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Yi C, Wang A, Cao C, Kuang Z, Tao X, Wang Z, Zhou F, Zhang G, Liu Z, Huang H, Cao Y, Li R, Wang N, Huang W, Wang J. Elevating Charge Transport Layer for Stable Perovskite Light-Emitting Diodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2400658. [PMID: 38782446 DOI: 10.1002/adma.202400658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Revised: 05/16/2024] [Indexed: 05/25/2024]
Abstract
Ion migration is a major factor affecting the long term stability of perovskite light-emitting diodes (LEDs), which limits their commercialization potential. The accumulation of excess halide ions at the grain boundaries of perovskite films is a primary cause of ion migration in these devices. Here, it is demonstrated that the channels of ion migrations can be effectively impeded by elevating the hole transport layer between the perovskite grain boundaries, resulting in highly stable perovskite LEDs. The unique structure is achieved by reducing the wettability of the perovskites, which prevents infiltration of the upper hole-transporting layer into the spaces of perovskite grain boundaries. Consequently, nanosized gaps are formed between the excess halide ions and the hole transport layer, effectively suppressing ion migration. With this structure, perovskite LEDs with operational half-lifetimes of 256 and 1774 h under current densities of 100 and 20 mA cm-2 respectively are achieved. These lifetimes surpass those of organic LEDs at high brightness. It is further found that this approach can be extended to various perovskite LEDs, showing great promise for promoting perovskite LEDs toward commercial applications.
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Affiliation(s)
- Chang Yi
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Airu Wang
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Chensi Cao
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Zhiyuan Kuang
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Xiangru Tao
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Zekun Wang
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Fuyi Zhou
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Guolin Zhang
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Ziping Liu
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Heyong Huang
- Center of Analysis and Testing, Nanjing Normal University, Nanjing, 210023, China
| | - Yu Cao
- Strait Laboratory of Flexible Electronics (SLoFE), Fuzhou, Fujian, 350117, China
- Strait Institute of Flexible Electronics (SIFE, Future Technologies), Fujian Normal University, Fuzhou, Fujian, 350117, China
| | - Renzhi Li
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Nana Wang
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Wei Huang
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
- Strait Laboratory of Flexible Electronics (SLoFE), Fuzhou, Fujian, 350117, China
- Shaanxi Institute of Flexible Electronics (SIFE), Xi'an Institute of Biomedical Materials and Engineering (IBME), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi'an, 710072, China
| | - Jianpu Wang
- Key Laboratory of Flexible Electronics (KLOFE), School of Flexible Electronics (Future Technologies) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
- Strait Laboratory of Flexible Electronics (SLoFE), Fuzhou, Fujian, 350117, China
- School of Materials Science and Engineering & School of Microelectronics and Control Engineering, Changzhou University, Changzhou, Jiangsu, 213164, China
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Jiang Y, Wang Z. Soft wetting: an analytical model for pillar topography- and softness-dependent droplet depinning force. SOFT MATTER 2024; 20:3593-3601. [PMID: 38530168 DOI: 10.1039/d4sm00128a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
Abstract
The extent to which a droplet pins on a textured substrate is determined by the dynamics of the contact line and the liquid-vapor interface. However, the synergistic contribution of contact line sliding and interface distortion to the droplet depinning force remains unknown. More strikingly, current models fail to predict the depinning force per unit length of droplets on soft pillar arrays. Therefore, we fabricate soft pillar arrays with varying geometrical dimensions and mechanical properties and measure the depinning forces per unit length by allowing droplets to evaporate on such substrates. We then analyze the decrease in excess Gibbs free energy of the apparent droplet caused by the detachment of the droplet boundary from the previously pinned pillars. In contrast to prior notions, based on the measured decreases in excess Gibbs free energy, we find that the coefficient, that governs the ratio of interface distortion's contribution to the depinning force to that of the sliding contact line, increases with a decrease in pillar packing density. By considering the combined contribution from contact line sliding, liquid-vapor interface distortion, and pillar deflection, we introduce an analytical model to predict the droplet depinning force per unit length and corroborate the model using experimental data reported in this and prior studies.
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Affiliation(s)
- Youhua Jiang
- Department of Mechanical Engineering (Robotics), Guangdong Technion - Israel Institute of Technology, Shantou, Guangdong 515063, China.
- Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Zhujiang Wang
- Department of Mechanical Engineering (Robotics), Guangdong Technion - Israel Institute of Technology, Shantou, Guangdong 515063, China.
- Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
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3
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Takeuchi K, Ireland PM, Webber GB, Wanless EJ, Hayashi M, Sakabe R, Fujii S. Electrostatic Adsorption Behaviors of Polymer Plates to a Droplet. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023. [PMID: 37392450 DOI: 10.1021/acs.langmuir.3c00485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/03/2023]
Abstract
Electrostatic transfer and adsorption of electrically conductive polymer-coated poly(ethylene terephthalate) plates from a particle bed to a water droplet were studied, with the influence of plate thickness and shape observed. After synthesis and confirmation of the particles' properties using stereo and scanning electron microscopies, elemental microanalysis, and water contact angle measurement, the electric field strength and droplet-bed separation distance required for transfer were measured. An electrometer and high-speed video footage were used to measure the charge transferred by each particle, and its orientation and adsorption behavior during transfer and at the droplet interface. The use of plates of consistent square cross section allowed the impact of contact-area-dependent particle cohesion and gravity on the electrostatic transfer of particles to be decoupled for the first time. The electrostatic force required to extract a plate was directly proportional to the plate mass (thickness), a trend very different from that previously observed for spherical particles of varied diameter (mass). This reflected the different relationship between mass, surface area, and cohesive forces for spherical and plate-shaped particles of different sizes. Thicker plates transferred more charge to the droplet, probably due to their remaining at the bed at higher field strengths. The impact of plate cross-sectional geometry was also assessed. Differences in the ease of transfer of square, hexagonal, and circular plates seemed to depend only on their mass, while other aspects of their comparative behavior are attributed to the more concentrated charge distribution present on particles with sharper vertices.
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Affiliation(s)
- Kazusa Takeuchi
- Division of Applied Chemistry, Environmental and Biomedical Engineering, Graduate School of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan
| | - Peter M Ireland
- ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Grant B Webber
- ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Erica J Wanless
- ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Masaki Hayashi
- Division of Applied Chemistry, Environmental and Biomedical Engineering, Graduate School of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan
| | - Ryuga Sakabe
- Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan
| | - Syuji Fujii
- Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan
- Nanomaterials Microdevices Research Center, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan
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4
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Issakhani S, Jadidi O, Farhadi J, Bazargan V. Geometrically-controlled evaporation-driven deposition of conductive carbon nanotube patterns on inclined surfaces. SOFT MATTER 2023; 19:1393-1406. [PMID: 36723256 DOI: 10.1039/d2sm01431a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Controllable accumulation of carbon nanotubes in self-assembly techniques is of critical importance in smart patterning and printed electronics. This study investigates how inclining the substrate and inhibiting the droplet spreading by sharp solid edges can affect the droplet contact angle and pinning time to improve the electrical conductivity and uniformity of the deposited patterns. Rectangular and circular pedestals were employed to investigate the effect of geometry on the deposition characteristics and to incorporate the gravitational effect by varying the substrate inclination angle. The results indicate that confining the droplet contact line to remain pinned to the pedestal edge can significantly alter the width, uniformity, and precision of the deposited patterns. These improvements correspond to the enhancement of the droplet pinning time (due to the edge effect) and to the further increase of the local evaporation rate near the contact line (due to the droplet elevation). By conducting experiments on different rectangular pedestals with varying solid-liquid interfacial areas and comparing their deposition characteristics, a rectangular pedestal with specific dimensions is selected in terms of pattern consistency and material usage efficiency. It is also shown that higher inclination angles further increase the deposited line accumulation density. Combining confinement and inclination techniques yields promising deposited patterns with high consistency and low resistivity, ranging from 8.75 kΩ mm-1 to a minimum of 0.63 kΩ mm-1 for a 3 × 6 mm2 rectangular pedestal.
