Flex PCBs Make Force-Mapping Pressure Sensor For Amputee

What prosthetic limbs can do these days is nothing short of miraculous, and can change the life of an amputee in so many ways. But no matter what advanced sensors and actuators are added to the prosthetic, it has to interface with the wearer’s body, and that can lead to problems.

Measuring and mapping the pressure on the residual limb is the business of this flexible force-sensing matrix. The idea for a two-dimensional force map came from one of [chris.coulson]’s classmates, an amputee who developed a single-channel pressure sensor to help him solve a painful fitting problem. [chris.coulson] was reminded of a piezoresistive yoga mat build from [Marco Reps], which we featured a while back, and figured a scaled-down version might be just the thing to map pressure points across the prosthetic interface. Rather than the expensive and tediously-applied web of copper tape [Marco] used, [chris] chose flexible PCBs to sandwich the Velostat piezoresistive material. An interface board multiplexes the 16 elements of the sensor array to a PIC which gathers and records testing data. [chris] even built a test stand with a solenoid to apply pressure to the sensor and test its frequency response to determine what sorts of measurements are possible.

We think the project is a great application for flex PCBs, and a perfect entry into our Flexible PCB Contest. You should enter too. Even though [chris] has a prototype, you don’t need one to enter: just an idea would do. Do something up on Fritzing, make a full EAGLE schematic, or just jot a block diagram down on a napkin. We want to see your ideas, and if it’s good enough you can win a flex PCB to get you started. What are you waiting for?

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