Reduced Graphene Oxide-Based Flexible Pressure Sensor for Biomedical Applications

Pressure sensing is a crucial technique for various biomedical applications, where it can provide valuable information about the health and function of different organs and systems. This article reports the development of a novel integrated pressure sensor based on modified reduced graphene oxide (rGO), a graphene-derivative material with enhanced piezoresistive properties. The sensor is fabricated on a flexible printed circuit board (PCB) substrate and conditioned by a smart current-based Wheatstone bridge circuit, which enables high sensitivity, wide detection range, fast response and recovery, and good stability under cyclic loading. The sensor achieves a measured sensitivity of 0.281 kPa(-1) (at 0.5 kPa load). A mechanical system is also designed to adapt the sensor to different anatomical sites and improve its elastic recovery. The sensor's functionality is initially demonstrated through its response to controlled mechanical stimulation, achieving a signal-to-noise ratio (SNR) of 25 dB. Subsequently, in a practical application, physiological signals from the carotid and femoral arteries of volunteers were acquired. The system effectively captured the pulse waveforms with high fidelity and accuracy (23.5-dB SNR) and measured the pulse transit time, an important parameter for estimating the pulse wave velocity (PWV) and arterial stiffness. The sensor is not limited to this specific application and can be easily extended to other domains where pressure sensing is required. In conclusion, it offers a low-cost, flexible, and user-friendly solution for noninvasive biomedical monitoring and diagnosis.