1
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Jin Y, Yang S, Sun M, Gao S, Cheng Y, Wu C, Xu Z, Guo Y, Xu W, Gao X, Wang S, Huang B, Wang Z. How liquids charge the superhydrophobic surfaces. Nat Commun 2024; 15:4762. [PMID: 38834547 DOI: 10.1038/s41467-024-49088-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 05/23/2024] [Indexed: 06/06/2024] Open
Abstract
Liquid-solid contact electrification (CE) is essential to diverse applications. Exploiting its full implementation requires an in-depth understanding and fine-grained control of charge carriers (electrons and/or ions) during CE. Here, we decouple the electrons and ions during liquid-solid CE by designing binary superhydrophobic surfaces that eliminate liquid and ion residues on the surfaces and simultaneously enable us to regulate surface properties, namely work function, to control electron transfers. We find the existence of a linear relationship between the work function of superhydrophobic surfaces and the as-generated charges in liquids, implying that liquid-solid CE arises from electron transfer due to the work function difference between two contacting surfaces. We also rule out the possibility of ion transfer during CE occurring on superhydrophobic surfaces by proving the absence of ions on superhydrophobic surfaces after contact with ion-enriched acidic, alkaline, and salt liquids. Our findings stand in contrast to existing liquid-solid CE studies, and the new insights learned offer the potential to explore more applications.
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Affiliation(s)
- Yuankai Jin
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, PR China
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong SAR, PR China
| | - Siyan Yang
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, PR China
| | - Mingzi Sun
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong SAR, PR China
| | - Shouwei Gao
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, PR China
| | - Yaqi Cheng
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong SAR, PR China
| | - Chenyang Wu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong SAR, PR China
| | - Zhenyu Xu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong SAR, PR China
| | - Yunting Guo
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong SAR, PR China
| | - Wanghuai Xu
- Department of Electrical and Electronic Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, PR China
| | - Xuefeng Gao
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, PR China
| | - Steven Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong SAR, PR China
| | - Bolong Huang
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong SAR, PR China.
| | - Zuankai Wang
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, PR China.
- Research Centre for Nature-Inspired Science and Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, PR China.
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2
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Darvish F, Shumaly S, Li X, Dong Y, Diaz D, Khani M, Vollmer D, Butt HJ. Control of spontaneous charging of sliding water drops by plasma-surface treatment. Sci Rep 2024; 14:10640. [PMID: 38724519 DOI: 10.1038/s41598-024-60595-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Accepted: 04/25/2024] [Indexed: 05/14/2024] Open
Abstract
Slide electrification is the spontaneous separation of electric charges at the rear of water drops sliding over solid surfaces. This study delves into how surfaces treated with a low-pressure plasma impact water slide electrification. Ar, O2, and N2 plasma treatment reduced the drop charge and contact angles on glass, quartz, and SU-8 coated with 1H,1H,2H,2H-perfluoroctyltrichlorosilane (PFOTS), and polystyrene. Conversely, 64% higher drop charge was achieved using electrode-facing treatment in plasma chamber. Based on the zeta potential, Kelvin potential, and XPS measurements, the plasma effects were attributed to alterations of the topmost layer's chemistry, such as oxidation and etching, and superficially charge deposition. The surface top layer charges were less negative after electrode-facing and more negative after bulk plasma treatment. As a result, the zeta potential was less negative after electrode-facing and more negative after bulk plasma treatment. Although the fluorinated layer was applied after plasma activation, we observed a discernible impact of plasma-glass treatment on drop charging. Plasma surface modification offers a means to adjust drop charges: electrode-facing treatment of the fluorinated layer leads to an enhanced drop charge, while plasma treatment on the substrate prior to fluorination diminishes drop charges, all without affecting contact angles or surface roughness.
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Affiliation(s)
- Fahimeh Darvish
- Max Planck Institute for Polymer Research (MPI-P), Ackermannweg 10, 55128, Mainz, Germany
| | - Sajjad Shumaly
- Max Planck Institute for Polymer Research (MPI-P), Ackermannweg 10, 55128, Mainz, Germany
| | - Xiaomei Li
- Max Planck Institute for Polymer Research (MPI-P), Ackermannweg 10, 55128, Mainz, Germany
| | - Yun Dong
- Max Planck Institute for Polymer Research (MPI-P), Ackermannweg 10, 55128, Mainz, Germany
| | - Diego Diaz
- Max Planck Institute for Polymer Research (MPI-P), Ackermannweg 10, 55128, Mainz, Germany
| | - Mohammadreza Khani
- Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Evin, Tehran, 1983963113, Iran
| | - Doris Vollmer
- Max Planck Institute for Polymer Research (MPI-P), Ackermannweg 10, 55128, Mainz, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research (MPI-P), Ackermannweg 10, 55128, Mainz, Germany.
