Droplet Spreading Induced Wrinkling and Its Use for Measuring the Elastic Modulus of Polymeric Thin Films

Wrinkling and liquid spreading are ubiquitous phenomena observed in nature and man-made engineering systems. Herein, we unified these two interesting phenomena to manifest a novel dynamic wrinkling phenomenon induced by the spreading of a silicone oil drop on a floating thin film. With the combined experimental validation and verification as well as theoretical formulation, we demonstrated that such a dynamic wrinkling approach can provide a highly valuable platform for providing insightful understandings on the wrinkling behavior through a continuous tracing of the droplet-induced wrinkle patterns in the bendability–confinement morphological phase space, and for offering a simple and inexpensive metrology on measuring the elastic moduli of nanofilms, such as the spin-coated polystyrene thin films and the as-synthesized polydopamine thin films as demonstrated in this work. It is expected that the droplet spreading induced dynamic wrinkling of a thin film can be used not only as a simple and reliable metrology for elastic modulus measurement of thin films but also as an experimental playground for exploring the scientific curiosity of elastocapillarity and the related wrinkling behavior and for developing more valuable applications in the field of soft materials, nanotechnology, and biology.