1
|
Li M, Xiao H, Sun Y, Wang T, Shi L, Wang X. Bioinspired film-terminated ridges for enhancing friction force on lubricated soft surfaces. J Mech Behav Biomed Mater 2024; 157:106660. [PMID: 39033558 DOI: 10.1016/j.jmbbm.2024.106660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2024] [Revised: 06/29/2024] [Accepted: 07/12/2024] [Indexed: 07/23/2024]
Abstract
Enhancing friction force in lubricated, compliant contacts is of particular interest due to its wide application in various engineering and biological systems. In this study, we have developed bioinspired surfaces featuring film-terminated ridges, which exhibit a significant increase in lubricated friction force compared to flat samples. We propose that the enhanced sliding friction can be attributed to the energy dissipation at the lubricated interface caused by elastic hysteresis resulting from cyclic terminal film deformation. Furthermore, increasing inter-ridge spacing or reducing terminal film thickness are favorable design criteria for achieving high friction performance. These findings contribute to our understanding of controlling lubricated friction and provide valuable insights into surface design strategies for novel functional devices.
Collapse
Affiliation(s)
- Meng Li
- Anhui Province Key Laboratory of Special and Heavy Load Robot, Anhui University of Technology, Ma'anshan, 243032, China; School of Mechanical Engineering, Anhui University of Technology, Ma'anshan, 243032, China
| | - Han Xiao
- School of Mechanical Engineering, Anhui University of Technology, Ma'anshan, 243032, China
| | - Yongjian Sun
- School of Mechanical Engineering, Anhui University of Technology, Ma'anshan, 243032, China
| | - Tao Wang
- Anhui Province Key Laboratory of Special and Heavy Load Robot, Anhui University of Technology, Ma'anshan, 243032, China; School of Mechanical Engineering, Anhui University of Technology, Ma'anshan, 243032, China
| | - Liping Shi
- School of Mechanical Engineering, Anhui University of Technology, Ma'anshan, 243032, China; Wuhu Technology and Innovation Research Institute, AHUT, Wuhu, 241000, China.
| | - Xiaolei Wang
- College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing, 210016, China.
| |
Collapse
|
2
|
Bureau L, Coupier G, Salez T. Lift at low Reynolds number. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:111. [PMID: 37957450 DOI: 10.1140/epje/s10189-023-00369-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 10/19/2023] [Indexed: 11/15/2023]
Abstract
Lift forces are widespread in hydrodynamics. These are typically observed for big and fast objects and are often associated with a combination of fluid inertia (i.e. large Reynolds numbers) and specific symmetry-breaking mechanisms. In contrast, the properties of viscosity-dominated (i.e. low Reynolds numbers) flows make it more difficult for such lift forces to emerge. However, the inclusion of boundary effects qualitatively changes this picture. Indeed, in the context of soft and biological matter, recent studies have revealed the emergence of novel lift forces generated by boundary softness, flow gradients and/or surface charges. The aim of the present review is to gather and analyse this corpus of literature, in order to identify and unify the questioning within the associated communities, and pave the way towards future research.
Collapse
Affiliation(s)
- Lionel Bureau
- Univ. Grenoble Alpes, CNRS, LIPhy, 38000, Grenoble, France.
| | | | - Thomas Salez
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, 33400, Talence, France.
| |
Collapse
|
3
|
Dong H, Moyle N, Wu H, Khripin CY, Hui CY, Jagota A. The transition from Elasto-Hydrodynamic to Mixed Regimes in Lubricated Friction of Soft Solid Surfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2211044. [PMID: 36779906 DOI: 10.1002/adma.202211044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 01/29/2023] [Indexed: 05/17/2023]
Abstract
Lubricated contacts in soft materials are common in various engineering and natural settings, such as tires, haptic applications, contact lenses, and the fabrication of soft electronic devices. Two major regimes are elasto-hydrodynamic lubrication (EHL), in which solid surfaces are fully separated by a fluid film, and mixed lubrication (ML), in which there is partial solid-to-solid contact. The transition between these regimes governs the minimum sliding friction achievable and is thus very important. Generally, the transition from EHL to ML regimes is believed to occur when the thickness of the lubricant layer is comparable with the amplitude of surface roughness. Here, it is reported that in lubricated sliding experiments on smooth, soft, poly(dimethylsiloxane) substrates, the transition can occur when the thickness of the liquid layer is much larger than the height of the asperities. Direct visualization of the "contact" region shows that the transition corresponds to the formation of wave-like surface wrinkles at the leading contact edge and associated instabilities at the trailing contact edge, which are believed to trigger the transition to the mixed regime. These results change the understanding of what governs the important EHL-ML transition in the lubricated sliding of soft solids.
