Magnetic alignment of graphite platelets in polyimide matrix toward a flexible electronic substrate with enhanced thermal conductivity

A soft and stable substrate is an essential component for realizing flexible electronics and displays. We fabricated flexible substrate films by compositing iron oxide nanoparticle-conjugated graphite platelets (mGPs) with polyimide (PI). We controlled the microstructure of the composite film by aligning the mGPs with a low magnetic field in the vertical direction during the PI curing process. After magnetic alignment, the through-plane thermal conductivity of the mGP-PI composite film was enhanced by a maximum of 132% with 20 wt% mGP content compared to that without magnetic alignment. The thermal conductivity of the composite film was constant up to 300 degrees C and increased with the filler content, reaching 11.3 W/mK with 60 wt% mGP content. In addition, the coefficient of thermal expansion (CTE) of the composite film along the in-plane direction decreased with increasing filler content, reaching approximately 9 ppm/K with 40 wt% mGP content. This work demonstrates a pathway toward a flexible electronics substrate with high thermal conductivity, high thermal stability, and low CTE.

Automated summary

The study demonstrated a method to enhance the thermal conductivity of flexible substrate films by magnetic alignment of mGPs, providing new possibilities for flexible electronics applications. Additionally, the thermal conductivity and coefficient of thermal expansion of the composite film increased and decreased, respectively, with the filler content, laying a foundation for the preparation of flexible electronics substrates with high thermal conductivity and stability.