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Affiliation(s)
- Shervin Issakhani
- School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
| | - Omid Jadidi
- School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
| | - Jafar Farhadi
- School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
| | - Vahid Bazargan
- School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
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5
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Wang X, Fu C, Zhang C, Qiu Z, Wang B. A Comprehensive Review of Wetting Transition Mechanism on the Surfaces of Microstructures from Theory and Testing Methods. MATERIALS (BASEL, SWITZERLAND) 2022; 15:4747. [PMID: 35888211 PMCID: PMC9317979 DOI: 10.3390/ma15144747] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/01/2022] [Accepted: 06/07/2022] [Indexed: 02/07/2023]
Abstract
Superhydrophobic surfaces have been widely employed in both fundamental research and industrial applications because of their self-cleaning, waterproof, and low-adhesion qualities. Maintaining the stability of the superhydrophobic state and avoiding water infiltration into the microstructure are the basis for realizing these characteristics, while the size, shape, and distribution of the heterogeneous microstructures affect both the static contact angle and the wetting transition mechanism. Here, we review various classical models of wettability, as well as the advanced models for the corrected static contact angle for heterogeneous surfaces, including the general roughness description, fractal theory description, re-entrant geometry description, and contact line description. Subsequently, we emphasize various wetting transition mechanisms on heterogeneous surfaces. The advanced testing strategies to investigate the wetting transition behavior will also be analyzed. In the end, future research priorities on the wetting transition mechanisms of heterogeneous surfaces are highlighted.
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Affiliation(s)
- Xiao Wang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
| | - Cheng Fu
- China Classification Society Quality Assurance Ltd., Beijing 100006, China;
| | - Chunlai Zhang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
| | - Zhengyao Qiu
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
| | - Bo Wang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
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6
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Jena AK, Bhimavarapu YVR, Tang S, Liu J, Das R, Gulec S, Vinod A, Yao CW, Cai T, Tadmor R. Stages That Lead to Drop Depinning and Onset of Motion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:92-99. [PMID: 34939810 DOI: 10.1021/acs.langmuir.1c02091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In this paper, we consider drops that are subjected to a gradually increasing lateral force and follow the stages of the motion of the drops. We show that the first time a drop slides as a whole is when the receding edge of the drop is pulled by the advancing edge (the advancing edge drags the receding edge). The generality of this phenomenon includes sessile and pendant drops and spans over various chemically and topographically different cases. Because this observation is true for both pendant and sessile cases, we exclude hydrostatic pressure as its reason. Instead, we explain it in terms of the wetting adaptation and interfacial modulus, that is, the difference in the energies of the solid interface at the advancing and receding edges. At the receding edge, a slight motion exposes to the air a recently wetted solid surface whose molecules had reoriented to the liquid and will take time to reorient back to the air. This results in a high surface energy at the solid-air interface which pulls on the triple line, that is, inhibits the motion of the receding edge. On the other hand, at the advancing edge, a slight advancement does not change the nature of the solid interfacial molecules outside the drop, and the advancing side's sliding can continue. Moreover, the solid molecules under the drop at the advancing edge take time to reorient, and hence, their configuration is not yet adapted for the liquid and therefore not adapted for retention of the advancing edge. Therefore, in sliding-drop experiments, the advancing edge moves before the receding one, typically a few times before the receding edge moves. For the same reason, the last motion of the receding edge usually happens as a result of the advancing edge pulling on it.
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Affiliation(s)
- Akash K Jena
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Yagna Valkya Reddy Bhimavarapu
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Sirui Tang
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Jie Liu
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Ratul Das
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Semih Gulec
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Appu Vinod
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Chun-Wei Yao
- Department of Mechanical Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Tianxing Cai
- Dan F. Smith Department of Chemical & Biomolecular Engineering, Lamar University, P.O. Box 10053, Beaumont Texas 77710, United States
| | - Rafael Tadmor
- Department of Mechanical Engineering, Ben Gurion University, Beer Sheva 84105, Israel
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He L, Ding L, Li B, Mu W, Li P, Liu F. Regulating Droplet Wetting and Pinning Behaviors on Pathogen-Modified Hydrophobic Surfaces: Strategies and Working Mechanisms. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:11720-11732. [PMID: 34550679 DOI: 10.1021/acs.jafc.1c04216] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Hydrophobic surfaces modified by pathogens in agricultural production are one of the main reasons to reduce the utilization of pesticides. Adding surfactants to pesticide solutions is a common method to improve their wetting and spreading properties. In this work, the interaction mechanism between pathogen-modified hydrophobic surfaces and mixtures of surfactants and a pesticide was studied in detail. The interaction mechanism was determined by characterizing the wetting and spreading behaviors of droplets on cucumber powdery mildew leaves at different growth stages. When surfactants were added, droplets on cucumber powdery mildew leaves were in the Wenzel wetting state, the pinning force weakened, the contact line speed accelerated, and the adhesion force increased. We explained the micellar state and aggregation behavior of surfactant molecules in a pesticide solution that was applied to the surface of cucumber powdery mildew leaves. Droplets of solutions containing nonionic surfactants easily formed semibald micelles, binding to the pathogen of powdery mildew, whereas droplets containing cationic surfactants did not do so. Because of the electrostatic interaction between cationic surfactant molecules and powdery mildew pathogens, cationic surfactant molecules did not wet the pathogens very well, so we suggest adding nonionic surfactants rather than cationic surfactants to improve the wetting and spreading of pesticide solutions on cucumber powdery mildew leaves. This study provides new insights into enhancing the wetting and deposition of droplets on pathogen-modified hydrophobic surfaces.
