Large Area Roller Embossing of Multilayered Ceramic Green Composites

In this paper, we will report our achievements in developing large area patterning of multilayered ceramic green composites using roller embossing. The aim of our research is to pattern large area ceramic green composites using a modified roller laminating apparatus, which is compatible with screen printing machines, for integration of embossing and screen printing. The instrumentation of our roller embossing apparatus, as shown in Figure1, consists of roller 1 and rollers 2. Roller 1 is heated up to the desired embossing temperature ; roller 2 is, however, kept at room temperature. The mould is a nickel template manufactured by plating nickel-based micro patterns (height : 50 $\mu$m) on a nickel film (thickness : 70 $\mu$m) ; the substrate for the roller embossing is a multilayered Heraeus Heralock HL 2000 ceramic green composite. Comparing with the conventional simultaneous embossing, the advantages of roller embossing include : (1) low embossing force ; (2) easiness of demoulding ; (3) localized area in contact with heater ; and etc. We have demonstrated the capability of large area roller embossing with a panel size of 150mmx 150mm on the mentioned substrate. We have explored and confirmed the impact of parameters (feed speed, temperature of roller and applied pressure) to the pattern quality of roller embossing. Furthermore, under the optimized process parameters, we characterized the variations of pattern dimension over the panel area, and calculated a scaling factor in order to make the panel compatible with other processes. Figure 2 shows the embossed patterns on a 150mmx 150mm green ceramic panel.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

Fabrication and Characterization of Miniaturized Components Based on Extruded Ceramic-Filled Polymer Blends

The objective of this work is to develop an improved manufacturing process for microstructured ceramic components that is based on co-extrusion. Co-extrusion of structured feedrods holds promise for development of multi-layered, functionally graded and/or textured structures. However, it requires a polymer binder that is difficult to remove before structures can be sintered to full density. A two-step debinding is introduced to eliminate debinding defects that are commonly observed in thermal debinding (TD). Cracking is a major issue due to a lack of pore spaces for outgassing of pyrolysis products in traditional TD. In two-step debinding, a soluble binder is removed partially by solvent extraction (SE) which creates a porous network and allows gases to escape in subsequent TD of remaining binder components. The feasibility of solvent extraction (SE) is documented for the extrusion of solid ceramic rods and co-extrusion of tubes, where alumina powder was batched with polyethylene butyl acrylate (PEBA) as backbone polymer and polyethylene glycol (PEG) as water soluble binder. SE for specimens with varying PEBA:PEG ratios were tested in water at three different temperatures for various times. Experiments were also performed with different grades of PEBA and EVA to investigate the effect of thermoplastics on SE. The 1:1 mixture showed a PEG removal up to 80wt.% of the original PEG content after 6h extraction. After subsequent thermal debinding, rods and tubes were sintered successfully without defects, demonstrating the viability of the process. Scanning electron microscopy and optical analysis were performed to characterize the process. In order to illustrate potential applications, microfluidic devices were manufactured using extrusion followed by hot embossing. Ceramic microfabricated components have advantages over silicon, glass or polymer devices in terms of their ability to sustain high temperatures without compromising their functional capabilities. Flat tapes were extruded to create substrates, which were subsequently embossing micro patterns using a brass metal mold. To seal the microchanneled feature, a glass slide was attached to the chip by thermal bonding. Though a good bond was obtained, small portions were found where poor bonding was observed. To check leakage, colored water was forced to flow through the channel,and no leakage of water was found. A low temperature sintered ceramic material was fabricated as a potential alternative to the commercial low temperature co-fired ceramic (LTCC) tape. Overall, the study describes new possibilities for microstructure fabrication on ceramic based substrate and established the embossing process as a promising technique for fabrication

