Wetting of dehydrated Pseudomonas fluorescens biofilms grown on glass substrates by an external liquid is employed as a means to investigate the complex morphology of these biofilms along with their capability to interact with external fluids. The porous structure left behind after dehydration induces interesting droplet spreading on the external surface and imbibition into pores upon wetting. Static contact angles and volume loss by imbibition measured right upon droplet deposition indicate that biofilms of higher incubation times show a higher porosity and effective hydrophilicity. Furthermore, during subsequent rotation tests, using Kerberos device, these properties dictate a peculiar forced wetting/spreading behavior. As rotation speed increases a long liquid tail forms progressively at the rear part of the droplet, which stays pinned at all times, while only the front part of the droplet depins and spreads. Interestingly, the experimentally determined retention force for the onset of droplet sliding on biofilm external surface is lower than that on pure glass. An effort is made to describe such complex forced wetting phenomena by presenting apparent contact angles, droplet length, droplet shape contours, and edges position as obtained from detailed image analysis.

中文翻译：

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脱水亲水性荧光假单胞菌生物膜在外力作用下的润湿

脱水荧光假单胞菌的润湿通过外部液体在玻璃基板上生长的生物膜被用作研究这些生物膜的复杂形态及其与外部流体相互作用的能力的手段。脱水后留下的多孔结构导致有趣的液滴在外表面扩散并在润湿时吸入孔隙。在液滴沉积时测量的静态接触角和吸液体积损失表明，孵育时间较长的生物膜显示出较高的孔隙率和有效的亲水性。此外，在随后的旋转测试中，使用 Kerberos 设备，这些特性决定了一种特殊的强制润湿/铺展行为。随着旋转速度的增加，在液滴的后部逐渐形成一条长长的液体尾部，始终保持固定状态，而只有液滴的前部脱落和扩散。有趣的是，实验确定的液滴在生物膜外表面上滑动的保持力低于纯玻璃。通过呈现从详细图像分析中获得的表观接触角、液滴长度、液滴形状轮廓和边缘位置，努力描述这种复杂的强制润湿现象。