Novel developments in mobile sensing based on the integration of microfluidic devices and smartphones

Abstract

Portable electronic devices and wireless communication systems enable a broad range of applications such as environmental and food safety monitoring, personalized medicine and healthcare management. Particularly, hybrid smartphone and microfluidic devices provide an integrated solution for the new generation of mobile sensing applications. Such mobile sensing based on microfluidic devices (broadly defined) and smartphones (MS(2)) offers a mobile laboratory for performing a wide range of bio-chemical detection and analysis functions such as water and food quality analysis, routine health tests and disease diagnosis. MS(2) offers significant advantages over traditional platforms in terms of test speed and control, low cost, mobility, ease-of-operation and data management. These improvements put MS(2) in a promising position in the fields of interdisciplinary basic and applied research. In particular, MS(2) enables applications to remote in-field testing, homecare, and healthcare in low-resource areas. The marriage of smartphones and microfluidic devices offers a powerful on-chip operating platform to enable various bio-chemical tests, remote sensing, data analysis and management in a mobile fashion. The implications of such integration are beyond telecommunication and microfluidic-related research and technology development. In this review, we will first provide the general background of microfluidic-based sensing, smartphone-based sensing, and their integration. Then, we will focus on several key application areas of MS(2) by systematically reviewing the important literature in each area. We will conclude by discussing our perspectives on the opportunities, issues and future directions of this emerging novel field.

Fig. 1. Historical development of microfluidic device, smartphone and MS²

Fig. 2. MS² for environmental and food safety monitoring

(a) Schematic illustration of E. coli detection with a cell phone using a quantum dotbased sandwich assay. (b) Smartphone application for Salmonella detection from a multi-channel microfluidic device. (c) An integrated mobile PoC system including a camera phone, an Arduino microcontroller on copper electrodes with a microfluidic chip slot, and a microfluidic ELISAon-a-chip. The figures are adapted from ref. , and with permission from the Royal Society of Chemistry for (a and b) and AIP Publishing LLC for (c), respectively.

Fig. 3. MS² application for heavy metal detection

Schematic illustration of a metal assay based on a 3D paper microfluidic device and a cell phone. Samples are added to the paper device for metal chromogenic reaction in the detection zone. The chromogenic signals are imaged using a camera cell phone and analyzed through a personal computer with image processing and analysis software. The figure is adapted from ref. with permission from Springer.

Fig. 4. MS² applications for nitrite, nitrate and pH detection

(a) Schematic illustration of a smartphone-based application for measurement of nitrite concentration and pH in combination with a low-cost paper-based microfluidic device. (b) A mobile EC sensing system for nitrate detection. It includes a miniaturized EC sensor and a mobile phone-based control platform. The figures are adapted from ref. and with permission from the American Chemical Society for (a) and Elsevier for (b), respectively

Fig. 5. MS² applications for routine health tests

(a) Schematic illustration of a smartphone-based optical biosensor for glucose monitoring in combination with a low-cost paper-based microfluidic device. (b) Smartphone-based health sweat and saliva biomarker monitoring on the test strip. The figures are adapted from ref. and with permission from Springer for (a) and the Royal Society of Chemistry for (b), respectively.

Fig. 6. MS² applications for genetic tests

(a) The Gene-Z prototype system with a disposable chip for E. coli detection. (b) A smartphone with a mini-fluorescence microscope to identify pathogenic nucleic acids from field and clinical samples using paper microfluidic chips. The figures are adapted from ref. and with permission from the Royal Society of Chemistry.

Fig. 7. MS² applications for pathogen detection

(a) A handheld smartphone-based optofluidic device for quantitative measurement of TSH based on Mie scattering and lateral flow assays. (b) A benchtop ELISA instrument based on a disposable microfluidic cassette and a smartphone for simultaneous pathogen detection in blood. The figures are adapted from ref. and with permission from Elsevier for (a) and the American Association for the Advancement of Science for (b), respectively.

Fig. 8. Summary of common issues of current MS² systems and future perspectives on MS² development

We identified sample introduction and contamination, operator safety, limitations in power, imaging, throughput and user-friendliness as the main common issues of the current MS² systems. We envision future MS² systems to have improved world-to-assay interface, assay automation and self-containment, incorporation of new power sources and optical fiber imaging, and integration of different tests and operation with high throughput, tolerance and reproducibility, which can be used even by untrained end-users. We believe that future MS² technologies will serve as a powerful experimental platform for scientific research, and will enable a wide range of practical diagnostic applications in environmental monitoring, food safety and healthcare. In addition, we believe that MS² will revolutionarily create new methodologies for science education.