Frictional behavior of one-dimensional materials: an experimental perspective

Abstract

The frictional behavior of one-dimensional (1D) materials, including nanotubes, nanowires, and nanofibers, significantly influences the efficient fabrication, functionality, and reliability of innovative devices integrating 1D components. Such devices comprise piezoelectric and triboelectric nanogenerators, biosensing and implantable devices, along with biomimetic adhesives based on 1D arrays. This review compiles and critically assesses recent experimental techniques for exploring the frictional behavior of 1D materials. Specifically, it underscores various measurement methods and technologies employing atomic force microscopy, electron microscopy, and optical microscopy nanomanipulation. The emphasis is on their primary applications and challenges in measuring and characterizing the frictional behavior of 1D materials. Additionally, we discuss key accomplishments over the past two decades in comprehending the frictional behaviors of 1D materials, with a focus on factors such as materials combination, interface roughness, environmental humidity, and non-uniformity. Finally, we offer a brief perspective on ongoing challenges and future directions, encompassing the systematic investigation of the testing environment and conditions, as well as the modification of surface friction through surface alterations.

Fig. 1. Schematic diagram for nanogenerators based on 1D materials: (a) PVDF–Ag NW composite and nylon fibers based TENG. Reproduced with permission. Copyright 2017, Wiley. (b) ZnO NW based PENG. Reprinted with permission. Copyright 2008, Springer Nature. (c) Generating piezoelectric charges from a PVDF-CNT foam device. Reprinted with permission. Copyright 2019, Springer Nature.

Fig. 2. (a and b) Frictional control model of traction forces of adherent cells by adhesion ligands on surfaces: (a) controlled movement of integrin–fibronectin complexes as they move directionally within the interlayer situated between the cell membrane and the substrate surface; (b) the relationship curve between velocity and the myosin motor characteristic force F_m (solid line) and sliding friction F_f (dashed lines) for ligand surface mobilities from 10⁴ to 10⁵ N ms⁻¹. Reproduced with permission. Copyright 2011, Elsevier. (c) Scanning electron microscopy (SEM) image depicting the deformation of NWs upon direct contact with the attached cell body. Reproduced with permission. Copyright 2016, ACS. (d) Schematic of the multiplexed detection for cancer marker proteins using an Si NW array. Reproduced with permission. Copyright 2005, Springer Nature. (e) SEM image of NW interface with cell membrane. Reproduced with permission. Copyright 2015, ACS. (f) A schematic illustration of DNA extraction from microbial cells using NW in a microchannel. A fluorescence images of DNA extraction from a single cell of subtilis (Upper right) and coli (Bottom right). Reproduced with permission. Copyright 2019, ACS.

Fig. 3. (a) Gecko foot attached to a glass substrate, (b) SEM images of setal array, and (c) spatulae at the tip. Reproduced with permission. Copyright 2004, Elsevier. (d) The vertically aligned CNT array and (e) the entangled top layer. Reproduced with permission. Copyright 2008, AAAS.

Fig. 4. Differences and similarities between macro and nanoscale friction: (a) macroscale contact and (b) microscale contact of rigid bodies. Reproduced with permission. Copyright 2009, IOP. (c) Rigid NW contact with rigid substrate and (d) ultra-compliant NW contact with rigid substrate. Here N is the applied normal force, A_true is the true contact area, A_apparent is the apparent contact area, µ is the friction coefficient, and σ is the shear strength. Reproduced with permission. Copyright 2017, Springer Nature.

Fig. 5. (a and b) AFM images of CNT's original position and after sliding. Inset in (b) shows the lateral force profile during the sliding manipulation. (c and d) AFM images of the during rolling and corresponding lateral force profile of a CNT. Reproduced with permission. Copyright 1999, Springer Nature.

Fig. 6. (a) AFM images of the translation motion of ZnO NW during manipulation when both pure sliding and rolling sliding. The arrow indicates the motion of the probe tip, while the dotted circle indicates the marker on the NW used to assess the degree of rolling. (b) Average dynamic frictional forces measured during the manipulation. Reproduced with permission. Copyright 2013, RSC.

