Quantitative, high-sensitivity measurement of liquid analytes using a smartphone compass

Area of Science:

• Biomedical Engineering
• Materials Science
• Analytical Chemistry

Background:

• Smartphone-based diagnostics predominantly rely on optical methods, limiting their use with certain sample types.
• Magnetic sensing modalities using smartphone magnetometers are largely unexplored for diagnostic applications.
• Existing methods often require external electronics or power sources, hindering portability.

Purpose of the Study:

• To develop an optics-free, portable diagnostic platform leveraging smartphone magnetometers.
• To utilize analyte-responsive magnetic-hydrogel composites for signal transduction.
• To demonstrate sensitive and quantitative analyte detection using smartphone-integrated magnetic sensing.

Main Methods:

• Development of magnetic-hydrogel composites that change volume in response to specific analytes.
• Integration of these composites with a smartphone's built-in magnetometer for signal detection.
• Utilizing a bilayer hydrogel geometry to amplify displacement and enhance sensitivity.
• Demonstration with glucose-specific and pH-responsive hydrogels for quantitative measurements.

Main Results:

• Successful demonstration of analyte sensing using smartphone magnetometers and magnetic hydrogels.
• Achieved sensitive glucose detection down to single-digit micromolar concentrations.
• Showcased the potential for optics-free, quantitative liquid-based analyte measurements.
• Verified the platform's adaptability to various measurands and potential for nanomolar sensitivity.

Conclusions:

• The developed platform offers a novel, inexpensive, and portable method for analyte sensing.
• Exploiting smartphone magnetometers opens new possibilities for diagnostics in challenging sample environments.
• This technology has the potential to enable widespread point-of-care testing for multiple biomarkers.