When a young person receives an artificial knee joint, they're left in a bit of a quandary – they're expected to stay active, yet too much of the wrong activity may cause the device to wear out prematurely. An experimental new implant could help address that situation.

Currently being developed through a multi-institute collaboration, the technology takes the form of an implantable artificial knee equipped with multiple pressure sensors. The idea is that these will track how much pressure is being placed on the joint by different activities, wirelessly alerting doctors to actions that may cause damage if not ceased or altered.

Although this setup could help postpone the need for surgery to replace a worn-out artificial knee, it would all be for nothing if operations were still required in order to change the battery that's powering the knee's electronics. To that end, instead of a battery, a triboelectric energy-harvesting system has been designed for the implant. This uses an integrated supercapacitor to store energy produced by the friction between two surfaces in the knee joint, that would rub together as the patient walked.

In tests conducted utilizing a gait simulator (the implant prototype can be seen on it above), it was found that the average person's walking gait and body load is capable of producing six microwatts of power. This ought to be more than enough to power the pressure sensors, which would require 4.6 microwatts.

Ultimately, it is hoped that the "smart" implant will not only allow patients to go for longer between replacement surgeries, but that data obtained from the device could also be used to developed longer-lasting artificial knees.

The research is being led by Asst. Prof. Shahrzad "Sherry" Towfighian of New York's Binghamton University, and also involves scientists from Stony Brook University and the University of Western Ontario. It is described in a paper that was recently published in the journal Smart Materials and Structures.

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