For a liquid to move from one point to another, you need one of two things — a sloping surface (which allows gravity to act on the liquid), or a pump (which provides the power needed to move the liquid against gravity). However, in a new study published Friday in the journal Science, a team of researchers describe the creation of a new kind of material that can move on its own.
This self-propelling fluid, which the authors of the study say holds promise for the creation of an entirely new class of fluids that can flow without any mechanical effort, was developed using filaments called microtubules and tiny molecular motors called kinesin.
"The breakthrough ... was achieved by reproducing in the lab the incredibly complex series of processes that allow cells to change shape and adapt to their environment," Brandeis University, whose researchers created the material, said in a statement. "Cells can do this because the building blocks of its scaffolding — hollow cylindrical tubes called microtubules — are capable of self-transformation. The microtubules grow, shrink, bend and stretch, altering the cell’s underlying structure."
For their research, the scientists extracted microtubules from the brain tissue of cows, and mixed them kinesin — a protein that attaches to the microtubules — and adenosine triphosphate (ATP) — often called the "molecular unit of currency" of intracellular energy transfer.
Fuelled by ATP, the kinesin molecules moved the microtubles in opposite directions. The researchers were able to get the swirls thus created to move in the same direction, resulting in a “coherent flow” that pushed the surrounding liquid forward as well.
"From a technology perspective, self-pumping active fluids set the stage for the engineering of soft self-organized machines that directly transform chemical energy into mechanical work" the researchers wrote in the study. "From a biology perspective, our results provide insight into collective many-body cellular phenomena such as cytoplasmic streaming, in which molecular motors generate local active stresses that power coherent flows of the entire cytoplasm, enhancing the nutrient transport that is essential for the development and survival of many organisms."
An instance of a real-world application of a self-propelling liquid that the authors of the study envisage is oil moving through pipelines without needing to be pumped — although, as the study co-author Zvonimir Dogic told Physics World, the engineering applications of this technology are "many, many years away."