A highly sensitive carbon nanotube/graphene/PDMS composite flexible film based on multifunctional stretchable strain sensor for human activity monitoring

In this study, polydimethylsiloxane (PDMS), polydopamine (PDA)-modified graphene nanosheets (PDA@GN), and amino-functionalized multi-walled carbon nanotubes (MWCNT-NH 2 ) were employed as the flexible substrate and conductive layers. A three-dimensional (3D) MWCNT-NH 2 /P@GNs/PDMS flexible strain sensor was fabricated via a straightforward template-transfer approach in conjunction with an economical solution-spraying technique. Firstly, during the preparation process, graphene was modified with dopamine hydrochloride. In combination with MWCNT-NH 2 , a synergistic effect was formed, which helped construct an efficient conductive network and consequently improved the charge transfer efficiency of the membrane film. Subsequently, a 3D structured film was fabricated using a mold to further enhance its conductivity. The 3D structured MWCNT-NH 2 /P@GNs/PDMS strain sensor demonstrated remarkable sensitivity gauge factor (GF) of 1.07 (0% < ε < 40%), 2.53 (40% < ε < 80%), and 4.06 (80% < ε < 120%). Additionally, the film demonstrated outstanding stability and durability over 1000 s, as well as stable strain-sensing performance. The resulting film possessed distinctive properties, such as high tensile strain (up to ∼ 120%), outstanding toughness (tensile strength of about 0.60 MPa), and high sensitivity (GF = 4.06). Furthermore, the film exhibited excellent thermal conductivity due to its enhanced electrical conductivity, reaching a temperature of approximately 163.5 ℃ at 24 V. Finally, the 3D structured MWCNT-NH 2 /P@GNs/PDMS strain sensor demonstrated increased sensitivity in detecting electrical signals from different human motions. These advantages allow the sensor to maintain stability and repeatability under strain, giving it broad application prospects in electronic skin, wearable electronics, and health monitoring.