A flexible electrode device, including a typically thin film polymer layer, a typically thin film metal layer bonded to the polymer layer to yield a composite strip, and a polymer substrate ultrasonically welded to the composite strip to yield a flexible electrode device. The flexible electrode device exhibits electrical conductivity of at least 1.0810.sup.6 S.Math.m.sup.1, at least 60% tensile elongation, and less than 5% change in the R/R.sub.0 after 50 peeling cycles. The flexible electrode is formed without annealing and is formed under ambient pressure and temperature conditions. The flexible electrode device can have any convenient shape.