Office for Technology Commercialization

Miniature Free Piston Engine for Fluid Power Applications

Technology #20120199

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HCCI EngineMiniature Free Piston Engine
William Durfee, PhD Department of Mechanical Engineering, School of Science and Engineering
Dr. Durfee’s research interests include design of medical devices, rehabilitation engineering, advanced orthotics, biomechanics and physiology of human muscle including electrical stimulation of muscle, product design and design education.
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Kevin Nickels
Technology Licensing Officer 612-625-7289
Patent Protection

Provisional Patent Application Filed

Miniature Engine and Compressor Package for Use in Pneumatic Applications

A design for a free piston engine and compressor package has been developed to deliver power in the form of compressed air. The system, which can be fabricated at a miniature scale for portable use and deliver up to 10 watts of power, is ideal for use in orthotic, power tools and robotic applications. The free piston engine does not involve a crankshaft, so is much easier to miniaturize. The device incorporates homogeneous charge compression ignition (HCCI), which negates the need for active control, reducing implementation costs.

MN-IP Try and Buy
This technology is available via a standard negotiated license agreement. Contact Larry Micek for specific details.

Fluid Power Delivers High Power Density

Fluid power actuations have several advantages over motor mechanical drives including higher power density and load holding without consuming energy. Conventionally, small fluid power sources are powered by a lithium ion battery; making use of the higher energy density hydrocarbons, miniature free piston engines can achieve lighter weight and longer run time compared to a battery/motor package. With its simple design, the device can also be easily scaled up or down for higher or lower power output target.


  • Up to 10W of power
  • Longer run time and lighter weight compared to a battery motor package
  • Small enough for orthotics, power tool and robotic applications