Scalable Fabrication of Height‐Variable Microstructures with a Revised Wetting Model

Varying the height of microstructures is crucial for tuning surface properties such as wettability, adhesion, and optical characteristics, which are essential in applications from microfluidics to biosensing. However, conventional techniques for fabricating height‐variable microstructures are often costly and labor‐intensive, involving multiple intricate steps. Herein, an innovative, rapid, and cost‐effective approach using CO 2 laser‐machined poly (methyl methacrylate) (PMMA) molds to produce height‐variable microstructures in polydimethylsiloxane (PDMS) is introduced. The method leverages varying laser fluence to precisely control feature depth on PMMA substrates, creating high‐fidelity negative molds without requiring surface chemical modifications. The applicability of Cassie–Baxter and Wenzel equations to height‐variable microstructures is systematically investigated. To this aim, six sharkskin surfaces with controlled height gradients are fabricated and their wettability behavior is studied. Results show pronounced anisotropic hydrophobicity, with variations in contact angles and sliding angles in one direction depending on height‐induced curvature effects. These conclusions establish that classical wetting models neglect to consider fully the effect of height gradients on droplet behavior. By proposing a modified equation that includes the variable contact plane curvature according to heights, the prediction validity of wettability onto structured surfaces is enhanced. These insights provide a fundamental understanding of wetting behavior on height‐variable microstructures.