Hydrogels as Durable Anti-Icing Coatings Inhibit and Delay Ice Nucleation

Abstract

The accumulation of ice on surfaces brings dangerous and costly problems to our daily life. Thus, it would be desirable to design anti-icing coatings for various surfaces. We report a durable anti-icing coating based on mussel-inspired chemistry, which is enabled via fabricating a liquid water layer, achieved by modifying solid substrates with the highly water absorbing property of sodium alginate. Dopamine, the main component of the mussel adhesive protein, is introduced to anchor the sodium alginate in order to render the coating applicable to all types of solid surfaces. Simultaneously, it serves as the cross-linking agent for sodium alginate; thus, the cross-linking degree of the coatings could be easily varied. The non-freezable and freezable water in the coatings with different cross-link degrees all remain liquid-like at subzero conditions and synergistically fulfill the aim of decreasing the temperature of ice nucleation. These anti-icing coatings display excellent stability even under harsh conditions. Furthermore, these coatings can be applied to almost all types of solid surfaces and have great promise in practical applications.

Keywords: anti-icing coating; cross-linking; hydrogels; sodium alginate.

Figure 1

Schematic representation of the process of the durable anti-icing coating.

Figure 2

(a) Structure of SA-g-DA conjugate(the reaction product of sodium alginate and dopamine); (b) ¹H-NMR spectra of SA and SA-g-DA conjugate; (c) X-ray photoelectron spectra of the silicon wafer surface (bottom) and the surface coated by SD1 conjugate and cross-linked via NaIO₄ (top), where SD1 denotes the silicon wafers functionalized with SD1 conjugate; (d) high-resolution XPS spectra of C 1s.

Figure 3

Atomic force microscope (AFM) height images (2μm × 2μm) of hydrogel coating (SD1) deposited on silicon wafers before (a) and after (b) cross-linking in the air, (c) SD8 coating, immersed in (d) 0.1 M NaOH, (e) 0.1 M HCl and (f) 5 M NaCl for 2 h.

Figure 4

(a) Microscopic images of water macrodroplets; (b) ice nucleation temperatures on a series of substrates coated by the cross-linked SA−DA conjugates (SD1 to SD10) during cooling from ambient temperature at a rate of 2 °C min⁻¹; (c) the dependence of T_h upon the cooling rate; (d) average delay times of ice nucleation measured at –23 °C on the hydrogel surfaces with different cross-linking degrees.

Figure 5

(a) Comparison of the ice nucleation temperature measured at 2 °C min⁻¹ on a wide range of substrates after the application of the hydrogel coating (SD1). Al and PE denote aluminum and polyethylene, respectively. (b) The value of ice nucleation temperature on the hydrogel coating (SD1) after immersion into three types of solution including alkaline, acid and salt solutions.