Department of Engineering, Texas A&M University, Corpus Christi, Texas, USA.
Nano Fabrication Center, University of Minnesota, Twin City, Minnesota, USA.
Sci Rep. 2018 May 15;8(1):7612. doi: 10.1038/s41598-018-25812-y.
Texturing a large surface with oily micro-drops with controlled size, shape and volume provides an unprecedented capability in investigating complex interactions of bacteria, cells and interfaces. It has particular implications in understanding key microbial processes involved in remediation of environmental disasters, such as Deepwater Horizon oil spill. This work presents a development of scalable micro-transfer molding to functionalize a substrate with oily drop array to generate a microcosm mimicking bacteria encountering a rising droplet cloud. The volume of each drop within a large "printed" surface can be tuned by varying base geometry and area with characteristic scales from 5 to 50 μm. Contrary to macroscopic counterparts, drops with non-Laplacian shapes, i.e. sharp corners, that appears to violate Young-Laplacian relationship locally, are produced. Although the drop relaxes into a spherical cap with constant mean curvature, the contact line with sharp corners remains pinned. Relaxation times from initial to asymptotic shape require extraordinarily long time (>7 days). We demonstrate that non-Laplacian drops are the direct results of self-pinning of contact line by nanoparticles in the oil. This technique has been applied to study biofilm formation at the oil-water interface and can be readily extended to other colloidal fluids.
用具有可控尺寸、形状和体积的油性微滴对大表面进行纹理处理，为研究细菌、细胞和界面的复杂相互作用提供了前所未有的能力。它在理解涉及环境灾难修复的关键微生物过程方面具有特殊意义，例如深水地平线石油泄漏。本工作提出了一种可扩展的微转移成型技术，用于对基底进行油性滴阵列功能化，以生成模拟细菌遇到上升液滴云的微环境。通过改变基底的几何形状和面积，可以在 5 到 50μm 的特征尺度范围内调整大“打印”表面上每个微滴的体积。与宏观对应物相反，会产生局部违反雅可比-拉普拉斯关系的非拉普拉斯形状的液滴，例如尖角。尽管液滴会松弛成具有恒定平均曲率的球形帽，但具有尖角的接触线仍被固定。从初始到渐近形状的松弛时间需要非常长的时间（>7 天）。我们证明，非拉普拉斯液滴是油中纳米颗粒自固定接触线的直接结果。该技术已应用于研究油水界面处的生物膜形成，并且可以很容易地扩展到其他胶体流体。
