Smartphone-Based and Point-of-Care Green Analytical Devices: Engineering Design for Resource-Limited Settings

Green analytical chemistry (GAC) aims to minimise the environmental impact of analytical methods, such as the amount of toxic chemicals, energy consumption and waste produced, while maintaining the analytical quality of the methods. The smartphone is a ubiquitous device that is carried by billions of users and has become a versatile and intuitive tool that naturally fits in with these goals, combining both illumination and detection capabilities, computation and connectivity within a single device, which the user already owns. This review covers engineering design of green analytical devices for resource-limited environments that are reliant on the smartphone for detection or analysis and are lacking in centralised laboratories, stable electrical power, cold-chain supply chains, trained operators, etc. We place these platforms into the context of the 12 principles of GAC, the family of greenness and applicability metrics (Analytical Eco-Scale, Green Analytical Procedure Index, Analytical GREEnness calculator, Blue Applicability Grade Index) and link them to the ASSURED and REASSURED criteria for ideal diagnostics. Then, we explore the hardware and software architecture of the smartphone reader, substrate and fabrication selection affecting cost and “green-ness”, principal detection modalities and controlling equations, and a calibration and validation framework that is required for credible field results. A structured survey of clinical, environmental, food and agricultural applications is given, and device attributes are explicitly mapped onto each GAC principle and REASSURED criterion. Finally, we speak about standardisation, reproducibility, validation and the electronic-waste paradox, and propose future trends in machine learning, connectivity and sustainable materials. Smartphone POC devices are demonstrated to be one of the most reliable practical applications of green analytical chemistry in low-resource areas.