Stain Screen

Discovery News is reporting that a new type of touchscreen is in the works, one inspired by ink-printing errors that resemble Coffee stains.
A slightly over-filled coffee cup often spills coffee down its sides, leaving a ring of coffee on the surface. (The center remains unstained because the cup prevented the coffee from entering the area.) This dries into a brown, unsightly ring. Likewise in printing, a drop of ink dries more quickly on its edge, pulling the liquid towards the edges, leaving a gap in the middle. Printers seek to avoid this, as outlined letters are less legible than filled ones.
Touchscreens need a certain density of silver-based molecules to notice where they are being touched, but these molecules also block light, making it useless as a screen. The coffee ring system allows a grid of conductive molecules to form that has gaps that light can be shown through, thus being effective both as a screen and a touch-observing system.
Israeli scientists also observe that the silver particles can absorb ambient light and convert it to electricity, so these coffee-ring touchscreens can recharge the device by being left in direct sunlight. These effects together would make a very excellent portable computer, rechargeable anywhere.