Microfluidic devices have several applications in different fields, such as chemistry, medicine and biotechnology. Many research activities are currently investigating the manufacturing of integrated microfluidic devices on a mass-production scale with relatively low costs. This is especially important for applications where disposable devices are used for medical analysis. Micromoulding of thermoplastic polymers is a developing process with great potential for producing low-cost microfluidic devices. Among different micromoulding techniques, micro-injection moulding is one of the most promising processes suitable for manufacturing polymeric disposable microfluidic devices. This review paper aims at presenting the main significant developments that have been achieved in different aspects of micro-injection moulding of microfluidic devices. Aspects covered include device design, machine capabilities, mould manufacturing, material selection and process parameters. Problems, challenges and potential areas for research are highlighted.

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Micro-injection moulding (-IM) has attracted a lot of interest because of its potential for the production of low-cost, miniaturised parts in high-volume. Applications of this technology are, amongst others, microfluidic components for lab-on-a-chip devices and micro-optical components. In both cases the control of the part flatness is a key aspect to maintaining the component's functionality. The objective of this work is to determine the factors affecting the flatness of a polymer part manufactured by -IM and to control the manufacturing process with the aim of minimising the in-process part deformation. As a case study a PMMA microfluidic substrate with overall dimensions of 10mm diameter and 1mm thickness was investigated by designing a -IM experiment having flatness as the experimental response. The part flatness was measured using a micro-coordinate measuring machine. Finite elements analysis was also carried out to study the optimal ejection pin configuration. The results of this work show that the control of the -IM process conditions can improve the flatness of the polymer part up to about 15m. Part flatness as low as 4m can be achieved by modifying the design of the ejection system according to suggested guidelines.

Micro-manufacturing is a fast developing area due to the increasing demand for components and systems of high-precision and small dimensions. A number of challenges are yet to be overcome before the full potential of such techniques is realised. Examples of such challenges include limitations in component geometry, materials selection and suitability for mass production. Some micro-manufacturing techniques are still at early development stages, whilst other technique are at higher stage of manufacturing readiness level but require adaptation in part design or manufacturing procedure to overcome such limitations. This paper presents a case

Abstract-The behaviour of blood flow in relation to microchannel surface roughness has been investigated. Special attention was focused on the techniques used to fabricate the microchannels and on the apparent viscosity of the blood as it flowed through these microchannels. For the experimental comparison of smooth and rough surface channels, each channel was designed to be 10mm long and rectangular in cross-section with aspect ratios of ≥100:1 for channel heights of 50 and 100μm. Polycarbonate was used as the material for the device construction. The shims, which created the heights of the channels, were machined from poly(ethylene terephthalate). Surface roughnesses of the channels were varied from Rz of 60nm to 1.8μm. Whole horse blood and filtered water were used as the test fluids and differential pressures ranged from 200 to 5000 Pa. The defibrinated horse blood was further treated to prevent coagulation. The results indicate that a roughness above an unknown value lowers the apparent viscosity of blood dramatically due to boundary effects. Furthermore, the roughness seemed to influence both water and whole blood almost equally. A set of design rules for channel fabrication is also presented in accordance with the experiments performed.