Via FastCompany, Idaho-based startup Rohinni is demoing a new application of LED lighting they are calling “Lightpaper”.  Rohinni is using a mixture of ultra-small LED die suspended in conductive ink:

In its current state, Lightpaper is manufactured by mixing ink and tiny LEDs together and printing them out on a conductive layer. That object is then sandwiched between two other layers and sealed. The tiny diodes are about the size of a red blood cell, and randomly dispersed on the material. When current runs through the diodes, they light up.

I’ve heard of this concept before, with the technique being pretty straightforward:  Electricity wants to flow through the easiest path, right?  So combining low-resistance LED die into a higher-resistance conductive ink means the electricity will try to flow through any LED die available.  I assume they’re working on ways to also combine phosphors directly into the mix to generate white light.

Such is the progress for LEDs:  This concept depends on LED wafer production dropping so much in price that huge quantities of ultra-small die can be produced (where there is lots of wasted epitaxy due to the kerf of making all those cuts).  It also depends on advances in conductive ink (which I’ve discussed in a few posts here, here and here).  It will be interesting to see how this matches up with OLED pricing.

And “paper” certainly seems to be a misnomer:  I’m guessing they have to encapsulate it in some sort of non-conductive plastic coating to seal the die from static discharge.

Of course, there is always a catch with every magical new technology:

The big problem with the product’s current, version one, is how it places the LEDs when printed. Right now, they aren’t distributed evenly on the printed surface. This can cause a shimmering, or starry night effect. Smoot explained that for a lot of applications, this won’t matter, but the challenge being worked on currently is to get specific placement of the diodes—to produce completely even light. Not an insurmountable task, a second version of Lightpaper is likely a few months out.

“A few months out…”  Good luck with that!