Gianluca Trotta

Rapid Prototyping of Plastic Lab-on-a-Chip by Femtosecond Laser Micromachining and Removable Insert Microinjection Molding

We have introduced a new hybrid fabrication method for lab-on-a-chip devices through the combination of femtosecond laser micromachining and removable insert micro-injection molding. This method is particularly suited for the fast prototyping of new devices, while maintaining a competitive low cost. To demonstrate the effectiveness of our approach, we designed, fabricated, and tested a completely integrated flow cytometer coupled to a portable media device. The system operation was tested with fluorescent plastic micro-bead solutions ranging from 100 beads/μL to 500 beads/μL. We demonstrated that this hybrid lab-on-a-chip fabrication technology is suitable for producing low-cost and portable biological microsystems and for effectively bridging the gap between new device concepts and their mass production.

Micro Electro Discharge Milling of Freeform Micro-Features With High Aspect Ratio

Micro Electrical Discharge Machining (μEDM) technology is widely used to process conductive materials, regardless to their hardness and strength, and realize micro-sized feature components for industrial application. μEDM proves to be a very competitive fabrication technology since micro-sized features within 1 μm of accuracy and with high surface quality (<0.1 μm Ra) can be attained. When High Aspect Ratio (HAR) micro-features are machined via μEDM milling, the main problem is to identify the technological parameters and settings mainly affecting the process performance. In the present study the influence of the adjustment factor and flushing conditions are investigated and discussed for the machining of HAR cavities with different Fill Factor (FF). Material Removal Rate (MRR) and Tool Wear Ratio (TWR) are evaluated when deep cavities having variable square sections are machined on Ni-Cr-Mo steel workpiece. All tests are performed using a state of the art micro-EDM milling machine, with a Tungsten Carbide electrode tool and a dielectric oil for flushing. The experimental results presented here highlight different trends in the machining performance in dependence of AR and FF. In particular, MRR exhibits a decreasing trend where the curve slopes are strictly related to the FF and the initial adjustment factor. On the contrary, TWR, for higher FF, displays two distinct trends characterized by opposite slopes in each curve. Finally a nozzle for micro-injection with varying Aspect Ratio and Fill Factor is machined and presented as demonstrator.Copyright

Micro Injection Moulding of Polymeric Components

Micro components and micro devices are strongly used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. A micro component is characterized by small dimensions of the product itself or small dimensions of the functional features. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. In this context, micro‐electrical discharge machining (EDM) for mould production and micro‐injection moulding of polymer materials are the key technologies for micro manufacturing. This paper will focus on the production and quality evaluation of polymeric micro components manufactured by micro injection moulding. In particular the authors want to investigate the process parameters on the overall quality of the product. The factors affecting micro flow behavior, components weights and dimension definition are experimentally studied basing on DoE app...

Effects of Process Parameters on the Properties of Replicated Polymeric Parts

The increasing demand for small and even micro scale parts is boosting the development of reliable micro system technologies. Micro-fabrication process capabilities should expand to encompass a wider range of materials and geometric forms, by defining processes and related process chains that can satisfy the specific functional and technical requirements of new emerging multi-material products, and ensure the compatibility of materials and processing technologies throughout these manufacturing chains. Micro injection moulding is the process of transferring the micron or even submicron precision of microstructured metallic moulds to a polymeric products. It represents one of the key technologies for micro manufacturing because its mass production capability and relatively low production cost. Polymers have relatively low cost, and offer good mechanical and thermal strength, electrical insulation, optical transparency, chemical stability and biocompatibility.In this work the authors investigate the micro injection moulding process parameters on the overall quality of a miniaturized dog-bone shaped specimen. The aim of the experimentation is to calibrate the process and set the machine for the correct filling of the component. A set of injection parameters are selected for study by experimental plan and simulation tool and then discussed. Simulation results are used to better understand the polymer flow behaviour during the filling phase. A commercial software is used and input data, collected during the micro injection moulding process, are included using as performance indicators flow front position and moulded mass. Process simulation can provide, at the present time, mostly qualitative input to the designer and process engineer. Two different polymers materials are tested and evaluated in relation to the process replication capability: Polyoxymethylene (POM) and Liquid Cristal Polymer (LCP). Finally, the moulding factors with significant statistical effects are identified. The holding pressure and holding time for POM and the holding pressure and injection velocity for LCP show the highest influence on achieving high part mass.Copyright

Imaging cytometry in a plastic ultra-mobile system

We present a cost-effective and highly-portable plastic prototype that can be interfaced with a cell phone to implement an optofluidic imaging cytometry platform. It is based on a PMMA microfluidic chip that fits inside an opto-mechanical platform fabricated by a 3D printer. The fluorescence excitation and imaging is performed using the LED and the CMOS from the cell phone increasing the compactness of the system. A custom developed application is used to analyze the images and provide a value of particle concentration.

