Microsystems Technology Group, School of Engineering & Computing Sciences, Durham University , Durham DH1 3LE, U.K.
Smart Materials and Surfaces Lab, Faculty of Engineering and Environment, Northumbria University , Newcastle upon Tyne NE1 8ST, U.K.
ACS Appl Mater Interfaces. 2016 Aug 31;8(34):22658-63. doi: 10.1021/acsami.6b06738. Epub 2016 Aug 16.
An energy saving Leidenfrost levitation method is introduced to transport microdroplets with virtually frictionless contact between the liquid and solid substrate. Through microengineering of the heating units, selective areas of the whole substrate can be electrothermally activated. A droplet can be levitated as a result of the Leidenfrost effect and further transported when the substrate is tilted slightly. Selective electroheating produces a uniform temperature distribution on the heating units within 1 s in response to a triggering voltage. Alongside these experimental observations, finite element simulations were conducted to understand the role of substrate thermal conductivity on the temperature profile of the selectively heated substrate. We also generated phase diagrams to verify the Leidenfrost regime for different substrate materials. Finally, we demonstrated the possibility of controlling low friction high speed droplet transportation (∼65 mm/s) when the substrate is tilted (∼7°) by structurally designing the substrate. This work establishes the basis for an entirely new approach to droplet microfluidics.
介绍了一种节能莱顿弗罗斯特悬浮方法，可实现微液滴与固体基底之间几乎无摩擦的接触运输。通过对加热单元进行微工程设计，可以对整个基底的选择区域进行电热激活。由于莱顿弗罗斯特效应，液滴可以被悬浮，并且当基底稍微倾斜时可以进一步运输。选择性加热在 1 秒内响应触发电压产生加热单元上的均匀温度分布。除了这些实验观察之外，还进行了有限元模拟以了解基底热导率对选择性加热基底的温度分布的作用。我们还生成了相图来验证不同基底材料的莱顿弗罗斯特状态。最后，我们通过结构设计基底证明了当基底倾斜（约 7°）时控制低摩擦高速液滴运输（约 65mm/s）的可能性。这项工作为全新的液滴微流控方法奠定了基础。
