Nucleation at the Contact Line Observed on Nanotextured Surfaces

Abstract

It has been conjectured that roughness plays a role in surface nucleation, the tendency for freezing to begin preferentially at the liquid-gas interface. Using high speed imaging, we sought evidence for freezing at the contact line on catalyst substrates with imposed characteristic length scales (texture). Length scales consistent with the critical nucleus size and with δ∼τ/σ, where τ is a relevant line tension and σ is the surface tension, range from nanometers to micrometers. It is found that nanoscale texture causes a shift in the nucleation of ice in supercooled water to the three-phase contact line, while microscale texture does not.

Comparing contact and immersion freezing from continuous flow diffusion chambers

“…A specific dependence on the INP for the enhancement of contact freezing relative to immersion freezing is in accordance with Gurganus et al (2014), who observed an increased efficiency for nucleation at the three-phase contact line in the case of nanoscale but not for microscale textures. In most experiments of contact freezing inside out, the position of the particle with respect to the droplet is fixed by the design of the experiment Fornea et al, 2009;Gurganus et al, 2014). Whether a particle adheres to the surface or becomes totally immersed in a droplet depends on the wetting of the particle with water.…”

“…Contact freezing (CF) in the original sense is understood as the process in which freezing of a supercooled droplet results from the collision with an aerosol particle (Ladino Moreno et al, 2013;Vali, 1985). This view of collisional contact freezing has been complemented by Durant and Shaw (2005), who found a higher ice nucleation temperature compared with the immersion mode, when an INP was in contact with the waterair interface of a droplet, from either the inside or the outside Gurganus et al, 2014;Fornea et al, 2009;Murray et al, 2012;Shaw et al, 2005). In the following, we refer to a contact nucleation process as adhesion freezing when the position of the INP on the water surface enhances the ice nucleation efficiency compared with immersion freezing and discriminate it from collisional contact freezing, which assumes an enhancement due to the collision of the particle with the droplet.…”

“…On the other hand, Gurganus et al (2011Gurganus et al ( , 2013 investigated the freezing of droplets deposited on clean and coated silicon wafers and did not observe any preference of nucleation at the contact line. The same group also studied this phenomenon on catalyst substrates with imposed surface structures and found that the preferred nucleation site was the contact line in the case of nanoscale texture but not for microscale texture (Gurganus et al, 2014). Djikaev and Ruckenstein (2008) proposed that the line tension associated with the three phase contact line may indeed play an important role.…”

Ice nucleation efficiency of AgI: review and new insights

“…This view of collisional contact freezing has been complemented by Durant and Shaw (2005), who found higher ice nucleation temperatures compared with the immersion mode when an ice nucleus was in contact with the water-air interface of a droplet, from either the inside or the outside Gurganus et al, 2014;Fornea et al, 2009;Murray et al, 2012;Shaw et al, 2005). We refer to a contact nucleation process as adhesion freezing when the position of the particle on the water surface enhances the ice nucleation efficiency compared with immersion freezing and discriminate it from collisional contact freezing, which assumes an enhancement due to the collision of the particle with the droplet (Nagare et al, 2016).…”

Janus effect of antifreeze proteins on ice nucleation

“…2C, Inset demonstrates that at various cooling rates, the ice nucleation temperature on the surfaces fully covered with IBFs remains higher than that on the GOPTS surface. For supercooled liquid water, ice nucleation of a droplet initiates at the most active site, and then ice grows spontaneously (29). Thus, to achieve lower ice nucleation temperature, it is required to sufficiently minimize the amount of nucleation active sites in contact with liquid water.…”