Processes for producing conductive and/or piezoresistive traces on polymeric substrates

A method for producing conductive and/or piezoresistive traces in a non-conductive polymeric substrate comprising irradiating said polymeric substrate by laser irradiation, wherein said polymeric substrate comprises composite polymeric material which comprises a matrix comprising a non char forming polymer and a dispersed phase which comprises carbon or carbon nitride nanotubes or carbon nanofibres, and wherein said composite material also comprises particles of a lamellar silicate in a quantity from about 0.1 to about 20% by weight, relative to the weight of the composite material.