Browsing by Author "Marson, Silvia"
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Item Open Access Computational modelling and optimisation of the fabrication of nano-structures using focused ion beam and imprint forming technologies(Institute of Physics (IoP), 2010-12-07T00:00:00Z) Stoyanov, S.; Bailey, C.; Tang, Y. K.; Marson, Silvia; Dyer, A.; Allen, David M.; Desmulliez, M.Focused Ion Beam (FIB) and Nano-Imprint Forming (NIF) have gained recently major interest because of their potential to enable the fabrication of precision engineering parts and to deliver high resolution, low-cost and high-throughput production of fine sub-micrometre structures respectively. Using computational modelling and simulation becomes increasingly important in assessing capabilities and risks of defects with respect to product manufacturability, quality, reliability and performance, as well as controlling and optimising the process parameters. A computational model that predicts the milling depth as function of the ion beam dwell times and a number of process parameters in the case of FIB milling is investigated and experimentally validated. The focus in the NIF study is on modelling the material deformation and the filling of the pattern grooves during the mould pressing using non-linear large deformation finite element analysis with hyperelastic non-compressive material behaviour. Simulation results are used to understand the risk of imperfections in the pattern replication and to identify the optimal process parameters and their interactionItem Open Access Design and fabrication of a three-dimensional microfluidic device for blood separation using micro-injection moulding(Sage, 2013-12-03) Attia, Usama M.; Marson, Silvia; Alcock, Jeffrey R.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, material selection and suitability for mass production. Some micro-manufacturing techniques are still at early development stages, while other techniques are at higher stage of manufacturing readiness level but require adaptation in part design or manufacturing procedure to overcome such limitations. This article presents a case study, where the design of a micro-scale, biomedical device is adapted for functionality and manufacturability by a high-volume micro-fabrication technique. Investigations are described towards a disposable three-dimensional, polymer-based device for the separation of blood cells and plasma. The importance of attempting a three-dimensional device design and fabrication route was to take advantage of the highthroughput per unit volume that such systems can, in principle, allow. The importance of a micro-moulding fabrication route was to allow such blood-containing devices to be cheaply manufactured for disposability. Initial device tests showed separation efficiency up to approximately 80% with diluted blood samples. The produced prototype indicated that the process flow was suitable for high-volume fabrication of three-dimensional microfluidics.Item Open Access Effects of channel surface finish on blood flow in microfluidic devices(Springer Science Business Media, 2010-01-12T00:00:00Z) Prentner, S.; Allen, David M.; Larcombe, L. D.; Marson, Silvia; Jenkins, Karl W.; Saumer, M.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 â ¥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 made of polyethylene 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 5000Pa. The defibrinated horse blood was treated further to prevent coagulation. The results indicate that a surface 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.Item Open Access Flatness optimization of micro-injection moulded parts: the case of a PMMA microfluidic component(Institute of Physics Publishing; 1999, 2011-10-20T00:00:00Z) Marson, Silvia; Attia, Usama M.; Lucchetta, G.; Wilson, A.; Alcock, Jeffrey R.; Allen, David M.Micro-injection moulding (µ-IM) has attracted a lot of interest because of its potential for the production of low-cost, miniaturized 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 µ-IM and to control the manufacturing process with the aim of minimizing the in-process part deformation. As a case study, a PMMA microfluidic substrate with overall dimensions of 10 mm diameter and 1 mm thickness was investigated by designing a µ-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 µ-IM process conditions can improve the flatness of the polymer part up to about 15 µm. Part flatness as low as 4 µm can be achieved by modifying the design of the ejection system according to suggested guidelinesItem Open Access Micro-Injection Moulding of Polymer Microfluidic Devices(Springer Science Business Media, 2009-07-01T00:00:00Z) Attia, Usama M.; Marson, Silvia; Alcock, Jeffrey R.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.Item Open Access Reconfigurable micro-mould for the manufacture of truly 3D polymer microfluidic devices(Cranfield University, 2009-03-31) Marson, Silvia; Attia, Usama M.; Allen, David M.; Tipler, P.; Jin, T.; Hedge, J.; Alcock, Jeffrey R.; Rajkumar Roy; Essam ShehabThis paper concerns the concept, the design and the manufacturing steps for the fabrication of a precision mould for micro-injection moulding of truly three dimensional microfluidic devices. The mould was designed using the concept of replaceable cavities to enable the flexible development of the complex microfluidic device and to reduce machining time and therefore costs during the prototyping, testing and subsequent production phase. The precision machining technique used for the cavity manufacture was micromilling.Item Open Access Sinusoidal CVD diamond