Study on the adhesion behaviors between droplet and polydimethylsiloxane film

Controllable Structure Design of an Organic Gel-Infused Porous Surface for Efficient Anti- and De-icing

Icing causes many problems in daily life and with equipment stability, and many efforts have been made to remove surface icing. Herein, a novel organic gel-infused porous material is developed to achieve excellent de-icing performance. Porous polydimethylsiloxane (P-PDMS) composites with different pore sizes were prepared by a template method. The two-phase skeletons and/or gel material was obtained by infusing PDMS gel into P-PDMS (GIP-PDMS). The ice adhesion strength of GIP-PDMS under static and dynamic icing conditions was comparatively investigated. The results show that GIP-PDMS displayed excellent anti-icing performance, and the delay freezing time of GIP-PDMS1 was ∼4554 s at -5 °C. The ice adhesion strength of GIP-PDMS was much lower than that of P-PDMS, owing to the distinct modulus between the two-phase skeletons and/or gel. The simulation results indicated that the stress concentration promoted ice fracture and contributed to weak ice adhesion. Molecular dynamics further showed that the state of the molecular chains and the interfacial interaction between ice and PDMS gel at 268 K helped to decrease the shear force.

Soft wetting: Substrate softness- and time-dependent droplet/bubble adhesion

HYPOTHESIS

The droplet/bubble adhesion characteristics depend on the length of the droplet/bubble three-phase contact line. Since the deformation caused by the liquid-gas interfacial tension on the soft substrate, referred as to the wetting ridge, retards contact line spreading and retraction, we conjecture that the droplet/bubble adhesion characteristics depend also on the substrate softness.

EXPERIMENTS

Soft substrates with various shear moduli are prepared and characterized by the spreading and receding dynamics of water droplets and underwater bubbles. Snap-in and normal adhesion forces of droplets/bubbles on such soft substrates are directly measured along with the visualized droplet/bubble shape profiles.

FINDINGS

The droplet/bubble snap-in force, which corresponds to the short-time spreading dynamics, decreases with a decrease in the substrate shear modulus because of the retarded contact line spreading. The droplet maximal adhesion force on a soft substrate can be counterintuitively either smaller or larger than its counterpart on the rigid substrate depending on different dwelling times, i.e., the droplet/bubble-substrate contact time before droplet/bubble-substrate separation. The former is attributed to the retarded contact line spreading, whereas the latter is attributed to the retarded contact line retraction. The substrate softness- and dwelling time-dependent droplet/bubble adhesion reported in this study will benefit various applications related to soft substrates.