Conductive and Elastomeric rGO@PDMS Piezoresistive Composite for Flexible Strain Sensing Applications: Joint Motion and Breathing Pattern Monitoring
Rodrigo G. Ferreira, Abílio P. Silva, J. Nunes‐Pereira
Abstract
In this work, a piezoresistive strain sensor based on a polydimethylsiloxane (PDMS) doped with reduced graphene oxide (rGO) composite was manufactured with the physical and electromechanical characteristics required for the effective detection of joint movement and breathing pattern monitoring. The samples were prepared via elements of solution casting and solvent casting, followed by the characterization of the piezoresistive effect, its mechanical, morphological, structural, and thermal properties, along with performance testing in volunteer’s body parts. It was possible to observe the influence of the PDMS’ elastomer-cross-linker ratio, cure temperature and time, along with the rGO content in the final performance of the sensor, with the possibility to tune certain characteristics to be better adjusted to specific applications. Samples reinforced with 3, 4, and 5 wt % rGO reached average gauge factors (GF) in the 7.49–14.85, 9.84–30.8, and 0.56–9.16 ranges, respectively, establishing these samples as effective piezoresistive sensors for bioengineering applications. The chosen elastomer-cross-linker was 15:1, cured at a temperature of 120 °C for 20 min, with isopropyl alcohol as the dispersant. The composites with 3 and 5 wt % rGO exhibited good mechanical linearity ( R 2 = 0.995, 0.999, 0.996) and satisfactory piezoresistive performance in the 1.54–2.87% flexural strain range. Stability was present in the 100 cycle 3-point bending tests, the tensile strength varied from 1.05 to 3.084 MPa, the degradation temperature ranged from 380 to 410 °C, as well as the ability to reversibly lose their electrical component prior to the loss of structural integrity, when tensile tested. Lastly, the sensors showed the potential to detect and monitor joint movement and breathing patterns in real-time.