Fig. 7. (a) MWCNT attached to AFM tip. (b) Friction versus load curves for both conventional and CNT probes were generated through the analysis of a scanning length set at 20 nm. (c) Friction and scanning length relationship diagram at various applied loads. Reproduced with permission. Copyright 2002, Elsevier.

Fig. 8. (a) Experimental schema for testing the frictional behavior between two individual CNTs. (b) SEM image of CNTs suspended on the top of a microtrench made of polycrystalline Si. (c) Cantilever tapping amplitude and (d) SEM profiles of the MWCNT tip during the first cycle, during the test, and after ∼500 cycles. Reproduced with permission. Copyright 2008, APS.

Fig. 9. (a) AFM topography image of a CNT. The fast-scanning direction of the AFM tip is indicated by an arrow (x direction). (b and c) Friction images of the highlighted longitudinal and transverse sections of the CNT. (d and e) Position and friction force profile across the CNT. The topography profile (black solid line) is along the white solid lines in (d) and (e). (f) Diagram of longitudinal and transversal shear strength as a function of CNT radius. Reproduced with permission. Copyright 2009, Springer Nature.

Fig. 10. (a and b) AFM images of the tobacco mosaic virus on graphite before and after AFM manipulation, respectively. (c and d) Schematic illustrations of the mechanical model for calculating frictional forces between a virus and a graphite substrate. Reproduced with permission. Copyright 1997, Elsevier.

Fig. 11. (a and b) AFM micrographs of InAs NWs on SiO₂ substrate before and after manipulation, respectively. The black arrow in (a) denotes the force vector to be applied to the NW, and the circles in (b) are the inner and outer curvature radii. Reproduced with permission. Copyright 2007, Wiley. (c) AFM image of a SWCNT manipulated into an S shape. The arrows in (c) are the frictional forces act on the SWCNT to prevent it from returning to its undeformed position. The forces have been normalized by the maximum frictional force per unit length. (d) Friction force distributions along the length of SWCNT. Reproduced with permission. Copyright 2009, IOP.

Fig. 12. (a) The most bent segment of a Si NW hook. The bending stress profile along the white middle line of the NW is shown. (b) The friction force per unit length necessary to balance the elastic forces in the bent NW. The length and orientation of the line segments give the amplitude and direction of the friction force from outside and inside of the hook toward the NW. (c) The profile of the friction force per unit length, f, shear force, V, and bending moment, M, as a function of distance, s, along the NW. Reproduced with permission. Copyright 2012, Springer Nature.

Fig. 13. (a) NW snap in due to the adhesion from the AFM tip (three different stages of NW loading are superimposed), (b) mechanical model for calculating forces acting on the NW in (a). Reproduced with permission. Copyright 2007, AIP. (c and d) SEM images of an individual NW before buckling and after buckling and just prior to sliding on the right end, respectively. (e) Mechanical model for calculating forces acting on the NW in (d). Reproduced with permission. Copyright 2010, Springer Nature.

Fig. 14. (a) Experimental scheme of the nanomanipulation of NW with AFM tip glued inside the AFM tip QTF inside the SEM. Reproduced with permission. Copyright 2015, IOP. (b–e) SEM images of a ZnO NW on the HOPG pushed to slide by the AFM tip from the initial to final shape. (f) Mechanical model for calculating the kinetic frictional force on the NW, and kinetic frictions measured as a function of NW diameter on HOPG and oxidized Si wafer. Reproduced with permission. Copyright 2012, Wiley.

Fig. 15. (a) SEM image of a bent ZnO NW lying on a substrate. (b) Schematics of the expected static friction force distributed along a bent NW. (c) Distribution diagram of static friction along the NW in (a) obtained from eqn (7). Reproduced with permission. Copyright 2012, Springer Nature.

Fig. 16. (a) SEM image of the bent ZnO NW held by the static friction from the substrate. The rows showed the normal component of static friction force. (b) Numerically calculated elastic energy. (c) Static friction forces distributions along NW using different models. Reproduced with permission. Copyright 2014, Elsevier.

