Implant packed for safety

Researchers at University College London are to carry out integrated circuit design and packaging for a project to develop an inner ear implant for people with conditions that affect their balance.

Seven European and US institutions will develop a closed-loop neural prosthesis implant for vestibular disorders during the three-year project, funded through the Future and Emerging Technologies (FET) initiative.

UCL has considerable experience in implantable neuroprosthetics, including an ongoing project to develop a spinal canal implant to restore neurological functions and some leg movement for people with serious spinal cord injury, which The Engineer has followed closely.

Prof Nick Donaldson of UCL's medical physics and bioengineering department, said: 'Our group has done a lot of work packaging prostheses. The standard packaging technology is a welded titanium container, like that used in pacemakers. The problem comes when you try to make something better and smaller or use inductively-powered devices that would be screened by the metal. There is very good evidence you don't need a barrier that prevents water vapour diffusing through the water structure to do that. You can surround your electronic components with a polymeric encapsulant to prevent corrosion and prevent leakage currents so they go on functioning for long periods.'

The team has also developed an electronic method of making implantable devices safer under fault conditions without using a bulky blocking capacitor.

The researchers use small capacitors on the integrated circuit that produce interleaved high-frequency pulses which, when added together, produce continuous current. 'This means the device can be smaller, you can put your electronics closer to the electrode and can get more function from such a small size,' said Donaldson.

Berenice Baker