Selective shape-change response by anisotropic endoskeletal droplets

Control of particle shape is of increased interest, as it can broaden the versatility of dispersed material applications. The design of targeted and selective response, such as shape-change, in synthetic materials offers an opportunity to mimic and understand biophysical motion, but also enhance commercial active material delivery. Although solids can experience a wide range of shape-change behavior, soft materials like viscoelastic droplets are also quite versatile, exhibiting shape-change and localized wrapping when triggered by external temperature or stress fields. Here we show, with elastocapillary concepts, that viscoelastic droplets can self-trigger shape-change and wrapping behavior in response to physical contact with targets below a threshold curvature. The model is in good agreement with experimental data on interactions between rod-shaped endoskeletal droplets and cylindrical targets of varying curvature. The concept of a pre-programmed physical sensing and response by simple, soft material shapes is explored and used to suggest additional applications and more complex applied modeling, shape designs, and responses.