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



Mark Ferris, Gary Zabow


Smartphone ubiquity has led to rapid developments in portable diagnostics. While successful, such platforms are predominantly optics-based, using the smartphone camera as the sensing interface. By contrast, magnetics-based modalities exploiting the smartphone compass (magnetometer) remain unexplored, despite inherent advantages in optically opaque, scattering or auto-fluorescing samples. Here we report smartphone analyte sensing utilizing the built-in magnetometer for signal transduction via analyte-responsive magnetic-hydrogel composites. As these hydrogels dilate in response to targeted stimuli, they displace attached magnetic material relative to the phone's magnetometer. Using a bilayer hydrogel geometry to amplify this motion allows for sensitive, optics-free, quantitative liquid-based analyte measurements that require neither any electronics nor power beyond that contained within the smartphone itself. We demonstrate this concept with glucose-specific and pH-responsive hydrogels, including glucose detection down to single-digit micromolar concentrations with potential for extension to nanomolar sensitivities. The platform is adaptable to numerous measurands, opening a path towards portable, inexpensive sensing of multiple analytes or biomarkers of interest.
Nature Communications


Smartphone, hydrogel, smart materials, magnetic sensing, diagnostics


Ferris, M. and Zabow, G. (2024), Quantitative, high-sensitivity measurement of liquid analytes using a smartphone compass, Nature Communications, [online],, (Accessed April 14, 2024)
Created April 2, 2024, Updated April 1, 2024