A soft, bistable valve for autonomous control of soft actuators

Philipp Rothemund; Alar Ainla; Lee Belding; Daniel J Preston; Sarah Kurihara; Zhigang Suo; George M Whitesides

doi:10.1126/scirobotics.aar7986

A soft, bistable valve for autonomous control of soft actuators

Sci Robot. 2018 Mar 21;3(16):eaar7986. doi: 10.1126/scirobotics.aar7986.

Authors

Philipp Rothemund^{1

2

3}, Alar Ainla², Lee Belding², Daniel J Preston², Sarah Kurihara², Zhigang Suo^{1

3}, George M Whitesides^{4

3

5}

Affiliations

¹ John A. Paulson School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA.
² Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
³ Kavli Institute for Bionano Science and Technology, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA.
⁴ Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA. gwhitesides@gmwgroup.harvard.edu.
⁵ Wyss Institute of Biologically Inspired Engineering, 60 Oxford Street, Cambridge, MA 02138, USA.

PMID: 33141749
DOI: 10.1126/scirobotics.aar7986

Abstract

Almost all pneumatic and hydraulic actuators useful for mesoscale functions rely on hard valves for control. This article describes a soft, elastomeric valve that contains a bistable membrane, which acts as a mechanical "switch" to control air flow. A structural instability-often called "snap-through"-enables rapid transition between two stable states of the membrane. The snap-upward pressure, ΔP ₁ (kilopascals), of the membrane differs from the snap-downward pressure, ΔP ₂ (kilopascals). The values ΔP ₁ and ΔP ₂ can be designed by changing the geometry and the material of the membrane. The valve does not require power to remain in either "open" or "closed" states (although switching does require energy), can be designed to be bistable, and can remain in either state without further applied pressure. When integrated in a feedback pneumatic circuit, the valve functions as a pneumatic oscillator (between the pressures ΔP ₁ and ΔP ₂), generating periodic motion using air from a single source of constant pressure. The valve, as a component of pneumatic circuits, enables (i) a gripper to grasp a ball autonomously and (ii) autonomous earthworm-like locomotion using an air source of constant pressure. These valves are fabricated using straightforward molding and offer a way of integrating simple control and logic functions directly into soft actuators and robots.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.