Micro-robots mimic movements of water-striding insects

The prototype devices mimic water-striding insects such as mosquitoes and water spiders, and could be used for military spy missions and water-pollution monitoring — among other applications.

While attempts have been made previously to develop such aquatic robots, no one has so far found a way to make them practical, agile and inexpensive.

Researchers from the Harbin Institute of Technology’s School of Chemical Engineering and Technology carefully analysed water striders’ locomotion to better understand exactly how the creatures are able to skim efficiently across the water.

They found that the radius and contact angle of the highly water-repellent (superhydrophobic) legs mainly accounts for the large supporting force.

In addition, small hairs on the legs of the water strider enable it form tiny swirling vortices, trapping small pockets of air and enabling them to skirt across water without drowning.

The scientists describe progress on a new robot in the journal ACS Applied Materials and Interfaces. The device has an overall leg-span of around 150mm with a body that measures 24mm in diameter; 10 water-repellent wire legs; and two movable, oar-like legs that are propelled by two miniature motors.

‘Because the weight of the micro-robot is equal to that of about 390 water striders, one might expect that it would sink quickly when placed on the water surface,’ the report noted. However, it stands effortlessly on water surfaces and also walks and turns freely, it added.