My oil droplet is smarter than your lab mouse
One of the images that says "science experiment" to the public is that
of a rat finding
its way through an experimenter's maze. We tend to associate the ability
of rats to quickly solve mazes with their navigational skills and
intelligence. Mazes also present an interesting challenge to robotics
researchers, who can use them to test the navigation skills of their
creations. But, as it turns out, some mazes can be navigated without all
that much in the way of smarts.
A team of chemists and chemical engineers from Northwestern University have developed an oil droplet that is capable of running through a simple maze, running along the optimal path no less. With no need for food, the oil drop found its way thanks to a combination of a surface active chemicals and a pH gradient that is present in the maze.
The system is described in the Journal of the American Chemical Society. The researchers flooded the 2 cm by 2 cm by ~1 mm tall maze with a basic solution. At the end of the maze, they placed a big chunk of gelatinous acid; over the course of a minute, a clean pH gradient appeared throughout the maze. The droplet was an inorganic solvent that had a bit of acid dispersed inside it. As the acid worked its way to the surface of the droplet, it would become deprotonated, and would be subsequenty be pushed out of the way by fresh, protonated acid.
This cycling causes an asymmetrical surface tension to develop, which produces convection currents that move the droplet along in the direction of decreasing pH—toward the big chunk of acid at the exit. Not all drops stayed on the ideal path. Some of them moved so quickly (up to 10 mm/s) that they would overshoot, and had to retrace their steps in order to find the path to the exit once again. Movies of the oil droplets running the maze are freely available on the supplemental information page for the article, found here.
The press release accompanying this article attempts to draw correlation between this work and that of "magic bullet" type cancer treatments—ones who only attack cancer cells, leaving healthy cells undamaged—saying that the decreased pH of cancerous cells could act as a blob at the end of the maze. The paper, on the other hand, does not make this leap. While the idea may be to go that direction in the future, it seems an attempt to draw more attention to work that is, in my opinion, interesting enough to stand on its own.
J. Am. Chem. Soc., 2010. DOI: 10.1021/ja9076793
- wong chee tat :)
A team of chemists and chemical engineers from Northwestern University have developed an oil droplet that is capable of running through a simple maze, running along the optimal path no less. With no need for food, the oil drop found its way thanks to a combination of a surface active chemicals and a pH gradient that is present in the maze.
The system is described in the Journal of the American Chemical Society. The researchers flooded the 2 cm by 2 cm by ~1 mm tall maze with a basic solution. At the end of the maze, they placed a big chunk of gelatinous acid; over the course of a minute, a clean pH gradient appeared throughout the maze. The droplet was an inorganic solvent that had a bit of acid dispersed inside it. As the acid worked its way to the surface of the droplet, it would become deprotonated, and would be subsequenty be pushed out of the way by fresh, protonated acid.
This cycling causes an asymmetrical surface tension to develop, which produces convection currents that move the droplet along in the direction of decreasing pH—toward the big chunk of acid at the exit. Not all drops stayed on the ideal path. Some of them moved so quickly (up to 10 mm/s) that they would overshoot, and had to retrace their steps in order to find the path to the exit once again. Movies of the oil droplets running the maze are freely available on the supplemental information page for the article, found here.
The press release accompanying this article attempts to draw correlation between this work and that of "magic bullet" type cancer treatments—ones who only attack cancer cells, leaving healthy cells undamaged—saying that the decreased pH of cancerous cells could act as a blob at the end of the maze. The paper, on the other hand, does not make this leap. While the idea may be to go that direction in the future, it seems an attempt to draw more attention to work that is, in my opinion, interesting enough to stand on its own.
J. Am. Chem. Soc., 2010. DOI: 10.1021/ja9076793
- wong chee tat :)
