At Photonics West, back in January, I saw a booth from InfiniLED which was promoting their microLED arrays. These are LEDs that are around 25 μm in size and can be fabricated into arrays with spacings between LEDs only a bit larger than the size of the LEDs themselves. There is an article by and about them in the newest issue of Photonics Spectra. Another company pursuing the same technology is mLED. Both companies are still in pretty early stages of technology development, but demo systems are available from both.
These could be a nice technology for photoactivation applications. The array sizes are still a bit small, but mLED, for example, has a 4096 pixel array of 16 μm pixels spaced 50 μm apart, and their LEDs can be manufactured to emit at 405 nm. Particularly if they could get to hundreds of thousands of LEDs, it’s easy to imagine placing one of these LED arrays at a conjugate imaging plane and using it to do spatially directed photoactivation.