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Braun F, Wagner MFP, Toimil-Molares ME, von Klitzing R. Comparison of Different Preparation Techniques of Thermophoretic Swimmers and Their Propulsion Velocity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:5606-5616. [PMID: 38501265 DOI: 10.1021/acs.langmuir.3c01776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
The motion of partly gold (Au)-coated Janus particles under laser irradiation is caused by self-thermophoresis. Despite numerous studies addressing this topic, the impact of the preparation method and the degree of coverage of the particle with Au on the resulting thermophoretic velocity has not yet been fully understood. A detailed understanding of the most important tuning parameters during the preparation process is crucial to design Janus particles that are optimized for Au coverage to receive a high thermophoretic velocity. In this study, we explore the influence of the fabrication process, which changes the Au cap size, on the resulting self-propulsion behavior of partly Au-coated polystyrene particles (Au-PS). Additionally, the impact of an underlying adhesion chromium layer is investigated. In addition to the most commonly used qualitative SEM and EDX measurements, we propose a novel and fast technique utilizing AFM studies to quantify the cap size. This non-invasive technique can be used to determine both the size and the maximum thickness of the Au cap. The Au cap size was systematically varied in a range between about 36 and 74% by different preparation strategies. Nevertheless, we showed that the differing Au cap sizes of the Janus particles in this range have no obvious effect on the thermophoretic velocity. This is a surprising result since one would expect an effect of the Au cap size due to different solvent flows around the Janus particles and is attributed to an additional torque near the surface of the measuring cell.
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Affiliation(s)
- Franziska Braun
- Soft Matter at Interfaces, Institute for Condensed Matter Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
| | | | | | - Regine von Klitzing
- Soft Matter at Interfaces, Institute for Condensed Matter Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
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Huang Y, Wu C, Dai J, Liu B, Cheng X, Li X, Cao Y, Chen J, Li Z, Tang J. Tunable Self-Thermophoretic Nanomotors with Polymeric Coating. J Am Chem Soc 2023; 145:19945-19952. [PMID: 37641545 DOI: 10.1021/jacs.3c06322] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Thermophoretic micro/nanomotors (MNMs) generate self-propulsion without a chemical reaction. Intrinsically, this promises excellent biocompatibility and is thus suitable for biomedical applications. However, their propulsion efficiency is severely limited due to the poor understanding of the thermophoretic process, which dominates the conversion from thermal energy into mechanical movement. We here developed a series of self-thermophoresis light-powered MNMs with variable surface coatings and discovered obvious self-thermophoresis propulsion enhancement of the polymeric layer. An intrinsically negative self-thermophoretic movement is also observed for the first time in the MNM system. We propose that enthalpic contributions from polymer-solvent interactions should play a fundamental role in the self-thermophoretic MNMs. Quantitative microcalorimetry and molecular dynamics simulations are performed to support our hypothesis. The polymer solvation enthalpy and coating thickness influences on self-thermophoresis are investigated, further highlighting the essential enthalpy contributions to thermophoresis. Our work indicates that surface grafting would be important in designing high-efficiency thermally driven nanorobotic systems for biomedical applications.
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Affiliation(s)
- Yaxin Huang
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Changjin Wu
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Jia Dai
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Biyuan Liu
- Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China
| | - Xiang Cheng
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Xiaofeng Li
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Yingnan Cao
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Jingyuan Chen
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Zhigang Li
- Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China
| | - Jinyao Tang
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
- State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Hong Kong 999077, China
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Raman H, Das S, Sharma H, Singh K, Gupta S, Mangal R. Dynamics of Active SiO 2-Pt Janus Colloids in Dilute Poly(ethylene oxide) Solutions. ACS PHYSICAL CHEMISTRY AU 2023; 3:279-289. [PMID: 37249935 PMCID: PMC10214528 DOI: 10.1021/acsphyschemau.2c00056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 01/06/2023] [Accepted: 01/06/2023] [Indexed: 05/31/2023]
Abstract
Self-propelled Janus colloids (JCs) have recently gained much attention due to their ability to move autonomously and mimic biological microswimmers. This ability makes them suitable for prospective drug/cargo-delivery applications in microscopic domains. Understanding their dynamics in surroundings doped with macromolecules such as polymers is crucial, as most of the target application media are complex in nature. In this study, we investigate the self-diffusiophoretic motion of hydrogen peroxide-fuelled SiO2-Pt JCs in the presence of dilute amounts of poly(ethylene oxide) (PEO). Despite the addition of PEO chains producing a Newtonian behavior with negligible increase in viscosity, the ballistic movement and rotational fluctuations of active JCs are observed to be significantly suppressed. With an increase in the polymer concentration, this leads to a transition from smooth to jittery to cage-hopping to the arrested motion of active JCs. We further propose that the anisotropic interaction of the polymers with the JC increases the "local drag" of the medium, resulting in the unusual impediment of the active motion.
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Affiliation(s)
- Harishwar Raman
- Department
of Chemical Engineering, Indian Institute
of Technology Kanpur, Kanpur208016, India
| | - Sneham Das
- Department
of Chemical Engineering, Jadavpur University, Kolkata700032, India
| | - Hrithik Sharma
- Department
of Chemical Engineering, Indian Institute
of Technology Kanpur, Kanpur208016, India
| | - Karnika Singh
- Department
of Chemical Engineering, Indian Institute
of Technology Kanpur, Kanpur208016, India
| | - Shruti Gupta
- Department
of Chemical Engineering, Indian Institute
of Technology Kanpur, Kanpur208016, India
| | - Rahul Mangal
- Department
of Chemical Engineering, Indian Institute
of Technology Kanpur, Kanpur208016, India
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Liebchen B, Mukhopadhyay AK. Interactions in active colloids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:083002. [PMID: 34788232 DOI: 10.1088/1361-648x/ac3a86] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 11/16/2021] [Indexed: 06/13/2023]
Abstract
The past two decades have seen a remarkable progress in the development of synthetic colloidal agents which are capable of creating directed motion in an unbiased environment at the microscale. These self-propelling particles are often praised for their enormous potential to self-organize into dynamic nonequilibrium structures such as living clusters, synchronized super-rotor structures or self-propelling molecules featuring a complexity which is rarely found outside of the living world. However, the precise mechanisms underlying the formation and dynamics of many of these structures are still barely understood, which is likely to hinge on the gaps in our understanding of how active colloids interact. In particular, besides showing comparatively short-ranged interactions which are well known from passive colloids (Van der Waals, electrostatic etc), active colloids show novel hydrodynamic interactions as well as phoretic and substrate-mediated 'osmotic' cross-interactions which hinge on the action of the phoretic field gradients which are induced by the colloids on other colloids in the system. The present article discusses the complexity and the intriguing properties of these interactions which in general are long-ranged, non-instantaneous, non-pairwise and non-reciprocal and which may serve as key ingredients for the design of future nonequilibrium colloidal materials. Besides providing a brief overview on the state of the art of our understanding of these interactions a key aim of this review is to emphasize open key questions and corresponding open challenges.
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Affiliation(s)
- Benno Liebchen
- Institute for Condensed Matter Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
| | - Aritra K Mukhopadhyay
- Institute for Condensed Matter Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
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