Flee jump sequence (via Flea-Inspired Catapult Mechanism for Miniature Jumping Robots)
We all know fleas spread disease (the great plague) and are able to jump up to 7 inches vertically and around 13 inches horizontally (ok maybe you didn’t know that last part). If that wasn’t bad enough, they’re now becoming robotic thanks to some scientists, led by Minkyun Noh, from Seoul National University in South Korea. The ‘flea inspired miniature robots’ have been developed to function much in the same manner as their biological counterparts (when it comes to jumping) but to understand this we need to take a look at how actual flea’s legs function. Siphonaptera (scientific name for flea) jump using their feet, known as tibiae, using a ‘spring’ method from stored energy derived from a protein called resilin rather than relying on their knees or brute muscle-power. A muscle attached to the flea’s femur compresses the elastic resilin and another muscle locks it in place using a biological ‘latch’. Another small muscle then trips the latch propelling the flea upwards or forwards (or both in combination) at distances 100 times their body length. This triggering process is known as torque reversal triggering. In order to replicate this catapult mechanism, the team turned to a unique form of metal alloy called ‘nitinol’ (nickel titanium) which exhibit two unusual properties that include shape memory and superelasticity. Nitrinol’s shape can be deformed through either heat or electricity and then regain its original shape using different temperatures or electrical current.
(via Flea-Inspired Catapult Mechanism for Miniature Jumping Robots)
In order to get their robotic flea off the ground (so to speak) the team designed three spring actuators (the flexor, extensor and trigger) made from nitrinol, a nickel/titanium alloy with shape memory and superelasticity properties. The flexor and extensor SMA (Shape Memory Alloy) actuators are positioned between the robot’s coxa and lower femur segment of the leg and act as ‘antagonistic actuators’ between each other. The scientists then placed the trigger SMA actuator perpendicularly to the extensor to achieve efficient triggering of the other two actuators. To get the robotic flea to jump the team sent an electrical current through the leg actuators which makes the flexor actuator contract and lock into place. Another electrical current passes through the extensor actuator and releases the SMA trigger actuator allowing the robot to jump. The scientists were successful at getting their robotic flea to jump 60 centimeters or almost 30 times its own body length! The next step for the team is to get a miniature power supply and electronics housed either on or in the robotic flea itself, as well as figuring out a way for the flea to remain upright and stable while jumping and landing.
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