Toward OLED-controlled live neural networks

May 11, 2016 //By Julien Happich
Toward OLED-controlled live neural networks
In a paper titled "Arrays of microscopic organic LEDs for high-resolution optogenetics" published in the Advance Sciences journal, scientists at the University of St Andrews detail how they leveraged very fine pixel pitch OLEDs in place of a Petri dish to individually trigger living cells and observe their electric activity.

Working with Dr Gareth Miles from the School of Psychology and Neuroscience, Professor Gather and his team used OLEDs as a substrate to manipulate individual, live cells from a human embryonic kidney cell line that were tweaked to produce a light-sensitive protein. Upon exposure to blue OLED light from pixels directly underneath the cell, the researchers stimulated the electric activity of individual targeted cells, while neighbouring cells remained in the dark and stayed inactive.

The real first here, was that the researchers used a 20mm2 OLED microarray (from Fraunhofer FEP, based on a CMOS backplane featuring 230,000 individually addressable pixels) with 6×9μm2 pixels, smaller than the actual cells under study. This enabled the team to optically stimulate not only discrete cells but also different parts of a given cell.

The OLED microarray with cells adhered on top of the array (not drawn to scale). The microarray is connected to a high-definition multimedia interface (HDMI) driver with a flexible connector. Each pixel of the array can be turned on and off by the driver and the CMOS backplane. Light-induced changes in cell membrane current are measured with a patch clamp electrode (voltage clamp mode, whole-cell configuration). The cross section on the right shows the layer structure of the OLED array.

To ensure the shortest optical path (from the OLED pixels used as a substrate) to the cells under study while protecting the OLED active layers, the team only applied a 1.5μm thin-film encapsulation barrier (three layers of Al2O3 and two layers of polymer), which they had reported, was enough to keep the OLED functional over several days without noticeable degradation even when fully immersed into a salt buffer solution. The microarray was then bonded to a flexible flat cable that connects to a custom HDMI driver interface.

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