Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Lab Chip. 2010 Feb 21;10(4):499-504. doi: 10.1039/b917624a. Epub 2009 Dec 1.
A wettability gradient to transport a droplet across superhydrophobic to hydrophilic surfaces is fabricated on combining a structure gradient and a self-assembled-monolayer (SAM) gradient. The combination of these two gradients is realized with a simple but versatile SAM technique, in which the textured silicon wafer strip is placed vertically in a bottle that contains a decyltrichlorosilane solution to form concurrently a saturated SAM below the liquid surface and a wettability gradient above. The platform fabricated in this way has a water-contact angle from 151.2 degrees to 39.7 degrees; the self-transport distance is hence increased significantly to about 9 mm. A theoretical model that approximates the shape of a moving drop to a spheroidal cap is developed to predict the self-transport behavior. Satisfactory agreement is shown for most regions except where the hysteresis effect is unmeasurable and an unsymmetrical deformation occurs. A double-directional gradient surface to alter the direction of movement of a droplet is also realized. The platforms we developed serve not only to transport a fluid over a long distance but also for a broad spectrum of biomedical applications such as protein adsorption, cell adhesion and DNA-based biosensors.
我们通过结构梯度和自组装单分子层（SAM）梯度的结合，制备了一种润湿性梯度，以将液滴从超疏水表面输送到亲水表面。通过一种简单但通用的 SAM 技术来实现这两种梯度的结合，其中将具有纹理的硅片条垂直放置在一个瓶子中，该瓶子中包含癸基三氯硅烷溶液，从而在液体表面下方形成饱和 SAM，并在其上方形成润湿性梯度。以这种方式制造的平台的水接触角从 151.2 度变化到 39.7 度；因此，自传输距离显著增加到约 9 毫米。我们开发了一个理论模型，将移动液滴的形状近似为一个扁球形帽，以预测自传输行为。除了滞后效应不可测量和出现不对称变形的区域外，该模型在大多数区域都显示出了令人满意的一致性。我们还实现了一个用于改变液滴运动方向的双方向梯度表面。我们开发的平台不仅可以远距离输送流体，还可以广泛应用于生物医学领域，如蛋白质吸附、细胞黏附和基于 DNA 的生物传感器。