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Affiliation(s)
- Lifei He
- Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong 271018, People's Republic of China
- College of Chemistry and Materials Science, Shandong Agricultural University, Tai'an, Shandong 271018, People's Republic of China
| | - Lei Ding
- Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong 271018, People's Republic of China
| | - Beixing Li
- Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong 271018, People's Republic of China
| | - Wei Mu
- Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong 271018, People's Republic of China
| | - Peiqiang Li
- College of Chemistry and Materials Science, Shandong Agricultural University, Tai'an, Shandong 271018, People's Republic of China
| | - Feng Liu
- Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong 271018, People's Republic of China
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8
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Air entrapment and bubble formation during droplet impact onto a single cubic pillar. Sci Rep 2021; 11:18018. [PMID: 34504203 PMCID: PMC8429739 DOI: 10.1038/s41598-021-97376-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 08/24/2021] [Indexed: 02/08/2023] Open
Abstract
We study the vertical impact of a droplet onto a cubic pillar of comparable size placed on a flat surface, by means of numerical simulations and experiments. Strikingly, during the impact a large volume of air is trapped around the pillar side faces. Impingement upon different positions of the pillar top surface strongly influences the size and the position of the entrapped air. By comparing the droplet morphological changes during the impact from both computations and experiments, we show that the direct numerical simulations, based on the Volume of Fluid method, provide additional and new insight into the droplet dynamics. We elucidate, with the computational results, the three-dimensional air entrapment process as well as the evolution of the entrapped air into bubbles.
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9
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Wang Z, Wang X, Miao Q, Gao F, Zhao YP. Spontaneous Motion and Rotation of Acid Droplets on the Surface of a Liquid Metal. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:4370-4379. [PMID: 33792321 DOI: 10.1021/acs.langmuir.1c00455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Self-propulsion of droplets is of great significance in many fields. The spontaneous horizontal motion and self-jumping of droplets have been well realized in various ways. However, there is still a lack of an effective method to enable a droplet to rotate spontaneously and steadily. In this paper, by employing an acid droplet and a liquid metal, the spontaneous and steady rotation of droplets is achieved. For an acid droplet, it may spontaneously move when it is deposited on the surface of the liquid metal. By adjusting experimental parameters to the proper range, the self-rotation of droplet happens. This phenomenon originates from the fluctuation of the droplet boundary and the collective movement of bubbles that are generated by the chemical reactions between the acid droplet and liquid metal. This rotation has a simpler implementation method and more steady rotation state. Its angular velocity is much higher than that driven by other mechanisms. Moreover, the movements of acid droplets on the liquid metal are classified according to experimental conditions. The internal flow fields, the movements and distribution of bubbles, and the fluctuation of the droplet boundary are also explored and discussed. The theoretical model describing the rotational droplet is given. Our work may deepen the understanding of the physical system transition affected by chemical reactions and provide a new way for the design of potential applications, e.g., micro- and nanodevices.
