Paper-pencil based IoT enabled pH sensor using LabVIEW

Generally, paper and pencil are used for writing and artwork because they are convenient, inexpensive, and disposable. The usage of paper and pencil is steering toward the development of conductive circuit traces and sensors. However, this fabrication method needs to be further investigated and optimized as a generic method to draw any conductive paths and sensors. This paper describes a pH sensor developed using pencil drawing through a steel metal mask over a paper substrate. Nafion was used as the proton exchange membrane. The authors tested the fabricated pH sensors using the different pH buffers, and a sensitivity of $\sim 15$ mV/pH change was noted. In addition, the paper-based pH sensor was also tested successfully for the pH levels of different fruit juices as well as beverages. Additionally, The authors have also successfully integrated the same with the Internet of Things (IoT) to monitor pH using the Thinkspeak.com web application through integration with LabVIEW. Although this initial attempt resulted in a lower sensitivity of the pH sensor, it demonstrated effective usage as a low-cost disposable and flexible pH sensor with simple fabrication steps and cloud-based remote data uploading and processing capabilities required for low-cost healthcare solutions.