ORIGINAL RESEARCH Printed Paper–Based Electrochemical Sensors for Low-Cost Point-of-Need Applications Suzanne Smith 1 & Phophi Madzivhandila 1 & Letta Ntuli 1 & Petrone Bezuidenhout 1 & Haitao Zheng 2 & Kevin Land 1 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Paper-based microfluidics is a rapidly developing field with applications for point-of-care disease and environmental diagnostics. In parallel, printed electronics has grown swiftly, particularly for wearable technologies. By combining these fields, fluidic sample processing and control, as well as automated sensing and readout can be integrated on a single device. Towards this goal, this work highlights the design, manufacture, and testing of paper-based electrochemical sensors, with focus on photo paper and chromatography paper substrates. These substrates are typically used for printed electronics and paper-based fluidics, respectively. The electrochemical sensors were screen printed using manual techniques. For chromatography paper sensors, wax-printed fluidic barriers were used to illustrate the potential integration of the sensors with typical paper-based microfluidic device formats. As an initial example, the detection of heavy metals (Cd(II) and Pb(II)) in buffer solution was demonstrated. Commercial DropSens sensors were used as reference with the limit of detection (LOD) of Cd(II) and Pb(II) on chromatography sensors showing comparable results to commercial DropSens sensors. It is worth noting that the chromatography paper sensors showed a higher repeatability than the commercial DropSens sensors. Tap water samples spiked with Cd(II) and Pb(II) were also tested and showed promising results. Future work will include sensor optimization and exploration of scale-up to provide low- cost solutions for effective point-of-need diagnostics—ranging from environmental monitoring to healthcare applications. Keywords Paper-based sensors . Printed sensors . Screen printing . Electrochemistry . Low-cost . Point-of-need Introduction The development of paper-based diagnostics has been a strong focus in recent years [1]. Paper provides many advantages as a favorable platform on which to develop diagnostic devices: low cost, disposability, fluidic handling capabilities, high vol- ume manufacturability, to name a few. These advantages are particularly well-suited to resource-limited settings [2, 3], which are found in many parts of South Africa and across developing countries. Paper-based microfluidics for point-of- need applications such as health and environmental diagnos- tics have thus seen rapid growth in recent years [4]. Electrochemical sensors have been utilized extensively in the past, with glucose detection being a well-known example [5]. Typical systems make use of a portable reader with ceramic-based single-use sensors. A number of commercially available sensors can be used for these applications and in- clude sensors from DropSens [6]. However, the need for ex- tremely low-cost diagnostics, and thus sensors, has become increasingly critical, particularly in resource-limited settings where the need for effective, low-cost diagnostics is greatest. The development of paper-based sensors has become fea- sible as a result of fields such as printed electronics, where printing of circuits and sensors onto flexible substrates— including paper—has become a reality. Printed electronics has enabled a number of components and systems to be real- ized. Previous work by our group has explored printed con- ductive tracks [7], multilayer structures, and integration of electronics on paper and microfluidics [8, 9]. Although a num- ber of printed electronic components and subsystems are well- * Suzanne Smith ssmith@csir.co.za * Haitao Zheng hzheng@csir.co.za 1 Materials Science and Manufacturing, Council for Scientific and Industrial Research (CSIR), Meiring Naude Road, Brummeria, Pretoria 0001, South Africa 2 Energy Centre, Council for Scientific and Industrial Research (CSIR), Meiring Naude Road, Brummeria, Pretoria 0001, South Africa Electrocatalysis https://doi.org/10.1007/s12678-019-0512-8