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

Published

April 2, 2024

Author(s)

Mark Ferris, Gary Zabow

Abstract

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.

Citation

Nature Communications

Volume

15

Pub Type

Journals

Download Paper

https://doi.org/10.1038/s41467-024-47073-2

Local Download

Keywords

Smartphone, hydrogel, smart materials, magnetic sensing, diagnostics

Citation

Ferris, M. and Zabow, G. (2024), Quantitative, high-sensitivity measurement of liquid analytes using a smartphone compass, Nature Communications, [online], https://doi.org/10.1038/s41467-024-47073-2, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956278 (Accessed October 14, 2025)