High-Sensitivity Pressure Sensors Using PPy/MWCNTs/PDMS@Melamine Foam for Human Motion Detection on Land and Underwater

Abstract

Flexible pressure sensors with high sensitivity and outstanding mechanical reliability are crucial for human motion detection. In this work, we fabricated a flexible pressure sensor with a bilayer conductive structure using PDMS/MWCNTs@polypyrrol@melamine foam (PMPM). Typically, the construction of extra conductive routes is facilitated by a porous structure to achieve a high sensitivity of 117.61 kPa–1 for pressure in a low detection limit and constant gauge factor (GF) of 6.39 over a linear compression strain range. Furthermore, the polypyrrole particles covering the surface of melamine foam could enhance electron transfer and spatial deformation. And such hierarchical structures can form highly interconnected conductive networks, providing sensitive sensing behavior for a pressure range from 0 to 100 kPa and a strain range from 0 to 60%. Moreover, the PMPM sensor presents superhydrophobicity (CA > 150°) and excellent reliability (∼1200 cycles). The PMPM sensors show good sensing performance in detecting typical human movements, such as bending of joints. The motion detection of human motion underwater without encapsulation is also realized. This work may provide an innovative scheme for accessing the next generation of health and sports monitoring electronics.

Research Progress of Flexible Piezoresistive Sensors Based on Polymer Porous Materials

“…To further improve the stability and reliability of the sensor, Cheng et al first realized the layer-by-layer (LbL) assembly on the MF foam framework by exploiting the electrostatic interaction between polyethylenimine (PEI) and GO, and then chemically reduced the GO to obtain the rGO wrinkled sheets, and then vacuum impregnated with poly(styrene- b -ethylene-butylene- b -styrene) (SEBS) solution (Figure d) to enhance the mechanical elasticity of MF@rGO, and the Young’s modulus reached 4.54 kPa. The introduction of PDMS thin film − onto the MF skeleton can not only improve the mechanical properties of the composite, the stress range reaches 0–1500 kPa, but also stably adhere the conductive materials to the skeleton. As shown in Figure e, MWCNTs and polypyrrol (PPy) form a double-layer conductive structure.…”

“…When an external force is applied, a new conductive path is created, and the resistivity changes significantly. In the stress range of 0–1 kPa, it exhibits an ultrahigh sensitivity of 117.61 kPa –1 , and initial satisfactory results have been obtained.…”

“…Copyright 2022 Elsevier. Panel e reproduced with permission from ref . Copyright 2023 American Chemical Society.…”

Ta4C3 Nanosheet/Melamine Sponges with High Sensitivity and Long-Term Stability for Wearable Piezoresistive Sensors

“…The Ta 4 C 3 nanosheet was prepared by etching an Al atomic layer from the Ta 4 AlC 3 precursor using an etching and intercalation route, as shown in Scheme . In this process, 1 g of Ta 4 AlC 3 precursor was mixed with 20 mL of preconcentrated 45% HF solution and stirred for 120 h at 50 °C to etch the Al atomic layer.…”

“…Sensors based on a melamine matrix with these conductive fillers have demonstrated remarkable sensing performance. For instance, poly­(dimethylsiloxane)/multiwalled carbon nanotubes@polypyrrol@melamine foam achieves a high sensitivity of 117.61 kPa –1 for pressure, with a low detection limit and constant gauge factor of 6.39 over a linear compression strain range . Melamine foam filled with rGO exhibits a sensitivity of 0.108 Pa –1 , a measurement range of 0.013–15 kPa, and rapid response/recovery times (83 and 166 ms) …”