Parallel manipulation of multiple ink droplets via near-infrared light on lubricant infused surface

Previous studies on light-driven droplet transport often use light to heat the substrate to generate a temperature difference, thereby changing the wettability or surface tension at two ends of a droplet, to propel the droplet forward, and not much attention has been paid to the droplets with photothermal properties. Herein, we introduce a method of ink droplet manipulation via near infrared light-driven on lubricant infused surfaces. Rather than heating the substrate itself, this method uses near-infrared light to irradiate one end of an ink droplet, creating a temperature gradient inside it and forming a Marangoni flow that pushes the droplet forward. It is demonstrated that the ink droplets would experience two stages during sliding, and the movement ability of the ink droplets depends on their absorbance and size; specifically, the average acceleration and steady velocity of the droplets are both positively correlated with their absorbance and negatively correlated with their volume. The work not only proves that the method can realize conventional individual droplet manipulation such as controllable transport along arbitrary paths, but also proposes a unique customized transport and merging strategy for multiple ink droplets. This investigation offers a simple and versatile manipulation approach for ink droplets, and the relevant results have potential applications in the fields of precise maneuver of light-driven droplets and droplet-based inkjet printing.