The thermoresistive response of multiwall carbon nanotube (MWCNT)/polymer composites is investigated, focusing on the role of the polymer matrix. This is achieved by experimentally investigating the cyclic thermoresistive response of MWCNT composites with three types of thermo-mechanically dissimilar matrices, viz. a thermosetting (vinyl ester) resin, an engineering thermoplastic (polysulfone), and a commodity thermoplastic (polypropylene). Thermoresistive characterization covered cyclic heating and cooling below (25 °C to −30 °C) and above (25 °C to 100 °C) room temperature. A strong influence of the polymer matrix was found, including different linearity in the response, thermoresistive sensitivity, and hysteresis, depending on the thermo-mechanical properties of the polymer. Polypropylene nanocomposites showed the highest sensitivity and overall lower hysteretic parameters, ascribed to its high coefficient of thermal expansion, low elastic modulus and low glass transition temperature. Polypropylene and polysulfone nanocomposites showed high fidelity in their implementation as thermistors, with readings close to those of a commercial thermistor.

Recent advances in nanomaterials render the possibility of fabricating tactile sensors suitable for electronic skin, haptic interfaces, and biomedical applications. Furthermore, the problem of performing complex inertial measurements generated during the tactile process of polymer composites can be tackled using artificial intelligence (AI). However, the implementation of AI-based signal processing on embedded devices still represents an open area of opportunity for the design of the next generation of smart wearable sensor systems. A novel nanostructured smart tactile sensing system for wearable applications is proposed, using a 3D-printed structure with embedded electronic devices. The highly sensitive piezoresistive tactile sensor is based on multiwall carbon nanotubes/polypropylene (MWCNT/PP) composites. The integration of electronic circuits for signal processing of an artificial neural network on a digital controller unit improve the tactile interpretation in the wearable embedded device. Experiments show that the pressure classification results on MWCNT/PP composites with 98% accuracy.

The electrical and electromechanical responses of ~200 µm thick extruded nanocomposite films comprising of 4 wt.% and 5 wt.% multiwall carbon nanotubes mixed with polypropylene are investigated under an alternating current (AC) and compared to their direct current (DC) response. The AC electrical response to frequency (f) and strain (piezoimpedance) is characterized using two configurations, namely one that promotes resistive dominance (resistive configuration) and the other that promotes the permittivity/capacitive contribution (dielectric configuration). For the resistive configuration, the frequency response indicated a resistive–capacitive (RC) behavior (negative phase angle, θ), with a significant contribution of capacitance for frequencies of 10⁴ Hz and above, depending on the nanotube content. The piezoimpedance characterization in the resistive configuration yielded an increasing impedance modulus (|Z|) and an increasing (negative) value of θ as the strain increased. The piezoimpedance sensitivity at f = 10 kHz was ~30% higher than the corresponding DC piezoresistive sensitivity, yielding a sensitivity factor of 9.9 for |Z| and a higher sensitivity factor (~12.7) for θ. The dielectric configuration enhanced the permittivity contribution to impedance, but it was the least sensitive to strain.