Scientists find a way to navigate a heavy climb

A team of scientists have discovered how heavy, motorized objects climb steep slopes – a recently discovered mechanism that also mimics the way climbers navigate slopes.

The results, published in the journal Soft matter, arise from a series of experiments in which motorized objects were placed in a liquid and then moved on inclined surfaces.

“These ‘micro-swimmers’ are about 20 times heavier than the fluid they swim in, but they were able to climb steep, almost vertical slopes,” said Jun Zhang, one of the article’s authors and physics professor. and mathematics at New York University’s Courant Institute of Mathematical Sciences and NYU Shanghai.

The work improves our understanding of “gravitaxis,” directional movement in response to gravity. The phenomenon is a vital consideration not only in engineering, but also in medicine and pharmaceutical development. It explains, in part, how bacteria move around the body and provides information on ways to create more efficient drug delivery mechanisms.

In the Soft matter Research, scientists have created swimmers, or nano rods, that are about 1 / 40th the width of a human hair. These motorized swimmers were tasked with ascending an inclined surface while submerged in a liquid solution inside a sided container. Swimmers were made up of two types of metals – gold and rhodium as well as gold and platinum – a composition that gave them unbalanced densities given the varying weights of these metals.

The composition, the liquid environment and the juxtaposition of the surfaces of the swimmers allowed them to move upwards, despite their heavy weight.

“These motors reorient themselves upwards against gravity thanks to their density imbalance, much like a swing reorients itself in response to the movement and weight of its riders,” adds Michael Shelley, professor at the Courant Institute and director of the Flatiron Institute’s Center for Computational Biology. “A hydrodynamic effect amplifies this movement – swimming next to a wall produces more torque by repositioning the motor bodies upwards. This is important because the microscopic world is noisy – for the motor it is always two steps away. up and down a step more torque improves their ability to move vertically. “

In previous work, published in Physical Review Letters, Zhang, Shelley and their colleagues created “nanomotors” to discover an effective means of movement against currents. The new research expands on these results by revealing how heavy objects can move on steeply inclined surfaces, offering the promise of even more sophisticated maneuvers.

“Now that these micro-swimmers are able to climb very steep slopes against gravity, we can consider developing even more difficult missions,” observes Zhang. “Future advanced engines will be designed to reach targeted locations and perform designated functions.”