Micro Injection Moulding Process and Product Characterization

Due to its high efficiency for the large scale production of polymeric parts, micro injection moulding is one of the key technologies of the new millennium. Although a lot of researches have been conducted to identify the most effective processing conditions for micro injection moulding, the comprehension of the influence of all parameters on the quality, the properties and the reliability of the moulded parts is still an issue. In this context, this study aims to evaluate the effects of the micro injection moulding process conditions on the tensile properties of micro parts, investigating the influence of three main process parameters: the injection speed, the mould temperature and the melt temperature. A full factorial plan has been applied to study the contributions of these parameters and a second study has been performed to understand the synergic interaction between the two temperatures on the tensile strength. Due to its high level of potential crystallinity, a typical semi-crystalline thermoplastic resin was used in the experiments. The results of the analysis showed a great influence of the mould temperature (Tmould ) on the ultimate tensile strength and of the melt temperature (Tmelt ) on the deformation at the point of breaking; whereas the injection speed was significant on the overall mechanical performance. A new studied factor (Tmelt -Tmould ) could affect the resulting molecular structure and consequently the mechanical behaviour, but itself is not sufficient to thoroughly explain the observed behaviour. Moreover, the visual inspection of the deformation mechanism at break shows three distinctive trends demonstrating the great variability of the mechanical properties of micro-injected specimens due to process conditions.Copyright

Disposable Optical Stretcher Fabricated by Microinjection Moulding

Microinjection moulding combined with the use of removable inserts is one of the most promising manufacturing processes for microfluidic devices, such as lab-on-chip, that have the potential to revolutionize the healthcare and diagnosis systems. In this work, we have designed, fabricated and tested a compact and disposable plastic optical stretcher. To produce the mould inserts, two micro manufacturing technologies have been used. Micro electro discharge machining (µEDM) was used to reproduce the inverse of the capillary tube connection characterized by elevated aspect ratio. The high accuracy of femtosecond laser micromachining (FLM) was exploited to manufacture the insert with perfectly aligned microfluidic channels and fibre slots, facilitating the final composition of the optical manipulation device. The optical stretcher operation was tested using microbeads and red blood cells solutions. The prototype presented in this work demonstrates the feasibility of this approach, which should guarantee real mass production of ready-to-use lab-on-chip devices.

Fabrication and assembling of a microfluidic optical stretcher polymeric chip combining femtosecond laser and micro injection molding technologies

Microfluidic optical stretchers are valuable optofluidic devices for studying single cell mechanical properties. These usually consist of a single microfluidic channel where cells, with dimensions ranging from 5 to 20 μm are trapped and manipulated through optical forces induced by two counter-propagating laser beams. Recently, monolithic optical stretchers have been directly fabricated in fused silica by femtosecond laser micromachining (FLM). Such a technology allows writing in a single step in the substrate volume both the microfluidic channel and the optical waveguides with a high degree of precision and flexibility. However, this method is very slow and cannot be applied to cheaper materials like polymers. Therefore, novel technological platforms are needed to boost the production of such devices on a mass scale. In this work, we propose integration of FLM with micro-injection moulding (μIM) as a novel route towards the cost-effective and flexible manufacturing of polymeric Lab-on-a-Chip (LOC) devices. In particular, we have fabricated and assembled a polymethylmethacrylate (PMMA) microfluidic optical stretcher by exploiting firstly FLM to manufacture a metallic mould prototype with reconfigurable inserts. Afterwards, such mould was employed for the production, through μIM, of the two PMMA thin plates composing the device. The microchannel with reservoirs and lodgings for the optical fibers delivering the laser radiation for cell trapping were reproduced on one plate, while the other included access holes to the channel. The device was assembled by direct fs-laser welding, ensuring sealing of the channel and avoiding thermal deformation and/or contamination.