Kim Nanoscale Research Letters 2011, 6:415 http://www.nanoscalereslett.com/content/6/1/415 Page 14 of 18 Figure 12 Relation between CHF and surface characteristics. (a) CHF of pure water vs. contact angle of a water droplet on nanoparticle- deposited surfaces. SEM pictures (b) and maximum capillary wicking height of pure water (c) for surfaces boiled in 10-3% (A) and 10-1% (B) water-TiO2 nanofluids, with the same contact angles of ~20° [60]. deposition. However, owing to the complexity of the phe- nomenon of CHF and to numerous factors affecting it, a sufficiently definite theory by which the nanoparticle layer results in such a high CHF enhancement has not yet emerged. According to the extensive reviews by Kim et al. [46] and Golubovic et al. [19], most hypotheses fall into one of the following four categories: 1. hydrodynamic instability model, 2. macrolayer dryout model, 3. bubble interaction model, 4. hot/dry spot model. In this section, the previous studies aiming to under- stand the physical mechanism of CHF enhancement in