Magnetically Enhanced Marangoni Convection for Efficient Mass and Heat Transfer like a Self‐Driving Liquid Conveyor Belt

Zhang, Hang; Lin, Feng; Liu, Laichen; Tong, Tian; Li, Runjia; Zhong, Hong; Chen, Zhongchen; Qin, Chengzhen; Wang, Qiaozhen; Yu, Qi; Wu, Changjin; Tong, Xin; Yu, Peng; Sun, Ke; Liu, Dong; Bao, Jiming; Wang, Zhiming

doi:10.1002/adfm.202202984

Cited by 6 publications

(9 citation statements)

References 36 publications

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“…Thermal infrared imaging has proven to be a valuable tool in studying and understanding photothermal convection in liquids, [12,15,33] so we employ the same technique to investigate the effect of magnetic fields on the flow patterns. Figure 3e presents the evolution of surface temperature in a weak magnetic field of 23 mT.…”

Section: Resultsmentioning

confidence: 99%

“…We propose that the observed flow patterns are characteristic thermomagnetic convections of ferrofluid, which differ from surface tension-driven convections typically observed in free surfaces. [12,15,32,33] Thermomagnetic convection occurs when there is a temperature-dependent magnetic susceptibility and a non-uniform magnetic field. [12][13][14]25,27] With the rising temperature, the magnetization of ferrofluid decreased linearly as shown in Figure S1b (Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

“…[12,15,32,33] Thermomagnetic convection occurs when there is a temperature-dependent magnetic susceptibility and a non-uniform magnetic field. [12][13][14]25,27] With the rising temperature, the magnetization of ferrofluid decreased linearly as shown in Figure S1b (Supporting Information). In our experimental setup, a heated ferrofluid with reduced magnetic susceptibility is displaced by colder ferrofluid from regions with weaker magnetic fields.…”

Section: Resultsmentioning

confidence: 99%

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Spinning a Liquid Wheel and Driving Surface Thermomagnetic Convection with Light

Liu,

Lin,

Qin

et al. 2023

Advanced Materials

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A typical Tesla thermomagnetic engine employs a solid magnetic wheel to convert thermal energy into mechanical energy, while thermomagnetic convection in ferrofluid is still challenging to observe because it is a volume convection that occurs in an enclosed space. Using a water‐based ferrofluid, we demonstrate a liquid Tesla thermomagnetic engine and report the observation of thermomagnetic convection on a free surface. Both types of fluid motions are driven by light and observed by simply placing ferrofluid on a cylindrical magnet. The surface thermomagnetic convection on the free surface is made possible by eliminating the Marangoni effect, while the spinning of the liquid wheel is achieved through the solid‐like behavior of the ferrofluid under a strong magnetic field. Increasing the magnetic field reveals a transition from simple thermomagnetic convection to a combination of the central spin of the spiky wheel surrounded by thermomagnetic convection in the outer region of the ferrofluid. We further demonstrate the coupling between multiple ferrofluid wheels through a fluid bridge. These demonstrations not only unveil the unique properties of ferrofluid but also provide a new platform for studying complex fluid dynamics and thermomagnetic convection, opening up exciting opportunities for light‐controlled fluid actuation and soft robotics.This article is protected by copyright. All rights reserved

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Spinning a Liquid Wheel and Driving Surface Thermomagnetic Convection with Light

Liu,

Lin,

Qin

et al. 2023

Advanced Materials

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“…The fluid then flew outward along the interface from the high-temperature region with respect to the laser-acted zone to the low-temperature region. An inward flow inside the droplet arose from the colder region due to mass conservation, forming a complete circulation loop. − Actually, this circular flow could be stable in the case of low laser power (38 mW), which was characterized by adding polystyrene (PS) tracer microspheres into the droplet to probe Marangoni convection. There was a stable Marangoni flow and no deformation of droplet interface (Movie S2).…”

mentioning

confidence: 99%

Light Fueled High-Throughput Binary Droplet Splitting and Transport on High-Energy Substrate

Wang

et al. 2023

J. Phys. Chem. Lett.

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High-throughput droplet splitting and controllable transport of generated microdroplets on open surfaces are crucial in a broad spectrum of applications. Herein, a light strategy for controlling high-throughput splitting of binary droplets and transport of generated microdroplets on a high-energy substrate endowed by a localized photothermal effect is reported. Strong Marangoni flow as a result of the surface tension gradient and limited inward flow at the droplet bottom as a result of the significant viscous effect are together responsible for binary droplet splitting. The temperature gradients across the generated microdroplets established at the core heating zone are responsible for their transport away from the laser-acted zone. Remarkably, assisted by hydrophobic stripes on a high-energy substrate, high-throughput binary droplet splitting and controllable transport of generated microdroplets can be realized. Successful applications in biosample droplets and parallelized microreactions highlight the promising potential of this light strategy in open droplet microfluidics, biological assays and diagnosis, etc.

