Investigation of methods to quantify silver screen-printed onto cellulosic substrate: towards recycling of printed electronics

The continued progress in electronics technology has led to unsustainable consumption of plastic-based products containing, in their majority, natural finite metallic resources. The substitution of these plastic materials by more sustainable ones, such as cellulosic substrates, is one of many measures applied by the industry to reduce their environmental impact. In this work, due to the lack of information in the literature, a fast and accurate method to measure the amount of metal deposited onto a paper-based substrate is proposed. The development of this method will contribute to the creation of a procedure for determining the quantity of metal present in end-of-life printed electronics. The present work investigates and compares four different methodologies. Image processing and geometrical analyses presented overestimated and non-precise results for printed Ag. A third method based on gravimetric measurements presented to be more accurate compared with the previous methods. The last method based on acid leaching of the printed electronic ashes outcome to be the more precise, reliable and simpler method, and overcomes challenges associated to the printed pattern geometry and the materials used during its production. These results will provide key information for the development of a quantitative methodology to determine the percentage of Ag used in paper-based electronics that can be adapted easily by the industry. Furthermore, this method is a prerequisite for recycling processes devoted to this type of electronics after reaching their end-of-life, considering Ag as one of the major components to be separated and, further, valorized.