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3
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Bista P, Ratschow AD, Stetten AZ, Butt HJ, Weber SAL. Surface charge density and induced currents by self-charging sliding drops. SOFT MATTER 2024. [PMID: 38639086 DOI: 10.1039/d4sm00205a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Spontaneous charge separation in drops sliding over a hydrophobized insulator surface is a well-known phenomenon and lots of efforts have been made to utilize this effect for energy harvesting. For maximizing the efficiency of such devices, a comprehensive understanding of the dewetted surface charge would be required to quantitatively predict the electric current signals, in particular for drop sequences. Here, we use a method based on mirror charge detection to locally measure the surface charge density after drops move over a hydrophobic surface. For this purpose, we position a metal electrode beneath the hydrophobic substrate to measure the capacitive current induced by the moving drop. Furthermore, we investigate drop-induced charging on different dielectric surfaces together with the surface neutralization processes. The surface neutralizes over a characteristic time, which is influenced by the substrate and the surrounding environment. We present an analytical model that describes the slide electrification using measurable parameters such as the surface charge density and its neutralization time. Understanding the model parameters and refining them will enable a targeted optimization of the efficiency in solid-liquid charge separation.
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Affiliation(s)
- Pravash Bista
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Aaron D Ratschow
- Institute for Nano- and Microfluidics, TU Darmstadt, Peter-Grünberg-Str. 10, 64289 Darmstadt, Germany
| | - Amy Z Stetten
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Stefan A L Weber
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Institute for Photovoltaics, University of Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart, Germany.
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4
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Hinduja C, Butt HJ, Berger R. Slide electrification of drops at low velocities. SOFT MATTER 2024; 20:3349-3358. [PMID: 38563221 PMCID: PMC11022544 DOI: 10.1039/d4sm00019f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 03/13/2024] [Indexed: 04/04/2024]
Abstract
Slide electrification of drops is mostly investigated on tilted plate setups. Hence, the drop charging at low sliding velocity remains unclear. We overcome the limitations by developing an electro drop friction force instrument (eDoFFI). Using eDoFFI, we investigate slide electrification at the onset of drop sliding and at low sliding velocities ≤ 1 cm s-1. The novelty of eDoFFI is the simultaneous measurements of the drop discharging current and the friction force acting on the drop. The eDoFFI tool facilitates control on drop length and width using differently shaped rings. Hereby, slide electrification experiments with the defined drop length-to-width ratios >1 and <1 are realized. We find that width of the drop is the main geometrical parameter which determines drop discharging current and charge separation. We combine Kawasaki-Furmidge friction force equation with our finding on drop discharging current. This combination facilitates the direct measurement of surface charge density (σ) deposited behind the drop. We calculate σ ≈ 45 μC m-2 on Trichloro(1H,1H,2H,2H-perfluorooctyl)silane (PFOTS) and ≈20 μC m-2 on Trichloro(octyl)silane (OTS) coated glass surfaces. We find that the charge separation by moving drops is independent of sliding velocity ≤ 1 cm s-1. The reverse sliding of drop along the same scanline facilitates calculation of the surface neutralization time constant. The eDoFFI links two scientific communities: one which focuses on the friction forces and one which focuses on the slide electrification of drops.
