Thin elastic sheets make surprisingly good wrappers for liquid droplets: surface tension will spontaneously pull an ultrathin sheet around a droplet, all while making efficient use of the sheet. The wrapper can be used for a variety of tasks: it provides a strong barrier for protecting the liquid cargo, it can deform the droplet into predictable shapes, and it provides a platform for adding a chemical pattern. But creating many such droplets requires a rapid and scalable process. A new technique uses droplet impact on a floating polymer film to achieve a tidy wrapping in a fraction of a second. The experiments were carried out by Deepak Kumar and Joseph Paulsen at UMass Amherst, and the results are published here.
Wrinkles are all around us — on hanging curtains, the skin of drying fruit, or a surprised forehead. The more a material is squished, the deeper and taller the wrinkles become, until they collapse into a fold. Typically, this process depends strongly on the materials in question, for example the thickness of the skin, or the softness of the flesh underneath. However, we show that a wrinkle-to-fold transition may be affected only by the shape of the compressed object, rather than by any mechanical properties! Continue reading “Geometry-driven folding in PRL”
The group welcomes postdoctoral researcher Yousra Timounay. Yousra comes from the groups of Florence Rouyer and Elise Lorenceau at the Navier Laboratory in Paris, France. Welcome, Yousra!
The Paulsen Group was recently awarded a “Doctoral New Investigator” grant from the ACS Petroleum Research Fund, for a project titled: “Hyperuniform Dispersal of Non-Brownian Particles in Viscous Liquids”. See a video profile here. Continue reading “Grant from American Chemical Society”
“Curvature-induced stiffness and the spatial variation of wavelength in wrinkled sheets” appeared in PNAS (link). This work proposes and experimentally tests a basic framework for predicting wrinkle wavelengths in curved and/or non-uniform topographies. Continue reading “Wrinkling on curved surfaces in PNAS”