Thanks to gravity, fluids flow downwards following the path of least resistance. To better control where they go, humans have spent thousands of years developing pipes and pumps, but now researchers at Brandeis University have mixed biological molecules into a substance that marks the first steps towards developing a self-propelling liquid that could flow free of human or gravitational influence.
Key to the mixture's continuous motion is the use of microtubules. These hollow tubes form a vital part of the structure of biological cells, and by flexing, stretching and changing size, they allow cells to adapt to changes in their surroundings.
Sourcing microtubules from the brains of cows, the researchers combined them in a solution with two other molecules often found in cells: the protein kinesin, and a nucelotide called adenosine triphosphate (ATP). These three components have a very specific reaction inside cells: kinesin consumes ATP as a fuel source, and uses that energy to "walk" along the outside of the microtubule, carrying vital "cargo" where its needed. The video below, animated to illustrate a Harvard research paper in 2006, is one of the best visualizations of that process (skip to the 1:14 mark).
The Brandeis team recreated that process to make a liquid that essentially pumps itself. First, the microtubules arrange themselves in parallel lines, before kinesins attach to the surface of one tube and connect it to an adjoining one. As they consume the ATP, the kinesins walk the length of one of the microtubules, pushing the adjacent tube in the opposite direction, causing the paired tubes to split up.
Once the microtubules are separated, another kinesin comes along and the cycle repeats, creating swirling patterns in the fluid. The researchers were able to manipulate those swirls so they all flowed together, which has the effect of moving the liquid as a whole in that direction. They called this "coherent flow."
It's very early days, but the researchers say this is the first step towards creating a liquid that could flow freely without human or mechanical support. The value of such a substance would be massive, including applications such as oil that doesn't need to be pumped through pipes, but carries itself.
The research was published in the journal Science, and the movement of the liquid can be seen in the two videos below.
Source: Brandeis University
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