Chapter 3 Static and Dynamic Capillarity in Silicon Based Nanochannels

摘要

In this chapter we review the fabrication of silicon based nanochannels and their use in capillarity studies. Static capillarity measurements of the pressure in isolated liquid plugs confined in hydrophilic nanochannels, confirm the existence of capillary negative pressure, quantitatively in accordance with the Young-Laplace equation. The negative pressure can be quantified through measurement of the elasto-capillary deformation of the channel capping due to the pressure difference with the atmospheric pressure. By measuring the capillary filling dynamics in nanochannels of uniform and accurately defined height, different (apparent) viscosity effects in confinement have been revealed. One effect ( visible in insulating sub-100-nm channels) is likely to be related to the influence of the electrical double layer (an electroviscous effect), while the other effect (visible in conductive sub-50 nm channels) seems to be related to a decrease in the effective channel due to a thin immobile layer close to the polar or charged channel wall.