Quantitative Probing of Strain-Robust Thermal Transport in Interfacially Engineered Graphene Oxide/Silk Fibroin...

For the reliable design of flexible and wearable devices, it is important to understand the effect of mechanical deformation on thermal transport in the constituent materials. Here, a scanning thermal microscopy (SThM) bending test is proposed for the quantitative evaluation of the in-plane thermal conductivity of suspended bionanofilms through controlled bending deflection. Graphene oxide (GO)/silk fibroin (SF) and water-vapor-annealed GO/SF bionanofilms (thickness: ∼40 nm) are examined to understand the role of interfacial interactions in bending-dependent thermal transport. In the bending test, changes in the in-plane thermal conductivity are evaluated by systematically comparing SThM probe signals under contact and noncontact conditions; such a comparison helps separate solid heat conduction through the bionanofilm from the background heat transfer. This approach can facilitate a quantitative analysis of bending-induced thermal conductivity changes. At a bending deflection of 50 nm, the normalized thermal conductivity retention of the water-vapor-annealed bionanofilm was 97.7%, while that of the unannealed bionanofilm was 90.6%. Furthermore, the thermal degradation rate of the annealed film was lower by 75.1% (0.47 vs 1.89 × 10-3 nm-1). This improved stability is attributed to annealing-enhanced interfacial coupling, which suppresses phonon scattering and promotes continuous in-plane heat transport through silk fibroin bridging. These results demonstrate the influence of mechanical deformation on thermal conductivity in flexible nanocomposites and offer practical design guidelines for flexible electronics, wearable sensors, and bendable thermal management materials.