A soft ring oscillator

Daniel J Preston; Haihui Joy Jiang; Vanessa Sanchez; Philipp Rothemund; Jeff Rawson; Markus P Nemitz; Won-Kyu Lee; Zhigang Suo; Conor J Walsh; George M Whitesides

doi:10.1126/scirobotics.aaw5496

A soft ring oscillator

Sci Robot. 2019 Jun 26;4(31):eaaw5496. doi: 10.1126/scirobotics.aaw5496.

Authors

Daniel J Preston^{1

2}, Haihui Joy Jiang^{1

3}, Vanessa Sanchez^{1

2

4}, Philipp Rothemund^{1

4

5}, Jeff Rawson¹, Markus P Nemitz^{1

2}, Won-Kyu Lee¹, Zhigang Suo^{4

5}, Conor J Walsh^{2

4}, George M Whitesides^{6

2

5}

Affiliations

¹ Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA.
² Wyss Institute for Biologically Inspired Engineering, 3 Blackfan Circle, Boston, MA 02115, USA.
³ School of Chemistry and Sydney Nano Institute, University of Sydney, Sydney, NSW 2006, Australia.
⁴ John A. Paulson School of Engineering and Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138, USA.
⁵ Kavli Institute for Bionano Science and Technology, Harvard University, 29 Oxford St., Cambridge, MA 02138, USA.
⁶ Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA. gwhitesides@gmwgroup.harvard.edu.

PMID: 33137768
DOI: 10.1126/scirobotics.aaw5496

Abstract

Periodic actuation of multiple soft, pneumatic actuators requires coordinated function of multiple, separate components. This work demonstrates a soft, pneumatic ring oscillator that induces temporally coordinated periodic motion in soft actuators using a single, constant-pressure source, without hard valves or electronic controls. The fundamental unit of this ring oscillator is a soft, pneumatic inverter (an inverting Schmitt trigger) that switches between its two states ("on" and "off") using two instabilities in elastomeric structures: buckling of internal tubing and snap-through of a hemispherical membrane. An odd number of these inverters connected in a loop produces the same number of periodically oscillating outputs, resulting from a third, system-level instability; the frequency of oscillation depends on three system parameters that can be adjusted. These oscillatory output pressures enable several applications, including undulating and rolling motions in soft robots, size-based particle separation, pneumatic mechanotherapy, and metering of fluids. The soft ring oscillator eliminates the need for hard valves and electronic controls in these applications.