Dynamics of Sliding Friction between Laser-Induced Periodic Surface Structures (LIPSS) on Stainless Steel and PMMA Microspheres

Abstract

In this work, we investigated the sliding friction measured between poly(methyl methacrylate) (PMMA) colloidal probes with two different diameters D (1.5 and 15 μm) and laser-induced periodic surface structures (LIPSS) on stainless steel with periodicities Λ of 0.42 and 0.9 μm, when the probes are elastically driven along two directions, perpendicular and parallel to the LIPSS. The time evolution of the friction shows the characteristic features of a reverse stick-slip mechanism recently reported on periodic gratings. The morphologies of colloidal probes and modified steel surfaces are geometrically convoluted in the atomic force microscopy (AFM) topographies simultaneously recorded with the friction measurements. The LIPSS periodicity is only revealed with smaller probes (D = 1.5 μm) and when Λ takes the largest value of 0.9 μm. The average value of the friction force is found to be proportional to the normal load, with a coefficient of friction μ varying between 0.23 and 0.54. The values of μ are rather independent of the direction of motion, and they reach their maximum when the small probe is scanned on the LIPSS with the larger periodicity. The friction is also found to decrease with increasing velocity in all cases, which is attributed to the corresponding decrease of the viscoelastic contact time. These results can be used to model the sliding contacts formed by a set of spherical asperities of different sizes driven on a rough solid surface.

Experimental validation of contact resonance AFM using long massive tips

“…In recent years, scientists have used AFM sensors equipped with nano-needles [3][4][5][6][7][8][9][10] and quartz tuning fork sensors [11][12][13][14][15][16] to probe biological samples in their natural physiological liquid environment, while the sensor's body remains out of the liquid and is therefore not affected by hydrodynamic forces (Trolling Mode). The colloidal probe is another form of large, massive-tip sensor, widely used by the AFM community [17][18][19][20][21][22][23][24] to probe samples that might be damaged from an ultra-sharp tip. The ability to probe the nanomechanical properties of biological samples is essential for using the AFM in medical diagnostics and healthcare [25][26][27].…”