Flexible and precise manipulation of droplet transport is of significance for scientific and engineering applications, but real-time and on-demand droplet manipulation remains a challenge. Herein, we report a strategy using light for the outstanding manipulation of binary droplet motion on a high-energy surface and reveal the underlying mechanism. Upon irradiation to a substrate by a focused light beam, the substrate can provide a localized heating source via photothermal conversion, and a binary droplet can be flexibly transported on a high-energy surface with free contact-line pinning, exhibiting light-propelled droplet transport. We theoretically showed that the surface tension gradient across the droplet interface resulting from the localized photothermal effect is responsible for actuating droplet transport. Remarkably, the high reconfigurability and flexibility of light allowed for binary droplet transport with dynamically tunable velocity and direction as well as arbitrary trajectory assisted by 2D channels on a high-energy surface. Complex droplet transportation, controllable droplet coalescence, and anti-gravity motion were realized. The promising applicability of this light-fueled droplet platform was also demonstrated by directional transport of biosample droplets containing DNA molecules and cells, as well as successional microreactions.
Herein, we propose a novel optical strategy for stable water droplet trapping in an immiscible oil phase by using a 1550 nm focused laser beam. Distinct from conventional optical strategies, this approach leverages a local photothermal effect-induced flow field surrounding the water droplet in the oil phase to achieve stable droplet trapping without prolonged interaction between the laser and the water droplet, allowing for low-temperature operation. This feature effectively minimizes potential thermal damage risks and thereby preserves the viability of samples within the droplet, which is particularly promising for biological applications. By analyzing the force balance in vertical and horizontal directions, the trapping sites are predicted, and the results agree well with experimental data. Remarkably, the local photothermal effect-induced flow field imparts rotational momentum to the water droplet, enabling self-rotation of the trapped droplet, which enhances the internal mixing efficiency. This unique feature is demonstrated by the synthesis of gold nanoparticles and E. coli cultivation. This optical strategy allows for highly precise droplet manipulation, eliminating physical contact with solid surfaces, thereby avoiding contamination risks and ensuring lossless transfer. This work presents an innovative optical strategy for droplet trapping in an immiscible phase, holding promise for various applications.
危险品化学品经营许可证（带存储）