Soft Tribometry of Cosmetic Powders: Particle-Enabled Lubrication in Skin-Mimetic Contacts.

Polymer powders are widely used to modify texture and perceived skin feel in cosmetics, yet how particulates influence friction in realistic, skin-like contacts remains unclear. This study quantifies the frictional response of cosmetic powders in compliant, model skin surfaces to provide formulation-relevant insights into tactile performance. We tested five powders of varying polymer types and particle sizes/distributions using a rheometer configured for friction measurements in skin-like contacts, with a fixed normal load and sliding speed. Commercial model counter faces with engineered microtopography reproduced the contact geometry and compliance of human skin. The coefficient of friction was measured, revealing a reproducible, sample-dependent trajectory. Complementary particle sizing/imaging, surface topography analysis, and trained panel testing supported interpretation of tribological data. Results show that finer powders promote particle entrainment into the contact, reducing the coefficient of friction. This offers actionable guidance for formulators aiming to optimize tactile comfort. This approach enabled discrimination of the powder samples by their frictional behavior.