Professor John Bernard Pethica
Distinguished for his contributions to the field of nanometre and atomic scale mechanics.
He invented and developed the technique of nanoindentation, revolutionising the mechanical characterisation of ultra-small volumes of materials. This has impacted the thin film and coatings industry, the reliable determination of local properties requested to model materials at larger scales, and led to the observation of novel nanomechanics.
He was the first to introduce the concept of forces acting between tip and surface in Scanning Tunnelling Microscopy, which lead directly to Binnig’s invention of Atomic Force Microscopy, and late to new STM imaging and to the single atom and molecule manipulation processes. His work is strongly linked to molecular dynamics modelling. Recently he has implemented a novel AFM using sub-Å modulation.
Force gradients can now be imaged directly with atomic resolution, and mapping of short-range interaction potential between surface and tip gives mechanical characterisation of individual chemical bonds. The method is now also being applied to liquids; molecular layering had been observed in water, and the lateral rigidity of confined fluid layers shown to depend strongly on commensurability of the gap, with significant implications for fundamentals of tribology.