Description

WP6 relates to aspects of the design and finishing of the cuffs, after they have been released from the wafer-sandwich. The self-curling PDMS sheets, on which the electrodes are formed are thin (~0.25mm) and the implant cable is very flexible. Between them is a micropackage, containing the integrated circuit, and the interconnection to the cable. These parts are relatively stiff and should be small to minimise the risk of nerve damage.

The objectives for the WP were: fatigue and electrical characterisation of a cable with lower resistance wire; to compare the under-water adhesion of the PDMS-to-silicon bonds formed by adhesive and by plasma-bonding; to make a test cuff (‘Continuity Cuff’) that allows the electrical connections between the cable and the package, and between package and electrode metallisation to be tested; and to test these under cyclic strain conditions to observe the reliability of these joints and of the electrode metallisation.

 

Achievements

Nerve interface electrodes move with soft tissue so cables must be very flexible and fatigue resistant but suitable wires tend to have high electrical resistance. Implant cable made with composite wire, with a silver core and 4-times lower resistance, has been fatigue tested in saline by this machine. Life is as good as previous tests with standard wire.