Soft pistons improve efficiency and reduce friction

Pistons have been a fundamental component for machines of most types since the age of steam. However, they are not without their problems. Researchers at Harvard have now redesigned this apparently simple mechanism with new materials which, they claim, can eliminate or reduce most of these long-standing drawbacks.

Several phenomena reduce the efficiency of pistons. The friction between the moving piston head and the chamber wall can lead to breakdown of the seal between moving static components, leakages and gradual or sudden malfunctions. Moreover, when operating at low pressure, energy efficiency and response speed are often limited.

Until now, such limitations have been accepted and worked around: perfecting the seal between piston components made up a great deal of the original research of steam engine pioneers such as James Watt and Richard Trevithick, three centuries ago; basic piston design has changed little since then.

The Harvard team, working at the Wyss Institute for Biologically Inspired Engineering, the John A Paulsen School of Engineering and Applied Sciences (SEAS) and collaborating with colleagues from the computer science and artificial intelligence laboratory (CSAIL) at Massachusetts Institute of Technology, has designed what they call a "tension piston" that replaces conventional rigid elements with a mechanism using compressible structures inside a membrane made of soft materials, and described this invention in a paper in Advanced Functional Materials.