Watair从空气中获得水.pptVIP

Watair从空气中获得水 于欣冉 李熵 李勍动 基于对生物表面特殊浸润性的研究基础和对生物表面水收集特性的探索，仔细观察自然界蜘蛛丝上微区水收集行为，发现了几十微米尺度的液滴能够在蜘蛛丝上从一个区域移到另一个区域而展示了运动的方向性，并从微纳米结构层次上揭示了其集水的“多协同效应”机制。 　　在探究中发现，筛孔蜘蛛（Uloborus Walckenaerius）的捕捉丝在遇到雾而润湿时，能由纳米细纤维组成的蓬松“Puff”和链接结构 变成周期的突起结构（称为“Spindle-knot”）和纤细的链接结构（称为“Joint” ）。有趣的是，在Spindle-knot上形成了无序分布的纳米纤维结构，而在Joint上则形成了有序排列的纳米纤维结构。这些结构特性在Spindle-knot和Joint之间形成了表面能量梯度，同时由于曲率梯度还产生拉普拉斯（Laplace）压差 。正是这些微观多结构的耦合，这两个梯度的力协同地作用到小尺度液滴上，使蜘蛛丝能够达成一个连续不断的水凝结，并完成凝结液滴从Joint到Spindle-knot的方向的传输。结果是较大的水滴能够被快速而效率地收集，并稳定地挂在蜘蛛丝上，因而产生超强的水收集能力。这种微纳米结构的多协同力效应，已在初步构建的仿生人造类蜘蛛丝纤维上，实现了小尺度液滴的方向性驱动。　 Many biological surfaces in both the plant and animal kingdom possess unusual structural features at the micro- and nanometre-scale that control their interaction with water and hence wettability1, 2, 3, 4, 5. An intriguing example is provided by desert beetles, which use micrometre-sized patterns of hydrophobic and hydrophilic regions on their backs to capture water from humid air6. As anyone who has admired spider webs adorned with dew drops will appreciate, spider silk is also capable of efficiently collecting water from air. Here we show that the water-collecting ability of the capture silk of the cribellate spider Uloborus walckenaerius is the result of a unique fibre structure that forms after wetting, with the ‘wet-rebuilt’ fibres characterized by periodic spindle-knots made of random nanofibrils and separated by joints made of aligned nanofibrils. These structural features result in a surface energy gradient between the spindle-knots and the joints and also in a difference in Laplace pressure, with both factors acting together to achieve continuous condensation and directional collection of water drops around spindle-knots. Submillimetre-sized liquid drops have been driven by surface energy gradients7, 8, 9 or a difference in Laplace pressure10, but until now neither force on its own has been used to overcome the larger hysteresis effects that make the movement of micrometre-sized drops more dif