Fig. 17. (a–d) SEM images of the suspended NW being pushed by the tip. (e) The corresponding force curve. Reproduced with permission. Copyright 2011, Elsevier. (f–i) SEM images for the manipulation process of an Ag nanodumbbell. (j) The corresponding recorded tip–nanodumbbell interaction force. Reproduced with permission. Copyright 2015, IOP.

Fig. 18. (a) Experimental setup diagram showing the nanosize force sensor oriented on a Tritor® piezo-actuator and the Si substrate (not up to scale). (b) Experimental setup under a 100× OM objective. (c) Force sensor (not up to scale) diagram and (d) the corresponding SEM image of the force sensor (inset: zoomed view of the displacement markers). (e) OM image of the NW positioned on the substrate with the intended contact length. (f) Friction loading and unloading curve of ZnO NW on Si substrate under ambient conditions. Reproduced with permission. Copyright 2009, IOP.

Fig. 19. (a) Experimental setup for the two-manipulator system. (b) Four-legged parallel beam cantilever. (c) Schematic of friction force measurement system. (d) Optical micrograph of two W probes and the targeted Pt wire. (e) The push–pull cycle of the wire against the probes, corresponding to the piezo displacement during friction measurement, and (f) frictional forces recorded at various cycles. Reproduced with permission. Copyright 2011, Elsevier.

Fig. 20. (a) PAN NFs mounted onto a MEMS device. (b) NF mounted between two glass beads. Inset: SEM micrograph of the PAN NF, showing the uniform diameter along its length. (c and d) Schematic of the normal and shear detachment test, respectively. The fibers are shown in blue color. (e) The top view of a part of the MEMS testing device, along with the two intersecting fibers on the right side, used in a shear experiment. The rigid body U-displacements of two components of the MEMS device, calculated through DIC, are superimposed onto the bottom. (f) Tangential and normal forces curve as the function of the displacement. The tests were conducted at a crosshead speed of 12 nm s⁻¹. Reproduced with permission. Copyright 2020, Elsevier.

Fig. 21. (a–d) Optical micrographs of the initial to most bending states of a Si NW after extracted the W tip. (e and f) AFM images of the initial and final state of the Si NW. (g) AFM image of Si NW in the most-bent state, with the digitized data points and the geometric relationship (inset). (h and i) Strain energy and lateral friction force distribution along the NW as a function of s in (g). (j) Frictional shear strength between Si NWs and PDMS substrate at different UVO treatment times. (k) Dependence of frictional shear strength on the water contact angle. Reproduced with permission. Copyright 2011, ASC.

Fig. 22. (a) Schematics of the mechanical model for a bent NW segment held on a substrate by the static friction. (b and c) Distribution of the friction along x and y directions. (d) NWs manipulated to the most-bent state by the W tip under OM. (e) Frictional shear stress calculated by different mechanical models versus the L/R_O value. The inset shows the corresponding values in the logarithmic coordinate. Reproduced with permission. Copyright 2015, IOP.

Fig. 23. (a) Optical micrograph of a NW, sliding on the Si substrate at a constant speed due to the push from a W tip. (b) Mechanical loading model for the sliding NW. (c and d) Optical micrographs of the same NW sliding on Si substrate pushed by tip 1 and tip 2, respectively. (e) The same NW to (c and d) slid on SiN substrate pushed by tip 2. (f) Frictional shear stress on Si and SiN substrates plotted as a function of the NW length. Reproduced with permission. Copyright 2015, AIP.

Fig. 24. Comparative test of ZnO NWs on SiN and SiO₂ substrates: (a) SEM image of a ZnO NW on SiO₂ substrate and (b) optical micrograph of the NW in (a) sliding on the substrate. The three dotted lines are the numerically modelled NW profiles using loads of 0.50, 1.00 and 1.50 MPa, respectively. (c) SEM image of a ZnO NW on SiN substrate. (d) Optical micrograph of the NW in (c) sliding on the substrate. The three curves represent the NW profiles simulated using loads of 1.77, 1.83 and 1.99 MPa, respectively. (e) The kinetic frictional shear stresses of ZnO NWs on SiN and SiO₂ substrates plotted as a function of the NW diameter. (f) AFM images of the SiN and SiO₂ substrate surfaces and their corresponding cross-sectional line profiles. Reproduced with permission. Copyright 2016, Elsevier.

