Stretchable tracks for laser-machined neural electrode arrays.

An easy and fast method for fabrication of neural electrode arrays is the patterning of platinum foil and spin-on silicone rubber using a laser. However, the mechanical flexibility of such electrode arrays is limited by the integrated tracks that connect the actual electrode sites and the contacts to which wires are welded. Changing the design from straight lines to meanders, the tracks can be stretched to a certain extend defined by the shape of the meanders. Horse-shoe-like designs described by an opening angle theta = 60 degrees and ratio between curvature radius r and track width w of r/w = 3.6 permitted stretching of 14.4% before track breakage. For r/w = 11.7 a maximum elongation at break of 19.7% was measured. Larger opening angles theta provided even better flexibility but with increasing theta, the tensile strength and the electrical conductance of a single track is compromised and the maximum integration density (tracks per area) decreases.