PneuNets Bending Actuators

PneuNets (pneumatic networks) are a class of soft actuator originally developed by the Whitesides Research Group at Harvard. They are made up of a series of channels and chambers inside an elastomer. These channels inflate when pressurized, creating motion.

The nature of this motion is controlled by modifying the geometry of the embedded chambers and the material properties of their walls. When a PneuNets actuator is pressurized, expansion occurs in the most compliant (least stiff) regions.

For example, if the PneuNet is composed of a single, homogenous elastomer, most expansion will occur at the thinnest structures. Designers can pre-program the behavior of the actuator by selecting wall thicknesses that will result in a desired type of motion.

In addition, different materials can be used in combination to enable further control over actuator behavior. If a PneuNets actuator contains layers of materials with different elastic behavior (as shown in the image to the right), the "stretchy" material will expand more than the "rigid" material when the actuator is pressurized. In this type of configuration, we call the more rigid material the "strain limiting layer", as it restricts the amount of strain that can occur. The "differential strain" effect can be used to achieve useful motions such as bending and twisting.

This documentation set contains files and instructions to support the design, fabrication, modeling, and testing of a specific PneuNets bending actuator. We also provide a case study of this actuator's use in an assistive glove for hand rehabilitation. While we focus on a particular example of a PneuNets actuator, the principles and guidelines presented here can be adapted to produce a wide range of actuators and devices.

The video below shows a soft gripper made from PneuNets:

Shepherd et al. (2011) used PneuNets to develop a quadruped robot capable of multiple modes of locomotion:

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