Facile Preparation of Durable Photothermal-Responsive PDMS-CB Surfaces for Droplet Manipulation

To address the issues of complex fabrication and poor mechanical stability associated with traditional light-controlled interfaces, we developed a highly durable photothermal surface based on a polydimethylsiloxane (PDMS)-carbon black (CB) composite using spin-coating and laser ablation techniques. Under 600 W/m² illumination, the 3 wt% PDMS-CB surface achieves a rapid photothermal response, reaching 104.7 °C within 150 s. Driven by a localized 0.5 W near-infrared laser, a 10 μL droplet exhibits high-speed transport at 6.53 mm/s. Uniquely, the platform enables flexible, programmable multi-modal maneuvers, including dynamic obstacle avoidance, controlled merging, and induced splitting by presetting the laser spot trajectory. At the same time, the coating surface exhibits excellent durability when subjected to external mechanical damage. Notably, because the photothermal-active CB is uniformly embedded within the durable PDMS matrix rather than superficially coated, the surface maintains reliable actuation performance (4.17 mm/s) even after multiple cyclic actuation experiments. This study provides a simple, robust solution with potential for multifunctional integration for advanced non-contact microfluidic control and lab on chip applications.