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Found 3 Results

Article

How a water drop removes a particle from a hydrophobic surface

Abhinav Naga, Anke Kaltbeitzel, William SY Wong, Lukas Hauer, Hans-Jürgen Butt, Doris Vollmer

2021Soft Matter17(7)1746-1755

Keywordsdrop, wetting

DisciplinesFluid Mechanics, Physics, Surface Chemistry

CategoriesLaboratory experiments, Theoretical modelling

Scale1e-6 to 1e-3 m / 1e-3 to 1 s, 1 to 60 s

Non-expert summaryThe authors use confocal microscopy to directly image how drops (approx. 1 mm diameter) capture and remove particles (approx. 250 µm diameter) from flat hydrophobic surfaces at a range of speeds (10-500 µm/s). The force acting on the drop during the removal process is also measured by imaging the deflection of a flexible cantilever with a known spring constant. At low speeds (50 µm/s), the particle attaches to the drop/air interface due to surface tension, and the particle is successfully removed. At high speeds (500 µm/s), the particle crosses the interface because surface tension is insufficient to overcome the friction force acting on the particle as it rolls on the surface. Consequently, the particle detaches from the drop and remains on the surface. In both cases, the viscous stress acting on the particle is small compared to surface tension and can be neglected when the liquid is water. These results suggest that two main forces govern the removal of particles from surfaces by drops: surface tension of the drop and friction force between the particle and the surface. These findings will help guide the design of self-cleaning surfaces.

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Article

2. Non-chlorine detergent formulations as an alternative for unpasteurised milk removal from stainless steel surfaces

1. Joels Wilson-Nieuwenhuis, Jim Taylour, Luciana C. Gomes, Stephen Lynch, David Whitehead, Kathryn A. Whitehead

20243. Journal of Food Engineering374112031

DisciplineSurface Chemistry

CategoryLaboratory experiments

Non-expert summaryHygiene is a major concern in the dairy industry, and detergents based on hypochlorite have commonly been utilised for cleaning-in-place (CIP) regimes. However, due to concerns about chlorate residues entering the milk processing chain, new detergent alternatives that are free of chlorate sources are required. This work looked at the cleaning efficacy of two new formulations were developed based on ethylenediaminetetraacetic acid (EDTA) and wetting agents. Stainless steel surfaces were fouled with milk and cleaned once or 10 times using water, a caustic-EDTA product, a sodium hypochlorite product, an acid, or new cleaning formulations (Product A and Product B). The results demonstrated that the use of acid did not result in successful cleaning. The two new products performed well, with Product B performing equivalently during cleaning compared with the established hypochlorite or caustic-EDTA products. Product A exhibited better cleanliness than the other detergents tested. When allergen removal was considered, residual material was found to be retained on the surfaces, regardless of the cleaning type used. This study suggests that the new product formulations may be used to replace hypochlorite-based detergents to increase the hygienic status of a surface.

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Article

Self-cleaning of a hydrophobic surface by a rolling water droplet

Hassan, G., Yilbas, B.S., Al-Sharafi, A., Al-Qahtani, H.

2019Scientific Reports95744

Keywordscleaning, drop, flow displacement, wetting

DisciplinesMechanical Engineering, Surface Chemistry

CategoriesLaboratory experiments, Theoretical modelling

Scale1e-6 to 1e-3 m, 1e-3 m, 1e-3 to 1 m / 1e-3 to 1 s, 1 to 60 s

Non-expert summaryThis is an experimental study of removal of dust particles from a hydrophobic surface by a rolling/sliding water droplet. The effect of surface inclination angle on droplet dynamics and dust removal is analyses and compared with a model. Droplet rolling dominates over sliding. Removal is mainly due to the droplet liquid coating the particles as it passes over the particle, and the removal efficiency is determined by the inclination of the surface.

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