Extreme Resistance of Superhydrophobic Surfaces to Impalement: Reversible Electrowetting Related to the Impacting/Bouncing Drop Test

• Published in: Langmuir Vol. 24; no. 19; pp. 11203 - 11208
• Main Authors: Brunet, P, Lapierre, F, Thomy, V, Coffinier, Y, Boukherroub, R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 07-10-2008
• Subjects: Chemistry; Colloidal state and disperse state; Condensed Matter; Engineering Sciences; Exact sciences and technology; General and physical chemistry; Materials Science; Materials: Nano-and Mesostructured Materials, Polymers, Gels, Liquid Crystals, Composites; Micro and nanotechnologies; Microelectronics; Physics; Surface physical chemistry; Resistance; Correlation; Wetting; Reversibility; Silicon; Contact angle; Structure; Density; Hysteresis; Drop
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la801268v

The paper reports on the comparison of the wetting properties of superhydrophobic silicon nanowires (NWs), using drop impact impalement and electrowetting (EW) experiments. A correlation between the resistance to impalement on both EW and drop impact is shown. From the results, it is evident that when increasing the length and density of NWs (i) the thresholds for drop impact and EW irreversibility increase and (ii) the contact-angle hysteresis after impalement decreases. This suggests that the structure of the NW network could allow for partial impalement, hence preserving the reversibility, and that EW acts the same way as an external pressure. The most robust of our surfaces shows a threshold to impalement higher than 35 kPa, while most of the superhydrophobic surfaces tested so far have impalement thresholds smaller than 10 kPa.