Mapping Nanowire-Substrate Static Friction from Nanowire Bending and a Comprehensive Mechanical Model

Abstract

The accurate determination of static friction at nanowire–substrate interfaces is critical for the design, fabrication, and reliability of nanowire-based micro/nano devices, as well as for advancing the fundamental understanding of tribology. The self-sensing test strategy, which infers friction from nanowire bending, offers a direct route for characterizing nanoscale friction. However, existing mechanical models often adopt simplified treatments, neglecting force components such as the axial friction component and introducing additional assumptions such as uniform stress distribution. Here, we develop a comprehensive mechanical model based on linear elasticity that explicitly incorporates both the tangential and axial components of static friction. This model enables the mapping of static friction force distribution from the bending profile of a nanowire under maximum static friction. The model is validated through optical microscopy–based nanomanipulation of bent SiC nanowires on Si substrates. Our results reveal that neglecting axial friction leads to profound errors in both the magnitude and direction of the inferred transverse friction. Furthermore, we measure a static-to-kinetic friction ratio of 1.68 ± 0.25 for SiC nanowires on Si substrate, slightly lower than the idealized value of ~ 2. This work provides a simple, intuitive, and accurate method for mapping static friction in nanowire–substrate systems, offering an important measurement platform for studying friction in low-dimensional materials.

Graphical Abstract