Integrating smartphone optical sensors with paper-based analytical devices: a future standalone platform for onsite detection and analysis

The beginning of this century has witnessed the emergence of many disruptive technologies changing the ways of sensing target analytes. Among these, smartphone-enabled analytical devices (SEADs) have gained attention as a promising technology, particularly in resource-limited settings. SEADs are recognized for being portable, cost-effective, user-friendly, and reliable platforms for detecting a wide range of analytes. In parallel, paper-based analytical devices (PADs) primarily relying on colorimetric or fluorescence signal transduction, have also attracted significant research interest across various applications. This review highlights the potential of integrating these two emerging analytical platforms, a combination that could revolutionize future onsite sensing. An overview of SEADs and PADs is provided, with focus on recent developments in optical detection. Advantages and limitations of integrating smartphones with PADs in different scenarios are presented. Additionally, recent applications of smartphone-coupled PADs are presented. Finally, key challenges associated with merging these two technologies are discussed.