Single-Input Control of Multiple Fluid-Driven Elastic Actuators via Interaction Between Bistability and Viscosity

Abstract

A leading concept in soft robotics actuation, as well as in microfluidics applications such as valves in lab-on-a-chip devices, is applying pressurized flow in cavities embedded within elastic bodies. Generating complex deformation patterns typically requires control of several inputs, which greatly complicates the system's operation. In this work, we present a novel method for single-input control of a serial chain of bi-stable elastic chambers connected by thin tubes. Controlling a single flow rate at the chain's inlet, we induce an irreversible sequence of transitions that can reach any desired state combination of all bi-stable elements. Mathematical formulation and analysis of the system's dynamics reveal that these transitions are enabled thanks to bi-stability combined with pressure lag induced by viscous resistance. The results are demonstrated via numerical simulations combined with experiments for chains of up to 5 chambers, using water-diluted glycerol as the injected fluid. The proposed technique has a promising potential for development of sophisticated soft actuators with minimalistic control.

Exploiting Mechanical Instabilities in Soft Robotics: Control, Sensing, and Actuation

“…[85,86] Ben-Haim et al proposed a method to reproduce different logic gates using an array of fluid-driven bistable elastic chambers connected by thin tubes (Figure 3A). [87] The flow rate of water-diluted glycerol in this series of elastic chambers is used as a single input to deterministically control their inflation sequence (Figure 3A.1). The inflated and deflated states correspond to the two pressure minima, denoting the stable states of Jiang et al fabricated snap-through buckling-based logic gates, using 3D printable hydrogel-elastomer composites, which use chemical stimuli as inputs.…”

“…[53,54,89,90] Yang et al developed a soft switchable metamaterial that exhibits phase transition and shape memory properties similar to ferroelastic materials (Figure 4A). [91] This metamaterial [87] Copyright 2020, Mary Ann Liebert. B) Bistable 3D-printed hydrogel-logic gates with a snap-through buckling-based transition, which triggers actuation in response to external stimuli.…”

On the inflation and deflation dynamics of liquid-filled, hyperelastic balloons

“…A formerly suggested configuration of a self-propelled soft robot consists of an array of serially connected spherical hyperelastic structures such as rubber balloons, which exhibit bi-stability, meaning that at a certain pressure range, they have two stable equilibrium radii (Ben-Haim et al 2019;Glozman et al 2010). Thanks to their bi-stability property, interconnection of these spherical balloons composes a multi-stable system, where each stable equilibrium corresponds to a pattern in which each balloon is inflated to one of its two stable equilibria.…”

“…The behaviour of spherical hyperelastic balloons is the subject of numerous studies, examining the validity of different hyperelastic models, the stability of their spherical shape, the behaviour of interconnected balloons, etc. (Ben-Haim et al 2019;Mangan & Destrade 2015;Müller & Strehlow 2004;Wang et al 2018). However, all of these studies consider a uniform pressure field inside the balloons, describing a quasistatic behaviour.…”

Underactuated fluidic control of a continuous multistable membrane

“…13), only a few researchers examined viscous flow interacting with bistable elasticity (e.g., refs. [14][15][16][17][18]. Previous relevant works involving bistability and viscous flow include the work by Hazel and Heil (19), who numerically studied the steady flow of a viscous fluid through a thin-walled elastic tube connected to two rigid tubes.…”