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Affiliation(s)
- Chirag Hinduja
- Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
| | - Rüdiger Berger
- Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
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5
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Leibauer B, Pop-Georgievski O, Sosa MD, Dong Y, Tremel W, Butt HJ, Steffen W. How Surface and Substrate Chemistry Affect Slide Electrification. J Am Chem Soc 2024; 146:10073-10083. [PMID: 38563738 PMCID: PMC11009953 DOI: 10.1021/jacs.4c01015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 03/15/2024] [Accepted: 03/15/2024] [Indexed: 04/04/2024]
Abstract
When water droplets move over a hydrophobic surface, they and the surface become oppositely charged by what is known as slide electrification. This effect can be used to generate electricity, but the physical and especially the chemical processes that cause droplet charging are still poorly understood. The most likely process is that at the base of the droplet, an electric double layer forms, and the interfacial charge remains on the surface behind the three-phase contact line. Here, we investigate the influence of the chemistry of surface (coating) and bulk (substrate) on the slide electrification. We measured the charge of a series of droplets sliding over hydrophobically coated (1-5 nm thickness) glass substrates. Within a series, the charge of the droplet decreases with the increasing droplet number and reaches a constant value after about 50 droplets (saturated state). We show that the charge of the first droplet depends on both coating and substrate chemistry. For a fully fluorinated or fully hydrogenated monolayer on glass, the influence of the substrate on the charge of the first droplet is negligible. In the saturated state, the chemistry of the substrate dominates. Charge separation can be considered as an acid base reaction between the ions of water and the surface. By exploiting the acidity (Pearson hardness) of elements such as aluminum, magnesium, or sodium, a positive saturated charge can be obtained by the counter charge remaining on the surface. With this knowledge, the droplet charge can be manipulated by the chemistry of the substrate.
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Affiliation(s)
- Benjamin Leibauer
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Ognen Pop-Georgievski
- Institute
of Macromolecular Chemistry, Heyrovského nám. 2, 162
00 Prague, Czech
Republic
| | - Mariana D. Sosa
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yun Dong
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Wolfgang Tremel
- Chemistry
Department, Johannes-Gutenberg University, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Werner Steffen
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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6
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Zhang H, Sundaresan S, Webb MA. Thermodynamic driving forces in contact electrification between polymeric materials. Nat Commun 2024; 15:2616. [PMID: 38521773 PMCID: PMC10960812 DOI: 10.1038/s41467-024-46932-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 03/13/2024] [Indexed: 03/25/2024] Open
Abstract
Contact electrification, or contact charging, refers to the process of static charge accumulation after rubbing, or even simple touching, of two materials. Despite its relevance in static electricity, various natural phenomena, and numerous technologies, contact charging remains poorly understood. For insulating materials, even the species of charge carrier may be unknown, and the direction of charge-transfer lacks firm molecular-level explanation. Here, we use all-atom molecular dynamics simulations to investigate whether thermodynamics can explain contact charging between insulating polymers. Based on prior work suggesting that water-ions, such as hydronium and hydroxide ions, are potential charge carriers, we predict preferred directions of charge-transfer between polymer surfaces according to the free energy of water-ions within water droplets on such surfaces. Broad agreement between our predictions and experimental triboelectric series indicate that thermodynamically driven ion-transfer likely influences contact charging of polymers. Furthermore, simulation analyses reveal how specific interactions of water and water-ions proximate to the polymer-water interface explain observed trends. This study establishes relevance of thermodynamic driving forces in contact charging of insulators with new evidence informed by molecular-level interactions. These insights have direct implications for future mechanistic studies and applications of contact charging involving polymeric materials.
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Affiliation(s)
- Hang Zhang
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Sankaran Sundaresan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Michael A Webb
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA.
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7
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Helseth LE. Charge Transfer Quenching and Maximum of a Liquid-Air Contact Line Moving over a Hydrophobic Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:4340-4349. [PMID: 38351538 PMCID: PMC10905998 DOI: 10.1021/acs.langmuir.3c03605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 02/05/2024] [Accepted: 02/06/2024] [Indexed: 02/28/2024]
Abstract
Charge transfer when a hydrophobic fluoropolymer surface comes in contact with salt solutions of water, methanol, and glycerol is investigated. It is found that the charge transfer decreases faster with an increasing fraction of glycerol in water than it does with methanol in water. It is also demonstrated that for both mixtures, the charge transfer increases with the amount of added sodium chloride for small concentrations but then reaches a maximum and subsequently decreases. Surprisingly, this maximum charge transfer shifts toward higher salt concentrations with increasing amount of glycerol in water. However, in water-methanol mixtures, one does not observe a similar shift in charge transfer maximum toward higher salt concentrations. These observations are explained using a model, taking into account the decreased shear distance from the hydrophobic surface for which ions are removed from the electrical double layer due to an interplay of forces acting on the ions.