micro-tools for the manufacture of microstructured surfaces used in bioremediation(2013-12-31T00:00:00Z) Marson, Silvia; Villa, Raffaella; Durazo-Cardenas, Isidro; Evans, R. W.; Storti, A.; Heaume, A.; Marinello, F.; Carmignato, S.; Fairley, M.; Jennings, P.; Allen, David M.Item Open Access Study of blood flow behavior in microchannels(2008-06-01T00:00:00Z) Marson, Silvia; Benade, M.; Attia, Usama M.; Allen, David M.; Kersaudy, Kerhoas M.; Hedge, J.; Morgan, S. L.; Larcombe, L. D.; Alcock, Jeffrey R.; van Brussel, H.; Brinksmeier, E.; Spaan, H.; Burke, T.Microfluidic (also known as lab-on-a-chip) devices offer the capability ofmanipulating very low volumes of fluids (of the order of micro litres) for severalapplications including medical diagnostics. This property makes microfluidicdevices very attractive when the fluid, such as blood, has a limited supply becausethe patients cannot easily and frequently provide a large sample. This is typically thecase for aged, diseased patients that do require frequent sampling during acute careor of older people that have the option of being treated and cared for at home [1].Prototype lab-on-a-chip devices for medical diagnostics comprise a number ofelements which separately perform different functions within the system. Activitywithin the research community is focusing on the better integration of devicefunctionalities with the long term goal of creating fully integrated, portable,affordable clinical devices. However, engineering these solutions for the largevolume production of lab-on-a-chip devices requires design rules which are not yetentirely available.This paper describes the results obtained from a set of experiments run to drawgeneric design rules for the manufacture of a cells/plasma micro separator [2]. Thecells/plasma micro separator was selected for investigation because it is a strategicelement required in the preparation of blood samples for many different analyticaldevices. The experiments focused on the study of the behaviour of whole bloodpassing through micro constrictions which are required for enhancing the separationeffect [3].The test microfluidic device was an aluminium specimen designed andmanufactured to incorporate micro constrictions of different width and length. The metallic aluminium test device was designed for manufacturing by micromilling anddiamond cutting processes in view of applying these techniques to the manufactureof micro-moulds for the high-volume production of plastic microfluidic devices viamicro-injection moulding.The widths of the constrictions were 23, 53 and 93µm and the lengths were 300 and700µm. The blood flow pattern and the level of haemolysis generated in the wholeblood were determined for flow rates between 0.2 and 1 ml/min. Initial resultssuggested that the above conditions generate a stable flow and do not cause bloodhaemolysis following passage through the narrow constrictions. This result impliesthat constrictions as narrow as 23 µm and as long as 700µm can be safely used inblood microfluidic devices under appropriate flow conditions without the risk ofdamaging the blood componeItem Open Access UV patternable metal organic systems for electroceramic films(2005) Marson, Silvia; Whatmore, Roger W.; Dorey, Robert A.This thesis concerns the development of a novel process for the production of thick PZT ceramic features by using a single deposition step and patterning of a photosensitive precursor solution. The preparation of thick films by a single deposition step using a precursor solution composed of PZT xerogel and 1,3 propanediol was examined initially. Viscosity measurements and particle size determination permitted the characteristics of the xerogel when re-dispersed in 1,3 propanediol to be determined. The results from the particle size measurements allowed the fluorescent behaviour of the PZT xerogel and PZT xerogel in 1,3 propanediol to be detected. This result was relevant in view of the use of PZT xerogel as part of a photosensitive system. The deposition and subsequent thermal treatment of the diol based solution allowed the preparation of uncracked ceramic films up to 0.3 jam thick. To overcome the limitation in the maximum thickness achievable by a single deposition step, and the requirement for a subsequent etching process, a photosensitive system was produced by dissolving a PZT xerogel in acrylic acid. The photosensitivity of the initial acrylic acid/PZT xerogel photosensitive system was improved by the addition of a photoinitiator. A procedure similar to a conventional photolithographic process was then developed and tailored to the newly developed system with the specific aim o f obtaining thick, uncracked ceramic features. Following deposition and exposure the patterned film was developed to obtain the image relief. The samples were only developed completely and rapidly in pure acetic acid at room temperature. As a result of the optimised photolithographic process and subsequent drying and firing it was possible to obtain two categories of uncracked ceramic features: structures with dimension ranging from 5 pm up to about 500 pm with a limit to uncracked thickness of 0 . 3 5 pm and structures approximately 2 pm thick with an uncracked feature limit size of about 3 pm. The procedure applied to the preparation of PZT features was found to be appropriate to the preparation of compositions other than PZT. A barium titanate (BT) photosensitive precursor solution was prepared and the deposited film was patterned by exposure to UV light. Following development and subsequent thermal treatments BT ceramic features were obtained.