3D complex shaped- dissolvable multi level micro/nano mould fabrication

There is growing interest in the development of fabrication techniques to cost effectively mass-produce high-resolution (micro/nano) 3D structures in a range of materials. Biomedical applications are particularly significant. This work demonstrates a novel technique to simultaneously fabricate a sacrificial mould having the inverse shape of the desired device structure and also create the desired device structure using electroplating deposition techniques. The mould is constructed of many thin layers using a photoresist material that is dissolvable and sensitive to UV light. At the same time the device is created in the emerging mould layers using Gold electroplating deposition technique. Choosing to fabricate the mould and the 3D structures in multiple thin layers allows the use of UV light and permits the potential cost-effective realization of 3D curved surfaces, the accuracy and geometric details of which are related to the number of layers used. In this work I present a novel idea to improve the LIGA process when using many masks to deposit multi thin layer over each other. Moreover, this technique can be utilized to produce a curved surface in the vertical direction with any diameter. Practically, a 2 µm thickness of layer is applied in the proposed technique. However, a layer of 0.5 µm or less can be deposited. An example is provided to explain the novel fabrication process and to outline the resulting design and fabrication constraints. With this technique, any structure could be made and any material used. The work employs conventional techniques to produce a 3D complex shape. By using conventional techniques with multi layers to produce a 3D structure, many problems are expected to occur during the process. Those problems were mentioned by many researchers in general but have not been addressed correctly. Most researchers have covered those problems by leaving the conventional and using a new technique they invented to produce the required product. However, in my work I have addressed those problems for the first time and I offered a new and effective technique to improve the MEMS technology and make this technology cheaper. This was achieved by using a research methodology requiring a rigorous review of existing processes, as outlined above, then by proposing a concept design for an improved process. This novel proposed process was then tested and validated by a series of experiments involving the manufacture of demo-devices. The conclusion is that this new process has the potential to be developed into a commercially implementable process

Focused ion beam technology : implementation in manufacturing platforms and process optimisation

Process chains are regarded as viable manufacturing platforms for the production of Microand Nano Technology (MNT) enabled products. In particular, by combining several manufacturing technologies, each utilised in its optimal process window, they could benefit from the unique advantages of high-profile research technologies such as the focused ion beam (FIB) machining. The present work concerns the development of process chains and the investigation of pilot cost-effective implementations of the FIB technology in manufacturing platforms forfabrication of serial replication masters.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Focused ion beam technology: implementation in manufacturing platforms and process optimisation

Process chains are regarded as viable manufacturing platforms for the production of Microand Nano Technology (MNT) enabled products. In particular, by combining several manufacturing technologies, each utilised in its optimal process window, they could benefit from the unique advantages of high-profile research technologies such as the focused ion beam (FIB) machining. The present work concerns the development of process chains and the investigation of pilot cost-effective implementations of the FIB technology in manufacturing platforms forfabrication of serial replication masters

Direct Patterning of Optical Coupling Devices in Polymer Waveguides

The aim of the present work was to design and fabricate all purpose, positioning-tolerant and efficient interconnects between single-mode fibers and integrated waveguides out of polymers. The developed structures are part of the optical packaging of integrated optical chips. Integrated optics have gathered tremendous interest throughout recent years from research as well as from the industry, and most likely the demand will further grow in the future. Today’s trend is to establish optical data communication not only in far-distance transmission but also in end-user or so called fiber-to-home configurations, or, in the near future, also on board or even chip level. In addition, integrated optical sensors are gaining more and more importance. In the future, lab-on-a-chip systems may be able to simplify and accelerate analysis methods within health care or allow for a continuous monitoring of almost any environmental variable. All these applications call for robust optical packaging solutions. Many integrated optical chips are using a silicon-on-insulator design. Technologies which were originally intended for the manufacturing of integrated circuits can be utilized for the fabrication of such silicon-on-insulator chips. Point-of-care testing, which is a considerable part of bio-sensing, in some cases only allows the use of disposable transducer elements. The fabrication of these transducers, also including almost all other system parts, may be possible using polymers. Alternative fabrication methods like nanoimprint lithography can be applied for the patterning of polymers. With these, the extension of already known working principles or even entirely new device architectures become feasible for mass production. The direct patterning of polymers by means of nanoimprint was used to fabricate interconnects for integrated waveguides. In contrast to conventional lithography approaches, where a patterned resist layer is used as a masking layer for subsequent process steps, direct patterning allows the immediate use of the structures as functional elements. Firstly, nanoimprint allows diffraction-unlimited patterning with nanometer resolutions as well as the replication of complex three-dimensional patterns. These unique properties were used within this work to pattern shallow gratings atop an integrated waveguide within only one single manufacturing step. The gratings are used as coupling elements and can be utilized either to couple light from external elements to the chip or vice versa. Considerations regarding the optical effects on single-mode polymer waveguides as well as grating couplers were obtained from simulation. They are specific to the chosen design and the used polymer and cannot be found elsewhere so far. Compared to similar designs and fabrication strategies proposed in literature, the ones followed here allow for a higher efficiency. The dimensions and process windows obtained from simulation did serve as a basis for the subsequent fabrication of the grating couplers. All steps which are necessary to turn the calculated design into reality, ranging from master fabrication, to working mold cast and imprint, are shown in detail. The use of a working mold strategy is of crucial importance for the fabrication process and is discussed in detail. The use of a working mold preserves a costly master and further allows for a cost-efficient production. Parameters which are relevant for the production as well as for the final polymer patterns were analyzed and discussed. On the basis of the obtained data, a process optimization was performed. The optical characterization was also part of the presented work. A comparison with the results obtained from simulation is included and additional effects were revealed. Most of them may be subject to further improvement in future designs. In summary, the present work contributes to the field of optical packaging. It shows a viable route for the design and fabrication of interconnects of single-mode polymer waveguides. The presented design can be used as a building block which can be placed at almost any positions within an integrated optical chip. The fabrication method includes a minimum number of process steps and is still able to increase performance compared to similar approaches. Moreover, all process steps allow for scaling and are potential candidates for mass production

