Better explicating the strengths and shortcomings of these models will help refine projections and improve transparency in the years ahead.
Image credit: Witsawat.S.
Edited by Andrea Prosperetti, Johns Hopkins University, Baltimore, MD, and accepted by the Editorial Board January 10, 2012 (received for review September 19, 2010)
Article Figures & SI
Figures
- Fig. 1.
Transparent nanochannel device. (A) A bonded nanochannel device with reservoirs on top. Each device includes two microchannels and four reservoirs. Microchannels are 1-cm long, 500-μm wide, and 40-μm deep. Reservoirs are through-holes with 1-mm diameter. (B) Zoom-in image of the nine sets of staggered nanochannels. Only one set of nanochannels is bridging to the two microchannels. These bridging nanochannels were used to measure channel height, whereas nonbridging nanochannels were used for cavitation experiments. (C) Zoom-in image of a set of nonbridging nanochannels with two ends in the same microchannel. Each set consists of 10 120-μm-long, 4-μm-wide silica nanochannels.
- Fig. 2.
Cavitations in 58-nm nanochannels. Instead of menisci recession, vapor bubbles occurred at the left entrance and two menisci were pinned at the entrances. Bubbles then moved toward the center of the channel and started expansion. There are two symmetric stationary positions in each channel that bubbles prefer to stay.
- Fig. 3.
Nanochannel cross-sectional images along the channel length direction. (A) Top view image of a set of nanochannels. The first nanochannel was “cut” by dry etching method for SEM cross-section (see SI Appendix). (B) SEM cross-sectional images of the nanochannel at the right end, center, and left end. (C) Height change along channel length direction. The maximum height difference is 22 nm.
- Fig. 4.
Vapor bubble growth rate in the presence of cavitation. (A) Total vapor bubble length (water evaporation length) as a function of time in 20-nm nanochannel with/without cavitation. Unlike normal evaporation where
, evaporation with cavitation follows L ∝ t, leading to a significant increase in evaporation rate. (B) Total vapor bubble length (water evaporation length) as a function of time in 20-, 41-, and 105-nm-deep nanochannels. Vapor bubbles always expand linearly with time, which is significantly different from vapor bubble growth in confined microchannels (13). (C) Experimental results as well as theoretical predictions of bubble growth rate in nanochannels with heights from 20 to 120 nm. Bubble growth rate decreases as the nanochannel height increases. Each experimental point represents the average growth rate in five nanochannels. The standard deviation is within 4% of the mean value, which is similar to the symbol size and thus not shown in the plot. The solid line represents a fit with Eq. 2, which gives the relative humidity 90.6%. - Fig. 5.
Bubble stationary locations in 120-μm-long nanochannels. (A) Snapshots of stationary locations in 20-, 52-, 98-, and 120-nm-deep nanochannels. (B) Experimental results as well as theoretical prediction of bubble stationary locations in nanochannels with heights from 20 to 120 nm. As the channel height increases, bubbles prefer to stop closer to the middle of the nanochannel. These stationary locations are determined by two competing migrations—i.e., the thermocapillary migration and the evaporation-induced migration.
Data supplements
Supporting Information
Files in this Data Supplement:
Evaporation-induced cavitation in nanofluidic channels
Article Classifications
- Physical Sciences
- Applied Physical Sciences
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