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A drop of innovation

Can water droplets be programmed to become an interactive element or a computer interface?

Udayan Umapathi with the programmable droplets system. Photo: MIT Media Lab
Udayan Umapathi with the programmable droplets system. Photo: MIT Media Lab

Let’s assume you want to paint a picture of a blue vase but are unable to get the right shade on your palette. Pick up your smartphone, click a photograph of the vase, and a computer system will pick up the colour from the photograph and digitally transmit it to a circuit board with two droplets of water. You add some colour to one drop and the two drops of water will then move on the circuit board and merge. The to and fro motion ensures that the water droplet mixes with the coloured droplet in the right proportion to get the exact shade you want. All you need to do now is dip your paintbrush into this coloured droplet and start painting.

These water droplets are programmed to move. Researchers at MIT Media Lab’s Tangible Media Group have developed a programmable droplets system which uses the “electrowetting on dielectric" (EWOD) technique to control these droplets. EWOD is basically a technique that allows precise control of droplets using an electric field. Water, a natural medium that carries chemical and biological information becomes an interactive element.

“Programmable droplets EWOD system is essentially just a grid of metal plates coated with a low-friction material. By programmatically controlling the electric field of the grid, we are able to change the shape of polarizable liquid droplets and move them around the surface," explains Udayan Umapathi, a researcher at the MIT Media Lab, on email. “The programmable electric (field) enables us to perform other operations, such as morphing, merging, and splitting multiple droplets simultaneously," he adds.

Umapathi, originally from Bengaluru, says their original goal was to use these programmable droplets to create computer interfaces that could leverage the user’s intuitive knowledge of the world. The idea behind the system is to use droplets in the environment and program them for information manipulation and human interaction.

In a video earlier this year, researchers demonstrated how water droplets could be used as information displays, an interactive medium for painting, and even gaming.

They integrated the device into a physical palette to automatically mix colours (like painting the vase). The system was also demonstrated as a “hand-held gaming console" that leverages the familiarity of a person’s understanding of the physical world; for example, using gravity to steer an object. “Our video shows an example (of a) game where a user steers a primary character (a red droplet) by tilting the device to engulf other characters (green, blue, white droplets). As the user-driven character gets closer, the system senses it and drives other characters away.... Think of this as a physical version of Pacman with water droplets," says Umapathi.

In the future, Umapathi says, the system can be integrated more seamlessly into living spaces to enable different interactions. In such scenarios, droplets that already exist in the user’s environment—for instance, trapping and programming water droplets on windows, cups or umbrellas—can be manipulated. “In a conceptual example," he adds, “we show how a programmable droplet display on a mirror can render messages sent from another digital device by regulating the shape and motion of the water droplets condensing on the mirror."

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