Improving safety of bionic devices

Physicists at the University of Sydney have developed a new method of testing if bionic devices are leak-proof.

Physicists at the University of Sydney have developed a new method of testing if bionic devices, including pacemakers, cochlear hearing implants and bionic eyes are leak-proof, proposing new standards to ensure the devices can’t be penetrated by water.

If bionic medical devices are penetrated by moisture from bodily fluids and tissues, they could fail, which would put a patient’s health in jeopardy. While large leaks are easily detected during manufacturing, tiny leaks can escape detection.

Currently, implantable biomedical devices are moisture-tested via a helium leak test, where helium gas is inserted into the device and the most sensitive method for detecting gas, known as mass spectrometry technology, is used to see if any escapes. But scientists have now found a way to directly measure gaseous or liquid water leakage without assuming that moisture behaves like helium.

The new method, developed by Professor David McKenzie from the School of Physics at the University of Sydney, together with Dr Wenwen Lei from the National Measurement Institute, uses a standard leak based on the use of a stable polymer (poly ether ether ketone or “PEEK”) together with the most sensitive method for detecting the water, mass spectrometry. The unknown leak is quickly and reliably assessed against the standard leak that is supplied with a calibration.

In a paper published in a scientific journal of the American Chemical Society, Professor McKenzie and Dr Lei compared water leakage with helium leakage in biomedical test structures. They found that water can leak at up to 10 times the rate of helium, indicating that some devices could leak at too high a rate even after they had been leak-tested with the helium test, unless the new findings were considered.

“This is serious because people who have implants in their bodies really rely on them to be reliable over many, many years,” Professor McKenzie said. “The body is a surprisingly aggressive environment in some ways, loaded with moisture, and if the moisture penetrates an implantable device it can cause corrosion and the device could fail. That could be very serious if it’s a life-preserving device like a heart pacemaker.”

Professor McKenzie said recent research had found tiny leakages – “nanoleaks” – could occur where moisture was able to penetrate tiny spaces in some special materials. “Any such ‘nanoleak’ would be very serious if it happened in medical devices.

“Helium testing of bionic devices is a good standard, but by improving the compliance by a factor of 10, we think the industry can further guarantee the safety of biomedical implants,” Professor McKenzie said.