We present a useful and effective conversion process for inkjet-printed conductive copper features on common polymer substrates. The process is based on causing burst nucleation from an as-printed copper complex ion pattern by an exposure to hydrazine vapor. This hydrazine based treatment at 150 degrees C for 1 min leads to copper patterns with a well-sintered microstructure and resistivity of 15.18 mu Omega cm. This new approach could be an alternative to a conventional hydrogen gas treatment and is suitable for organometallic or metal complex based inks as well as most commercial plastic and paper substrates for flexible and disposable electronics. (C) 2016 Elsevier B.V. All rights reserved.