1
|
Galy PE, Guitton-Spassky T, Sella C, Thouin L, Vitale MR, Baigl D. Redox Control of Particle Deposition from Drying Drops. ACS Appl Mater Interfaces 2022; 14:3374-3384. [PMID: 34994535 DOI: 10.1021/acsami.1c18933] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The coffee-ring effect (CRE), which denotes the accumulation of nonvolatile compounds at the periphery of a pinned sessile drying drop, is a universal and ubiquitous yet complex phenomenon. It is crucial to better understand and control it, either to avoid its various deleterious consequences in many processes requiring homogeneous deposition or to exploit it for applications ranging from controlled particle patterning to low cost diagnostics. Here, we report for the first time the use of a reduction-oxidation (redox) stimulus to cancel the CRE or harness it, leading to a robust and tunable control of particle deposition in drying sessile drops. This is achieved by implementing redox-sensitive ferrocenyl cationic surfactants of different chain lengths in drying drops containing anionic colloids. Varying surfactant hydrophobicity, concentration, and redox state allows us not only to control the overall distribution of deposited particles, including the possibility to fully cancel the CRE, but also to modify the microscopic organization of particles inside the deposit. Notably, with all other parameters being fixed, this method allows the adjustment of the deposited particle patterns, from polycrystalline rings to uniform disks, as a function of the oxidation rate. We show that the redox control can be achieved either chemically by the addition of oxidants or electrochemically by applying a potential for additive-free and reversible actuation in a closed system. This correlation between the redox state and the particle pattern opens a perspective for both redox-programmable particle patterning and original diagnostic applications based on the visual determination of a redox state. It also contributes to clarify the role of surfactant charge and its amphiphilic character in directing particle deposition from drying suspensions.
Collapse
Affiliation(s)
- Pauline E Galy
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Tiffany Guitton-Spassky
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Catherine Sella
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Laurent Thouin
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Maxime R Vitale
- UMR 7203, Department of Chemistry, Ecole Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Damien Baigl
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| |
Collapse
|
2
|
Galy PE, Rudiuk S, Morel M, Baigl D. Self-Propelled Water Drops on Bare Glass Substrates in Air: Fast, Controllable, and Easy Transport Powered by Surfactants. Langmuir 2020; 36:6916-6923. [PMID: 32074453 DOI: 10.1021/acs.langmuir.9b03727] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Self-propelled drops are capable of motion without external intervention. As such, they constitute attractive entities for fundamental investigations in active soft matter, hydrodynamics, and surface sciences, as well as promising systems for autonomous microfluidic operations. In contrast with most of the examples relying on organic drops or specifically treated substrates, here we describe the first system of nonreactive water drops in air that can propel themselves on a commercially available ordinary glass substrate that was used as received. This is achieved by exploiting the dynamic adsorption behavior of common n-alkyltrimethylammonium bromide (CnTAB) surfactants added to the drop. We precisely analyze the drop motion for a broad series of surfactants carrying n = 6 to 18 carbon atoms in their tail and establish how the motion characteristics (speed, probability of motion) are tuned by both the hydrophobicity and the concentration of the surfactant. We show that motion occurs regardless of the n value but only in a specific concentration range with a maximum speed at around one tenth of the critical micelle concentration (CMC/10) for most of the tested surfactants. Surfactants of intermediate hydrophobicity are shown to be the best candidates to power drops that can move at a high speed (1-10 cm s-1), the optimal performance being reached with [C12TAB] = 800 μM. We propose a mechanism where the motion originates from the anisotropic wettability of the substrate created by the electrostatic adsorption of surfactants beneath the moving drop. Simply drawing lines with a marker pen allows us to create guiding paths for drop motion and to achieve operations such as complex trajectory control, programmed drop fusion, drop refilling, as well as drop moving vertically against gravity. This work revisits the role of surfactants in dynamic wetting and self-propelled motion as well as brings an original strategy to build the future of microfluidics with lower-cost, simpler, and more autonomous portable devices that could be made available to everyone and everywhere.
Collapse
Affiliation(s)
- Pauline E Galy
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Sergii Rudiuk
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Mathieu Morel
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Damien Baigl
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| |
Collapse
|