To slide or not to slide

We show that friction between silicon surfaces varies with humidity in unexpected ways, with some wet surfaces being less slippery. This behavior can be captured using our adhesion model without adjustable parameters, yielding predictable macroscopic friction from first-principles. Physical Review Letters 2022

We quantitatively show that when two silicon surfaces slide, the resistance comes from atomic stickiness—countless tiny chemical handshakes (chemical Si-O-Si bonds) at the interface. Physical Review Letters 2023

We show experimentally and numerically how small-scale “grip-and-release” events lead to a surprising large-scale twist: pressing surfaces harder can reduce their maximum static friction coefficient, making the onset of sliding relatively easier. Physical Review Letters 2025

We use a fluorescent probe to directly observe the areas where rough surfaces actually touch and the space available for lubricant molecules at the sliding interface. Using a simple model, we show that lubrication works best when plenty of lubricant molecules are free to move—keeping surfaces sliding smoothly instead of sticking. ACS Applied Materials & Interfaces 2023

We show how tiny liquid capillary bridges “grab” two sliding surfaces, increasing nanoscale sliding resistance on both corroded and non-corroded polycrystalline diamond, a key material in the semiconductor industry. Carbon 2023

We measure and model how electrostatic attraction pulls two rough macroscopic silicon surfaces tightly together, hindering their sliding, by charging the interface. Remarkably, polycrystalline silicon is less affected under positive voltage, as internal charge traps act like tiny buffers, keeping opposing charges farther apart and weakening the pull. arXiv

We reveal how surfactants reduce friction from the molecular level. We show that the surfactant molecules stick to the substrate surface through electrostatic attraction, forming a stable lubrication layer that greatly lowers sliding resistance. arXiv