Tunable Nanoengineered Surfaces for Microfluidics and Energy
报告人:
Evelyn Wang
Prof. Evelyn Wang Department of Mechanical Engineering MIT
报告时间:
2009-06-18 10:00
报告地点:
精密仪器系四楼大会议室
主办单位:
精仪系
简介:
ABSTRACT: Developing and utilizing nanostructures to control fluidic behavior has attracted significant interest for a variety of applications including thermal management, energy, and lab-on-a-chip. In particular, such nanostructures can be used to create superhydrophobic, superhydrophilic, and tunable surfaces for droplet/bubble manipulation and liquid spreading. In this presentation, we will describe work on both spreading on superhydrophilic surfaces and droplet manipulation on superhydrophobic surfaces. We fabricated silicon nanopillars ranging from 200 nm to 800 nm in diameter. For the superhydrophilic surfaces, we experimentally characterized liquid spreading on the nanostructures using diffraction limited microscopy and with an environmental scanning electron micrograph. We observed a multi-layer spreading effect and directional spreading due to the geometry of the nanostructures. Simultaneously, we developed an energy-based model to understand the effect of pillar spacing, height, and diameter on liquid behavior. For superhydrophobic surfaces, we coated the nanostructures with a silane chemistry to achieve contact angles greater than 150 degrees with water droplets. We investigated the ability to dynamically control fluid-nanostructure interactions via voltage and current modulation. We demonstrated reversible droplet manipulation from a non-wetted state (>90 degrees) to a wetted state (<90 degrees) by electrowetting with a voltage applied across the droplet, and heating with a short pulse of current through the nanostructured substrate. The mechanism associated with the droplet reversibility was investigated with experimental techniques including high-speed imaging and infrared thermometry, and with model development.
