Energy-recycling artificial foot

In a PLoS-One paper, Steven H. Collins (Department of Biomechanical Engineering, Delft University of Technology) and Arthur D. Kuo (Departments of Mechanical and Biomedical Engineering, University of Michigan) describe an ingenious new prosthetic foot that uses a microcontroller to guide a device that stores the energy of the downstep and releases it for the upstep, mimicking the natural functioning of unmodified human ankles.

We developed a microprocessor-controlled artificial foot that captures some of the energy that is normally dissipated by the leg and "recycles" it as positive ankle work. In tests on subjects walking with an artificially-impaired ankle, a conventional prosthesis reduced ankle push-off work and increased net metabolic energy expenditure by 23% compared to normal walking. Energy recycling restored ankle push-off to normal and reduced the net metabolic energy penalty to 14%.

Recycling Energy to Restore Impaired Ankle Function during Human Walking
(via PhysOrg)