Strong and Highly Conductive Poly(vinyl alcohol)/Carbon Dot/EGaIn Composite Films for Flexible and Transient Electronics

Composite films with comprehensive high tensile strength, great electrical conductivity, and excellent degradable property meet the requirement to serve as flexible and transient electronics; however, integrating these properties together remains to be achieved. In this work, poly(vinyl alcohol) (PVA)–carbon dot (CCD)–EGaIn composite films combining these admirable properties were prepared using nontoxic raw materials and facile cast-dropping methods. In the obtained PVA–CCD–EGaIn composite films, CCD acted as a physical cross-linker to improve the mechanical properties due to the H-bond interactions between PVA and CCD, contributing to an improved tensile strength of 65.0 MPa (relative variation of 22.2%) and a high tensile modulus of 2.24 GPa (relative variation of 96.5%). EGaIn acted as a conductive additive to endow the composite film with a high electrical conductivity (5.35 S/m). The resultant PVA–CCD–EGaIn composite films also demonstrated preferable thermal stability and advantageous photothermal conversion behavior. Moreover, the electrical conductivity of composite films was stable under repeated bending–unbending tests, allowing for the real-time detection of human activities. Interestingly, the composite films were also degradable in a HCl solution (pH = 5), which was an attractive feature for the emerging transient electronics. This work provides a workable guideline for the fabrication of green and economical multifunctional composite materials.