The innovation engine for new materials

Niall Robertson


Trinity College


Theoretical Physics


Himanshu Mishra

Faculty Sponsor(s): 

Jacob Israelachvili

Faculty Sponsor's Department: 

Chemical Engineering

Project Title: 

Stick-Slip at the Solid/ Liquid/Vapor Interface

Project Description: 

The phenomenon of "stick-slip" at the interface of a solid with a liquid is ubiquitous in both natural and engineered systems. Examples include hopping of drops during liquid advancement and recession onto a solid substrate, inkjet printing, evaporative cooling, coffee-ring effect, and lubrication and tribology of sliding mechanical components in engines. In all of these examples a static period of “stick” is followed by a sudden “slip”. However despite the pervasiveness of “stick-slip” behavior, the underlying mechanisms for “stick” and  “slip” have remained unclear. Using a contact angle cell, we investigated the “stick-slip” behavior of advancing and receding liquid droplets over a variety of solid surfaces ranging from polydimethylsiloxane, Teflon, silicon dioxide films (smooth and textured) and aluminum foils. A review of the scientific literature showed that the existing theoretical models are inconsistent with experimental data. The key physicochemical properties and experimental observables during “stick-slip” were found to be: (1) surface roughness and chemical heterogeneity of the solid, (2) rate of advancement (or recession) of the liquid, (3) waiting times during advancement (or recession), and (4) molecular nature of the liquid (Hydrogen bonding, or van der Waals dominated) dictating long-range correlations at the solid-liquid-vapor interface. To explain these experimental findings we extended a theoretical model proposed by Shanahan and co-workers to include viscosity effects and non-axisymmetric slips and compared with experimental data from our contact angle cell measurements.