The combination of wettability, X-ray photoelectron spectroscopy and scanning force microscopy has been used to analyse the changes to the surface after plasma treatment of poly(ethylene terephthalate) film. Calculations on contact angle data with a combination of polar and non-polar liquids have shown that argon plasma treatment considerably enhances the work of solid-(polar) liquid adhesion and the surface free energy of the films due to the creation of acidic and basic functions on the polymer surface. In contrast, Lifshitz-van der Waals (apolar) interactions decrease slightly as a consequence of plasma-induced chain-scission. We present the first study of a plasma-treated polymer by chemical force microscopy. Plasma-modified surfaces exhibit substantially higher friction than untreated material and are more easily disrupted by the movement of the tip during scanning. Friction is reduced when methyl-functionalised tips are employed. There is a correlation, on plasma treatment, between the rapid increases in surface friction probed by lateral force microscopy and surface free energy probed by wettability and X-ray photoelectron spectroscopy. The modified mechanical properties and polar group incorporation both result from scission of polymer chains and contribute to the lateral force contrast.

In this review, the operating principles of the nano-impact test technique are described, compared and contrasted to micro- and macro-scale impact tests. Impact fatigue mechanisms are discussed, and the impact behaviour of three different industrially relevant coating systems has been investigated in detail. The coating systems are (i) ultra-thin hard carbon films on silicon, (ii) DLC on hardened tool steel and (iii) nitrides on WC-Co. The influence of the mechanical properties of the substrate and the load-carrying capacity (H³/E²) of the coating, the use of the test to simulate erosion, studies modelling the nano- and micro-impact test and performing nano- and micro-impact tests at elevated temperature are also discussed.