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Raspberry (RB) particles (12 μm microparticle) with different roughness, expressed as nanoparticle diameter. (A) 100, (B) 200, (C) 300, (D) 400, and (E) 500 nm. (F) Effective friction coefficient μ of RB particles with different nanoparticle diameters (100–500 nm) on a rough substrate decorated with 100 nm nanoparticles. (G) Evolution of the rotation of the RB particles in (F), expressed as a percentage relative to pure rolling without slip, as a function of the applied normal force.
