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Soft systems that respond to external stimuli, such as heat, magnetic field, and light, find applications in a range of fields including soft robotics, energy harvesting, and biomedicine. However, most of the existing systems exhibit nondirectional, nastic movement as they can neither grow nor sense the direction of stimuli. In this regard, artificial systems are outperformed by organisms capable of directional growth in response to the sense of stimuli or tropic growth. Inspired by tropic growth schemes of plant cells and fungal hyphae, here we report an artificial multistimuli-responsive tropic tip-growing system based on nonsolvent-induced phase separation of polymer solution, where polymer precipitates as its solvent dissolves into surrounding nonsolvent. We provide a theoretical framework to predict the size and velocity of growing precipitates and demonstrate its capability of sensing the directions of gravity, mechanical contact, and light and adjusting its growing direction in response. Exploiting the embedded physical intelligence of sensing and responding to external stimuli, our soft material system achieves multiple tasks including printing 3D structures in a confined space, bypassing mechanical obstacles, and shielded transport of liquids within water. [ABSTRACT FROM AUTHOR]

We propose an optimal cold sink temperature for thermoelectric dehumidifiers based on theoretical and experimental investigations. We show that the optimal condition is such that the latent heat absorption rate per unit power supplied to the dehumidifier is maximized. In consideration of the cooling ability of Peltier pellet and the heat exchange characteristics of the cold sink, we estimate the condensation rate as a function of the cold sink temperature. The theoretical predictions are compared with the results of experiments by using a prototype dehumidifier. We emphasize that the cold sink temperature is a critical parameter that determines the performance of dehumidification. Our study may provide an important insight to the thermoelectric dehumidification system and to designing a cold sink for thermoelectric dehumidifiers with improved energy efficiency. [ABSTRACT FROM AUTHOR]

Fish respire through gills, which have evolved to extract aqueous oxygen. Fish gills consist of filaments with well-ordered lamellar structures, which play a role in maximizing oxygen diffusion. It is interesting that when we anatomically observe the gills of various fish species, gill interlamellar distances (d) vary little among them, despite large variations in body mass (Mb). Noting that the small channels formed by densely packed lamellae cause significant viscous resistance to water flow, we construct and test a model of oxygen transfer rate as a function of the lamellar dimensions and pumping pressure, which allows us to predict the optimal interlamellar distance that maximizes the oxygen transfer rate in the gill. Comparing our theory with biological data supports the hypothesis that fish gills have evolved to form the optimal interlamellar distances for maximizing oxygen transfer. This explains the weak scaling dependence of d on Mb: d ∼ Mb 1/6. [ABSTRACT FROM AUTHOR]