This research presents grating photoresist structures by imprint and focused ion beam (FIB) techniques. Imprint technique is not limited to the physical properties of optical lithography. In the imprinting process, the quartz mold designed for imprinting process is fabricated by focused ion beam techniques to imprint photoresist (SU-8). To select imprint temperature of resist by Differential Scanning Calorimetry, and several kind of pressure are tested and evaluated for imprint. In this study, trichloro(1H, 1H, 2H, 2H- perfluorooctyl)silane (PFOTCS) are used for self-assembled monolayers (SAM) on mold as releasing and anti-sticking layer for nanoimprint. We use contact angle system to discuss the surface energy of any contact surface. The results demonstrated that the resist surface revealed the lower defect and roughness after separation of imprinting mold with SAMs of PFOTCS monolayer, ascribed to the PFOTCS monolayer with a large amount of -CF2 resulted in lower surface energy. This research has successfully defined 50~400 nm width resist features on the mold and transferred to the polymer after imprinting.

Miniaturization has become a product trend due to technological advancements, thus giving rise to nanoimprint lithography printing. Miniaturization is also a trend regarding process features. nanoimprint lithography has great potential for its simple process, low cost, mass-production capacity, and ease to produce nanoscale microstructure. After making a fence structure of line width less than 100nm on quartz glass with FIB, this study printed the fence structure of line width less than 100nm with the nanoimprint lithography using PDMS mold and quartz soft mold. Though PDMS molding is fast and convenient, it is uncommon with regard to small-size press. This study investigated the application of PDMS molds to nanoimprint lithography in order to verify the optimal parameters of PDMS molding and the results of nanoimprint lithography with PDMS soft modes. After obtaining the optimal molding press, the optimal molding parameters and press pressure were applied to find the optimal experimental results. Results show that the combination can successfully print a fence structure with a line width of 40nm.

The negative epoxy-based photoresist of SU-8 has a variety of applications within microelectromechanical systems (MEMS) and lab-on-a-chip systems. Herein, SU-8 was functionalized with antigenic peptides to HIV-1 gp41 or HIV-2 gp36 and the detection of antibody against HIV-1/2 was carried out by an electrochemical immunoassay combining an alkaline phosphatase conjugated secondary antibody and p-aminophenyl phosphate. The by- product of the reaction (p-aminophenol) was quantitated electrochemically using differential pulse voltammetry, and the current derived from the oxidation of the hydrolysis product increased linearly over a wide primary antibody concentration range (0.001 – 1 μg/mL), with a detection limit of 1 ng mL-1 (6.7 pM) for both HIV-1 and HIV-2. This level of sensitivity is clinically relevant, and feasibility of this approach for clinical sample testing was also evaluated with HIV clinical patient samples.

The negative epoxy-based photoresist of SU-8 has a variety of applications within microelectromechanical systems (MEMS) and lab-on-a-chip systems. Herein, SU-8 was functionalized with antigenic peptides to HIV-1 gp41 or HIV-2 gp36 and the detection of antibody against HIV-1/2 was carried out by an electrochemical immunoassay combining an alkaline phosphatase conjugated secondary antibody and p-aminophenyl phosphate. The by- product of the reaction (p-aminophenol) was quantitated electrochemically using differential pulse voltammetry, and the current derived from the oxidation of the hydrolysis product increased linearly over a wide primary antibody concentration range (0.001 – 1 μg/mL), with a detection limit of 1 ng mL-1 (6.7 pM) for both HIV-1 and HIV-2. This level of sensitivity is clinically relevant, and feasibility of this approach for clinical sample testing was also evaluated with HIV clinical patient samples.

Stress in electrochemically deposited (ECD) magnetic films is an important parameter that can have a critical effect on the performance of MEMS devices such as microinductors. This is especially the case when thick layers of materials are required and where it is important to monitor and hence control stress to prevent cracking and delamination. The reliability of devices, therefore, deeply depends on process parameters and conditions used in depositing these materials on silicon wafers. A MEMS technique for measuring stress spatially around such a wafer has been developed and used to characterise the materials involved in the fabrication of a microinductor. This thesis discusses the design and fabrication of test structures, along with a custom built automatic measurement technique to wafer map the spatial variation of strain, on any sized wafers. The effect of agitation on the grain structure of NiFe has been observed to affect strain which were spatially mapped and correlated with the film composition and thickness. Film uniformity were also shown to improve in the absence of agitation in the bath. To further understand the fundamentals of ECD small scale beaker level galvano-static experiments have been employed to use the same test structures fabricated on small Si chips. The effects of hydrogen evolution on film stress and efficiency with the inclusion of boric acid and saccharin, have been discussed. It was concluded that the tensile stress developed in Ni and NiFe films have an inversely proportional relationship with the plating efficiency. The characterisation of electrodeposited copper films is also of importance as copper films are integrated with magnetic materials in the form of windings for microinductors. The variations in recrystallization and evolution of grains of ECD copper, is for the first time demonstrated spatially using the test structures. The effect of additives in bath on film uniformity was investigated and it was observed that with carrier and additive together the three phases of self annealing were more pronounced. Finally the use of these strain test structures have been demonstrated on thick polymer SU-8 films, which is employed as a structural material in microinductors. The effect of UV exposure dose on the cross linking properties of SU-8 has also been studied. It was observed that non-uniformity in the coated film thickness over the wafer can cause variations in the UV exposure during photolithography that effects the cross linking of the polymer hence, inducing different levels of tensile stress in the material. This unique methodology has therefore opened up many possibilities and can be used for characterising newer materials employed in MEMS, fine-tuning the manufacturing processes to achieve set goals in terms of material properties as well as uniformity and gaining a better understanding of the influence of processing conditions on the produced films.

