱ��resulting fabric can operate as a display, monitor various inputs, or store energy for later use. ̽��ֱ��fabric can detect radiofrequency signals, touch, light and temperature. It can also be rolled up, and because it’s made using commercial textile manufacturing techniques, large rolls of functional fabric could be made this way.

̽��ֱ��researchers say their prototype display paves the way to next-generation e-textile applications in sectors such as smart and energy-efficient buildings that can generate and store their own energy, Internet of Things (IoT), distributed sensor networks and interactive displays that are flexible and wearable when integrated with fabrics.

“Our approach is built on the convergence of micro and nanotechnology, advanced displays, sensors, energy and technical textile manufacturing,” said Professor Jong min Kim, from Cambridge’s Department of Engineering, who co-led the research with Dr Luigi Occhipinti and Professor Manish Chhowalla. “This is a step towards the full exploitation of sustainable, convenient e-fibres and e-textiles in daily applications. And it’s only the beginning.”

“By integrating fibre-based electronics, photonic, sensing and energy functionalities, we can achieve a whole new class of smart devices and systems,” said Occhipinti, also from Cambridge’s Department of Engineering. “By unleashing the full potential of textile manufacturing, we could soon see smart and energy-autonomous Internet of Things devices that are seamlessly integrated into everyday objects and many other sector applications.”

̽��ֱ��researchers are working with European collaborators to make the technology sustainable and useable for everyday objects. They are also working to integrate sustainable materials as fibre components, providing a new class of energy textile systems. Their flexible and functional smart fabric could eventually be made into batteries, supercapacitors, solar panels and other devices.

̽��ֱ��research was funded in part by the European Commission and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
HW Choi et al. ‘Smart textile lighting/display system with multifunctional fibre devices for large scale smart home and IoT applications.’ Nature Communications (2022). DOI: 10.1038/s41467-022-28459-6

Researchers have developed a 46-inch (116cm) woven display with smart sensors, energy harvesting and storage integrated directly into the fabric.

By integrating fibre-based electronics, photonic, sensing and energy functionalities, we can achieve a whole new class of smart devices and systems

Luigi Occhipinti

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