Photomanipulation of a Droplet by the Chromocapillary Effect
Photomanipulation of a Droplet by the Chromocapillary Effect
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DOI：
10.1002/anie.200904868
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发表时间：
2009-01-01
影响因子：
16.6
通讯作者：
Baigl, Damien
中科院分区：
文献类型：
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作者：
Diguet, Antoine;Guillermic, Reine-Marie;Baigl, Damien
对少量液体的操作(驱动、混合和处理)通常依赖于涉及主动(泵和阀)和被动(通道)元件的复杂结构。[1]因此，用光操纵液滴是一种前景光明但具有挑战性的替代方案。实现这一目标的最常见策略是使用具有特定光敏表面属性的固体表面。[2]当液体液滴沉积在此类衬底上时，光的照射会引起润湿性梯度，从而导致液滴的简单低速运动(约30μms±1)。在这里，我们表明，光可以用来在液/液界面上产生依赖于波长的界面张力梯度，从而诱导能够产生液滴在与梯度相反的方向上运动的界面流动。这种现象，即色毛细效应，是通过照射漂浮在水浴中的油滴而获得的，水浴中含有一种表面活性剂，其极性取决于照明波长。首先，液滴的部分照明导致液滴的可逆、波长相关的运动，这可以在几个循环中重复。然后，双色同心照明允许人们建立一个“色毛细管陷阱”，用于操纵液滴沿任何所需形状的轨迹，速度为300ms±1，且精度良好。
Operations (driving, mixing, and handling) with small amounts of liquid usually rely on complex architectures that involve active (pumps and valves) and passive (channels) elements.[1] Manipulation of liquid droplets by light is thus a promising yet challenging alternative. The most common strategy toward this goal uses solid surfaces with specific photosensitive surface properties.[2] When a liquid droplet is deposited on such substrates, illumination by light induces a gradient of wettability to result in simple and low-speed motion (ca. 30 μmsÀ1) of the droplet. Herein we show that light can be used to create a wavelength-dependent interfacial tension gradient at a liquid/liquid interface, thus inducing an interfacial flow that is able to generate droplet motion in the opposite direction to the gradient. This phenomenon, the chromocapillary effect, is obtained by illuminating an oil droplet that floats on a water bath containing a surfactant whose polarity depends on the illumination wavelength. Firstly, the partial illumination of the droplet results in a reversible, wavelength-dependent motion of the droplet that can be repeated over several cycles. Then, a two-color concentric illumination allows one to build a “chromocapillary trap”, which is used to manipulate the droplet along trajectories of any desired shapes, with a speed of 300 μmsÀ1 and good precision.