Directional take-off and aerial control of ultrafast jumps in springtails and robots

Spring-latch mechanisms are found in biological and engineered systems to achieve accelerations greater than what direct motor or muscle actuation can achieve. However, once the latch is released in these mechanisms, controlling the flow of elastic energy to modulate dynamic outputs is a challenge. Here we show certain species of springtails include an elastic hinge in their furca, a jumping appendage, that bends during a jump, affecting their take-off and jump dynamics. Springtails are a group of small, non-insect hexapods that use ultrafast jumps to evade predators, disperse in their environment, and even migrate. We investigate how furca morphology and kinematics affect the jump dynamics across species of springtails and whether including passive elastic elements in mathematical and physical models shows increased control of ultrafast movement. We analyzed the takeoff kinematics across several species of springtails leaping off rigid and compliant substrates. Results show that some species with longer furcas bend the furca during a jump, these species have lower take-off angles and have less body spin than species with long, rigidly held furcas. We use mathematical and robophysical modeling to explore whether including a joint is sufficient to reduce take-off angles and angular velocity. Our findings offer novel insights into how ultrafast biological systems control their jumps and inform potential constraints on the flow of elastic energy through materials at millisecond timescales.