Flow passing carbon nanotube arrays
Dense arrays of aligned carbon nanotubes are designed into strips, nanowicks, as a miniature wicking element for liquid delivery and potential microfluidic chemical analysis devices. Liquid wicks away along the nanowicks spontaneously. This delivery function of nanowicks enables novel fluid transport devices to run without any power input, moving parts or external pump. Liquid flow formats around and inside a nanowick are described in several flow characteristics such as valley flow, surface flow and interstitial flow. The main course for valley flow and surface flow follows Washburn behavior, and can deliver liquid centimeters away from the input blob with a speed on the order of millimeters per second depending on the nanowick configuration and the amount of input liquid. Interstitial flow dominates the late stage. It is driven by both capillary force and concentration-gradient-induced Marangoni force. The concentration gradient is determined by two competing rates: surfactant diffusion in solution and adsorption onto nanotube surfaces. The flow inside nanowicks may wick hundreds of microns in seconds or tens of seconds. A non-conventional advancing front may develop in the flow around nanowicks. They are seen as (i) Rayleigh instability-induced fingering in surface flow on millimeter-wide nanowicks, (ii) viscous instability-induced branching near almost-stagnant surface film at low surfactant concentration, and (iii) disjointed wetting domains at very low concentration. These instability-induced nonlinear phenomena in flow progression leave characteristic traces in the nanotube arrays. And such traces not only allow liquid diagnosis any time after sampling, but also enable analysis of flow at a nanoscale resolution with scanning electron microscopy.
Ji-jie Zhou M. Gharib Xiao Huang
School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 California Institute of Technology, Pasadena CA91125, USA
国际会议
The 5th International Conference on Nonlinear Mechanics(第五届国际非线性力学会议)
上海
英文
1205-1209
2007-06-11（万方平台首次上网日期，不代表论文的发表时间）