ABSTRACT

Capillarity at the nanoscale is referred to as the filling of a fluid into a nanochannel. Similar to the capillarity at the macroscale discussed in Chapter 1, nanoscale capillarity also depends on the surface tension of the fluid and the surface energy of the nanochannel, which determine the contact angle θ of the fluid. If the channel surface energy is high such that θ < 90° (e.g., hydrophilic channels), the surface tension of the concave meniscus of the fluid will pull the fluid into the channel, as illustrated in Figure 5.1a. However, if θ > 90°, a pressure is required to drive the fluid into the channel (Figure 5.1b), which is usually called fluid infiltration.