Construct a 3D skeleton by bridging graphene nanosheets with soft liquid metal to enhance thermal conductivity of flexible PDMS matrix composites

Constructing continuous three-dimensional (3D) thermally conductive pathways within the polymer matrix has emerged as a promising strategy to enhance the thermal conductivity of composites. However, the potential benefits of these 3D thermally conductive networks in improving the thermal conductivity performance of composites remain largely unexploited due to significant thermal resistance at the polymer-filler and filler-filler interfaces. Herein, based on the bridging effect during the powder compaction process, flowable liquid metal (LM) and graphene nanoplatelets (GNPs) were selected as thermally conductive fillers. A 3D interconnected polydimethylsiloxane/GNPs/LM (PDMS/GNPs/LM) foam scaffold was fabricated using the salt-template-assisted method, followed by the preparation of corresponding PDMS/GNPs/LM composites through PDMS impregnation and thermal pressure curing. Benefiting from the unique flowability of LM, it infiltrates the gaps between adjacent GNPs during the thermal pressing process, thereby increasing the contact area between fillers and reducing the interfacial resistance at the polymer-filler and filler-filler interfaces. At GNPs and LM loadings of 4.4 wt% and 9.2 wt%, respectively, the thermal conductivity of the PDMS/GNPs/LM composite reaches a value of 1.86 W m −1  K −1 , representing a 322.7 % increase compared to pure PDMS. Finite element simulations confirmed that the bridging effect of LM between adjacent GNPs significantly enhances the heat transfer efficiency of the composite. Furthermore, the composite exhibits outstanding mechanical flexibility, high-sensitivity sensing performance, and excellent hydrophobic properties. This research presents a straightforward and widely applicable method for preparing highly thermally conductive and multifunctional PDMS-based flexible thermal management materials.