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Affiliation(s)
- Zhanlong Wang
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Xiaohe Wang
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Qing Miao
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Feifei Gao
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Ya-Pu Zhao
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
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Chen X, Li X, Zuo P, Liang M, Li X, Xu C, Yuan Y, Wang S. Three-Dimensional Maskless Fabrication of Bionic Unidirectional Liquid Spreading Surfaces Using a Phase Spatially Shaped Femtosecond Laser. ACS APPLIED MATERIALS & INTERFACES 2021; 13:13781-13791. [PMID: 33703880 DOI: 10.1021/acsami.0c22080] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ubiquitous biological processes exhibit the ability to achieve spontaneous directionally guided droplet transport. Maskless three-dimensional (3D) fabrication of various miniature bionic structures, a method applicable to various materials, is subject to processing method limitations. This remains a large obstacle to realizing self-driven, continuous, and controllable unidirectional liquid spreading. Thus, we present a flexible maskless 3D method for fabricating bionic unidirectional liquid spreading surfaces by using a phase spatially shaped femtosecond laser. The laser can be transformed from having Gaussian distributions to having 3D bionic structure field distributions. Furthermore, we fabricated Syntrichia caninervis bionic structures with a spiculate end for unidirectional water spreading; 1 μL droplets had a 16 mm flow length on Si surfaces when the S. caninervis single structure was 34 (length), 8 (width), and 12 μm (height). Furthermore, various bionic structures-Nepenthes, cactus, and moth structures-were fabricated on Si, SiO2, and Ti. We also demonstrated the measurability of two-dimensional (S-shaped) curved flows on Si wafers as well as 3D curved flows on a Ti pipe turning 120° within 2320 ms. Our method can realize high-efficiency maskless 3D processing of various materials and structures (especially asymmetric structures); it is both flexible and fast, effectively expanding the processing capacity of micro-/nanostructures on patterned surfaces. This is of great significance to various domains such as microfluids, fog collection, and chemical reaction control.
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Affiliation(s)
- Xiaozhe Chen
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Xin Li
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Pei Zuo
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - MiSheng Liang
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Xiaojie Li
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Chenyang Xu
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Yongjiu Yuan
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Sumei Wang
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
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12
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Ozcelik HG, Satiroglu E, Barisik M. Size dependent influence of contact line pinning on wetting of nano-textured/patterned silica surfaces. NANOSCALE 2020; 12:21376-21391. [PMID: 33078810 DOI: 10.1039/d0nr05392a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Wetting behavior on a heterogeneous surface undergoes contact angle hysteresis as the droplet stabilized at a metastable state with a contact angle significantly different from its equilibrium value due to contact line pinning. However, there is a lack of consensus on how to calculate the influence of pinning forces. In general, the pinning effect can be characterized as (i) microscopic behavior when a droplet is pinned and the contact angle increases/decreases as the droplet volume increases/decreases and (ii) macroscopic behavior as the pinning effects decrease and ultimately, disappear with the increase of the droplet size. The current work studied both behaviors using molecular dynamics (MD) simulation with more than 300 different size water droplets on silica surfaces with three different patterns across two different wetting conditions. Results showed that the contact angle increases linearly with increasing droplet volume through the microscopic behavior, while the droplet is pinned on top of a certain number of patterns. When we normalized the droplet size with the corresponding pattern size, we observed a "wetting similarity" that linear microscopic contact angle variations over different size heterogeneities continuously line up. This shows that the pinning force remains constant and the resulting pinning effects are scalable by the size ratio between the droplet and pattern, independent of the size-scale. The slope of these microscopic linear variations decreases with an increase in the droplet size as observed through the macroscopic behavior. We further found a universal behavior in the variation of the corresponding pinning forces, independent of the wetting condition. In macroscopic behavior, pinning effects become negligible and the contact angle reaches the equilibrium value of the corresponding surface when the diameter of the free-standing droplet is approximately equal to 24 times the size of the surface structure. We found that the pinning effect is scalable with the droplet volume, not the size of the droplet base.
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Affiliation(s)
- H Gokberk Ozcelik
- Department of Mechanical Engineering, Izmir Institute of Technology, Izmir, 35430, Turkey.
| | - Ezgi Satiroglu
- Department of Energy Systems Engineering, Izmir Institute of Technology, Izmir, 35430, Turkey
| | - Murat Barisik
- Department of Mechanical Engineering, Izmir Institute of Technology, Izmir, 35430, Turkey.
