Roboticists from Harvard’s Wyss Institute, SEAS, and MIT have reinvented the 300-year-old piston design by replacing its rigid elements with soft flexible materials.
Pistons first gained attention in the late 1700s, when French-born British physicist Denis Papin made waves by proposing the piston principle.
It has since then been used to harness the power of fluids to perform work in numerous machines and devices such as engines, hydraulic lifters and cranes.
These pistons nevertheless suffer from several shortcomings: the high friction between the moving piston and the chamber wall can lead to breakdown of the seal, leakage, and gradual or sudden malfunctions.
In addition, energy efficiencies and response speeds are often limited, especially in the lower pressure-spectrum.
The Harvard-MIT team has now sought to remedy this by replacing a piston’s rigid elements with compressible structures made of soft materials.
According to the scientists, the resulting ‘tension pistons’ generate more than three times the force of comparable conventional pistons, eliminate much of the friction, and are at low pressures up to 40% more energy efficient.
The scientists contend that their invention could help open a new chapter in piston architecture.
“They could be dropped into machines, replacing conventional pistons, providing improved energy efficiency,” says co-corresponding author, professor Robert Wood.
The tension piston concept is built on the team’s ‘Fluid-Driven Origami-Inspired Artificial Muscles’ (FOAMs).
These artificial muscles use soft materials to give soft robots more power and motion control while maintaining their flexible architectures.
FOAMs are made of a folded structure that is embedded within a fluid in a flexible and hermetically sealed skin.
Changing the fluid pressure triggers the origami-like structure to unfold or collapse along a preconfigured geometrical path, which induces a shape-shift in the entire FOAM.
This allows it to grasp or release objects or to perform other kinds of work.
“Better pistons could fundamentally transform the way we design and utilize many types of systems, from shock absorbers and car engines to bulldozers and mining equipment,” says co-author and MIT CSAIL professor Daniela Rus.
“We think that an approach like this could help engineers devise different ways to make their creations stronger and more energy-efficient.”
Image and content: Wyss Institute at Harvard University