A buckling-sheet ring oscillator for electronics-free, multimodal locomotion

Abstract

Locomotion of soft robots typically relies on control of multiple inflatable actuators by electronic computers and hard valves. Soft pneumatic oscillators can reduce the demand on controllers by generating complex movements required for locomotion from a single, constant input pressure, but either have been constrained to low rates of flow of air or have required complex fabrication processes. Here, we describe a pneumatic oscillator fabricated from flexible, but inextensible, sheets that provides high rates of airflow for practical locomotion by combining three instabilities: out-of-plane buckling of the sheets, kinking of tubing attached to the sheets, and a system-level instability resulting from connection of an odd number of pneumatic inverters made from these sheets in a loop. This device, which we call a “buckling-sheet ring oscillator” (BRO), directly generates movement from its own interaction with its surroundings and consists only of readily available materials assembled in a simple process—specifically, stacking acetate sheets, nylon film, and double-sided tape, and attaching an elastomeric tube. A device incorporating a BRO is capable of both translational and rotational motion over varied terrain (even without a tether) and can climb upward against gravity and downward against the buoyant force encountered under water.

Programmable soft valves for digital and analog control

“…In addition to improved logic gate functionality (greater than 165-kPa maximum pressure and 10 times faster oscillation frequencies compared to previous CMOS-type valves), the valves presented in this paper bring several higher-level advantages relative to other approaches already reported ( 3 , 4 , 28 , 29 ). The modularity of our valves means that a wide range of functions (digital and analog control, nonvolatile memory, linear actuation, and human-operated pneumatic switches) can all be achieved using largely the same soft device design and fabrication process.…”

“…However, there is a demonstrated need for higher-frequency oscillation in applications including haptics, communication, grasping, and reaching ( 48 ). Ring oscillators assembled from inverters that require pull-down resistors to function have reached frequencies of 10 to 15 Hz ( 28 , 29 ). However, the loss of pressure inherent to architectures utilizing resistors limits the ratio of output pressure to input pressure P o / P i ; previous oscillators have demonstrated P o / P i ratios of 0.76 and 0.24.…”

“…Similarly, Lee et al. ( 29 ) have demonstrated a buckling-sheet valve that controls pressures up to 80 kPa. Both systems reach high frequencies when configured as ring oscillators (15 and 10 Hz, respectively) but are limited by pressure loss introduced by pull-down resistors; the ratio of oscillator output pressure to input pressure is 0.24 for the TBL oscillator and 0.76 for the buckling-sheet ring oscillator.…”

Cell Differentiation-Inspired, Salt-Induced Multifunctional Gels for an Intelligent Soft Robot with an Artificial Reflex Arc

“…The emulation of this process becomes a promising technology in bioinspired electronics for intelligent robotics. For example, to produce the bionic electric skin, there are numerous skilled designs in both structure and materials for accurate and efficient stimuli sensing. − Meanwhile, various artificial muscles based on asymmetric expansion, , pneumatic inflation, − and hydraulic actuation , with specific system programming were developed, for instance. Consequently, in terms of mimicking biological conditioned reflex, which receives external stimuli and produces informative synaptic-responsive and motor outputs, the complex and incompatible production processes of electric skins and artificial muscles lead to high production costs and delicate preparation of intelligent robotics. , Therefore, one of the key challenges in the field of commercial intelligent soft robotics construction is developing a kind of novel multifunctional intelligent material for an efficient manufacturing process.…”

A low-cost wearable device for portable sequential compression therapy

“…While textiles, a subset of sheet-based materials, are the least used category of soft materials in soft robotic components ( Jumet et al, 2022a ), they offer unique advantages in actuation (due to their ability to be designed for both strength and compliance) and in human-machine interfaces (because textiles are already ubiquitous in interfacing directly with humans). By leveraging their pliable geometry, the functions of sheet-based devices are diverse, ranging from oscillating actuators ( Lee et al, 2022 ) to instability driven locomotion ( Nagarkar et al, 2021 ). Going further, sheet-based devices made from textiles have been demonstrated in useful soft systems, such as functionally complete logic control ( Rajappan et al, 2022 ) and power generation from walking ( Shveda et al, 2022 ).…”