Recently, flexible wearable electronic devices have attracted immense interest as an alternative for conventional rigid metallic conductors in personal healthcare monitoring, human motion detection, and sensory skins, owing to their intrinsic characteristics. However, the practical applications of most wearable sensors are generally limited by their poor stretchability and sensitivity, unsatisfactory strength, lower conductivity, and single sensory function. Here a hydrogen bond cross‐linked network based on carboxylic styrene butadiene rubber (XSBR) and hydrophilic sericin (SS) non‐covalently modified carbon nanotubes (CNTs) is rationally designed and then fabricated into multi‐functional sensors. The resultant versatile sensors are able to detect both weak and large deformations, which owns a low detection limit of 1% strain, high stretchability up to 217%, superior strength of 12.58 MPa, high sensitivity with a gauge factor up to 25.98, high conductivity of 0.071 S m−1, and lower percolation threshold of 0.504 wt%. Moreover, the prepared sensors also possess an impressively thermal response (0.01636 °C−1) and realize the application in the measurement of human body temperature. The multifunctional and scalable XSBR/SSCNT sensor with the integrated tracking capabilities of real‐time and in situ physiological signals, providing a promising route to develop wearable artificial intelligence in human health and sporting applications.
Self-healing based
on noncovalent bonds and mechanical strengthening
based on fillers are contradictions for commercial rubbers. To solve
this problem, in this paper, we constructed a hydrogen bonding supramolecular
hybrid network by incorporating carboxymethyl chitosan (CMCS) into
epoxidized natural rubber (ENR) through a solution-mixing method.
The regenerated CMCS with multiple hydrophilic groups formed hydrogen
bonding interactions with ENR chains, which served as multifunctional
linkages to construct the supramolecular hybrid network. In this way,
the regenerated CMCS belonged to the hydrogen bonding healing system
and simultaneously improved the mechanical properties of the ENR/CMCS
composites. The dispersion, structure of regenerated CMCS, and formation
of the hydrogen bonding supramolecular hybrid network in the ENR/CMCS
composites were studied and confirmed by Fourier-transform infrared
spectroscopy, scanning electron microscopy, transmission electron
microscopy, differential scanning calorimetry, X-ray diffraction,
dynamic mechanical analysis, and equilibrium swelling experiment.
It was found that the ENR with 5 and 10 wt % CMCS possessed improved
tensile strengths of 1.40 and 1.92 MPa, respectively, and simultaneously
exhibited considerable self-healing efficiency of about 90% (room
temperature, healing 12 h). When the CMCS content exceeded 10 wt %,
although the mechanical property increased continuously, the self-healing
effect decreased significantly because of the unavoidable negative
effect of filler restriction. The dynamic nature of hydrogen bonding
interactions facilitated the rearrangement of the supramolecular hybrid
network, which endowed ENR/CMCS composites with derived recycling
capacity. However, the mechanical properties are reduced after multi-recycling.
With the development
of artificial intelligence,
people are not satisfied with the traditional conductive materials
and tend to focus on stretchable and flexible electronic systems.
Flexible conductive rubbers have great potential applications in wearable
strain sensors. However, the rapid propagation of bacteria during
the use of wearable sensors may be an ineluctable threat to humans’
health. Herein, a conductive rubber film is fabricated based on carboxylic
styrene–butadiene rubber (XSBR), citric acid (CA), and silver
nitrate (AgNO3) via a convenient approach,
where Ag nanoparticles (Ag NPs) are in situ reduced
without sintering at elevated temperatures. The resultant films exhibit
many desirable and impressive features, such as strengthened mechanical
properties, flexibility, and conductivity. More importantly, the Ag
NP flexible conductive films exhibit excellent antibacterial activity
against Escherichia coli (Gram-negative
bacteria) and Staphylococcus aureus (Gram-positive bacteria), which have potential applications as flexible
antibacterial materials to monitor movements of the human body in
real time. Also, because of the hygroscopicity of CA, the resistance
of our conductive film is sensitive to various humidities, which can
be applied in the humidity sensor.
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