Osmosis-driven, non-vascular-plant-inspired soft composites

Even without the aid of muscle, plant tissue drives large, forceful motion via osmosis-driven fluid flow. In this work, we demonstrate that a synthetic, plant tissue analog (PTA) can mimic the closed-cell structure and osmotic actuation of non-vascular plant tissue, enabling the emergence of turgor-pressure-induced stiffness and leading to more forceful swelling deformations. PTAs consist of micron-sized saltwater droplets embedded within thin, highly stretchable, selectively-permeable polydimethylsiloxane PDMS walls. When immersed in water, these PTAs reach a state of equilibrium governed by the initial osmolyte concentration (higher produces more swelling) and cell wall mechanical response (stiffer and less stretchable yields less swelling). These structures represent an alternate class of aqueous, autonomous synthetic materials that, like hydrogels, may be useful in biomedical applications. However, unlike hydrogels, which soften upon swelling, PTA turgor-driven actuation supports much larger loads, even for similar modulus initial states in these highly hydrated classes of soft materials.