Abstract
The high demand for multifunctional devices for smart clothing applications, human motion detection, soft robotics, and artificial electronic skins has encouraged researchers to develop new high-performance flexible sensors. In this work, we fabricated and tested new 3D squeezable Ecoflex® open cell foams loaded with different concentrations of graphene nanoplatelets (GNPs) in order to obtain lightweight, soft, and cost-effective piezoresistive sensors with high sensitivity in a low-pressure regime. We analyzed the morphology of the produced materials and characterized both the mechanical and piezoresistive response of samples through quasi-static cyclic compression tests. Results indicated that sensors infiltrated with 1 mg of ethanol/GNP solution with a GNP concentration of 3 mg/mL were more sensitive and stable compared to those infiltrated with the same amount of ethanol/GNP solution but with a lower GNP concentration. The electromechanical response of the sensors showed a negative piezoresistive behavior up to ~10 kPa and an opposite trend for the 10–40 kPa range. The sensors were particularly sensitive at very low deformations, thus obtaining a maximum sensitivity of 0.28 kPa−1 for pressures lower than 10 kPa.
Highlights
In recent years, the growing demand for novel, highly flexible, and sensitive pressure sensors has been mainly driven by the great interest towards soft robotics for human cooperation and rehabilitation as well as wearable electronics for human healthcare and activity monitoring [1,2].A pressure sensor converts a strain/pressure stimulus into an electrical signal
We developed, for the first time, novel conducting polymeric Ecoflex® foams loaded with graphene nanoplatelets (GNPs) as piezoresistive low-pressure sensors
The obtained results make the Ecoflex® -based foams extremely promising porous structures for light, flexible, biocompatible, and wearable pressure sensors. This belief led us to investigate the possibility of enhancing the performance of the GNP/PDMS foams developed in [20] in the low-pressure range using the new elastomer
Summary
The growing demand for novel, highly flexible, and sensitive pressure sensors has been mainly driven by the great interest towards soft robotics for human cooperation and rehabilitation as well as wearable electronics for human healthcare and activity monitoring [1,2]. Piezoresistive sensors are able to convert the stimulus into an electrical resistance variation They can detect both transient and static deformations, are low in cost, can be fabricated through simple manufacturing processes, require simple electronic circuits for easy acquisition, and have fast response and a wide detection range [4]. With those of different polymers, such as polydimethylsiloxane (PDMS) [11,12], Ecoflex® [13,14], rubber [15,16], or polyurethane (PU) [17], have recently shown high flexibility and excellent responsiveness to torsion, tension, and compression These kinds of materials can be barely exploited when extremely lightweight and sensitive devices, able to detect pressures lower than some tens of kPa, are required. It can be seen that our sensor was produced with one of the simplest and most cost-effective manufacturing processes
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