3 dimensional proton beam writing for micro electromechanical systems applications.

Proton beam writing is a direct write lithographic technique that uses finely focused MeV proton beams to create structures in a target material. The depth the protons travel in a material is dependent on its energy, this unique property of proton beams allow multi level structures to be created in materials. PBW has been demonstrated successfully on semiconductor materials, glass and polymers. This thesis is a study of the application of PBW in creating Micro Electro-Mechanical Systems (MEMS) in a polymer SU 8 and SU 8 polymer nano composite with silver, and shows experimental steps, theory and computer simulations involved in creating an electrostatic actuated micro-gripping device. Proton beam writing in silver SU 8 composite results in the creation of electrically conducting microstructures. The unique predictability of the range of protons in materials is leveraged in the creating of free standing conducting cantilevers structures which are used as the building blocks for a micro gripping device. The electrostatic actuation has been modelled using a finite element modelling software Sugar 3.1, and the results are comparable with actual actuations in a realized micro-gripping device

Ultra-violet lithography of thick photoresist for the applications in BioMEMS and micro optics

UV lithography of thick photoresist is widely used in microelectromechanical systems (MEMS) and micro-optoelectromechanical systems (MOEMS). SU-8 is a typical negative tone thick photoresist for micro systems, and can be used for both structural material and pattern transfer. This dissertation presents an effort to comprehensively study these important subjects. The first part, and the most fundamental part of this dissertation concentrated on the numerical analysis and experimental study of the wavelength dependent absorbance of SU-8 and the diffraction effects on the sidewall profiles of the microstructures made using UV lithography of SU-8. This study has laid the foundation for all the designs and analysis for the BioMEMS and Micro-optic components and systems using UV lithography of SU-8 in the following chapters of the dissertation. After a full discussion of UV lithography of SU-8, the applications of SU-8 in BioMEMS and micro optics were presented in the following areas: 1) design, analysis, and molding fabrication of biodegradable PLGA microstructures for implanted drug delivery application; 2) design, fabrication, and test of a novel three-dimensional micro mixer/reactor based on arrays of spatially impinging micro-jets; 3) design, analysis, fabrication, and test of a novel new type of truly three-dimensional hydro-focusing unit for flow cytometry applications based on SU-8; 4) Study on a new technology to fabricate out-of-plane pre-aligned microlens and microlens array, and the application of the microlens in a fiber bundle coupler. Finally, a new negative tone thick photoresist based on the composition of EPON resins 165 and 154 were introduced. The synthesis, physical properties, and UV-lithography properties of this new photoresist have been completed. The experimental results have proved it can be a better alternative to SU-8 and can be used in various MEMS and MOEMS applications. Most of the contents have been published or accepted for publications in technical journals or international conferences. Two US patent applications are pending and two more disclosures have been filed for the new technologies presented in this dissertation. There are obviously more work to be done in this promising area and these are presented in the section for future work

Process window and variation characterization of the micro embossing process

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006."June 2006."Includes bibliographical references.The micro embossing process on polymethylmethacrylate (PMMA) is demonstrated experimentally to be a useful process to produce micro fluidic and optical devices. Because this process is a one step thermoplastic deformation process, it is possible to reach high production rates and low cost in manufacturing compared to the standard clean room processes. Currently, the research about this process is still on the feasibility level, with not a quantitative work to optimize the process parameters and assure product quality. In this thesis, an experimental study on process window and variation of Micro Embossing is presented. This study includes the design and manufacturing of an embossing die, the development of an embossing product quality assessment protocol, the process window characterization and the process variation identification. The research results based on the experimental set up in this thesis show that we should apply constant 800N embossing force at an embossing velocity of 1000N/min in order to obtain well formed parts to maintain low process cycle time.(cont.) An embossing temperature of 120°C and de-embossing temperature of 55°C are shown to be the optimal embossing condition to yield good replication and repeatability. These embossing parameters operating window can change with the variation of working piece material, die material and die design.by Qi Wang.S.M