Self powered sensor for monitoring injured knees
5 July 2008
A sensor that can monitor progress during knee operations and
generates power from body movement has been developed by a researcher at
Southampton University. This new sensor, called a serial in-vivo
transducer (SIT) could measure tendon force during anterior cruciate
ligament (ACL) reconstruction.
As part of his final year project in his Masters degree in
electromechanical engineering at Southhampton University's School of
Electronics and Computer Science (ECS), Fauzan Baharudin explored the
potential for the use of thick-film technology in the development of
medical sensors that could be embedded in the knee during surgery.
The ACL is the most commonly injured ligament and is commonly damaged
by athletes, in fact it is reported that this is the ligament associated
with golfer Tiger Woods’ injury.
Fauzan’s project was supervised by Professor Neil White at ECS, who,
in 1991 developed thick film piezoelectric material which made it
possible to produce a sensor that could power itself if it were
installed in a device that vibrates. This is suitable for appliances
where external physical connections are difficult.
Professor White said: "Although this work is still in its infancy,
our earlier research in thick-film sensors has shown that it is feasible
to apply the technology to medical applications such as prosthetic
"We have also shown that it is possible to harvest energy from the
human body using piezoelectric materials and the knee is subjected to
very high levels of force during everyday activities. It therefore seems
logical to combine the two approaches to deliver a new type of embedded,
Fauzan has also incorporated some of this energy harvesting
capability into the serial in-vivo transducer, which means that it will
be self-powered. "I chose knee surgery because this has been very little
research carried out in this field and I felt a self-powered device
could work well in the knee," he said.
Before developing SIT, Fauzan reviewed the existing devices in this
field and concluded that due to its flexibility in fabrication, low
capital cost, fast lead time and its suitability for use in the body,
thick film technology is the best solution for ACL surgery. Assessment
of the energy harvesting feature revealed that the device could produce
more than enough energy to power itself.
"It remains a mystery to me, given how common knee injuries are among
athletes, that devices like ours have not been developed before now,"
said Fauzan. "A sensible assumption for this is that thick-film
technology does not reach medical researchers as quickly as it does
within the microelectronics community hence the delay in realising the
huge potential in developing in vivo transducers."