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“…Due to the Marangoni effect, the temperature gradient will induce a surface tension gradient of the liquid and produce microscopic Marangoni flows. [2,[15][16][17][18][19] The Marangoni flow propels the actuator to complete the macroscopic actuation behavior on the liquid surface. There are two essential features for an efficient opticallydriven actuation on the water surface.…”

mentioning

confidence: 99%

Fast and Multifunctional Optically‐Driven Actuators based on Stable, Efficient, and Superhydrophobic Photothermal Paper Films

Wang

Jing

et al. 2022

Advanced Optical Materials

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By applying external energy such as electrical, magnetic, and light, the actuators can be manipulated to move or perform designed actions. [2,5,6] Electrically-driven actuators require a wired connection, and magnetically-driven actuation requires strong magnets or a short distance between the magnet and the actuator. [7][8][9] Compared to their electric and magnetic counterparts, opticallydriven actuators are wireless and can be controlled remotely. Various propulsion strategies such as photochemical reactions, photoelectric effect, self-thermophoresis, and Marangoni effect have been developed to realize the optically induced actuation. [10][11][12][13][14] Among these strategies, driving the actuators via the photothermally-promoted Marangoni propulsion has been found to be an efficient and facile method. [15,16] Marangoni propulsion relies on the heat generated by photothermal conversion on the actuator to form a temperature gradient on a liquid surface. Due to the Marangoni effect, the temperature gradient will induce a surface tension gradient of the liquid and produce microscopic Marangoni flows. [2,[15][16][17][18][19] The Marangoni flow propels the actuator to complete the macroscopic actuation behavior on the liquid surface. There are two essential features for an efficient opticallydriven actuation on the water surface. It should primarily have efficient photothermal conversion characteristics to rapidly form temperature and surface tension gradients on the water surface. Additionally, the drag force should be minimized when the Marangoni flow propels the actuator. Materials with high absorption can be used for efficient photothermal conversion and reduce drag by fabricating the superhydrophobic surface. [15,20] However, several challenges limit the wide application of optically-driven actuators with the Marangoni effect. Preparation methods for actuators based on superhydrophobic photothermal materials are usually complicated and fluorinecontaining reagents used for superhydrophobic chemical modification are environmentally harmful. [21][22][23] The fabrication of actuators based on superhydrophobic photothermal materials synthesized in an environmentally friendly way is crucial for Remotely controlled self-propelled optically-driven actuators are increasingly attractive for sensing and robotic applications. However, complexities in material synthesis, multifunctionality, dynamic response, and the response rate limit their use for wide-ranging application. This work uses a simple and efficient spraying method to prepare optically-driven actuators based on TiN@PDMS-PVDF (TiN@polydimethylsiloxane-polyvinylidene difluoride) papers. The actuator exhibits stable superhydrophobicity for photothermal heating and corrosive solutions with a contact angle and sliding angle of 169.9° and 2.3°, respectively. The superhydrophobic actuators exhibit an efficient photothermal conversion aided by a very high optical absorption of the material approaching 97%. The optically-driven actuator based on the TiN@PDMS-PVDF pap...

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Magnetically Enhanced Marangoni Convection for Efficient Mass and Heat Transfer like a Self‐Driving Liquid Conveyor Belt

Cited by 6 publications

References 36 publications

Spinning a Liquid Wheel and Driving Surface Thermomagnetic Convection with Light

Spinning a Liquid Wheel and Driving Surface Thermomagnetic Convection with Light

Light Fueled High-Throughput Binary Droplet Splitting and Transport on High-Energy Substrate

Fast and Multifunctional Optically‐Driven Actuators based on Stable, Efficient, and Superhydrophobic Photothermal Paper Films

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