  Tissue-like materials are required in many robotic systems to improve
human-machine interactions. However, the mechanical properties of living
tissues are difficult to replicate. Synthetic materials are not usually capable
of simultaneously displaying the behaviors of the cellular ensemble and the
extracellular matrix. A particular challenge is identification of a cell-like
synthetic component which is tightly integrated with its matrix and also
responsive to external stimuli at the population level. Here, we demonstrate
that cellular-scale hydrated starch granules, an underexplored component in
materials science, can turn conventional hydrogels into tissue-like materials
when composites are formed. Using several synchrotron-based X-ray techniques,
we reveal the mechanically-induced motion and training dynamics of the starch
granules in the hydrogel matrix. These dynamic behaviors enable multiple
tissue-like properties such as strain-stiffening, anisotropy, mechanical
heterogeneity, programmability, mechanochemistry, impact absorption, and
self-healability. The starch-hydrogel composites can be processed as robotic
skins that maintain these tissue-like characteristics.
