Bi‐Shell Valve for Fast Actuation of Soft Pneumatic Actuators via Shell Snapping Interaction

Abstract

Rapid motion in soft pneumatic robots is typically achieved through actuators that either use a fast volume input generated from pressure control, employ an integrated power source, such as chemical explosions, or are designed to embed elastic instabilities in the body of the robot. This paper presents a bi‐shell valve that can fast actuate soft actuators neither relying on the fast volume input provided by pressure control strategies nor requiring modifications to the architecture of the actuator. The bi‐shell valve consists of a spherical cap and an imperfect shell with a geometrically tuned defect that enables shell snapping interaction to convert a slowly dispensed volume input into a fast volume output. This function is beyond those of current valves capable to perform fluidic flow regulation. Validated through experiments, the analysis unveils that the spherical cap sets the threshold of the snapping pressure along with the upper bounds of volume and energy output, while the imperfect shell interacts with the cap to store and deliver the desired output for rapid actuation. Geometry variations of the bi‐shell valve are provided to show that the concept is versatile. A final demonstration shows that the soft valve can quickly actuate a striker.

Programming Multistable Metamaterials to Discover Latent Functionalities

“…Having two bistable cells with F 1 max < F 2 max in series, F 1 min < F 2 min and F 1 min > F 2 min result in three (Figure 2b4) and four (Figure 2c8) stable states, respectively. [16,17] The theory is evaluated by a set of experiments on a chain with two unit cells (Figure 3).…”

“…Elastic released energy and shape-reconfigurability have been the subject of recent studies. [15][16][17] However, two challenges are yet to be addressed: first, programming the released energy by controlling the instability forces; and second, predicting and controlling the deformation sequences to leverage all attainable configurations of a material/structure by applying stimuli merely at a single point on its exterior boundary. In addition, metamaterials are commonly topologically designed in the pre-fabrication stage to deliver properties beyond what is found in naturally occurring materials (e.g., negative incremental stiffness, [18] Poisson's ratio, [19] compressibility, [20] and electromagnetic permittivity [21] ).…”

Oscillating light engine realized by photothermal solvent evaporation

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