High Precision, Wide Linear Range Capacitive Pressure Sensor Based on PMMA Microspheres for Motion and Breath Monitoring

With the growing interest in human health and wearable smart electronics, flexible pressure sensors, especially those with real-time, remote and wireless monitoring capabilities, have gained significant attention for their potential application in motion monitoring and intelligent healthcare systems. However, achieving a wide detection range while maintaining high sensitivity and linearity remains a challenge. Here, a flexible capacitive pressure sensor was designed and fabricated utilizing polymethyl methacrylate (PMMA) microspheres as the dielectric layer, which is sandwiched between carbon nanotubes (CNTs) interdigital electrode and a MXene-based microstructured electrode. Integrating a sensitive layer with hierarchical microstructure and a periodic microsphere spacer, allows the electrodes to establish multilevel direct contact, thereby significantly enhancing the linearity and detection precision of the sensors. The pressure sensor exhibits a wide detection range of 14.7 Pa–109.2 kPa, a high detection precision of 0.92‰ in full scale (FS), and an exceptional linearity (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{{2}} \gt 0.997$ </tex-math></inline-formula>) in medium pressure range. Moreover, the sensor exhibits a robust durability over 10 000 cycles, and a fast response time of 132 ms during pressure loading. The constructed sensor holds great promise for deployment in real-time wireless monitoring of pressure responses, making it suitable for applications such as motion tracking, breath monitoring, and integration into wearable healthcare devices.