Meeting Abstract
Quadrupedal animals locomote by coordinating their limbs to generate different gaits. While limb coordination is thought to be an exclusive capability of macroscopic systems, microscopic organisms have been found to exhibit similar capabilities. Different species of micron-sized, pond dwelling algae are capable of coordinating four flagella to generate swimming gaits similar to those of quadrupeds (Wan & Goldstein, 2016). To explore microscopic locomotion control, we developed a robophysical model of quadriflagellate microorganisms which models swimming at low-Reynolds number. We focus on two distinct gaits – the pronk and the trot. The pronk gait consists of moving each flagellum simultaneously, without any phase difference between flagella. The trot gait consists of two alternating pairs of flagella each of which generates a pattern analogous to a breaststroke. The robophysical model includes four two-link flagella connected by a joint that allows each flagellum to bend, breaking drag symmetry during locomotion. The robot emulates microorganism swimming patterns, forward motion was measured at 0.30±0.09 body lengths per gait cycle (BL/cyc) using the trot gait and at 0.19±0.03 BL/cyc using the pronk gait. Results are comparable to microorganisms’ performance, where using the trot gait enables a higher speed (0.39±0.18 BL/cyc) than the pronk gait (0.18±0.05 BL/cyc). The results show that hydrodynamic performance is highly sensitive to swimming gait, consistent with recent findings which suggest flagellates are capable of actively modulating flagellar phase differences for gait selection and directional navigation. However, unlike the organisms, the robot does not swim smoothly, suggesting a role of the algal cytoskeleton for gait stabilization.
