Applications abound for newly licensed microLEDs

Laura S. Marshall, laura.marshall@photonics.com

Communications and life sciences can expect a boost from a newly formed company in Glasgow.

In a spinout deal, the University of Strathclyde has formed mLED Ltd., a company dedicated to promoting its newly licensed microLEDs, dense arrays of up to several thousand miniature light sources per square millimeter. The arrays are pattern-programmable and do not require a plethora of external components – such as optics or switching matrices – to modulate the light pattern. This makes them more efficient and compact than other, similar technologies.

Shown is the array of microLEDs licensed by mLED.

“The LEDs give out light by electroluminescence upon injection of an electrical current in exactly the same way as conventional large-area LEDs familiar in indicator lamps, traffic lights and moving message displays,” said professor Martin Dawson, director of research at the university’s Institute of Photonics. “Because of their small size, however, they emit light at high optical power densities and can be switched at very high speeds.

“The light pattern is produced by direct electrical control of the individual microLED elements and, therefore, does not rely on switchable polarizers or mirrors, as is the case in liquid crystal displays or digital light projection systems, for example.”

In this 64 x 64 green matrix-addressed array, each LED pixel is 20 μm in diameter.

The devices are compatible with silicon CMOS electronic control, Dawson added, enabling different modulation as needed for specific applications and allowing for integrated photodetection to be used in optical microsystems.

“In communications, the devices can be modulated at data rates up to 1 GB/s per pixel and can be used in free-space visible light communications or polymer optical fiber communications,” he said. “They also offer the prospect of photopumping organic semiconductor lasers integrated on-chip.”

Mask-free photolithography and UV direct writing make up other areas where microLEDs could prove beneficial.

“Projecting the array optical patterns into photoresists, for example, allows semiconductor microfabrication without mask aligners and hard customized optical masks,” Dawson said. “Indeed, we are now using the microLED arrays in this way to produce new microLED arrays.

“In the life sciences, the technology is very suitable for integrated lab on a chip. For example, the arrays can produce light-patterned electrode structures suitable for ‘optoelectronic tweezers,’ enabling manipulation of cells or microparticles on-chip. In fast-pulsed operation, in conjunction with photon-counting electronics, they can be used for highly parallel, on-chip, time-resolved photoluminescence measurements.”

Optogenetics research and the development of retinal prosthetics also could benefit from microLEDs, he said. “The devices also have implications for microscopy, where sequential scanning of special striped format microLEDs can allow wide-field depth-sectioned images of biomaterials to be obtained.”

The technology was developed at the Institute of Photonics, and the researchers involved – Dawson; Dr. Erdan Gu, associate director; and Dr. Gareth Valentine, research technologist – will act as consultants to mLED. Dawson noted that they have been working on the topic since 2001.

Left to right: Dr. Jim Bonar, chief executive of mLED Ltd.; professor Martin Dawson, director of research of the Institute of Photonics at the University of Strathclyde; and Dr. Erdan Gu, associate director of the institute, with the array of microLEDs licensed by mLED. Images courtesy of the University of Strathclyde and mLED Ltd.

Funding for the new company was led by Braveheart Investment Group, investing via the Strathclyde Innovation Fund and the Alpha EIS Fund. Additional funding came from Scottish Enterprise’s Scottish Seed Fund.

“MicroLEDs have particularly strong potential for evolving life science markets such as neuroscience and for the emerging telecoms market of pico projectors, as well as for printing, microscopy and next-generation general lighting arrangements,” said Dr. Jim Bonar, chief executive of the new company.

“We have easy-to-use, turnkey demonstrator kits available for sale so that developers can see if the microLEDs fit with their own innovative applications. The stand-alone graphical user interface permits simple and effective control of the microLED platform,” he noted, adding that mLED has already begun shipping products to customers.

“Research in new areas will carry on, and we look forward to working with mLED in bringing this advancing technology to rapidly expanding marketplaces,” said Simon Andrews of the Institute of Photonics.