考虑完全开放的微管道中液体输运不稳定, 不利于生物气溶胶采样和监测的自动化集成, 本文提出了用覆盖有疏水网的开放微管道来实现液体的可靠输运。通过理论分析得到了该微管道液体输运特性的估计公式, 并用水作为试验介质对其输运特性进行了实验分析。分析实验显示, 开放微管道中液体输运的稳定性依赖于栅网特性、液体性质和流动速度、管道尺寸和表面特性。栅网表面疏水性越好, 孔径越小, 微管道中液体的最大许可压强就越大, 液体输运就会越稳定。对于孔径50 μm、表面涂覆有Teflon的栅网, 最大许可压强可达2 000 Pa。管道中的最大许可流速取决于管道尺寸和最大许可压强; 对于较浅、较长的管道, 最大许可流速较小。当液体流过干的疏水管道时, 液体的表面张力会阻碍流动, 管道截面尺寸越小, 表面张力的阻碍效果越明显。

Because unstable transportation of the fluid in an open microchannel restrains the integration of sampling and detection for bioaerosols, this paper proposes an open microchannel covered with a hydrophobic mesh to transport water in stability. On the basis of theoretical calculation, it gives a estimation formula of fluid transportation characteristics for the open microchannel and analyzes experimentally the fluid transportation characteristics by taking the water as transported media. The results in analysis and experiments demonstrate that the stability is dependent on the mesh properties and flow velocity, and is sensitive to the geometric parameters and the surface properties of the microchannel. The more hydrophobic the mesh is and the smaller the mesh holes are, the higher the maximum allowable pressure in the microchannel is and thus the water transportation is more stable. For a Teflon-coated mesh with a hole size of 50 μm, the maximum allowable pressure is up to about 2 000 Pa. Furthermore, the maximum allowable flow velocity in the channel is determined by the channel geometric parameters and the maximum allowable pressure of the mesh film. The maximum allowable velocity decreases with the decreasing height and increasing length of the microchannel. For a hydrophobic channel, the capillary pressure originated from the surface tension deteriorates the stability of the water transportation, and the adverse effect is more significant in a smaller channel.