Collapse
Affiliation(s)
- Hao Dong
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Nichole Moyle
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Haibin Wu
- Department of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, 14853, USA
| | | | - Chung-Yuen Hui
- Department of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, 14853, USA
| | - Anand Jagota
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
- Department of Bioengineering, Lehigh University, Bethlehem, PA, 18015, USA
| |
Collapse
|
4
|
Peng Y, Serfass CM, Kawazoe A, Shao Y, Gutierrez K, Hill CN, Santos VJ, Visell Y, Hsiao LC. Elastohydrodynamic friction of robotic and human fingers on soft micropatterned substrates. NATURE MATERIALS 2021; 20:1707-1711. [PMID: 33927390 DOI: 10.1038/s41563-021-00990-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 03/18/2021] [Indexed: 05/10/2023]
Abstract
Frictional sliding between patterned surfaces is of fundamental and practical importance in the haptic engineering of soft materials. In emerging applications such as remote surgery and soft robotics, thin fluid films between solid surfaces lead to a multiphysics coupling between solid deformation and fluid dissipation. Here, we report a scaling law that governs the peak friction values of elastohydrodynamic lubrication on patterned surfaces. These peaks, absent in smooth tribopairs, arise due to a separation of length scales in the lubricant flow. The framework is generated by varying the geometry, elasticity and fluid properties of soft tribopairs and measuring the lubricated friction with a triborheometer. The model correctly predicts the elastohydrodynamic lubrication friction of a bioinspired robotic fingertip and human fingers. Its broad applicability can inform the future design of robotic hands or grippers in realistic conditions, and open up new ways of encoding friction into haptic signals.
Collapse
Affiliation(s)
- Yunhu Peng
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Christopher M Serfass
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Anzu Kawazoe
- Department of Electrical and Computer Engineering, University of California-Santa Barbara, Santa Barbara, CA, USA
| | - Yitian Shao
- Department of Electrical and Computer Engineering, University of California-Santa Barbara, Santa Barbara, CA, USA
| | - Kenneth Gutierrez
- Department of Mechanical and Aerospace Engineering, University of California-Los Angeles, Los Angeles, CA, USA
| | - Catherine N Hill
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Veronica J Santos
- Department of Mechanical and Aerospace Engineering, University of California-Los Angeles, Los Angeles, CA, USA
| | - Yon Visell
- Department of Electrical and Computer Engineering, University of California-Santa Barbara, Santa Barbara, CA, USA
| | - Lilian C Hsiao
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA.
| |
Collapse
|
5
|
Wu H, Moyle N, Jagota A, Hui CY. Lubricated steady sliding of a rigid sphere on a soft elastic substrate: hydrodynamic friction in the Hertz limit. SOFT MATTER 2020; 16:2760-2773. [PMID: 32100796 DOI: 10.1039/c9sm02447f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Lubricated sliding on soft elastic substrates occurs in a variety of natural and technological settings. It very often occurs in the iso-viscous elasto-hydrodynamic lubrication (EHL) regime (e.g., soft solid, low pressure). In this regime, for sliding of a smooth sphere on a soft solid, a "Hertz-like" effective contact region forms. Much of the fluid is squeezed out of the contact region although enough is retained to keep the solid surfaces fully separated. This is accompanied by complex deformation of the soft solid. The behavior of such soft lubricated contacts is controlled by a single dimensionless parameter 1/β that can be interpreted as a normalized sliding velocity. Solving this fundamental soft-lubrication problem poses significant computational difficulty for large β, which is the limit relevant for soft solids. As a consequence, little is known about the structure of the flow field under soft lubrication in the intake and outlet regions. Here we present a new solution of this soft lubrication problem focusing on the "Hertz" limit. We develop a formulation in polar coordinates that handles difficult computational issues much better than previous methods. We study how hydrodynamic pressure, film thickness and hydrodynamic friction vary with β. Scaling laws for these relationships are given in closed form for a range of β not previously accessible theoretically but that is typical in applications. The computational method presented here can be used to study other soft lubrication problems.
Collapse
Affiliation(s)
- Haibin Wu
- Department of Mechanical and Aerospace Engineering, Field of Theoretical and Applied Mechanics, Cornell University, Ithaca, NY 14853, USA.
| | | | | | | |
Collapse
|