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, ultralow 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, or as 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–1) in the pressure range 0–6 kPa, with a limit of detection of 50 Pa. 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.

Flexible pressure sensors are becoming increasingly popular due to their potential applications in multifunctional wearable devices. Among flexible pressure sensors, capacitive pressure sensors based on porous foams of poly(dimethylsiloxane) (PDMS) are widely investigated. In this work, we develop highly sensitive capacitive pressure sensors operating in a low-pressure range (<10 kPa) using graphene-coated PDMS foams with different ranges of pore sizes, obtained either by sugar templating or a combination of sugar templating and emulsion templating. Our analysis reveals that pressure sensors with the highest variation in pore sizes over a wide pore size range are the most sensitive and reach a high sensitivity of ∼3.7 kPa −1 (for a range of 2−6 kPa). These pressure sensors have a low limit of detection of ∼20 Pa and are able to detect small changes in pressure in many situations, demonstrating potential applications in wearable biomedical sensors. Our result shows future pathways for developing pressure sensors with higher sensitivities and, therefore, highly relevant for research in pressure sensors based on conductive foams.

Water pollution is a global issue because of potentially lethal toxins. Polymeric nanomaterials are making their way into water treatment processes and are being utilized to efficiently remove a variety of pollutants. Polymeric nanomaterials are a popular option for a solution because they have a high adsorption capacity and a high surface charge. Nanocomposites have recently come to the attention of those working in the field of water treatment in order to more effectively remove contaminants. Polymeric composites are based on biopolymers and are being developed. These all quickly reached the industrial standards because of their low impact on the natural world. Chitosan is one of the biopolymers that are used extensively. Moreover, it is one of the most highly preferred biopolymers. It is simple to scale up and is readily available. The incorporation of nanomaterials into the biopolymer enables better control over the shape, size, and morphology of the particle, as well as an increase in the efficiency with which contaminants are removed. This is an excellent review that examines recent developments in the formation of chitosan-based polymeric nanocomposites and their performance in removing various contaminants including heavy metals, dyes, pesticides, pharmaceutical waste, and radionuclides from water.

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