Spontaneous Charging of Drops on Lubricant-Infused Surfaces

• Published in: Langmuir Vol. 38; no. 41; pp. 12610 - 12616
• Main Authors: Li, Shuai, Bista, Pravash, Weber, Stefan A. L., Kappl, Michael, Butt, Hans-Jürgen
• Format: Journal Article
• Language: English
• Published: American Chemical Society 18-10-2022
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.2c02085

When a drop of a polar liquid slides over a hydrophobic surface, it acquires a charge. As a result, the surface charges oppositely. For applications such as the generation of electric energy, lubricant-infused surfaces (LIS) may be important because they show a low friction for drops. However, slide electrification on LIS has not been studied yet. Here, slide electrification on lubricant-infused surfaces was studied by measuring the charge generated by series of water drops sliding down inclined surfaces. As LIS, we used PDMS-coated glass with micrometer-thick silicone oil films on top. For PDMS-coated glass without lubricant, the charge for the first drop is highest. Then it decreases and saturates at a steady state charge per drop. With lubricant, the drop charge starts from 0, then it increases and reaches a maximum charge per drop. Afterward, it decreases again before reaching its steady-state value. This dependency is not a unique phenomenon for lubricant-infused PDMS; it also occurs on lubricant-infused micropillar surfaces. We attribute this dependency of charge on drop numbers to a change in surface conductivity and depletion of lubricant. These findings are helpful for understanding the charge process and optimizing solid–liquid nanogenerator devices in applications.