Photophoretic Levitation of Macroscopic Nanocardboard Plates
Photophoretic Levitation of Macroscopic Nanocardboard Plates
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DOI：
10.1002/adma.201906878
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发表时间：
2020-02-20
影响因子：
29.4
通讯作者：
Bargatin, Igor
中科院分区：
文献类型：
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作者：
Cortes, John;Stanczak, Christopher;Bargatin, Igor
由于复杂的电子要求、制造限制以及低雷诺数下粘性阻尼的增加，将微型旋翼机和扑翼飞行器缩小到亚厘米尺寸是具有挑战性的。光泳，或光驱动的流体流动，以前被用来悬浮固体颗粒没有任何移动部件，但只有1-20 μ m的大小。在这里，利用具有50 nm厚度的结构化超材料板来实现毫米至厘米尺度的电泳悬浮。纳米纸板板不是通过传统的转子或机翼产生升力，而是由于通过板内的微通道的光诱导热蒸发而悬浮，这是由于其极低的质量和导热性。在大气压下，通过在板下方产生气垫，板在固体基底上方以约0.5mm的高度悬停。此外，在降低的压力（10-200 Pa）下，通过板的通道的热蒸发的增加的速度产生空气射流，其能够实现空中悬浮并允许板承载比板本身重的小的有效载荷。宏观超材料结构展示了这种新的飞行机制的潜力，以实现纳米技术使飞行器没有任何移动部件在地球的高层大气和其他行星的表面。
Scaling down miniature rotorcraft and flapping-wing flyers to sub-centimeter dimensions is challenging due to complex electronics requirements, manufacturing limitations, and the increase in viscous damping at low Reynolds numbers. Photophoresis, or light-driven fluid flow, was previously used to levitate solid particles without any moving parts, but only with sizes of 1-20 mu m. Here, architected metamaterial plates with 50 nm thickness are leveraged to realize photophoretic levitation at the millimeter to centimeter scales. Instead of creating lift through conventional rotors or wings, the nanocardboard plates levitate due to light-induced thermal transpiration through microchannels within the plates, enabled by their extremely low mass and thermal conductivity. At atmospheric pressure, the plates hover above a solid substrate at heights of approximate to 0.5 mm by creating an air cushion beneath the plate. Moreover, at reduced pressures (10-200 Pa), the increased speed of thermal transpiration through the plate's channels creates an air jet that enables mid-air levitation and allows the plates to carry small payloads heavier than the plates themselves. The macroscopic metamaterial structures demonstrate the potential of this new mechanism of flight to realize nanotechnology-enabled flying vehicles without any moving parts in the Earth's upper atmosphere and at the surface of other planets.