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Dašić M, Almog R, Agmon L, Yehezkel S, Halfin T, Jopp J, Yaakobovitz A, Berkovich R, Stanković I. Role of Trapped Molecules at Sliding Contacts in Lattice-Resolved Friction. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 39105730 DOI: 10.1021/acsami.4c08226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/07/2024]
Abstract
Understanding atomic friction within a liquid environment is crucial for engineering friction mechanisms and characterizing surfaces. It has been suggested that the lattice resolution of friction force microscope in liquid environments stems from a dry contact state, with all liquid molecules expelled from the area of closest approach between the tip and substrate. Here, we revisit this assertion by performing in-depth friction force microscopy experiments and molecular dynamics simulations of the influence of surrounding water molecules on the dynamic behavior of the nanotribological contact between an amorphous SiO2 probe and a monolayer MoS2 substrate. An analysis of simulation and experimental stick-slip patterns demonstrates the entrapment of water molecules at the contact interface. These trapped water molecules behave as an integral component of the probe and participate in its interaction with the substrate, affecting the dynamics of the probe and preventing long slips. Significantly, surrounding water from the capillary or layer exhibits a replenishing effect, acting as a water reservoir during sliding. This phenomenon facilitates the preservation of lattice-scale resolution across a range of applied normal loads.
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Affiliation(s)
- Miljan Dašić
- Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, Belgrade 11080, Serbia
| | - Roy Almog
- Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
| | - Liron Agmon
- Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
| | - Stav Yehezkel
- Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
| | - Tal Halfin
- Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
| | - Jürgen Jopp
- The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
| | - Assaf Yaakobovitz
- The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
| | - Ronen Berkovich
- Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
- The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva Blvd 1, Beer Sheva 84105, Israel
| | - Igor Stanković
- Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, Belgrade 11080, Serbia
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Qin X, Dong M, Li Q. Insight into the hydration friction of lipid bilayers. NANOSCALE 2024; 16:2402-2408. [PMID: 38226708 DOI: 10.1039/d3nr05517e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2024]
Abstract
Hydration layers formed on charged sites play crucial roles in many hydration lubrication systems in aqueous media. However, the underlying molecular mechanism is not well understood. Herein, we explored the hydration friction of lipid bilayers with different charged headgroups at the nanoscale through a combination of frequency-modulation atomic force microscopy and friction force microscopy. The nanoscale friction experiments showed that the hydration friction coefficient and frictional energy dissipation of a cationic lipid (DPTAP) were much lower than those of zwitterionic (DPPE) and anionic (DPPG) lipids. The hydration layer probing at the surfaces of different lipid bilayers clearly revealed the relationship between the charged lipid headgroups and hydration layer structures. Our detailed analysis demonstrated that the cationic lipid had the largest hydration force in comparison with zwitterionic and anionic lipids. These friction and hydration force results indicated that the difference of the lipid headgroup charge resulted in different hydration strengths which led to the difference of hydration friction behaviors. The findings in this study provide molecular insights into the hydration friction of lipid bilayers, which has potential implications for the development of efficient hydration lubrication systems with boundary lipid bilayers in aqueous media.
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Affiliation(s)
- Xiaoxue Qin
- Key Laboratory of Colloid and Interface Chemistry of the Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China.
| | - Mingdong Dong
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus C, DK 8000, Denmark.
| | - Qiang Li
- Key Laboratory of Colloid and Interface Chemistry of the Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China.
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