Soft Material Actuation

Project title: Bio-Inspired Active Skins for Surface Texture Morphing

Source of support: UC San Diego

There has been tremendous interest in optimizing artificial surfaces that can continuously morph their surface texture for various purposes, such as camouflage, signaling, and hunting. In recent years, smart materials like stimuli-responsive polymers and hydrogels were leveraged to achieve surface texture morphing. However, their real-world applications are limited given their slow actuation and weak mechanical properties. Thus, the aim of this research is to broaden the current knowledge of surface texture morphing by designing instability-induced morphable structures using patterned, auxetic geometries. This project introduced 3D-printed and thin-film-like Active Skins based on a star-reentrant geometry, and it was shown that unique patterns of out-of-plane deformations could be induced when uniaxial strains were applied. Moreover, geometrical imperfections or notches were introduced to program the surface morphing behavior of Active Skin in a desired manner. More recently, the geometrical dependence of surface morphing response (i.e., the nonlinear response of 3D-printed Active Skins) was characterized using both experiments and finite element model (FEM) simulations. First, experimentally calibrated FEM simulations were employed to design the unit cell geometries. Second, the locations of geometrical imperfections were judiciously selected according to the desired Active Skin functionality. Last, unit cells with these designed imperfections were replicated by 3D-printing.  Both the experimental and FEM results confirmed that the Active Skins could deploy pre-programmed 3D features on-demand, reversibly, and effectively through a controlled buckling-induced deformation mechanism.  

Peer-Reviewed Publications:

1. Y. Park and K. J. Loh, 2020, “Surface Morphing of Geometrically Patterned Active Skins,” MRS Advances (2059-8521), Cambridge Core, 5(14-15): 743-750. DOI: 10.1557/adv.2020.185 

2. Y. Park, G. Vella, and K. J. Loh, 2019, “Bio-Inspired Active Skins for Surface Morphing,” Scientific Reports (2045-2322), Nature, 9(18609): 1-10. DOI: 10.1038/s41598-019-55163-1