Nagelberg Sara, Totz Jan F, Mittasch Matthäus, Sresht Vishnu, Zeininger Lukas, Swager Timothy M, Kreysing Moritz, Kolle Mathias
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2021 Oct 1;127(14):144503. doi: 10.1103/PhysRevLett.127.144503.
Microscale Janus emulsions represent a versatile material platform for dynamic refractive, reflective, and light-emitting optical components. Here, we present a mechanism for droplet actuation that exploits thermocapillarity. Using optically induced thermal gradients, an interfacial tension differential is generated across the surfactant-free internal capillary interface of Janus droplets. The interfacial tension differential causes droplet-internal Marangoni flows and a net torque, resulting in a predictable and controllable reorientation of the droplets. The effect can be quantitatively described with a simple model that balances gravitational and thermal torques. Occurring in small thermal gradients, these optothermally induced Marangoni dynamics represent a promising mechanism for controlling droplet-based micro-optical components.
微尺度Janus乳液是用于动态折射、反射和发光光学元件的通用材料平台。在此，我们提出了一种利用热毛细作用的液滴驱动机制。利用光诱导热梯度，在Janus液滴无表面活性剂的内部毛细界面上产生界面张力差。界面张力差导致液滴内部的马兰戈尼流和净扭矩，从而使液滴产生可预测和可控的重新定向。这种效应可以用一个平衡重力和热扭矩的简单模型进行定量描述。这些光热诱导的马兰戈尼动力学发生在小的热梯度中，是控制基于液滴的微光学元件的一种很有前景的机制。
