{"title":"From AB Stacking to Twist: A Practical Route to Tunable Graphene Friction","authors":"Tuana Karakoyun Barandır, Dilara Ickecan, Özhan Ünverdi, Cem Çelebi, Dogan Erbahar","doi":"10.1007/s11249-026-02199-w","DOIUrl":null,"url":null,"abstract":"<div><p>Twisted bilayer graphene adds a simple—yet powerful—control knob to carbon interfaces: rotation. By changing the twist angle, a moiré superlattice emerges and reshapes the registry landscape that governs interfacial energy dissipation. Here, we combine lateral force microscopy (LFM) on transfer-processed bilayer graphene with molecular dynamics simulations of an idealized/defect-free Si/graphene sliding junction to quantify when twist control is robust and when it is masked by real-interface variability. Experimentally, kinetic friction coefficients are obtained from friction–load slopes measured at multiple locations. Among the twisted samples (2.3° to 10.2°), the mean kinetic friction coefficient increases from ≈ 0.034 to ≈ 0.078 (≈ 2.3×). Extending the comparison to the AB-stacked (0°) sample, synthesized via a distinct single-step growth route and treated as a qualitative baseline, yields an overall increase from ≈ 0.024 (≈ 3×), while spatial scatter highlights the sensitivity to local disorder, relaxation/strain, and surface residue. In parallel, molecular dynamics isolates intrinsic registry effects under controlled load, velocity, and pulling direction: the small-angle response is comparatively weak, whereas broader angle sampling reveals pronounced, non-monotonic changes and angle-specific anisotropy reaching a magnitude comparable to the experimental spread. Guided by moiré-based theory emphasizing registry averaging alongside finite-contact/boundary contributions, we interpret the experimental trend as an interplay between twist-engineered registry physics and extrinsic heterogeneity. Beyond establishing twist-tunable friction in a scalable carbon material, the study positions twisted bilayer graphene as a benchmark interface that <i>bridges</i> atomistic mechanisms and higher-level tribological observables, providing quantitative targets for multiscale modelling and design of graphene-coated sliding contacts.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":806,"journal":{"name":"Tribology Letters","volume":"74 4","pages":""},"PeriodicalIF":3.5000,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Tribology Letters","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s11249-026-02199-w","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, CHEMICAL","Score":null,"Total":0}
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Abstract
Twisted bilayer graphene adds a simple—yet powerful—control knob to carbon interfaces: rotation. By changing the twist angle, a moiré superlattice emerges and reshapes the registry landscape that governs interfacial energy dissipation. Here, we combine lateral force microscopy (LFM) on transfer-processed bilayer graphene with molecular dynamics simulations of an idealized/defect-free Si/graphene sliding junction to quantify when twist control is robust and when it is masked by real-interface variability. Experimentally, kinetic friction coefficients are obtained from friction–load slopes measured at multiple locations. Among the twisted samples (2.3° to 10.2°), the mean kinetic friction coefficient increases from ≈ 0.034 to ≈ 0.078 (≈ 2.3×). Extending the comparison to the AB-stacked (0°) sample, synthesized via a distinct single-step growth route and treated as a qualitative baseline, yields an overall increase from ≈ 0.024 (≈ 3×), while spatial scatter highlights the sensitivity to local disorder, relaxation/strain, and surface residue. In parallel, molecular dynamics isolates intrinsic registry effects under controlled load, velocity, and pulling direction: the small-angle response is comparatively weak, whereas broader angle sampling reveals pronounced, non-monotonic changes and angle-specific anisotropy reaching a magnitude comparable to the experimental spread. Guided by moiré-based theory emphasizing registry averaging alongside finite-contact/boundary contributions, we interpret the experimental trend as an interplay between twist-engineered registry physics and extrinsic heterogeneity. Beyond establishing twist-tunable friction in a scalable carbon material, the study positions twisted bilayer graphene as a benchmark interface that bridges atomistic mechanisms and higher-level tribological observables, providing quantitative targets for multiscale modelling and design of graphene-coated sliding contacts.
期刊介绍：
Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.
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