Mandsberg Nikolaj Kofoed, Hansen Ole, Taboryski Rafael
Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark.
Sci Rep. 2017 Oct 6;7(1):12794. doi: 10.1038/s41598-017-12658-z.
Droplet array chips were realized using an alignment-free fabrication process in silicon. The chips were textured with a homogeneous nano-scale surface roughness but were partially covered with a self-assembled monolayer of perfluorodecyltrichlorosilane (FDTS), resulting in a super-biphilic surface. When submerged in water and withdrawn again, microliter sized droplets are formed due to pinning of water on the hydrophilic spots. The entrained droplet volumes were investigated under variation of spot size and withdrawal velocity. Two regimes of droplet formation were revealed: at low speeds, the droplet volume achieved finite values even for vanishing speeds, while at higher speeds the volume was governed by fluid inertia. A simple 2D boundary layer model describes the behavior at high speeds well. Entrained droplet volume could be altered, post-fabrication, by more than a factor of 15, which opens up for more applications of the dip-coating technique due to the significant increase in versatility of the micro-droplet array platform.
液滴阵列芯片是通过硅中的无对准制造工艺实现的。芯片具有均匀的纳米级表面粗糙度纹理，但部分覆盖有全氟癸基三氯硅烷（FDTS）的自组装单分子层，从而形成超双亲表面。当浸入水中并再次取出时，由于水在亲水性斑点上的钉扎作用，会形成微升大小的液滴。在斑点尺寸和取出速度变化的情况下，对夹带的液滴体积进行了研究。揭示了两种液滴形成机制：在低速时，即使速度为零液滴体积也能达到有限值，而在高速时体积则受流体惯性支配。一个简单的二维边界层模型能很好地描述高速时的行为。制造后，夹带的液滴体积可以改变超过15倍，这由于微滴阵列平台多功能性的显著增加，为浸涂技术开辟了更多应用领域。
