On‐Demand Thermal Transport Modulation with Photoactive Nanofluid

Efficient thermal management is at the core of energy generation and is crucial for modern high-performance electronics. Nanofluids, consisting of metal or inorganic nanoparticles suspended in a base fluid, can significantly enhance thermal transport performance, which is extensively studied for decades. On the other hand, with the growing need for thermal management, it will be desirable to access novel materials with in situ tunable thermal conductivity, allowing programmable delivery of thermal energy on demand. Here, a new type of thermal management material is demonstrated, a photoactive nanofluid, consisting of self-propelling active colloids suspended in a base fluid, where the overall thermal conductivity can be finely controlled through a light-driven chemical reaction. In particular, it is demonstrated that the active nanofluid, formulated with light-propelled colloids, can induce strong local convection, which not only prevents particle sedimentation but also enhances the overall heat transfer by over 100%, thereby allowing for on-demand thermal transport modulation with localized illumination.