Water Droplets’ Collision is New Concept of Computing

By using droplets as bits of digital information, the Aalto University researchers have developed a new concept of computing.

The discovery is based on the fact that two droplets of water bounce back like billiard balls on colliding with each other on a highly water repellent surface. The researchers have experimentally determined the conditions for rebounding of water droplets moving on a super hydrophobic surface.

For this a copper surface was coated with silver and then chemically modified it with a fluorinated compound. This makes the surface water repellent and water droplets roll off when the surface is slightly tilted.

In the previous studies that used super hydrophobic tracks, it was used to carry the water droplets along the intended trail. 

The researchers thus projected that water droplets can be turned into technology 'super hydrophobic droplets logic' by using the concept of tracks.

Devices for elementary Boolean logic operations were demonstrated. These simple devices are building blocks for computing.

They even loaded the water droplets with reactive chemical load, the onset of a chemical reaction could be controlled by droplet collisions. The mixture of the collision-controlled chemical reactions triggers the programmable chemical reactions where single droplets serve as both a small reactors and also bits for computing. 

"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," explains a member of the research group, Henrikki Mertaniemi, who 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 anticipate that this new finding will result in new technology that is based on super hydrophobic droplet logic.

The study has been published in the journal Advanced Materials.