目标:自我驱动的行动,像运动一样,是生命的基本特征。今天,激烈的研究集中在液滴运动的动力学。量化宏观运动和探索潜在的机制是至关重要的自我结构和自我修复材料,软机器人技术的进步,自我清洁环境过程的创新,以及制药行业内的进步。通常,诱导宏观运动的驱动力在分子尺度上起作用,使他们的实时和高分辨率的调查具有挑战性。具有高横向分辨率的无标记表面敏感测量可以原位测量分子尺度相互作用和微观运动。
方法:我们使用表面敏感的无标记传感器来研究在硝基苯液滴的自推进运动过程中,在基底表面上三甲基(十八烷基)氮杂氯表面活性剂的自组装单层的动力学变化。表面活性剂在各种浓度下的吸附-解吸,由于移动的有机液滴,并且在液滴访问区域的重建机制都得到了很好的研究,空间,和表面质量密度分辨率。
结果:我们发现了浓度依赖的速度波动,估计表面活性剂分子的吸附量,并在高浓度下显示多层覆盖。油滴微观运动过程中表面活性剂的解吸速率(18.4s-1)是通过原位区分油滴访问区域和非访问区域来确定的。
OBJECTIVE: Self-driven actions, like motion, are fundamental characteristics of life. Today, intense research focuses on the kinetics of droplet motion. Quantifying macroscopic motion and exploring the underlying mechanisms are crucial in self-structuring and self-healing materials, advancements in soft robotics, innovations in self-cleaning environmental processes, and progress within the pharmaceutical industry. Usually, the driving forces inducing macroscopic motion act at the molecular scale, making their real-time and high-resolution investigation challenging. Label-free surface sensitive measurements with high lateral resolution could in situ measure both molecular-scale interactions and microscopic motion.
METHODS: We employ surface-sensitive label-free sensors to investigate the kinetic changes in a self-assembled monolayer of the trimethyl(octadecyl)azanium chloride surfactant on a substrate surface during the self-propelled motion of nitrobenzene droplets. The adsorption-desorption of the surfactant at various concentrations, its removal due to the moving organic droplet, and rebuilding mechanisms at droplet-visited areas are all investigated with excellent time, spatial, and surface mass density resolution.
RESULTS: We discovered concentration dependent velocity fluctuations, estimated the adsorbed amount of surfactant molecules, and revealed multilayer coverage at high concentrations. The desorption rate of surfactant (18.4 s-1) during the microscopic motion of oil droplets was determined by in situ differentiating between droplet visited and non-visited areas.