Surface contamination with droplets containing bacteria is of concern in the food industry and other environments where hygiene control is essential. Deposition patterns after the drying of contaminated droplets is affected by numerous parameters. The present study evaluated the rate of evaporation and the shape of deposition patterns after the drying of water droplets on a panel of materials with different surface properties (topography, hydrophobicity). The influence of the particle properties (in this study 1 μm-microspheres and two bacterial spores) was also investigated. Polystyrene microspheres were hydrophobic, while Bacillus spores were hydrophilic or hydrophobic, and surrounded by different surface features. In contrast to material topography, hydrophobicity was shown to deeply affect droplet evaporation, with the formation of small, thick deposits with microspheres or hydrophilic spores. Among the particle properties, the spore morphology (size and round/ovoid shape) did not clearly affect the deposition pattern. Conversely, hydrophobic spores aggregated to form clusters, which quickly settled on the materials and either failed to migrate, or only migrated to a slight extent on the surface, resulting in a steady distribution of spores or spore clusters over the whole contaminated area.

Adherent bacteria or spores are known to be highly resistant to many stressful environmental conditions. In view of all the quite different patterns obtained following drying of spore-containing droplets, it seems likely that some of these would entail enhanced resistance to hygienic processes.

在食品工业和其他必须进行卫生控制的环境中，含有细菌的小滴对表面的污染令人关注。干燥受污染的液滴后的沉积方式会受到许多参数的影响。本研究评估了水滴在具有不同表面特性（形貌，疏水性）的一组材料上干燥后的蒸发速率和沉积图案的形状。还研究了颗粒性质（在本研究中为1μm微球和两个细菌孢子）的影响。聚苯乙烯微球是疏水的，而芽孢杆菌孢子是亲水的或疏水的，并被不同的表面特征所包围。与材料形貌相反，疏水性显示出对液滴蒸发的深远影响，形成了带有微球或亲水性孢子的小而厚的沉积物。在颗粒性质中，孢子形态（大小和圆形/卵形）没有明显影响沉积模式。相反，疏水性孢子聚集形成团簇，其迅速沉降在材料上，要么迁移失败，要么仅迁移至表面上的一小部分，导致孢子或孢子簇在整个受污染区域的稳定分布。

已知粘附的细菌或孢子对许多压力环境条件具有高度抗性。考虑到干燥含孢子的液滴之后获得的所有完全不同的模式，其中一些似乎可能需要增强对卫生过程的抵抗力。