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Kumar M, Bhardwaj R. Wetting characteristics of Colocasia esculenta (Taro) leaf and a bioinspired surface thereof. Sci Rep 2020; 10:935. [PMID: 31969578 PMCID: PMC6976613 DOI: 10.1038/s41598-020-57410-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 12/31/2019] [Indexed: 11/29/2022] Open
Abstract
We investigate wetting and water repellency characteristics of Colocasia esculenta (taro) leaf and an engineered surface, bioinspired by the morphology of the surface of the leaf. Scanning electron microscopic images of the leaf surface reveal a two-tier honeycomb-like microstructures, as compared to previously-reported two-tier micropillars on a Nelumbo nucifera (lotus) leaf. We measured static, advancing, and receding angle on the taro leaf and these values are around 10% lesser than those for the lotus leaf. Using standard photolithography techniques, we manufactured bioinspired surfaces with hexagonal cavities of different sizes. The ratio of inner to the outer radius of the circumscribed circle to the hexagon (b/a) was varied. We found that the measured static contact angle on the bioinspired surface varies with b/a and this variation is consistent with a free-energy based model for a droplet in Cassie-Baxter state. The static contact angle on the bioinspired surface is closer to that for the leaf for b/a ≈ 1. However, the contact angle hysteresis is much larger on these surfaces as compared to that on the leaf and the droplet sticks to the surfaces. We explain this behavior using a first-order model based on force balance on the contact line. Finally, the droplet impact dynamics was recorded on the leaf and different bioinspired surfaces. The droplets bounce on the leaf beyond a critical Weber number (We ~ 1.1), exhibiting remarkable water-repellency characteristics. However, the droplet sticks to the bioinspired surfaces in all cases of We. At larger We, we recorded droplet breakup on the surface with larger b/a and droplet assumes full or partial Wenzel state. The breakup is found to be a function of We and b/a and the measured angles in full Wenzel state are closer to the predictions of the free-energy based model. The sticky bioinspired surfaces are potentially useful in applications such as water-harvesting.
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Affiliation(s)
- Manish Kumar
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Rajneesh Bhardwaj
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India.
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Zhang Z, Guo X, Tang H, Ding J, Zheng YG, Li S. Unidirectional Self-Driving Liquid Droplet Transport on a Monolayer Graphene-Covered Textured Substrate. ACS APPLIED MATERIALS & INTERFACES 2019; 11:28562-28570. [PMID: 31304739 DOI: 10.1021/acsami.9b09219] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Controllable directional transport of liquid droplets on a functionalized surface has been a challenge in the field of microfluidics because it does not require energy supply, and the physical mechanism of such self-driving transport exhibits extraordinary contribution to fundamental understanding of some biological processes and the design of microfluidic apparatus. In this paper, we report a novel design of a surface microstructure that can realize unidirectional self-driving liquid mercury (Hg) droplet transport on a graphene-covered copper (Cu) substrate with a three-dimensional surface microstructure. We have demonstrated that a liquid Hg droplet spontaneously propagates on a grooved Cu substrate covered by a monolayer graphene without any external force fields. Classical molecular dynamics results provide a profound insight on the self-driving process of Hg droplets. It shows that the Hg droplet undergoes acceleration, deceleration, and return stages successively from the narrow to wide ends of the gradient groove. Intriguingly, Hg droplets can move continuously and unidirectionally on the three-dimensional graphene-covered surface microstructure when they accumulate enough kinetic energy from the gradient groove to break the energy barrier at the step junctions between the two neighboring unit cells. The design of the zigzag textured surface covered by a monolayer graphene artfully uses the facts; (1) the monolayer graphene can effectively reduce the droplet pinning on the textured surface, (2) the hydrophobic graphene layer reduces the friction between Hg droplets and the substrate, and (3) the textured surface can permeably interact with the droplets through the monolayer graphene to achieve a continuous self-driving process. The findings reported here open a door to explore the graphene-covered functional surface to directional transport of liquid droplets and provide an in-depth understanding of the self-driving mechanism for liquid droplets on graphene-covered textured substrates.
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Affiliation(s)
- Zhongqiang Zhang
- Micro/Nano Science and Technology Center , Jiangsu University , Zhenjiang 212013 , P. R. China
- Department of Civil and Environmental Engineering , University of California , Berkeley , California 94720-1710 , United States
- State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics , Dalian University of Technology , Dalian 116024 , P. R. China
- Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering , Changzhou University , Changzhou 213164 , P. R. China
| | - Xinfeng Guo
- Micro/Nano Science and Technology Center , Jiangsu University , Zhenjiang 212013 , P. R. China
| | - Huayuan Tang
- State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics , Dalian University of Technology , Dalian 116024 , P. R. China
| | - Jianning Ding
- Micro/Nano Science and Technology Center , Jiangsu University , Zhenjiang 212013 , P. R. China
- Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering , Changzhou University , Changzhou 213164 , P. R. China
| | - Yong-Gang Zheng
- State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics , Dalian University of Technology , Dalian 116024 , P. R. China
| | - Shaofan Li
- Department of Civil and Environmental Engineering , University of California , Berkeley , California 94720-1710 , United States
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