Wettability and/or shape gradient induced spontaneous droplet motion on solid surfaces

This research investigates the dynamics of spontaneous droplet motion induced by wettability and shape gradients on microscale substrates. The study compares and analyzes the effects of different driving sources, including wettability gradient, shape gradient, and their combination. Findings reveal that the combination of wettability and shape gradients on a wedge-shaped track produces unique droplet motion patterns. Results demonstrate that, despite a slower initial acceleration, the combined driving force on the wedge-shaped track leads to a larger peak velocity compared to tracks with individual gradients. Additionally, the study explores the impact of track end contact angle and wedge angle on droplet motion. It highlights the preference for uniform wettability tracks for faster droplet motion, emphasizing the role of overall contact angle and wetting area. The research concludes that track size influences droplet motion, with larger wedge angles promoting faster and more stable motion. Overall, the study provides valuable insights into controlling and understanding droplet dynamics on structured surfaces.