Dielectrophoretic alignment of Al2O3/PDMS composites: Enhancement of thermal and dielectric properties through structural sedimentation analysis

Abstract Thermally conductive composites have emerged as a promising lead towards a more suitable and efficient alternative for thermal management. Their advantage lies in the coupling of different but complementary properties such as thermal conductivity for heat dissipation and flexibility for fitting surface irregularities. However, such materials consisting of ceramic fillers dispersed in a polymeric matrix generally suffer from particle sedimentation that ultimately affects their performance. Therefore, the overall properties of these composites can be further enhanced through structural improvements. Dielectrophoretic alignment has proven to be an effective and practical method to reach better structures that eventually improve the composites’ properties. This paper focuses on the enhancement of thermal and dielectric properties of Al2O3/PDMS composites through dielectrophoretic alignment. A novel method for measuring sedimentation effects is presented with a particular emphasis on the role of dielectrophoresis in counteracting those undesired effects. The influence of the relevant parameters such as the amplitude and frequency of the applied electric field is analyzed in order to draw the best structuring conditions. The thermal conductivity as well as the dielectric response are then compared between structured and unstructured composites. This comparison revealed a significant structural improvement that led to enhanced thermal conductivities while keeping the insulating properties unchanged.