  Flexible pressure sensors are an attractive area of research due to their
potential applications in biomedical sensing and wearable devices. Among
flexible and wearable pressure sensors, capacitive pressure sensors show
significant advantages, owing to their potential low cost, ultra-low power
consumption, tolerance to temperature variations, high sensitivity, and low
hysteresis. In this work, we develop capacitive flexible pressure sensors using
graphene based conductive foams. In these soft and porous conductive foams,
graphene is present either as a coating of the pores in the foam, inside the
structure of the foam itself, or a combination of both. We demonstrate that
they are durable and sensitive at low pressure ranges (<10 kPa). Systematic
analysis of the different pressure sensors revealed that the porous foams with
graphene coated pores are the most sensitive (~ 0.137/kPa) in the pressure
range 0-6kPa. Additionally, we achieved very low limit of detection of 0.14 Pa,
which is one of the lowest values reported. Further, we demonstrated the
potential applications of our pressure sensors by showing detection of weak
physiological signals of the body. Our work is highly relevant for research in
flexible pressure sensors based on conductive foams as it shows the impact of
different ways of incorporating conductive material on performance of pressure
sensors.

Applied Physics;Materials Science;Instrumentation and Detectors