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Affiliation(s)
- Lars Egil Helseth
- Department of Physics and
Technology, University of Bergen, Allegaten 55, Bergen 5020, Norway
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8
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Sbeih S, Lüleci A, Weber S, Steffen W. The influence of ions and humidity on charging of solid hydrophobic surfaces in slide electrification. SOFT MATTER 2024; 20:558-565. [PMID: 38126532 DOI: 10.1039/d3sm01153d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Water drops sliding down inclined hydrophobic, insulating surfaces spontaneously deposit electric charges. However, it is not yet clear how the charges are deposited. The influence of added non-hydrolysable salt, acid, or base in the sliding water drops as well as the surrounding humidity on surface electrification and charge formation is also not yet fully understood. Here, we measure the charging on hydrophobic solid surfaces (coated with PFOTS or PDMS) by sliding drops with varying concentration for different types of solutions. Solutions of NaCl, CaCl2, KNO3, HCl, and NaOH, were studied whose concentrations varied in a range of 0.01 to 100 mM. The charge increased slightly at low concentrations and decreased at higher concentrations. We attribute this decrease to the combined effect of charge screening as the non-hydrolysable salt concentration increases and pH driven charge regulation. The effect of humidity on the measured charge was tested over the range from 10% to 90% of humidity. It was found that the influence of humidity on the charge measurements below 70% humidity is low.
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Affiliation(s)
- Suhad Sbeih
- School of Basic Sciences and Humanities, German Jordanian University, Amman 11180, Jordan
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
| | - Aziz Lüleci
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
| | - Stefan Weber
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
| | - Werner Steffen
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
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9
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Bista P, Ratschow AD, Butt HJ, Weber SAL. High Voltages in Sliding Water Drops. J Phys Chem Lett 2023; 14:11110-11116. [PMID: 38052008 PMCID: PMC10726385 DOI: 10.1021/acs.jpclett.3c02864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 11/22/2023] [Accepted: 11/28/2023] [Indexed: 12/07/2023]
Abstract
Water drops on insulating hydrophobic substrates can generate electric potentials of kilovolts upon sliding for a few centimeters. We show that the drop saturation voltage corresponds to an amplified value of the solid-liquid surface potential at the substrate. The amplification is given by the substrate geometry, the drop and substrate dielectric properties, and the Debye length within the liquid. Next to enabling an easy and low-cost way to measure surface- and zeta- potentials, the high drop voltages have implications for energy harvesting, droplet microfluidics, and electrostatic discharge protection.
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Affiliation(s)
- Pravash Bista
- Max
Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Aaron D. Ratschow
- Institute
for Nano- and Microfluidics, TU Darmstadt, Peter-Grünberg-Strasse 10, Darmstadt 64289, Germany
| | - Hans-Jürgen Butt
- Max
Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Stefan A. L. Weber
- Max
Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
- Department
of Physics, Johannes Gutenberg University, Staudingerweg 10, Mainz 55128, Germany
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10
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Li X, Ratschow AD, Hardt S, Butt HJ. Surface Charge Deposition by Moving Drops Reduces Contact Angles. PHYSICAL REVIEW LETTERS 2023; 131:228201. [PMID: 38101382 DOI: 10.1103/physrevlett.131.228201] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 10/19/2023] [Indexed: 12/17/2023]
Abstract
Slide electrification-the spontaneous charge separation by sliding aqueous drops-can lead to an electrostatic potential in the order of 1 kV and change drop motion substantially. To find out how slide electrification influences the contact angles of moving drops, we analyzed the dynamic contact angles of aqueous drops sliding down tilted plates with insulated surfaces, grounded surfaces, and while grounding the drop. The observed decrease in dynamic contact angles at different salt concentrations is attributed to two effects: An electrocapillary reduction of contact angles caused by drop charging and a change in the free surface energy of the solid due to surface charging.
