Please check out the full preprint on the arxiv!

arxiv.org/abs/2504.14170

A big thanks to authors Akash Vardhan, Ram Avinery, Hosain Bagheri, Velin Kojohourav, Shengkai Li, Hridesh Kedia, Tianyu Wang, Daniel Soto, Kurt Wiesenfeld, and Dan Goldman for their great work!

These principles—emergent behavior arising from actively-driven, deformable objects—are relevant to many living systems. From single-celled organisms to swarms of insects, "smart" behavior can arise from groups of "dumb" individuals, modulated by simple mechanical interactions.

These dyads form even when the robots have no ability to modulate their gait. However, a force-sensing feedback loop can increase the lifetime of the dyad, and therefore the distance traveled by the pair.

When motion was initiated for seven densely-packed smarticles, it was expected that they would push each other away and expand to a relaxed state. Instead, 64% of trials formed long-lived pairs of robots, called "dyads", which moved together for more than 100 gait periods.

The robots, dubbed "smarticles", are formed from three links and two motors, inspired by Purcell’s three-link swimmer. The motion of the arms causes the smarticles to repel one another, but they are unable to move significant distances on their own.

To learn more, please check out the full paper—now available in PRX Life! Congratulations to the authors Chris Pierce, Yang Ding, Lucinda Peng, Xuefei Lu, Baxi Chong, Hang Lu, and Dan Goldman.

doi.org/10.1103/PRXL...

They built a mechanical model showing that phase lags result from a combination of internal elastic torques and external resistive forces. The worm's gait pattern is not purely neural—it's shaped by physics!

In low viscosity media, these phase lags are evenly distributed across the body. In viscous buffer, or in agar, the phase lag grows along the body before dropping near the tail.

Using calcium imaging, the Goldman Lab was able to measure the difference in phase between undulatory movements and the activation waves that cause them—called neuromechanical phase lags (NPLs). The NPLs vary with medium, including fluids of different viscosity and agar.

Dan has been recognized "for distinguished contributions to the field of biological physics and nonlinear dynamics at the interface of #biomechanics, #robotics, and granular #physics."

Read more in the full press release!

news.gatech.edu/news/2025/03...