Highly sensitive iontronic sensor enabled by spherical boron nitride for intelligent pulse monitoring

Abstract

Reliable acquisition of arterial pulse waves is important for wearable cardiovascular monitoring; however, weak wrist-surface vibrations are susceptible to variations in contact pressure, motion artifacts, and physiological conditions. Herein, we report an iontronic pressure sensor that integrates magnetron-sputtered Pt interdigitated electrodes with a microdome-structured thermoplastic polyurethane/spherical boron nitride/ionic liquid composite layer. The device operates over a pressure range of 0–1500 kPa, with a maximum sensitivity of 67.89 kPa⁻¹, response/recovery times of 136/30 ms, resolved response at the minimum demonstrated pressure of 173 Pa, and repeated operation over 7000 loading-unloading cycles with a maximum signal deviation of 3.72%. Hierarchical spherical boron nitride interfaces are expected to influence local ion organization and interfacial polarization, whereas mechanical tests indicate higher dynamic stiffness and lower cyclic peak force variation following the incorporation of spherical boron nitride under the tested conditions. As a proof-of-concept, 14 standardized pulse patterns were classified using multiple feature-based strategies, with the best-performing classifier achieving a five-fold mean accuracy of 98.23%. A wireless system recorded radial artery pulse waves before and after exercise and enabled Fourier-transform analysis of heart rate variation. These pulse patterns and single-participant on-body demonstrations support sensor-based pulse acquisition and analysis but do not constitute a clinical validation.

Graphical abstract

Keywords

flexible pressure sensor / iontronic sensor / spherical boron nitride / pulse monitoring / machine learning

References

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