In this thesis, three different processes for the fabrication of microchannels in three different base materials were experimentally and numerically modelled in detail in order to understand the effects of processing conditions on process fabrication capabilities. CO2 and Nd:YAG laser processing systems as well as a xurography technique were employed in this work for the development of microfluidic channels. The effects of CO2 laser processing on the process of directly writing microchannels on surface of four different types of glass: soda lime, fused silica, borosilicate and quartz were studied. Mathematical models were developed to relate the process input parameters to the dimensions of the microchannels. The effect of laser processing on the optical transmission capabilities of the glass was also assessed. A novel method, using Nd:YAG laser system, was employed for the fabrication of internal microchannels inside polymeric materials. Microchannels up to three millimetres long were successfully created inside a polycarbonate within a single laser processing step. Mathematical models were developed to express the relationship between laser processing input parameters and the width of these internal microchannels. The Nd:YAG processing parameters for laser welding of polycarbonate sheets were also determined. A new rapid low-cost prototyping method for the fabrication of multilayer microfluidic devices from cyclic olefin copolymer (COC) films was developed. CO2 laser cutting and xurography techniques were employed for the fabrication of the microfluidic features, followed by multilayer lamination via cyclohexane vapour exposure. Process parameters were optimised including solvent exposure time. Functional UV-transparent microfluidic mixing devices were demonstrated which included internally bound polymer monolithic columns within the microfluidic channels. There is a growing interest to use technologies which are in this thesis, the three different developed processes for the fabrication of microchannels in three different base materials provides the basis for achieving higher dimensional accuracies and novel designs within lab-on-a-chip microfluidic sensing devices.