Brain-implanted electrodes have numerous uses, ranging from the controlling of prosthetic arms to the monitoring of neural activity. They could soon be more effective than ever, as scientists have now developed ones that are soft and squishy.

Ordinarily, electrodes are made mainly of rigid metal. As a result, when they're implanted in soft brain tissue, inflammation and the buildup of scar tissue may occur. Led by MIT's Prof. Xuanhe Zhao, a team from the US and China set out to develop a more patient-friendly alternative.

The researchers began with an existing electrically-conductive polymer, known as PEDOT:PS. In its usual form, the substance is quite liquid and runny – it's intended to be used as a coating, not as a construction material for standalone objects.

This limitation was addressed by freeze-drying the PEDOT:PS, removing its liquid component and leaving behind a dry matrix of conductive nanofibers. Those fibers were then mixed with water and an organic solvent, creating a viscous hydrogel that could be extruded through the nozzle of a 3D printer to form the rubbery electrodes.

In lab tests, one of these electrodes was implanted into the brain of a live mouse, and successfully used to read the electrical signals of a single neuron. Such signals are produced by the brain in the form of ions, which are typically only detected on the surface of traditional metal electrodes. Because this is not the case with the MIT electrodes, the scientists believe that they should be more accurate at reading the signals.

"The beauty of a conducting polymer hydrogel is, on top of its soft mechanical properties, it is made of hydrogel, which is ionically conductive, and also a porous sponge of nanofibers, which the ions can flow in and out of," says team member Baoyang Lu, from Jiangxi Science and Technology Normal University. "Because the electrode’s whole volume is active, its sensitivity is enhanced."

A paper on the research, which also involved scientists from Zheijiang University, was recently published in the journal Nature Communications.

Source: MIT

