Nearly every modern cellphone has a built-in compass, or magnetometer, that detects the direction of Earth’s magnetic field, providing critical information for navigation. Now a team of researchers at the National Institute of Standards and Technology (NIST) has developed a technique that uses an ordinary cellphone magnetometer for an entirely different purpose — to measure the concentration of glucose, a marker for diabetes, to high accuracy.
The same technique, which uses the magnetometer in conjunction with magnetic materials designed to change their shape in response to biological or environmental cues, could be used to rapidly and cheaply measure a host of other biomedical properties for monitoring or diagnosing human disease. The method also has the potential to detect environmental toxins, said NIST scientist Gary Zabow.
In their proof-of-concept study, Zabow and fellow NIST researcher Mark Ferris clamped to a cellphone a tiny well containing the solution to be tested and a strip of hydrogel — a porous material that swells when immersed in water. The researchers embedded tiny magnetic particles within the hydrogel, which they had engineered to react either to the presence of glucose or to pH levels (a measure of acidity) by expanding or contracting. Changing pH levels can be associated with a variety of biological disorders.
Illustration shows how a smartphone magnetometer can measure a host of biomedical properties in liquid samples using a magnetized hydrogel.
Credit: K. Dill/NIST
As the hydrogels enlarged or shrunk, they moved the magnetic particles closer to or farther from the cellphone’s magnetometer, which detected the corresponding changes in the strength of the magnetic field. Employing this strategy, the researchers measured glucose concentrations as small as a few millionths of a mole (the scientific unit for a certain number of atoms or molecule ..
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