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414 99 Biologically Inspired Engineering: Efficient Evaporation From a Synthetic Leaf K. S. Haaning DTU Physics, Technical University of Denmark INTRODUCTION Chemical separation, such as evaporation, drying and distillation, accounts for 10-15% of the world’s total energy consumption 1. Methods to purify chemicals that are more energy efficient could cut costs and reduce carbon dioxide emissions significantly. Unfortunately, alternative technologies are underdeveloped or expensive to scale up. We propose a completely new system for efficient evaporation inspired by gas exchange through small pores in plant leaves. Our results show that this biomimetic device can achieve gas exchange rates comparable to an open container, although the pores cover only a few percent of the surface area. Implementing the biomimetic membrane in evaporation processes may reduce heat loss, without impeding evaporation rates. BACKGROUND Photosynthesis is a fundamental process to plant life on Earth, converting CO2 to oxygen. Plants utilize small, specialized pores on the surface of their leaves called stomata, to control the exchange of CO2 and oxygen between the interior of the leaf and the atmosphere. This makes these vital structures an important focus of research. There is a striking diversity in the size and density of stomata pores and the overall pattern shows that plants possess either a few large stomata or a numerous collection of smaller stomata. By controlling the number of stomata and the aperture of the stomatal pore the exchange of gas can be regulated. RESULTS In this project we examined the exchange of gas of stomata and used a combination of theory and experiments on 3D printed synthetic leaves, to rationalize the observed changes in stomatal geometry. The synthetic leaf is designed to mimic the diffusive transport through stomata pores. Evaporation experiments on the synthetic leaves showed correlations between stomatal size and density, which are consistent with the hypothesis that plants favor efficient use of space and maximum control of dynamic gas conductivity. With pores covering only a few percent of the surface the evaporation rates were up to 50% of a free surface. The experiments also showed a trend in the stomata distribution. Such trends have previously been used to infer prehistoric atmospheric CO2 content and have surprisingly remained approximately constant over the last 300 million years. Even though these trends are used for such inferences, the physical mechanism and design principles responsible for major trends in stomatal patterning, are not yet understood. CONCLUSION In conclusion, our experiments show that gas exchange rates comparable with the free surface rate can be obtained using a perforated biomimetic membrane with pores covering only a few percent of the surface. Using such biomimetic engineering, chemical separation processes, which account for a significant portion of the world‘s total energy consumption, could be optimized with regards to energy efficiency. 1 Sholl, D. S., & Lively, R. P. (2016). Seven chemical separations to change the world. Nature, 532(7600), 435-437. doi:10.1038/532435a PRODUCTS AND SUSTAINABILITY POSTER IDEA BACHELOR FINAL ASSIGNMENT


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