## 1 Introduction  
The focus of this paper is on the development of a low-cost inkjet-printed paper-based sensing system that produces comparable results to that of a laboratory-based potentiostat. Various educational, environmental, healthcare, energy provision and storage challenges exist that can benefit from a point-of-need, effective, low-cost, user-friendly and portable solution [1; 2; 3]. The ASSURED criteria established by the World Health Organization stipulates that point-of-need solutions should be Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment free and Deliverable to end-users [4]. Advantageous properties of paper, such as disposability and low cost, provide a favorable platform on which to implement diagnostic tools, aligning well with the ASSURED criteria [4; 5; 6; 7; 8]. The advantages of paper include processing versatility allowing for broad application areas. Furthermore, compared to paper, other substrates such as Polyethylene terephthalate (PET) and Polyethylene napthhalate (PEN) are not as suited for remote environmental monitoring when considering the increase in substrate cost, and the environmental impact of these oil-based materials [9]. The cost of commercial resin coated paper used in printed electronics are approximately a sixth of the cost of PET, enabling paper to be further optimized and/or customized without exceeding the cost of PET [9]. These customizations enable the integration of paper-based microfluidics and paper-based electronics, used for a variety of environmental and health applications. Various researchers have focused on smart papers that have both hydrophobic and hydrophilic properties to accommodate both liquid flow and printed electronics, enabling smart, low-cost, point-of-need sensors and biosensing systems to be realized in fields such as water monitoring [2; 10]. Conformal printing technologies are important where electronic circuits must be printed on or around three-dimensional objects, such as in hybrid integration of three-dimensional components with printed electronics circuits on flexible substrates. Challenges created include local defects on high curvature areas. An example of a potentiostat integrated on a mouthguard highlighted the integration challenges between flexible substrates and rigid components, as well as the conductive adhesion between different substrates [1; 11]. Inkjet printing is a contactless deposition method that does not require patterning masks, and is therefore ideally suited to direct printing on a variety of non-planar substrates [12]. Furthermore, the use of inkjet printing to print on water soluble substrates have been reported, which allows conformal printing that directly adheres to any three-dimensional object [13], advancing the ubiquitous use of printed electronics technologies. Fields investigated in non-planar printing include applications such as gas chromatography, as well as electronic noses and electronic tongues, which have been successfully used to perform food freshness evaluations. These applications broaden the utilization scope of a printed point-of-need potentiostat [12]. The investigation of conformal printing challenges in hybrid printed electronics integration formed part of prior work, which contributed to the development of the low-cost inkjet-printed potentiostat presented in this work [7; 14; 15]. Commercial off-the-shelf components were connected to a paper substrate using inkjet-printing to create non-planar connections. The flexibility of the silver tracks and connections were verified by bending the various circuits consisting of surface mount components around a 31 mm diameter object in different directions. The number of effective connections between the components and circuits before the bending test and after the bending procedure were the same, validating the proof of concept [7]. Other authors have reported on silver tracks on paper being bent around a 1.5 mm radius during a 10,000 cycle bending test [16].