Novel patterning technology for the LTCC based packaging of an optical encoder

Powder blasting technology is proposed in this thesis as a new structuring tool for Low Temperature Co-fired Ceramic (LTCC). The process, consisting of mechanical abrasion through high speed particles, is mostly used on brittle material but was successfully adapted for the patterning of microstructures onto the fragile green tape substrate, through the manufacturing of novel stencil masks. These masks are based on high resolution patterned nickel sheet produced using UV-LIGA process or laser cutting coated with a thin layer of photopolymer which prevents efficiently the metal sheet deformations under particles bombardment. The magnetic properties of the metal allowed magnetic clamping to be used to maintain the mask down onto the substrate. The etching rate of the metal was shown to be low enough at a pressure of 50 psi (344kPa) at a distance nozzle-substrate (N-S) of 20mm and 50mm so that the mask could be re-used several times and ensured good pattern transfer quality from the mask to the substrate. The process was systematically characterised on DuPont 951 P2 (~165μm thick) green tapes. The erosion of the green tape ceramic was then characterised with the micro-patterned electroplated masks. It showed that the powder blasted structures had U shape walls and verticality of the walls closed to 90o can be obtained with increasing the number of passes. The structures have smooth edges and do not have any melting parts. Smoother structures were obtained with distance nozzle-substrate of 50mm favouring lower under etching of about 15-20μm at the expense of a three times increase in process duration. Vias as small as 62μm in entry diameter and 20μm exit diameter were produced along with beams 25μm top width and 54μm bottom width were produced. Following the green tape characterisation, a LTCC package for an optical encoder featuring 16 layers with the glass cavity was manufactured. 45x45mm nickel masks coated with LF55gn flexopolymer were produced featuring stacking pins, fiducials, cavities and circular apertures ranging from 100μm to 400μm diameters for interconnections. Each mask was powder blasted at 50 psi for a flow rate of about 0.1g/s, a distance N-S of 20mm and a speed of 5mm/s. The optical encoder was successfully attached on the package and tested

Fabrications and Applications of Micro/nanofluidics in Oil and Gas Recovery: A Comprehensive Review

Understanding fluid flow characteristics in porous medium, which determines the development of oil and gas oilfields, has been a significant research subject for decades. Although using core samples is still essential, micro/nanofluidics have been attracting increasing attention in oil recovery fields since it offers direct visualization and quantification of fluid flow at the pore level. This work provides the latest techniques and development history of micro/nanofluidics in oil and gas recovery by summarizing and discussing the fabrication methods, materials and corresponding applications. Compared with other reviews of micro/nanofluidics, this comprehensive review is in the perspective of solving specific issues in oil and gas industry, including fluid characterization, multiphase fluid flow, enhanced oil recovery mechanisms, and fluid flow in nano-scale porous media of unconventional reservoirs, by covering most of the representative visible studies using micro/nanomodels. Finally, we present the challenges of applying micro/nanomodels and future research directions based on the work

Diode laser modules based on laser-machined, multi-layer ceramic substrates with integrated water cooling and micro-optics

This thesis presents a study on the use of low temperature co-fired ceramic (LTCC) material as a new platform for the packaging of multiple broad area single emitter diode lasers. This will address the recent trend in the laser industry of combining multiple laser diodes in a common package to reach the beam brightness and power required for pumping fibre lasers and for direct-diode industrial applications, such as welding, cutting, and etching. Packages based on multiple single emitters offer advantages over those derived from monolithic diode bars such as higher brightness, negligible thermal crosstalk between neighbouring emitters and protection against cascading failed emitters. In addition, insulated sub-mounted laser diodes based on telecommunication standards are preferred to diode bars and stacks because of the degree of assembly automation, and improved lifetime. At present, lasers are packaged on Cu or CuW platforms, whose high thermal conductivities allow an efficient passive cooling. However, as the number of emitters per package increases and improvements in the laser technology enable higher output power, the passive cooling will become insufficient. To overcome this problem, a LTCC platform capable of actively removing the heat generated by the lasers through impingement jet cooling was developed. It was provided with an internal water manifold capable to impinge water at 0.15 lmin-1 flow rate on the back surface of each laser with a variation of less than 2 °C in the temperature between the diodes. The thermal impedance of 2.7°C/W obtained allows the LTCC structure to cool the latest commercial broad area single emitter diode lasers which deliver up to 13 W of optical power. Commonly, the emitters are placed in a “staircase” formation to stack the emitters in the fast-axis, maintaining the brightness of the diode lasers. However, due to technical difficulties of machining the LTCC structure with a staircase-shaped face, a novel out-plane beam shaping method was proposed to obtain an elegant and compact free space combination of the laser beam on board using inexpensive optics. A compact arrangement was obtained using aligned folding mirrors, which stacked the beams on top of each other in the fast direction with the minimum dead space

Fabrication of ceramic and ceramic composite microcomponents using soft lithography

This PhD project is set out to develop a high precision ceramic fabrication approach suitable for mass production, and to meet the needs of microengine application. A group of new processes have been developed and the results are characterized for fabrication of high precision ceramic oxides and composite microcomponents using soft lithography and colloidal powder processing. The materials chosen in the research are alumina, yttria stabilised zirconia and their composite for their excellent properties at high temperature

