NYU Researchers Discover How Heavy Motorized Objects Can Climb Steep Slopes

Scientists at NYU have announced they have discovered how heavy, motorized objects can climb a steep slope. This is a newly discovered mechanism that mimics how rock climbers navigate inclines. Their findings come from a series of experiments using motorized objects placed in liquid and then moved up tilted surfaces.

Researchers note their micro-swimmers are about 20 times heavier than the fluid they swim in but can climb steep slopes near vertical. The work enhances the understanding of "gravitaxies," which is directional movement in response to gravity. The phenomenon is said to be an important consideration in engineering, medicine, and pharmaceutical development.

It explains, in part, how bacteria can move through the body and provides insight into how to create more effective drug delivery mechanisms. In the study, the researchers created swimmers or nanorods with a length of about 1/40th the width of a strand of human hair. The motorized swimmers had to move up an inclined surface while immersed in a liquid solution inside a walled container.

The swimmers were made of two types of metal, including gold and rhodium, as well as gold and platinum. Their construction gave them unbalanced densities, given the metals they were constructed from varied in weight. Despite their significant weight, the composition of the tiny swimmers, the liquid environment, and the juxtaposition of surfaces allowed them to move upward.

Researcher Michael Shelley said that the motors reorient themselves upward against gravity thanks to their density imbalance. Shelley says the hydrodynamic effect amplifies the movement, and swimming next to a wall yields a bigger torque in repositioning the body of the motors upwards. Higher torque improves the ability of the swimmers to move vertically. In the future, advanced motors will be designed to reach targeted locations and perform designated functions when they arrive.