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)

• [Ted8305]

  That foot assumes a heel-pounding gait. Would it even work for people who walk “normally” ?

  • [EvilSpirit]

    @3: Given that they had actual test subject walk on the thing, I’m not sure what the point is of the hypothetical question.

  • [dculberson]

    What do you consider a “normal” walk? Heel contact is the first thing in a walking gait as far as I know. Ie:

    http://me.queensu.ca/people/deluzio/GaitAnalysis.php

    or

    http://orthoteers.com/images/uploaded/images7/gait4.jpg

    Notice the first thing to contact is the heel, then it transitions to the toe. The force of the heel impact might change, but you’re still going to get energy input from the heel and output from the toe.

    • [Antinous / Moderator]

      Heel contact is the first thing in a walking gait as far as I know.

      That would be an unhealthy gait derived from wearing shoes.

• [Anonymous]

  I would really like to know where I can get one of these. Congenital club foot, Misses Dancing way too much….

• [nixiebunny]

  The standard-issue FlexFoot that’s worn by all active amputees achieves this springiness with a carbon fiber leaf spring. It’s quite effective, and has no moving parts or microprocessors to fail.

  As to #3′s concern, if your ankle was rigid, you’d have a heel-pounding gait. My sweetheart’s left shoe (the one with the FlexFoot in it) gets worn quite a bit on the back of the heel, while the right shoe doesn’t.

  The only problem most of us have with this is the standard health-care problem – it will cost as much as space flight equipment, since cost is of little concern in advanced prosthetics.

• [RedShirt77]

  A while back after looking at some bike design I thought how cool it would be if a bike could store breaking energy mechanically and release it to give you a boost after restarting from a dead stop. Anybody want to help me design one?

  On this thing, it does seem to require a particular gate for it to work, which actually isn’ the end of the world if you don’t have knee joints to protect from heel strike impacts. might be a bit odd for those with one original leg and one replacement.

• [Anonymous]

  I think the advantage over the flex foot is that you can get the energy savings over a wide range of gait speeds. True, it will have electronics, but it seems amazingly simple to me compared to motorized prosthetics.

• [MrsBug]

  Okay, I’m going to be juvenile about this: woohoo, Michigan reprezent! ;)

• [Anonymous]

  It should be muvh smaller!

• [Anonymous]

  Insert obligatory Six Million Dollar Man quote here.

• [lysdexia]

  Is it wrong that the first thing I thought was: “I wonder what Aimee Mullen will wear with this”?

• [Anonymous]

  the first thing I thought was “I want some metal legs!”

• [djn]

  Cyborg overlords: 1
  Intelligent Design: 0