Computing with Water Droplets: Drops of Water as Bits of Information

September 7th, 2012 by James Ayre



A radical new concept for computing has been developed that uses drops of water as bits of digital information. This new concept was spurred by the recent discovery that when two water droplets collide with each other on a highly water-repellent surface, they simply bounce off of each other similar to billiard balls.

The research, just published in the journal Advanced Materials, was done by experimentally determining the ideal conditions necessary for the rebounding of water droplets when moving on superhydrophobic surfaces.

“In the study, a copper surface coated with silver and chemically modified with a fluorinated compound was used. This method enables the surface to be so water-repellent that water droplets roll off when the surface is tilted slightly. Superhydrophobic tracks, developed during a previous study, were employed for guiding droplets along designed paths.”







By making use of the tracks, the researchers were able to demonstrate that water droplets could be used as “superhydrophobic droplet logic.” As an example, a memory device was designed that allowed water droplets to be used as bits of digital information. Devices that are capable of elementary Boolean logic operations were also constructed. It’s these basic devices that make up the building blocks of computing.

Video (Superhydrophobic droplet logic: flip-flop memory):

Even more interesting, though, is that when the water droplets are “loaded with reactive chemical cargo, the onset of a chemical reaction could be controlled by droplet collisions.” By combining the droplet logic operations with the collision-controlled chemical reactions, there is the potential to make programmable chemical reactions, single droplets then serving the simultaneous function as bits of digital information and as miniature reactors.

Video (Chemical reaction controlled by droplet collisions):

“It is fascinating to observe a new physical phenomenon for such everyday objects — water droplets,” says Robin Ras, an Academy Research Fellow in the Molecular Materials research group.

“I was surprised that such rebounding collisions between two droplets were never reported before, as it indeed is an easily accessible phenomenon: I conducted some of the early experiments on water-repellent plant leaves from my mother’s garden,” said Henrikki Mertaniemi, the researcher that “discovered the rebounding droplet collisions two years ago during a summer student project in the research group of Ras and Academy Professor Olli Ikkala.”

The researchers think that the present research will lead to useful technology that is based on superhydrophobic droplet logic. Some of the possible applications are autonomous and simple logic devices that don’t need electricity, and biochemical analysis devices that are programmable.

Source: Aalto University









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