Flexible Superamphiphobic Film with a 3D Conductive Network for Wearable Strain Sensors in Humid Conditions

Abstract

A three-dimensional (3D) conductive network with high sensitivity and a wide response range is applicable for wearable strain sensors. However, structural deformation of the 3D network under mechanical stimuli gives rise to mass pores, which are easily soaked by rain, sweat, oil, and so on, thus affecting the sensitivity of the sensors. Herein, a stretchable film with outstanding superhydrophobicity is proposed for reliable strain sensors based on a 3D conductive network. First, superconductive carbon black (SCB) nanoparticles are assembled on electrospun fibers of thermoplastic polyurethane (TPU) to form a TPU/SCB conductive film. Then, a dispersion of carbon nanotubes (CNTs) and fluorinated silica (F-SiO2) is sprayed on the TPU/SCB film to form a conductive TPU/SCB@CNTs/F-SiO2 composite film. After immersion of the composite film in a mixed solution of poly­(dimethylsiloxane) (PDMS) and perfluorodecyltrichlorosilane (PFDTS) and drying, a flexible conductive superamphiphobic film was obtained. When the film was used as a strain sensor, it showed superior sensitivity (12.05–60.42), a wide strain range (0–100%), a fast response time (75–100 ms), and good stability in stretching–relaxing cycles. Benefiting from the favorable superamphiphobicity, the obtained strain sensor could be effectively utilized to display stable electrical signals underwater and monitor human motions under dry/sweat exposure, showing significant potential in practical wearable sensors for stretchable, breathable, and reliable human behavior monitoring.

Fabrication of a Superhydrophobic Conductive Porous Film with Water-Resistance for Wearable Sensors

“…After ultrasonic treatment, the CB nanoparticle could uniformly adhere to surface of TPU fibers. The ultrasonication, as the driving force, promoted the CB nanoparticles assembly into the TPU fibers, which was due to the interfacial collision between CB and the TPU nanofibers with sufficient viscoelasticity. , The PEI adhesive between the CB and TPU macromolecules further facilitated the decorative CB on the TPU nanofibers. After constructing the CB network, the TPU/CB film was added into the PFDTES solution to enable the hydrophobic C–F bonds of PFDTES on the TPU/CB fibers to form a superhydrophobic surface. ,− The PFDTES was stored in a porous network of the TPU/CB film via physical absorption, which gave the superhydrophobic surface self-healing ability. − The PFDTES superhydrophobic layer made CB conductive network with high conductivity, and these conductive nanofibers with large aspect ratio provided a stretchable conductive network.…”

“…The ultrasonication, as the driving force, promoted the CB nanoparticles assembly into the TPU fibers, which was due to the interfacial collision between CB and the TPU nanofibers with sufficient viscoelasticity. 23,24 The PEI adhesive between the CB and TPU macromolecules further facilitated the decorative CB on the TPU nanofibers. After constructing the CB network, the TPU/CB film was added into the PFDTES solution to enable the hydrophobic C−F bonds of PFDTES on the TPU/CB fibers to form a superhydrophobic surface.…”

Engineering Design, Implementation, and Sensing Mechanisms of Wearable Bioelectronic Sensors in Clinical Settings

“…As a strain sensor, the film demonstrated exceptional sensitivity of 12.05 to 60.42, a broad strain range of 0-100 %, and a rapid, responsive time of 75 to 100 ms with excellent stability in stretching-relaxing sessions. The designed strain sensor can effectively display consistent electrical impulses underwater and track human movements during dry/wet exposure, demonstrating substantial promise in practical wearable devices for breathable and reliable human activity monitoring [91]. Later, Lin et al proposed the design of a wearable multifunctional CNTsbased wearable sensing device with a broad range of sensitivity and flexibility for tracking user temperature and mobility.…”

Stretchable Polyaniline@Epoxidized Natural Rubber Composites with Strong 3D Conductive Networks for High Performance Strain Sensors

“…The construction of strong 3D conductive networks is beneficial for enhancing the electrical and electromechanical performances of composites. It is an attractive strategy for improving the working range and long-term stability of strain sensors, while electrostatic spinning [24][25][26][27] and 3D printing [28][29][30] are the main technical tools. For instance, Ma et al [31] used 3D printing to construct stretchable graphene conductive networks.…”