Miniature insect-like robots revolutionise micro-robotics

Smallest, lightest, fastest micro-robots redefine possibilities

waterskimmer-photo-by-Bob-Hubner-WSU-Photo-Services The WaterStrider, one of the smallest, lightest, and fastest fully functional micro-robots ever created, weighs only 55 milligrams and can move at a speed of 6 millimeters per second | Bob Hubner, WSU Photo Services

In a remarkable feat of engineering, scientists at Washington State University have successfully developed two insect-inspired robots that are not only the smallest and lightest of their kind but also the fastest fully functional micro-robots known to date. These awe-inspiring creations, resembling a mini-bug and a water strider, hold immense potential for a wide range of applications, including artificial pollination, search and rescue operations, environmental monitoring, micro-fabrication, and even robotic-assisted surgery.

Presenting their groundbreaking work at the prestigious IEEE Robotics and Automation Society's International Conference on Intelligent Robots and Systems, the team unveiled the incredible capabilities of their mini-bug, weighing a mere eight milligrams, and the water strider, tipping the scales at a feather-light 55 milligrams. Despite their minuscule size, both robots are capable of achieving impressive speeds of approximately six millimeters per second.

Conor Trygstad, a talented PhD student in the School of Mechanical and Materials Engineering and the lead author of this remarkable study, highlighted the robots' exceptional performance while acknowledging that their biological counterparts still outpace them. For instance, an ant, weighing up to five milligrams, can scurry at nearly a meter per second.

The secret behind these diminutive robots lies in their tiny actuators, responsible for their fluid movements. Trygstad ingeniously employed a novel fabrication technique to miniaturize the actuator to an unprecedented scale, weighing less than a milligram. This breakthrough marks the birth of the smallest and fastest actuators ever developed for micro-robotics, as explained by Néstor O. Pérez-Arancibia, the Flaherty Associate Professor in Engineering at WSU's School of Mechanical and Materials Engineering and the leader of this groundbreaking project.

The actuator's design harnesses the unique properties of a shape memory alloy, a material capable of changing shape when heated. Aptly named 'shape memory,' this alloy has the remarkable ability to revert to its original form. Unlike conventional motors that drive robot motion, these alloys rely on a simple yet ingenious mechanism, devoid of any moving parts or spinning components.

Trygstad further emphasized the mechanical robustness of these actuators, stating, "They're very mechanically sound." The development of these ultralightweight actuators ushers in a new era for micro-robotics, offering exciting possibilities for the future.

Typically, shape memory alloys are not suitable for large-scale robotic movements due to their slow response times. However, the WSU robots utilize actuators comprising two minuscule shape memory alloy wires, measuring a mere 1/1000 of an inch in diameter. With a minute amount of current, these wires can be rapidly heated and cooled, enabling the robots to flap their fins or move their feet an astonishing 40 times per second. In preliminary tests, the actuator demonstrated its remarkable strength by effortlessly lifting more than 150 times its own weight.

In addition to their superior performance, the SMA (shape memory alloy) technology employed in these robots requires only minimal electrical power or heat to initiate movement. Trygstad pointed out that "The SMA system requires a lot less sophisticated systems to power them." This efficiency opens up new avenues for energy-efficient micro-robotics.

Inspired by the graceful movements of water striders, Trygstad, an avid fly fisherman, hopes to delve deeper into studying their locomotion. While the WSU water strider robot currently employs a flat flapping motion to propel itself, the natural insect employs a more efficient rowing motion with its legs, allowing it to achieve remarkable speeds. The research team aims to replicate this intricate motion in their robots, ultimately developing a water strider-type robot capable of traversing both the water's surface and its depths. Additionally, they are actively exploring ways to make their robots fully autonomous and untethered from a power supply, whether through the use of miniature batteries or catalytic combustion.

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