Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 78: Vacuum Science & Technology: Theory and Applications I
O 78.6: Talk
Thursday, March 12, 2026, 12:00–12:15, HSZ/0401
A dynamic analysis of the static friction in microscopic Hertzian contacts: Size effects and 2D-material assisted superlubricity — •Ahmed Uluca1,2, Pierce Sinnott1,2, and Graham Cross1,2 — 1School of Physics, Trinity College Dublin, Dublin, Ireland — 2CRANN, Trinity College Dublin, Dublin, Ireland
Friction governs how objects start to move, yet our understanding still relies on empirical laws that vary across materials and length scales. To build a more fundamental picture, we focus on the interfacial shear strength (ISS)-a concept adapted from fracture mechanics that describes friction in terms of shear stress over the contact area.
We developed a mesoscale dynamic analysis method capable of probing contact radii from tens of nanometers to micrometers with sub-nanometer displacement and 10-nanonewton force resolution. Starting from static contact, we gradually increase lateral oscillation amplitude while tracking contact radius and laterally stuck zone radius. This enables us to monitor the transition from sticking to sliding in real time while simultaneously measuring contact radius.
Using diamond-fused silica pairs, we map ISS across pressures from tens of MPa to several GPa and compare the results with theoretical models spanning from the Peierls (lattice) stress to the upper bound of a perfectly commensurate interface. Our findings reveal a pressure and scale dependent shear strength that is consistent with the dislocation emission models, extended to include the effects of deformation mode, nanoroughness, junction growth and interfacial modification by graphene layers.
Keywords: static friction; 2D-indentation; shear strength; superlubricity; size effects