Open AccessTuning the Charge of Sliding Water Drops
Author(s) -
William S. Y. Wong,
Pravash Bista,
Xiaomei Li,
Lothar Veith,
Azadeh Sharifi-Aghili,
Stefan Weber,
HansJürgen Butt
Publication year - 2022
Publication title -
langmuir
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.042
H-Index - 333
eISSN - 1520-5827
pISSN - 0743-7463
DOI - 10.1021/acs.langmuir.2c00941
Subject(s) - drop (telecommunication) , contact electrification , surface charge , chemical physics , amine gas treating , chemical engineering , contact angle , chemistry , materials science , fluorocarbon , organic chemistry , composite material , triboelectric effect , telecommunications , computer science , engineering
When a water drop slides over a hydrophobic surface, it usually acquires a positive charge and deposits the negative countercharge on the surface. Although the electrification of solid surfaces induced after contact with a liquid is intensively studied, the actual mechanisms of charge separation, so-termed slide electrification, are still unclear. Here, slide electrification is studied by measuring the charge of a series of water drops sliding down inclined glass plates. The glass was coated with hydrophobic (hydrocarbon/fluorocarbon) and amine-terminated silanes. On hydrophobic surfaces, drops charge positively while the surfaces charge negatively. Hydrophobic surfaces coated with a mono-amine (3-aminopropyltriethyoxysilane) lead to negatively charged drops and positively charged surfaces. When coated with a multiamine ( N -(3-trimethoxysilylpropyl)diethylenetriamine), a gradual transition from positively to negatively charged drops is observed. We attribute this tunable drop charging to surface-directed ion transfer. Some of the protons accepted by the amine-functionalized surfaces (-NH 2 with H + acceptor) remain on the surface even after drop departure. These findings demonstrate the facile tunability of surface-controlled slide electrification.