The Lightest Light Source

A team of scientists from the University of St Andrews has developed a new way of making the most durable, light­weight and thinnest light source available so far, which could revolutionize the future of mobile techno­logies and pave the way for new advances in brain science. The new research into the development of organic LEDs has impli­cations not only for the future designs of mobile phones and tablets but could also play a key role in neuroscience research and clinical techno­logies used to help patients who suffer from neuro­logical diseases.

Flexible, ultra-lightweight and highly durable organic LEDs promise new forms of wearable displays. (Source: U. St Andrews)

Using a combination of organic electro­luminescent molecules, metal oxide and bio­compatible polymer protection layers, the scientists created organic LEDs that are as thin and flexible as the everyday cling film we use at home. The new light sources developed will have future impli­cations for digital displays and can be used to make lighter and thinner displays for phones and tablets; displays that are big when we look at them, but that can be folded or rolled up when not in use. In the longer term, these new LEDs could also see use in treatments for neurological diseases in which light-gated proteins are deployed to modulate brain activity in patients.

Earlier attempts to develop ultra-thin organic LEDs found they struggled with poor stability in air and moist environ­ments. However, the new LEDs were found to be extremely robust with tests showing they can survive under water for weeks and withstand exposure to solvents and gas plasmas. The LEDs can also be bent around the edge of a razor blade thousands of times and still function perfectly – a simple experiment that highlights their extreme dura­bility. The robustness, extreme form factor and mechanical flexi­bility of the new light sources opens several possi­bilities for future use and appli­cations beyond mobile technologies. For instance, they might be integrated into work surfaces, packaging and clothing as self-emissive indicators without adding weight and volume to the product. Furthermore, their stability under high humidity and in water makes them ideally suited for wearable appli­cations requiring skin-contact and for use as implants in biomedical research.

Lead scientist Malte Gather from the School of Physics and Astronomy, said: “Our organic LEDs are very well suited to become new tools in biomedical and neuro­science research and may well find their way into the clinic in the future.” Working with Stefan Pulver from the School of Psychology and Neuro­science, the scientists used light from an array of miniature organic LEDs and optogenetics to direct the locomotion of fly larvae in a highly controlled fashion. Delivering light to specific body segments of crawling fly larvae allowed the researchers to stimulate and silence sensory neurons in a reliable manner. Depending on when and where light was delivered, larvae started to crawl forward or backward, with the dynamics of light stimulation controlling the speed of crawling and other aspects of animal movement.

“While the precise neuronal mechanism behind the animal response remains unknown, we are now in a much better position to test a range of hypotheses related to the locomotion of these organisms,” explains Caroline Murawski. The researchers are currently combining their breakthrough in making light, flexible and robust organic LEDs with what they have learned about controlling neural activity in flies to make light sources that can be implanted into the brain of vertebrate organisms. This will allow researchers to study brain function in a less invasive and more versatile manner than existing techniques.

In addition to contri­buting to future development of mobile displays, and opening new avenues for basic research, the technologies developed in these studies could ulti­mately be used to improve clinical treatments by creating optical inter­faces that send information directly to the brain of human patients who suffer from a loss of vision, hearing or sense of touch. (Source: U. St. Andrews)

References: C. Keum et al.: A substrateless, flexible, and water-resistant organic light-emitting diode, Nat. Commun. 11, 6250 (2020); DOI: 10.1038/s41467-020-20016-3C. Murawski et al.: Segment-specific optogenetic stimulation in Drosophila melanogaster with linear arrays of organic light-emitting diodes, Nat. Commun. 11, 6248 (2020); DOI: 10.1038/s41467-020-20013-6

Link: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK

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