Department of Mechanical engineering
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1921
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Item Diamond turned hierarchically textured surface for inducing water repellency: Analytical model and experimental investigations(Elsevier, 2021-03) Roy, TribeniFunctional surfaces have gained a lot of interest due to enhancement in water repellency for advanced engineering applications. In the present era, single and multi-level texturing is usually carried out on surfaces for inducing complete water repellency. The role of a hierarchical textured surface for enhancing the contact angle (CA), however, has not been extensively studied and understood. In the present work, the physical interpretation of water droplet activity on a hierarchical textured surface has been studied by the development of a mathematical model taking into account different forces responsible for inducing water repellency. Subsequently, hierarchical textured surface i.e., arrays of major pillars with rectangular sub-micron minor pillars over its top surface, were fabricated with high precision by using a diamond turn machining (DTM) process. The fabricated hierarchical textured surface was investigated based on the structural dimension and static CA. Also, the effects of variation of spacing between major pillars (p), the ratio of spacing between minor pillars to the minor pillar width and ratio of minor pillar to major pillar width with CA were studied. The developed mathematical model was able to predict the water CA with dimensions similar to experimentally fabricated hierarchical textured surface with an error of 6.67%. The model is capable of designing and optimizing the hierarchical textured surface of various sizes, which enables their manufacturing in a cost-effective way.Item Mathematical modelling of superhydrophobic surfaces for determining the correlation between water contact angle and geometrical parameters(Elsevier, 2020-01) Roy, TribeniWater-repellent surfaces have recently become an active area of research due to the desire to achieve self-cleaning, anti-sticking, and non-wetting properties on surfaces. These surfaces are required for different engineering applications. A superhydrophobic (SHP) surface achieves a water contact angle (CA) of 150° or greater. The physical understanding of the process by which surfaces attain superhydrophobicity is still limited, making it difficult to fabricate such surfaces by machining due to the hierarchical scale of the features involved. This work, therefore, aims to shed light on the physical understanding of the behaviour of a water droplet as it rests on a micro textured surface. In the first part of the work, a mathematical model is developed that follows a basic and novel approach of force balance considering a water drop sitting on a surface under static conditions. The various forces responsible for equilibrium are individually evaluated. The model used to describe a surface's interaction with water establishes the relationships between various parameters in the force balance system. From these relationships, the water contact angle (CA) required for superhydrophobicity was found through a simulation. In the second part of this work, arrays of projected micro-features were fabricated on different materials using deep X-Ray lithography (DXRL), micro wire EDM, and the wire wound method. The measured values of the CA on the fabricated surfaces were similar to the values obtained from the model. The proposed model, therefore, helps in designing SHP surfaces (SHSs) on large-scale arrayed micro-features based on several geometrical parameters.