Robots mimicking organic lifeforms is not exactly a novelty in the contemporary realm of science and engineering. But this time around, South Korean scientists at the Seoul National University, have really notched it up a level by designing a robotic insect that is capable of performing delicate actions like jumping and landing on an aquatic surface. In other words, these bio-inspired robots can replicate the fascinating ability of a few insects (like water striders) that allows them to literally launch off from a water surface by virtue of their special physical arrangement.
Now in biological terms, a water strider (a type of semi-aquatic arthropod) demonstrates this unique ability due to the advantage of its very low body mass, complemented by its superhydrophobic property (that repels water). In fact, the insect can entirely support itself on its foot by just using the surface-tension of the water. Such light-weight credentials are bolstered by the organism’s capability to utilize the right kind of physical attributes needed for the climactic leaping action.
For example, the researchers in this case were able to identify how the water strider is able to rotate its curved leg tips slightly towards an inner axis. This posture is applied in a refined manner with a tepid force that does not exceed the magnitude needed for disturbing the water surface. When translated to a figure, this force comes exactly at 144 milli-Newtons/meter. Furthermore, the motion of the legs going inwards allows the insect to pull them across the water – thus making sure that the water surface doesn’t retreat too rapidly (that could lead to loss of contact).
As a result, fueled by all these physical advantages, the water strider can generate a whopping 42 percent more force over the surface of the water. Analyzing such fascinating biological features, the scientists were able to design their synthetic version in the form of a 68 milligram robot. To that end, the bio-mimicking robot has its curving wire legs coated with a superhydrophobic material. But more importantly, its crucial ‘muscle’ that does the leaping, conforms to what is known as torque reversal catapult mechanism. This allows the robot to generate torque in its legs, which in turn drives them in a downward angle – thus leading to the maximum vertical acceleration of around 14 g.
The numbers game suggests that the resultant peak velocity produced by the robot equates to a substantial 1.6 m/s, which achieves a jump height of around 14 cm. Interestingly, the researchers also deduced that the robot can jump better from the water surface when compared to land – probably due to reduction of leg vibrations (helped by dampness). Now of course, the question naturally arises – what is the practical significance of a robotic water strider? Well for now, the scientists are pretty happy in just emulating the biological advantage of such organisms. Though it still remains to be seen if such incredible physical abilities can be replicated by bigger-scale mechanisms of the future.
The study was originally published in Science.