The role of material characteristics and process optimisation for TENG will be addressed here using a bespoke Pin-on-Disk piezo-controlled micro-tribometer.  Contact mechanics under sliding traction will be analysed to deliver a mechanistic understanding of the role of shear stress and strain rate on charge transfer.  At the same time experimental work using bespoke hi-resolution environmentally controlled (nitrogen and air, both dry and humid, 1-50%RH) single particle micro-tribometry methods (Fn: ~10 µN to 1 N) will be used to simulate simple indentation, dynamic (including impact) contact and sliding (δ: 10 nm to 2 mm) in particle-particle and particle-plane contact configurations.  In-situ electrical contact charge measurement will provide real-time measurement of charge transfer during contact.  Indentation Fn-δ and tribological friction forces will be spatially resolved under piezo-controlled actuation, whilst simultaneously measuring contact charge transfer.  The influence of contact deformation type, i.e. elastic, elasto-plastic, fracture/wear on collisional and sliding contacts will be investigated in collaboration with WP5.  Surface and structural features will be correlated with the resulting frictional/charge transfer characteristics, which will be investigated systematically. Surfaces will be interrogated pre and post testing using surface metrology (AFM, VSI, SEM) and surface chemical (RAMAN, XPS) methods.  This WP will make use of developments in WPs 1 & 2 for a predictive approach to material selection for TENG, but in the first instance several commonly used materials, such as PTFE, PDMS, and newly developed cellulose-based materials will be used.