Microstructured hybrid nanocomposite flexible piezoresistive sensor and its sensitivity analysis by mechanical finite-element simulation

The flexible piezoresistive sensor is the key component used to obtain human biological information via wearable electronic systems, and forms the basis of this technology. In order to improve the sensitivity, stability, and simplicity of the flexible piezoresistive sensor, this study innovatively prepared multi-walled carbon nanotube/silver nanowire/polyurethane (MWNT/AgNW/PU) films whose surface had a one-dimensional cube microstructure by using a mixed solution template method, and integrated the resulting microstructured hybrid nanocomposite films (MNFs) with a single-sided interdigital copper electrode. Meanwhile, mechanical finite-element models of MNF were constructed to study the influence of the structure parameters on the response sensitivity. The piezoresistive experiment results show that, within a pressure range of 0-2 kPa, the sensitivity of the sensor is as high as 42.6 kPa^-1. Moreover, with the hybridization of MWNTs and AgNW, the mechanical stability, linearity, and hysteresis of the sensor have been significantly improved. The hysteresis error and nonlinear error of sensors with 5 wt% MWNTs and 5 wt% AgNWs can be as low as ±4.15% and ±12.5%, respectively, which is 93.24% and 78.93% lower compared with MWNTs/PU. The simulation experiments show that the contact area of the MNF and the single-sided electrode has a negative correlation with the piezoresistive sensitivity of the sensors. Furthermore, the prepared flexible piezoresistive sensor is used for human body physiological signal monitoring. It provides the possibility of expanding and optimizing the application of flexible sensors in electronic skin, wearable health monitor devices, smart textiles, clothing, and so on.