Endoskeletal droplets are a new class of responsive materials consisting of an oil-in-water emulsion with an internal scaffold consisting of soft network of crystalline solids that provides the ability to hold a non-spherical shape. The balance of forces in these metastable structures can be used to trigger reorganization in shape in response to external stimuli. A simple stability model captures the overall responsiveness of the endoskeletal droplets as a function of temperature (mechanics of the crystalline solid skeleton) and surface tension. Next, a more detailed model of the drop mechanics was developed to analyze the shape stability of complex shaped droplets, such as a ball-and-stick. We consider the external (traction) forces acting on the body and the internal reaction forces to maintain mechanical equilibrium. After calculating the principal stresses in the endoskeletal droplet, the von Mises yield criterion is used to predict the droplet stability. The detailed model for instance predicts that the neck region of the ball-and-stick fails first, in agreement with experiments. This model provides a means for engineering endoskeletal drops with geometries tailored for specific mechanical responses.

Mechanics of nonspherical, shape-changing edoskeletal droplets

246th National Meeting (2013)

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