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.
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.