The use of thin-film techniques for the fabrication of microfluidic devices has gained attention over the last decade, particularly for three-dimensional channel structures. The reasons for this include effective use of chip volume, mechanical flexibility, dead volume reduction, enhanced design capabilities, integration of passive elements, and scalability. Several fabrication techniques have been adapted for use on thin films: laser ablation and hot embossing are popular for channel fabrication, and lamination is widely used for channel enclosure. However, none of the previous studies have been able to achieve a strong bond that is reliable under moderate positive pressures. The present work aims to develop a thin-film process that provides design versatility, speed, channel profile homogeneity, and the reliability that others fail to achieve. The three building blocks of the proposed baseline were fifty-micron poly(methyl methacrylate) thin films as substrates, channel patterning by laser ablation, and device assembly by thermal-fusion bonding. Channel fabrication was characterized and tuned to produce the desired dimensions and surface roughness. Thermal bonding was performed using an adapted mechanical testing device and optimized to produce the maximum bonding strength without significant channel deformation. Bonding multilayered devices, incorporating conduction lines, and integrating various types of membranes as passive elements demonstrated the versatility of the process. Finally, this baseline was used to fabricate a droplet generator and a DNA detection chip based on micro-bead agglomeration. It was found that a combination of low laser power and scanning speed produced channel surfaces with better uniformity than those obtained with higher values. In addition, the implemented bonding technique provided the process with the most reliable bond strength reported, so far, for thin-film microfluidics. Overall, the present work proved to be versatile, reliable, and fast, making it a good candidate to reproduce several on-chip functions. Future work includes implementing thick-substrate bonding techniques to further improve the process and decrease energy requirements.

Nonwoven-fabrics have been in use since 1930s. Their advantages over other web fonnation methods like knitting and weaving have attracted many industries such as aerospace, automotive, sports, geotextiles, composites, battery separators etc. to explore and increase their usage. During nonwoven manufacturing, most of the laid loose webs have an insufficient strength as fonned, and require an additional bonding procedure in order to provide the produced nonwoven with its intended properties. To achieve the desired properties of the nonwoven web, the bonding process is therefore, the most important part during production. The thennal bonding through air is one of the modem techniques which is incrementally improved to increase the yield of manufactured nonwoven properties. The system has a disadvantage which is, that the production capacity and energy efficiency is very low. The entitled research aims an industrial optimisation of the thermal bonding through air by entailing a strategic approach and encompassing the whole process chain of the thennal bonding process. The comprehensive and flexible optimisation opportunities provided by the CFD has been used to aid in the control and optimisation of the thermal bonding process and machinery. To optimise the process and product quality, the complex system composing of several components and various physical phenomena occurring during processing is simulated using a hierarchical methodology. More specifically a hierarchical decomposition procedure to recast the original multi scale problem as a sequence of three scale decoupled macro-, meso-, and micro scale subproblems is exploited. The methodology is applied in conjunction with the validation of experiments on through-air bonding product lines. 2D and 3D computational fluid dynamics (CFD) models based on the continuum modelling approach and the theory of porous media coupled with the theory of mixtures are developed to treat the flow behavior, heat transfer, phase change and air moisture transport within the whole through-air bonding system. The model is concluded to be an economic computational tool hence providing rapid process optimisation and valuable infonnation early in the process, which can replace costly experiments and ensure product consistency under variable process and climate conditions. 2D and 3D hybrid modelling considering parametric discrete and continuum parts is also perfonned using conjugate heat transfer analyses. The approach precisely permits the optimisation of the machine component design and the associated optimisation of consistent process and product properties.