Electromagnetic-Based Deformation Monitoring for PANI-CA Breath Acetone Sensors

We report a novel electromagnetic (EM) based mechanism for quantifying bending in PANI-CA chemo-actuators that detect breath acetone and validate feasibility in a proof-of-concept
in vitro
setup. Breath acetone serves as a biomarker of human metabolism, yet previously reported techniques are invasive, non-continuous, and/or operate at high temperatures. To overcome these limitations, we rely on previously reported polyaniline and cellulose acetate (PANI-CA) chemo-actuators that are known to flex up to 30° in response to breath acetone levels (i.e., up to 1250 ppm) in a reversible process. Our approach comprises of resonant loops placed in proximity to as well as embedded in 4 cm × 3 mm PANI-CA strips and operates at room temperature. To minimize impact to the strip's mechanical performance, loops are realized on lightweight conductive threads. Using Faraday's law as the strip deforms and the loops misalign, the sensor is shown to monitor acetone-headspace concentration at a limit of detection and resolution of 26.1 ppm experimentally and 1 ppm through interpolation. We also demonstrate that our EM mechanism in conjunction with PANI-CA strips: (a) is suitable for acetone sensing up to 2610 ppm (70° flexion) relevant to other applications beyond breath, and (b) can be modified to monitor deformation of up to 170° shall more sensitive chemo-actuating strips be implemented in the future. This technology can be integrated into a wearable device for-instance mask or mouthpiece. Personalized, non-invasive and continuous sensing of acetone biomarker can bolster monitoring of various health diagnostics, such as fat-metabolism, weight loss, and ketosis.