Highly thermally conductive polydimethylsiloxane composites with bidirectional thermal conduction pathways

Constructing ordered thermally conductive pathways within polymer-based composites can optimize heat transfer routes, thereby significantly enhancing the thermal conductivity of the composites. In this work, polydimethylsiloxane (PDMS) was employed as the matrix, while magnetically responsive boron nitride nanosheets (BNNS@Ni) and surface-functionalized gallium-indium liquid metal ( f -LM) were utilized as hybrid thermally conductive fillers to fabricate H-‍BNNS@Ni/ f -LM/PDMS composites with bidirectional thermally conductive pathways in both the in-plane and through-plane directions via magnetic field orientation. At a H-BNNS@Ni to f -LM mass ratio of 4:1 and a total filler loading of 50 wt%, the in-plane thermal conductivity ( λ _∥) and through-plane thermal conductivity ( λ _⊥) of the H-‍BNNS@Ni/ f -LM/PDMS composites reached 6.31 W/(m·K) and 0.98 W/(m·K), corresponding to 33.2 and 9.8 times those of pure PDMS, respectively. The H-BNNS@Ni/ f -LM/PDMS composites also exhibited outstanding thermal stability (thermal resistance index of 261.8^°C), photothermal conversion capability (surface temperature reaching 161.4^°C after 30 s of near-infrared light irradiation at 0.95 W·cm⁻²), and hydrophobicity (water contact angle of 120.0^o), indicating their considerable potential for applications in next-generation flexible electronic devices.