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Affiliation(s)
- Xiaomei Li
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Aaron D Ratschow
- Institute for Nano- and Microfluidics, TU Darmstadt, Peter-Grünberg-Str. 10, D-64289 Darmstadt, Germany
| | - Steffen Hardt
- Institute for Nano- and Microfluidics, TU Darmstadt, Peter-Grünberg-Str. 10, D-64289 Darmstadt, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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11
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Zhang H, Sundaresan S, Webb MA. Molecular Dynamics Investigation of Nanoscale Hydrophobicity of Polymer Surfaces: What Makes Water Wet? J Phys Chem B 2023. [PMID: 37043668 DOI: 10.1021/acs.jpcb.3c00616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
The wettability of a polymer surface─related to its hydrophobicity or tendency to repel water─can be crucial for determining its utility, such as for a coating or a purification membrane. While wettability is commonly associated with the macroscopic measurement of a contact angle between surface, water, and air, the molecular physics that underlie these macroscopic observations are not fully known, and anticipating the relative behavior of different polymers is challenging. To address this gap in molecular-level understanding, we use molecular dynamics simulations to investigate and contrast interactions of water with six chemically distinct polymers: polytetrafluoroethylene, polyethylene, polyvinyl chloride, poly(methyl methacrylate), Nylon-66, and poly(vinyl alcohol). We show that several prospective quantitative metrics for hydrophobicity agree well with experimental contact angles. Moreover, the behavior of water in proximity to these polymer surfaces can be distinguished with analysis of interfacial water dynamics, extent of hydrogen bonding, and molecular orientation─even when macroscopic measures of hydrophobicity are similar. The predominant factor dictating wettability is found to be the extent of hydrogen bonding between polymer and water, but the precise manifestation of hydrogen bonding and its impact on surface water structure varies. In the absence of hydrogen bonding, other molecular interactions and polymer mechanics control hydrophobic ordering. These results provide new insights into how polymer chemistry specifically impacts water-polymer interactions and translates to surface hydrophobicity. Such factors may facilitate the design or processing of polymer surfaces to achieve targeted wetting behavior, and presented analyses can be useful in studying the interfacial physics of other systems.
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Affiliation(s)
- Hang Zhang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Sankaran Sundaresan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Michael A Webb
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
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12
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Helseth LE. Ion Concentration Influences the Charge Transfer Due to a Water-Air Contact Line Moving over a Hydrophobic Surface: Charge Measurements and Theoretical Models. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:1826-1837. [PMID: 36696661 PMCID: PMC9910047 DOI: 10.1021/acs.langmuir.2c02716] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 01/11/2023] [Indexed: 05/28/2023]
Abstract
A metal electrode covered by an inert, hydrophobic polymer surface is dipped into water, and the charge transfer was measured as a function of ion concentration for different chlorides, sulfates, and nitrates. A generic behavior is observed wherein the charge transfer first increases and then decreases as the ion concentration increases. However, for acids, the charge transfer decreases monotonously with concentration and even reverses polarity. Two different models, both in which the charge transfer is attributed to removal of ions from the electrical double layer as the contact line passes by, are discussed and shown to provide possible explanations of the experimental data.
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13
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A reusable electret filter media based on water droplet charging/cleaning. Chem Eng Sci 2023. [DOI: 10.1016/j.ces.2022.118237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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14
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Song Y, Xu W, Liu Y, Zheng H, Cui M, Zhou Y, Zhang B, Yan X, Wang L, Li P, Xu X, Yang Z, Wang Z. Achieving ultra-stable and superior electricity generation by integrating transistor-like design with lubricant armor. Innovation (N Y) 2022; 3:100301. [PMID: 36051817 PMCID: PMC9425077 DOI: 10.1016/j.xinn.2022.100301] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 08/08/2022] [Indexed: 11/18/2022] Open
Abstract
Extensive work have been done to harvest untapped water energy in formats of raindrops, flows, waves, and others. However, attaining stable and efficient electricity generation from these low-frequency water kinetic energies at both individual device and large-scale system level remains challenging, partially owing to the difficulty in designing a unit that possesses stable liquid and charge transfer properties, and also can be seamlessly integrated to achieve preferential collective performances without the introduction of tortuous wiring and redundant node connection with external circuit. Here, we report the design of water electricity generators featuring the combination of lubricant layer and transistor-like electrode architecture that endows enhanced electrical performances in different working environments. Such a design is scalable in manufacturing and suitable for facile integration, characterized by significant reduction in the numbers of wiring and nodes and elimination of complex interfacing problems, and represents a significant step toward large-scale, real-life applications. A lubricant-armored transistor-like electricity generator is proposed The transistor-like electrode architecture causes high electrical output The lubricant armor ensures stable performance in extreme environments The design is scalable in manufacturing and suitable for facile integration
