A Portable Smartphone-Based Platform with an Offline Image Processing Tool for Rapid Paper-Based Colorimetric Detection of Glucose in Artificial Saliva

Paper-based sensors have great potential for use in a variety of areas, from environmental monitoring to clinical and pointof-care testings. Here, a microfluidic paper-based analytical device (µPAD) was integrated with a smartphone app capable of offline (without internet access) image processing and analysis for rapid colorimetric detection of glucose. A self-inking stamp was used to form hydrophobic channels on a piece of paper-towel due to its superior water absorption efficiency. As demonstrated, the developed sensor was employed for colorimetric detection of glucose in artificial saliva in the linear scope of 0-1 mM with a calculated detection limit of 29.65 µM. In addition, experimental results show that quantitative analysis of glucose with the proposed smartphone platform could be completed in less than one minute. The app developed for the smartphone platform is capable of extracting the color changing area with an embedded image processing tool which could address the problem of color uniformity in detection zones of µPAD. The total cost of a µPAD is less than $0.2. By integrating µPAD with a smartphone and user-friendly app together, the proposed smartphone-based platform could be used for the quantitative analysis of glucose with advantages such as portability, simple operation, rapid response, ultra-low cost, field-deployable, selectivity and sensitivity. The results show that the integrated platform has great potential to be used for non-invasive measurement of glucose in body fluids like a tear, sweat and saliva.