In the most common type of ink-jet, a pulse of current heats a coil of wire, creating bubbles that force a small volume of ink down a tube and onto the page at high speed. The Keio team use the same hardware to squirt scent. Working with printer maker Canon, they converted the guts of an off-the-shelf printer into what they call an olfactory display, capable of rapidly switching between four aromas.
They found that a standard Canon ink-jet can eject as little as a picolitre of scent droplets in 0.7 milliseconds. That is too little to smell, but pulses 100 milliseconds long produced perceivable aromas of lemon, vanilla, lavender, apple, cinnamon, grapefruit and mint. Better still, a 100-millisecond ink-jet burst dissipates fast, at least in the team's small-scale experiment. After an average of two human breaths it has gone, allowing a different smell to be activated.
Link via Fanboy | Photo by Flickr user CarbonNYC used under Creative Commons license