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Affiliation(s)
- Yuxin Song
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Wanghuai Xu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Yuan Liu
- School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China
| | - Huanxi Zheng
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Miaomiao Cui
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Yongsen Zhou
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Baoping Zhang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Xiantong Yan
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Lili Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Pengyu Li
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Xiaote Xu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Zhengbao Yang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
| | - Zuankai Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China
- Research Center for Nature-Inspired Engineering, City University of Hong Kong, Hong Kong 999077, China
- Shenzhen Research Institute of City University of Hong Kong, Shenzhen 518057, China
- Corresponding author
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15
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Sosa MD, D'Accorso NB, Martínez Ricci ML, Negri RM. Liquid-Polymer Contact Electrification: Modeling the Dependence of Surface Charges and ξ-Potential on pH and Added-Salt Concentration. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:8817-8828. [PMID: 35834348 DOI: 10.1021/acs.langmuir.2c00813] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Here, a mathematical model is presented, which accounts for the dependence of the surface electrical charge density (σ) on pH and the concentration of added salts (Cs), generated when a water drop rolls or slides on the surface of a hydrophobic polymer, a process known as liquid-polymer contact electrification (LPCE). The same model was successfully applied to fit the isotherms of ξ-potential as a function of pH, reported in the literature by other authors for water-poly(tetrafluoroethylene) (PTFE) interfaces. Hence, the dependence of σ and ξ on pH was described using the same concept: acid-base equilibria at the water-polymer interface. Equilibrium constants were estimated by fitting experimental isotherms. The experimental results and the model are consistent with a number of 10-100 acid-base sites/μm2. The model predicts the increase of |σ| and |ξ| with pH in the range of 2-10 and the existence of a zero-charge point at pHzcp ≅ 3 for PTFE (independent of Cs). Excellent fits were obtained with Ka/Kb ∼ 9 × 107, where Ka and Kb are the respective acid and base equilibrium constants. On the other hand, the observed decrease in |σ| and |ξ| with Cs at fixed pH is quantitatively described by introducing an activity factor associated with the quenching of water activity by the salt ions at the polymer-water interface, with quenching constant Kq. Additionally, the quenching predicts a decrease in |σ| and |ξ| at extreme pH, where I > (1/Kq) (I: ionic strength), in agreement with literature reports.
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Affiliation(s)
- Mariana D Sosa
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
| | - Norma B D'Accorso
- Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
- Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR), CONICET, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
| | - M Luz Martínez Ricci
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
| | - R Martín Negri
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
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Wong WSY, Bista P, Li X, Veith L, Sharifi-Aghili A, Weber SAL, Butt HJ. Tuning the Charge of Sliding Water Drops. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6224-6230. [PMID: 35500291 PMCID: PMC9118544 DOI: 10.1021/acs.langmuir.2c00941] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 04/16/2022] [Indexed: 05/28/2023]
Abstract
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 (-NH2 with H+ acceptor) remain on the surface even after drop departure. These findings demonstrate the facile tunability of surface-controlled slide electrification.
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Díaz D, Garcia-Gonzalez D, Bista P, Weber SAL, Butt HJ, Stetten A, Kappl M. Charging of drops impacting onto superhydrophobic surfaces. SOFT MATTER 2022; 18:1628-1635. [PMID: 35113106 DOI: 10.1039/d1sm01725j] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
When neutral water drops impact and rebound from superhydrophobic surfaces, they acquire a positive electrical charge. To measure the charge, we analyzed the trajectory of rebounding drops in an external electric field by high-speed video imaging. Although this charging phenomenon has been observed in the past, little is known about the controlling parameters for the amount of drop charging. Here we investigate the relative importance of five of these potential variables: impact speed, drop contact area, contact line retraction speed, drop size, and type of surface. We additionally apply our previously reported model for sliding drop electrification to the case of impacting drops, suggesting that the two cases contain the same charge separation mechanism at the contact line. Both our experimental results and our theoretical model indicate that maximum contact area is the dominant control parameter for charge separation.
