Jerome Rifkin

 

What is your background? How did you become interested in prosthetics?

My background is in BioMedical Engineering, but my interest in prosthetics started before I went to college, from when my shoulder was rebuilt due to a wrestling injury back when I was 16.  I decided that I wanted to help people like the surgeons had helped me. But I wanted to do so by making devices that could assist people, not by actually performing the surgeries myself.  I believed that a mass produced device would help more people than one practitioner ever could.

How does your prosthetic foot work? How does it differ from the prosthetics already available on the market? What are its advantages?

The foot works far more like the natural anatomy of the foot and ankle, as I developed it to have biomimetic joint torque curves.  For example, it is very easy to move your ankle through most of it’s the range of motion, and it gets very stiff in the last few degrees of deflection.  That is not the case with most prosthetic feet and ankles on the market. The majority of products on the market are based on a carbon fiber leaf-spring paradigm.  Those work well for running but not very well for walking.  That can be seen in the metabolic penalty that amputees have when using industry products.  An amputee’s most efficient walking is like a non-amputee wearing a 50 pound backpack. In our experiments, people become much more efficient, like taking 20 to 35 pounds out of that pack. Amputees have also given a lot of great verbal feedback about the foot, saying it feels more natural than anything they’ve tried, and that it is far more comfortable than other feet they’ve worn.

How has rapid manufacturing (RM) affected your project? What rapid technology have you used to make your product possible?

I’ve been using RP more that RM, as I am still prototyping, not manufacturing. I’ve been using an old fused deposition modeling machine (FDM) extensively to get my designs off the screen and into my hands. My first “wearable” devices—ones that could stand up to body weight—were laser sintered steel. When I fully understood my weight restrictions, I moved to a rubber-plaster molded magnes-ium alloy, which is where I am now; my next mag pour may be into printed plaster, and before that I might try printed titanium.  We’ll just have to see what makes the most sense.

What stage is the project in right now? When do you see it going to market?

We’ve just received our phase II SBIR funding (750k over two years), so we’ll be making more prototypes soon.  First we need to finish our qualification tests.  That could take a few months.  Assuming those go well, we’ll make a very small batch of perhaps three devices, just to make sure amputees like them at least as well as the first generation prototype.  Then we’ll start looking to make a larger batch of about 20, and re-run our human subjects tests to verify that the metabolic changes are at least as good as what we have seen before and to achieve ISO certification of  million fatigue cycles.  Then we’ll be ready to run much larger batches in the low hundreds. It could take until Q1 2010 before we are ready to go.  Of course, I’m always looking to speed that up.

What’s next?

After this foot is finally to market, I’d like to move on to designing other prosthetics, and potentially powered orthotics like the Sarcos exoskeleton project (www.sarcos.com).  I think using tensegrity joint technology can help bring their power requirements under control, and that seems to be a major stumbling block before we can have our Ironman.

For more information on Jerome, visit www.tenspro.com.
To see a YouTube video of Jerome’s prosthetic foot in motion, visit www.youtube.com/watch?v=_GlryDRO9k8.