Another entry in my “bizarre use of bodily fluids but that has a really cool result” category for nanoscience, is this paper published a couple of weeks ago in the Advanced Materials journal. The problem the researchers from Tel Aviv university were trying to solve is simple: we can make white LEDs now easily enough, but they’re complex to manufacture and complexity means expensive!
Producing ‘white light’ for humans is quite simple, more than likely your computer monitor is employing this trick right now, you simply produce equal amounts of red, green and blue light from the same pixel – this is what we humans perceive as white light. The problem with LEDs is that to get these colours, you use 3 different dyes – but when you put these dyes close together they distort the colour produced by the neighboring dye, and so you don’t end up with white light! What existing LEDs do is mount these dyes in a ‘inorganic matrix’ (translation: they stick them in a thin plastic sheet), to hold the dyes far apart enough so prevent the distortion, but the matrix they currently use is difficult to work with, insoluble in water and hence expensive. What the Tel Aviv researchers did is find a new, cheap, ‘green’, sustainable matrix: mucus.
More specifically they used the protein that makes up around 80% of mucus: mucin. Using “bovine submaxillary mucin” (mucus from a cow’s mouth) they were able to stick the dye molecules onto the mucin protein, make this mix into a thin film, and then excite them to produce white light (above). Finally, they coated an ultraviolet LED with their white-dye/mucin mix, turned it on and, low and behold, they had a white LED!
Yes it’s a little gross, but seriously cool – a great example of the many uses of Protein Luminescent Films (PLUFs).
1) N.Hendler “Efficient Separation of Dyes by Mucin: Toward bioinspired White-Luminescent Devices” Adv. Mater. (2011) doi:10.1002/adma.201100529