Electric Plastics: Better bionic eyes and ears

A young UNSW researcher has created conductive bioplastics which will transform the performance of bionic devices such as the cochlear ear and the proposed bionic eye.

“Our plastics will lead to smaller devices that use safer smaller currents and that encourage nerve interaction,” says biomedical engineer Rylie Green.

Bionic eye test electrode, with one set of metal electrodes (left) and conducting bioplastic electrodes (right) (photo: Rylie Green)

“The plastics can carry natural proteins which will aid the survival of damaged and diseased nerves,” Rylie says. Her research was published in Biomaterials earlier this year.

Her plastics are already being tested in prototype bionic eyes and she hopes they will find application in bionic ears, robotic limbs – wherever researchers are attempting to integrate electronics with the human body.

Prototype bionic eye electrodes (left) are coated with conducting bioplastics (right) (photo: Rylie Green)

Her work will be presented for the first time in public this week at Fresh Science, a communication boot camp for early career scientists held at the Melbourne Museum. Rylie is one of 16 winners from across Australia.

“Using conductive plastics for medical electrodes is set to revolutionise the performance of bionic implants. They will improve both safety and versatility.”

Scanning electron microscope images of electrode surfaces (photo: Rylie Green)

Bionic devices, such as cochlear implants or robotic limbs, connect into the nervous system. At present, the electrodes they use are made out of metals such as platinum and iridium. But because metals have smooth surfaces, the body immediately tags them as foreign material and tries to wall them off by growing fibrous, scar tissue around the implant.

An artists depiction of how bioplastics can make nerves grow into the surface of an electrode. The metal electrode on the left is not recognised by the body and “walled off”, but the bioplastic encourages nerves to attach to the electrodes (image: Rylie Green)

So, over time, larger and larger electrical currents must be used to stimulate the nerves through the scar tissue. Eventually, this results in the surrounding tissue and body fluids being subjected to unnatural changes in acidity and to toxins produced from the metal contacts, both of which damage cells.

Neural cells growing on the conducting bioplastic electrodes (photo: Rylie Green)

Conductive plastics or polymers are an alternative to metals. They have rough surfaces which encourage the attachment of cells, meaning they offer potential for improved performance and longevity when implanted in the body as electrodes. Additionally, the highly textured polymer surface can pass electrical current to cells more efficiently than smooth metals.

Rylie has also been able to improve their performance by incorporating natural body proteins. Upon implantation, these proteins help the cells near the electrode to survive and grow, and can reduce the formation of scar tissue. This is especially important in implant recipients where the existing tissue is damaged, as is the case with most deaf and blind patients.

Rylie Green is one of 16 early-career scientists presenting their research to the public for the first time thanks to Fresh Science, a national program sponsored by the Australian Government. Her challenges include presenting her discoveries in verse at a Melbourne pub.

For further information, contact Rylie Green at r.green@unsw.edu.au

Additional Images

Rylie Green (photo: Mike Coulson)

Rylie Green pitching her story (photo: Mike Coulson)