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Affiliation(s)
- Diego Díaz
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Diana Garcia-Gonzalez
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
- Physics of Fluids Group, Max Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, University of Twente, P.O. Box 217, Enschede 7500 AE, The Netherlands
| | - Pravash Bista
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Stefan A L Weber
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
- Department of Physics, Johannes Gutenberg University, Staudingerweg 10, 55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Amy Stetten
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Michael Kappl
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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Dong J, Fan FR, Tian ZQ. Droplet-based nanogenerators for energy harvesting and self-powered sensing. NANOSCALE 2021; 13:17290-17309. [PMID: 34647553 DOI: 10.1039/d1nr05386h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The energy crisis is a continuing topic for all human beings, threatening the development of human society. Accordingly, harvesting energy from the surrounding environment, such as wind, water flow and solar power, has become a promising direction for the research community. Water contains tremendous energy in a variety of forms, such as rivers, ocean waves, tides, and raindrops. Among them, raindrop energy is the most abundant. Raindrop energy not only can complement other forms of energy, such as solar energy, but also have potential applications in wearable and universal energy collectors. Over the past few years, droplet-based electricity nanogenerators (DENG) have attracted significant attention due to their advantages of small size and high power. To date, a variety of fundamental materials and ingenious structural designs have been proposed to achieve efficient droplet-based energy harvesting. The research and application of DENG in various fields have received widespread attention. In this review, we focus on the fundamental mechanism and recent progress of droplet-based nanogenerators in the following three aspects: droplet properties, energy harvesting and self-powered sensing. Finally, some challenges and further outlook for droplet-based nanogenerators are discussed to boost the future development of this promising field.
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Affiliation(s)
- Jianing Dong
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Tan Kah Kee Innovation Laboratory, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Feng Ru Fan
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Tan Kah Kee Innovation Laboratory, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Zhong-Qun Tian
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Tan Kah Kee Innovation Laboratory, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
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Thakur S, Dasmahapatra AK, Bandyopadhyay D. Functional liquid droplets for analyte sensing and energy harvesting. Adv Colloid Interface Sci 2021; 294:102453. [PMID: 34120038 DOI: 10.1016/j.cis.2021.102453] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 05/25/2021] [Accepted: 05/25/2021] [Indexed: 02/06/2023]
Abstract
Over the past century, rapid miniaturization of technologies has helped in the development of efficient, flexible, portable, robust, and compact applications with minimal wastage of materials. In this direction, of late, the usage of mesoscale liquid droplets has emerged as an alternative platform because of the following advantages: (i) a droplet is incompressible and at the same time deformable, (ii) interfacial area of a spherical droplet is minimum for a given amount of mass; and (iii) a droplet interface allows facile mass, momentum, and energy transfer. Subsequently, such attributes have aided towards the design of diverse droplet-based microfluidic technologies. For example, the microdroplets have been utilized as micro-reactors, colorimetric or electrochemical (EC) sensors, drug-delivery vehicles, and energy harvesters. Further, a number of recently reported lab-on-a-chip technologies exploit the motility, storage, and mixing capacities of the microdroplets. In view of this background, the review initiates discussion by highlighting the different attributes of the microdroplets such as size, shape, surface to volume ratio, wettability, and contact line. Thereafter, the effects of the surface or body forces on the properties of the droplets have been elaborated. Finally, the different aspects of such liquid droplet systems towards technological adaptations in health care, sensing, and energy harvesting have been presented. The review concludes with a tight summary on the potential avenues for further developments.
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Affiliation(s)
- Siddharth Thakur
- Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam 781039, India
| | - Ashok Kumar Dasmahapatra
- Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam 781039, India; Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam 781039, India
| | - Dipankar Bandyopadhyay
- Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam 781039, India; Centre for Nanotechnology, Indian Institute of Technology Guwahati, Assam 781039, India.
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Abstract
Interfaces between a liquid and a solid (L-S) are the most important surface science in chemistry, catalysis, energy, and even biology. Formation of an electric double layer (EDL) at the L-S interface has been attributed due to the adsorption of a layer of ions at the solid surface, which causes the ions in the liquid to redistribute. Although the existence of a layer of charges on a solid surface is always assumed, the origin of the charges is not extensively explored. Recent studies of contact electrification (CE) between a liquid and a solid suggest that electron transfer plays a dominant role at the initial stage for forming the charge layer at the L-S interface. Here, we review the recent works about electron transfer in liquid-solid CE, including scenerios such as liquid-insulator, liquid-semiconductor, and liquid-metal. Formation of the EDL is revisited considering the existence of electron transfer at the L-S interface. Furthermore, the triboelectric nanogenerator (TENG) technique based on the liquid-solid CE is introduced, which can be used not only for harvesting mechanical energy from a liquid but also as a probe for probing the charge transfer at liquid-solid interfaces.
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Affiliation(s)
- Shiquan Lin
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, P. R. China.,School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Xiangyu Chen
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, P. R. China.,School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhong Lin Wang
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, P. R. China.,School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
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