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How To Make An Oil Droplet Act Like A Mouse

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Researchers have created oil droplets that can find their way through a maze. Getting inanimate objects to trace the path to the area they're most needed is a difficult prospect at the best of times.

In order to work on this problem, researchers at Northwestern have developed a way to send oil droplets through a maze with impressive accuracy. Their goal? Getting cancer drugs where they're needed, via blood vessels that create a difficult-to-navigate labyrinth.


They crafted mazes around 6.5 square centimeters in size, and flooded them with a basic solution of potassium hydroxide. A slightly acidic droplet of mineral oil or dichloromethane was placed at the entrance, and at the end was a chunk of agarose gel that had been soaked in hydrochloric acid. The acid from the gel would soak into the fluid near the goal of the maze, creating a more acidic environment.

The basic solution interacts with the acid droplet, propelling it towards the more acidic end of the maze. There's a gradient of acidity throughout the solution, and the more basic area of it reacts with the droplet more, making the part of the droplet facing the entrance more basic, and the part facing the exit more acidic. The causes a difference in surface tension, which moves the droplet to the end of the maze, along the shortest possible path.


The real world application of this comes from the fact that cancer is more acidic than the rest of the body. By utilizing this motion from a basic environment towards acid, there might just be a way of delivering drugs in a far more targeted way.

[Journal of the American Chemical Society, via ScienceNow]