Speaker: Prof. Dr. Peter Fratzl
Max Planck Institute for Colloids and Interfaces, Potsdam
Title: Naturally grown robotic devices
Many plants synthesize materials that actuate with varying humidity in order to provide motility in the context of seed dispersal. These (non-living) shape-changing materials are based on composites of cellulose nanofibrils and a polysaccharide-rich matrix that swell with water uptake. This combination of a swellable matrix and inextensible fibrils provides a predefined actuation, depending on the fiber architecture [1,2]. The energy source for the movement is the interaction of water from the atmosphere with cellulose and other polysaccharides in the cell wall . Such structures can be rationalized through numerical modelling and concepts for actuation systems may be derived from them . More recently, we investigated seed pods from the genus Banksia, in which fire triggers the opening of the woody fruits, followed by humidity-mediated seed release after the passage of fire . The fruits may rest for many years on the plant without being destroyed by predators and microbial disintegration due to a self-sealing wax layer . They withstand the bush fire and shed the seeds when environmental conditions are most favorable for germination. All this happens without the intervention of living cells. In summary, plant seed pods are interesting models for a wide range of small robotic devices that fulfil simple predefined functions in remote locations .
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