Strain sensors with high sensitivity, long-term durability, and stretchability are required for flexible and wearable electronic devices. This paper reports a bilayer strain sensor consisting of carboxyl-functionalized carbon nanotubes (CNTs) and ionically crosslinked polysiloxane substrates based on unsaturated acid–amine interactions. Vacuum filtration was adopted to prepare the CNT films (2.74–4.70 μm in thickness) onto the polysiloxane substrates to prepare stretchable conductive strain sensors. The strain sensor exhibited self-healing ability, self-adhesiveness, high sensitivity, linearity, low hysteresis, and long-term durability with a gauge factor of 33.99 at 55% strain. The sensitivity and linearity could be adjusted by the thickness of the CNT layer. A crack-related mechanism was proposed in which increasing the thickness of the CNT layer led to simultaneously enhanced sensitivity and linearity. Finally, we investigated the detection of human activities (bending/unbending of fingers or knees) and subtle motions (coughing and swallowing). The fabricated strain sensor succeeded in meeting various needs with satisfactory sensing performance.

A dicarboxylic acids functional aromatic disulfide (DTSA) and a dimer aliphatic acid (DAA) were used to crosslink epoxidized soybean oil (ESO) to obtain a bio-based epoxy elastomer with comprehensive properties of toughness and stretchability. This work addresses some urgent needs for epoxy networks, such as recyclability, degradability, and mechanical properties. Ratios of permanent and dynamic crosslinks were tuned to yield epoxy elastomers with various characteristics. The biobased epoxy elastomer in this work took advantages of dynamic aromatic disulfide bonds which can rapidly exchange even at room temperature without external stimuli. Therefore, the epoxy elastomer reported here presented almost quantitative self-healing efficiency and high recovery in terms of mechanical properties after being reprocessed for many times. Besides, incorporation of permanent chemical crosslinks with DAA caused low hysteresis, which made them suitable for fabricating sensitive and durable strain sensor against cyclic strain.

Dynamic coordination between aluminum and amines promotes rapid self-healing for polysiloxane elastomers at lower temperature.

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