An investigation of yarn spinning from electrospun nanofibres

The aim of the thesis is to investigate yarn spinning from electrospun nanofibres. The concepts of staple and core yarn spinning on electrospun nanofibres has been investigated by examining nanofibre uniformity, alignment, twist insertion and yarn take up by engining and engineering a new take up mechanism. Nylon 6 nanofibres have been fabricated and used throughout this work. The effects of varying the electrospinning parameters such as applied voltage, polymer solution concentration and electrospinning distance on fibre morphology have been established for process optimization. A novel nanofibre aligning mechanism has been devised and systematically revised to enable optimization of alignment process parameters. MWCNTs have been successfully dispersed into nylon 6 nanofibres and have been aligned along the nanofibre body by manipulating the electric and stretching forces with the aid of the alignment mechanism. Novel mechanisms for spinning continuous twisted nanofibre/composite nanofibre yarn and core electrospun yarn have been researched, developed and implemented by making samples. It has been found that defining the velocity and count of the nanofibres entering the spinning zone is important for controlling the yarn count and twist per unit length. By modelling the electrospinning jet, mathematical equations for theoretically calculating the velocity of the jet and nanofibres and their count have been established, necessary for process control. Aspects of practical measurement and comparison of jet and nanofibre velocities have been described and discussed. Tensile testing of single nanofibre and nanofibre mats has been attempted for mechanical characterization. Initial results show the range of tensile strength of nylon 6 nanofibre assemblies and indicate the effect of change of process parameters. A review of those engineering mechanisms related to various nanofibre architectures and their industrial and commercial importance has also been reviewed, described and discussed

Micro/Nano Manufacturing

Micro manufacturing involves dealing with the fabrication of structures in the size range of 0.1 to 1000 µm. The scope of nano manufacturing extends the size range of manufactured features to even smaller length scales—below 100 nm. A strict borderline between micro and nano manufacturing can hardly be drawn, such that both domains are treated as complementary and mutually beneficial within a closely interconnected scientific community. Both micro and nano manufacturing can be considered as important enablers for high-end products. This Special Issue of Applied Sciences is dedicated to recent advances in research and development within the field of micro and nano manufacturing. The included papers report recent findings and advances in manufacturing technologies for producing products with micro and nano scale features and structures as well as applications underpinned by the advances in these technologies

Nanopatterning with PFPE elastomers: materials and photovoltaic applications

Nanoscale fabrication is the foundation for emerging nanotechnology applications. This work describes the development and investigation of a soft lithography technique that utilizes perfluoropolyether (PFPE) elastomers for fabricating nanostructures from a variety of organic and inorganic materials. Inorganic oxides such as anatase phase TiO2 are patterned from sol-gel routes pi-conjugated polymers are patterned into a myriad of shapes and sizes on the sub 500 nm length scale from both organic-based and aqueous solutions. Patterns are constructed with and without flash layers, over large areas, with varying aspect ratios, on different substrates, and from precursor materials that are not traditionally used in soft lithography applications. Ordered bulk heterojunction solar cells are made from nanostructured titania and P3HT. Compared to a flat reference bilayer device, the short-circuit current was doubled upon nanostructuring, while the open-circuit voltage remained the same. The nanostructured device with the Z907 interfacial modification led to a power conversion efficiency of 0.6%. Photovoltaic devices comprised solely of organic materials were also fabricated, showing an increase in PV performance for nanopatterned devices compared to flat bilayer devices. Several PFPE-based elastomers are explored for high resolution replica molding applications. The modulus of the elastomeric molds was varied using synthetic and additive approaches. High resolution nanofabrication techniques are reviewed, and the relationship between mold material properties and pattern fidelity is presented. Composite molds were used to form flexible molds out of stiff, high modulus materials. High arial density, sub-20 nm nanostructures are replicated using composite molds. Mold stability is experimentally investigated using sub-100 nm periodicity grating structures fabricated using e-beam lithography. It was observed that as the feature spacing decreased, high modulus PFPE-tetramethacrylate (TMA) composite molds were able to effectively replicate the nanograting structures without cracking or tear-out defects that typically occur with high modulus elastomers. In addition, the amount of fluorinated residue on a surface after contacting a PFPE molds is analyzed as a function of mold material and surface polarity. Suggestions for future directions of PFPE-based molding techniques are also presented