Harvard Scientists Design Soft Ring Oscillator, Giving Robots New Motion Dynamics

Scientists from Harvard’s Wyss Institute for Biologically Inspired Engineering and the Woodford L. and Ann A. Flowers University Professor at Harvard have developed the world’s first soft ring oscillator, which allows soft robots to roll, undulate, sort, meter liquids, and even swallow. Those same scientists were responsible for creating soft actuators, and soft digital logic — thus removing all the remaining hard components for building soft robots.

According to post-doctorate fellow Daniel J. Preston and lead author of A Soft Ring Oscillator, “It’s another tool in the toolkit to make these smart, soft robots without any electronics, and without any hard valves.” Traditionally, ring oscillators are designed using electronic transistors, or microfluidics, which relies on hard components to function, while the soft version replaces that hardware with inverters that manipulate air pressure. Those inverters (NOT digital logic gates) manage the air pressure in a soft robot’s rubber tubes. When the air pressure input is high, the output will be low pressure, and chaining an odd number of these together in a ring, one gate shift triggers the next, and so forth, giving robots new dynamic motions.

To test the soft ring oscillator, the scientists built several soft robot prototypes, each using a constant flow of air pressure to drive three inverters. One prototype pushes a ball around a ring (pictured above), another undulates a stage to keep beads of two different sizes rolling against a circular edge, enabling the smaller beads to fall through holes, sorting themselves.

They also created a mechanotherapeutic wrap that uses the soft ring oscillator to control pneumatic valves that exert coordinated pressure to pump fluid up a patient’s leg. While the soft ring oscillator relies on tethered air pressure, the scientists are currently looking at ways to remove that connection to let soft robots work in remote locations or hazardous areas.