In this thesis, the phenomenon of a microdrop impacting onto and spreading over surfaces of constant and variable wettability is investigated. The study is motivated by wide-ranging industrial applications of ink-jet printing technologies, in particular used by our industrial sponsor Kodak Ltd. Mathematical models for dynamic wetting phenomena are incorporated into a specially developed finite element based numerical platform. By examining different models, it was found for the first time that the interface formation model is capable of describing the experimentally observed non-uniqueness of the relationship between the contact-line speed and the dynamic contact angle. It is shown that, the interface formation model naturally captures the effect which variations in the wettability of the solid surface have on an adjacent flow, so that the model can be used, without any ad-hoc alterations, to consider the spreading of microdrops on such solids. An investigation of the effect that variation of the model's parameters has on the characteristics of the impact and spreading of microdrops has been carried out.

The EU-funded SATIN project sought to provide a multimodal interface to aid product designers in judging the quality of curved shapes. This thesis outlines a research programme designed to assist in the exploration of fundamental issues related to this project, and provide a means to evaluate the success of such interfaces more generally. Therefore, three studies were undertaken with the aim of exploring the value of haptic and sound feedback in the perception of curve shape differences, and through the knowledge gained provide an evaluative framework for the assessment of such interfaces. The first study found that visual, haptic, and visual-haptic perception was insufficient to judge discontinuities in curvature without some further augmentation. This led to a second study which explored the use of sound for conveying curve shape information. It was found that sine waves or harmonic sounds were most suited to for this task. The third study combined visual-haptic and auditory information. It was found that sound improved the perception of curve shape differences, although this was dependent upon the type of sonification method used. Further to this, data from studies one and three were used to identify gradient as the active mechanism of curve shape differentiation and provided a model for the prediction of these differences. Similarly performance data (response time, accuracy, and confidence) were analysed to produce a model for the prediction of user performance at varying degrees of task difficulty. The research undertaken across these studies was used to develop a framework to evaluate multimodal interfaces for curve shape exploration. In particular a ‘discount’ psychophysical method was proposed, along with predictive tools for the creation of perceptual and performance metrics, plus guidelines to aid development. This research has added to fundamental knowledge and provided a useful framework through which future multimodal interfaces may be evaluated.