KAIST develops flexible vertical micro LED
New process produces optical power density three times higher than lateral micro LEDs The team has used the technology to control mouse behaviour via optogenetic stimulation of the f-VLEDs.
A team at the Korean Institute of Advanced Technology (KAIST) led by Keon Jae Lee from the Department of Materials Science and Engineering and Daesoo Kim from the Department of Biological Sciences has developed flexible vertical micro LEDs (f-VLEDs) using anisotropic conductive film (ACF)-based transfer and interconnection technology.
The team also succeeded in controlling animal behaviour via optogenetic stimulation of the f-VLEDs.
Flexible micro LEDs have become a strong candidate for the next-generation display due to their ultra-low power consumption, fast response speed, and excellent flexibility. However, the previous micro LED technology had critical issues such as poor device efficiency, low thermal reliability, and the lack of interconnection technology for high-resolution micro LED displays.
The research team has designed new transfer equipment and fabricated a f-VLED array (50x50) using simultaneous transfer and interconnection through the precise alignment of ACF bonding process. These f-VLEDs achieved optical power density (30 mW/mm2) three times higher than that of lateral micro LEDs, improving thermal reliability and lifetime by reducing heat generation within the thin film LEDs.
These f-VLEDs (thickness: 5µm, size: below 80µm) can be applied to optogenetics for controlling the behaviour of neuron cells and brains. In contrast to the electrical stimulation that activates all of the neurons in brain, optogenetics can stimulate specific excitatory or inhibitory neurons within the localised cortical areas of the brain, which facilitates precise analysis, high-resolution mapping, and neuron modulation of animal brains.
(Refer to the author's previous ACS Nano paper of "Optogenetic Mapping of Functional Connectivity in Freely Moving Mice via Insertable Wrapping Electrode Array Beneath the Skull." )
In this work, they inserted the innovative f-VLEDs into the narrow space between the skull and the brain surface and succeeded in controlling mouse behaviour by illuminating motor neurons on two-dimensional cortical areas located deep below the brain surface.
Lee said, "The flexible vertical micro LED can be used in low-power smart watches, mobile displays, and wearable lighting. In addition, these flexible optoelectronic devices are suitable for biomedical applications such as brain science, phototherapeutic treatment, and contact lens biosensors."
He recently established a startup company (FRONICS ) based on micro LED technology and is looking for global partnerships for commercialisation.
'Optogenetic Control of Body Movements via Flexible Vertical Light-Emitting Diodes on Brain Surface' was published in the February 2018 issue of Nano Energy.
