Lee Minki, Lim Hosub, Lee Jinkee
School of Mechanical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea.
Sci Rep. 2017 Nov 7;7(1):14735. doi: 10.1038/s41598-017-15275-y.
Plants transport water from roots to leaves via xylem through transpiration, which is an evaporation process that occurs at the leaves. During transpiration, suction pressure is generated by the porous structure of mesophyll cells in the leaves. Here, we fabricate artificial leaf consisting of micro and nano hierarchy structures similar to the mesophyll cells and veins of a leaf using cryo-gel method. We show that the microchannels in agarose gel greatly decrease the flow resistance in dye diffusion and permeability experiments. Capillary tube and silicone oil are used for measuring the suction pressure of the artificial leaf. We maintain low humidity (20%) condition for measuring suction pressure that is limited by Laplace pressure, which is smaller than the water potential of air followed by the Kelvin-Laplace relation. Suction pressure of the artificial leaf is maximized by changing physical conditions, e.g., pore size, wettability of the structure. We change the agarose gel's concentration to decrease the pore size down to 200 nm and add the titanium nano particles to increase the wettability by changing contact angle from 63.6° to 49.4°. As a result, the measured suction pressure of the artificial leaf can be as large as 7.9 kPa.
植物通过蒸腾作用经木质部将水从根部输送到叶片，蒸腾作用是发生在叶片上的一个蒸发过程。在蒸腾过程中，叶片中叶肉细胞的多孔结构会产生吸力。在此，我们采用冷冻凝胶法制造了由类似于叶片叶肉细胞和叶脉的微米和纳米层次结构组成的人造叶片。我们表明，琼脂糖凝胶中的微通道在染料扩散和渗透性实验中极大地降低了流动阻力。毛细管和硅油用于测量人造叶片的吸力。我们在低湿度（20%）条件下测量受拉普拉斯压力限制的吸力，根据开尔文 - 拉普拉斯关系，该压力小于空气的水势。通过改变物理条件，例如孔径、结构的润湿性，可使人造叶片的吸力最大化。我们改变琼脂糖凝胶的浓度将孔径减小至200纳米，并添加钛纳米颗粒，通过将接触角从63.6°变为49.4°来提高润湿性。结果，人造叶片测得的吸力可高达7.9千帕。