Fig. 25. (a–c) Optical micrographs of three NW segments with difference lengths pushed to slide along the Si substrate by a W tip. (d) Optical micrograph of the NW shown in (c) after tip removal. (e) The comparison of NW profiles before tip removal from the tests and the FEM simulations. (f) Distribution of elastic energies per unit length of the bent NW shown in (c) and (d), and (g) the corresponding the swept area A_swept (crossed). Reproduced with permission. Copyright 2016, IOP.

Fig. 26. (a–c) Initial bending status and final bending status of a NW on substrate after the tip withdrawal, and the simulated final bending statuses at different friction forces compared to the experimental, respectively. Reproduced with permission. Copyright 2015, Springer Nature. (d) The cantilever model for a NW sliding in a stable manner on a substrate at a constant speed. Reproduced with permission. Copyright 2022, Springer Nature.

Fig. 27. (a and b) Sketches for OM-nanomanipulation system and positioning of NWs for friction testing, respectively. (c–g) Optical snapshots of a target NW being deflected by a manipulator NW during friction testing. Reproduced with permission. Copyright 2018, IOP.

Fig. 28. (a) Physical photograph for the OM-nanomanipulation system. (b) Top-view SEM image of a Si TEM grid. (c) Cross-section of the grid's window edge (Side-view image). (d) Optical micrograph showing two SiC NWs on a Si TEM grid during shearing. (e) 3D model showing the geometry of the contact area between the two SiC NWs. (f and g) Schematic illustration of the mechanical models for the calculation of static and kinetic frictional forces between two individual NWs, respectively. Reproduced with permission. Copyright 2022, Wiley.

Fig. 29. (a–g) High-magnification OM images (x–y plane view) of t-NW being deflected by m-NW during shearing at different stages. (h) Stick-slip curve obtained by plotting displacements at the contact point of the t-NW and m-NW as a function of the displacement of the m-NW. (i) Low-magnification x–y plane-view SEM image of (g) state. (j and l) The high-magnification x–y plane view SEM images of the lateral profiles of t and m-NWs. (k and m) The high-magnification SEM images of cross-sectional profiles of t and m-NWs. Reproduced with permission. Copyright 2022, Wiley.

Fig. 30. (a) Optical image of a ZnO NW sliding stably on the graphite substrate. (b) SEM image of the ZnO NW in (a) after the test. The inset in (b) shows the hexagonal structure of the NW. (c) The kinetic shear stresses of ZnO NWs on graphite substrate plotted as a function of the diameter of NWs. (d) Optical image of a ZnO NW sliding stably on the mica substrate. The SEM image inset in (d) shows the hexagonal structure and diameter of the ZnO NW. (e) The kinetic shear stresses of ZnO NWs on mica substrate plotted as a function of the diameter of NWs. Reproduced with permission. Copyright 2022, Springer Nature.

Fig. 31. (a) Frictional shear stress of SiC NWs against the surface roughness of SiN substrate. Reproduced with permission. Copyright 2017, Springer Nature. (b) Dependences of frictional shear stress of ZnO NWs on HOPG and NG substrates on the NW diameter. (c) Sketches of a NW conforming to a wavy substrate surface and the step-induced gap between the NW and substrate surface. Reproduced with permission. Copyright 2022, Springer Nature.

Fig. 32. (a) The average static and kinetic frictional shear strengths of all tested NW pairs plotted as a function of environmental RH. (b and c) Characteristic deflection/shear stress progression of selected NW pairs obtained at 74% and 29% RH, respectively. (d–f) Schematic diagrams to show the effects of humidity on the shearing behavior between two intersected NWs. The blue mesh in (d–f) illustrates the presence of a water film and meniscus. Reproduced with permission. Copyright 2022, Wiley.

Tursunay Yibibulla

Lizhen Hou

James L. Mead

Han Huang

Sergej Fatikow

Shiliang Wang