Figure 8

Interaction of two swimmers in water and hydrogel.

(a), Two swimmers undergoing clockwise motions in water firmly lockthemselves together after snapping into contact, as shown in Supplementary Video 10. (b), Two swimmers in hydrogel, a mediumthat suppresses acoustic streaming, come apart after collision. The swimmertrajectories across the collision are traced in magenta and green. Thisevent is also shown in Supplementary Video 11.