The number of applications in which infrared radiation sensors are used is increasing. In some applications, the cost of the sensor itself is an issue, and simple solutions are thus required. In this thesis, the investigations have related to the use of thin polymer membranes in thermal infrared sensors, such as bolometers and thermopiles. Infrared sensors are usually subcategorized into photonic sensors and thermal sensors. For detection of infrared radiation using a photodetector, there is a requirement for low band-gap material. The need of cooling makes infrared photodetectors rather expensive, and not an alternative for low-cost applications. In thermal sensors, the heat generated from the incident infrared radiation is converted into an electrical output by means of a heat sensitive element. Thermal sensors operate at room temperature, which makes them a low-cost alternative. The basic structure of thermal sensors consists of a temperature sensitive element connected to a heat sink through a structure with low thermal conductance. It is common to use thin membranes of Silicon or Silicon Nitride as thermal insulation between the heat sink and the sensitive element. In comparison, polymers have a thermal conductance that is lower than in these materials, and this increases the generated temperature in the sensitive element. A polymer such as SU-8 has a low thermal conductivity and is applied using a spin coater. This reduces the number of complex processing steps. This thesis presents a new application of SU-8 as a closed membrane in a thermal sensor. The concept was initially demonstrated by fabricating a nickel bolometer and titanium/nickel thermopile structure with a 5 µm SU-8 / SiO2 membrane. However, for the sensor responsivity to be able to compete with commercial thermal sensors the structures, some optimization was required. Since the thermopile generates its own voltage output and requires no external bias, the optimizations were focused on this structure. There exist a number available software tools for thermal simulation of components. However, to the author’s best knowledge, there exist no tool for design optimization of thermopiles with closed membranes. An optimization tool using iterative thermal simulations was developed and evaluated. A new thermopile structure, based on the optimization results, was both fabricated and characterized. Using an infrared laser with a small spot, the measured responsivity of the manufactured thermopile was higher than that of a commercial sensor. In the case of a defocused spot and for longer wavelengths, the infrared absorption in the absorption layer reduces and degrades the responsivity. The thermopile was further evaluated as a sensor in a carbon dioxide meter application based on the NDIR principle. An increase in the CO2 concentration demonstrated a clear decrease in the thermopile voltage response, as was expected. By normalizing the voltage response and comparing it with a commercial sensor, this showed that the SU-8 based thermopile is relatively more sensitive to changes in the CO2 concentration. / STC

This paper proposed a low-cost and high-throughput method to fabricate lensed optical fibers. SU-8 Photoresist is used as the material for fabricating the proposed lens structure and is directly applied on two kinds of optical fiber tip, single mode glass fibers (O.D.=125 £gm) and plastic graded-index plastic fiber (O.D.=500 £gm), utilizing surface tension force to form a hemi-circular shape lens structure. The hemi-circular shape SU-8 lens is then electrostatically pulled to form non-spherical shape in an uniform electric field at a temperature higher than the glass temperature (Tg) of SU-8. Microlens with various radius of curvature can be easily produced by tuning the applied electric fields during the electrostatic pulling process. In addition, this study also measures the UV-Vis-NIR spectrum SU-8 photoresist to confirm the optical property of SU-8. Results indicate the SU-8 has high optical transmittance from the wavelength range of 380-1600 nm. SEM observation also indicates the fabricated SU-8 microlens has excellent surface smoothness which is essential for optical applications. A commercial optical simulation software of ZEMAX® is used to predict the light path of the fabricated lensed fiber. The numerical results show good agreement with the experimental test obtained by projecting laser light into a diluted fluorescence solution. Furthermore, a Fabry-Perot laser chip with the wavelength of 1310 nm is used for light coupling test for the fabricated lensed fibers. Results show the coupling efficiency is up to 78% at working distance of 90 £gm while using the plastic lensed fiber (R =48 £gm), which is around 2 fold higher than that of a flat-end fiber. The coupling efficiency of glass lensed fiber (R =23 £gm) is up to 72% at working distance of 24 £gm, which is around 2.3 fold higher than that of a flat-end fiber. The proposed method is feasible of producing high-quality lensed optical fiber in a high throughput and low-cost way. The method proposed in the current study may give substantial impacts on fabricating lensed fiber in the future.

No description available.

Microstructure manipulation is a fundamental process to the study of biology and medicine, as well as to advance micro- and nano-system applications. Manipulation of microstructures has been achieved through various microgripper devices developed recently, which lead to advances in micromachine assembly, and single cell manipulation, among others. Only two kinds of integrated feedback have been demonstrated so far, force sensing and optical binary feedback. As a result, the physical, mechanical, optical, and chemical information about the microstructure under study must be extracted from macroscopic instrumentation, such as confocal fluorescence microscopy and Raman spectroscopy. In this research work, novel Micro-Opto-Electro-Mechanical-System (MOEMS) microgrippers are presented. These devices utilize flexible optical waveguides as gripping arms, which provide the physical means for grasping a microobject, while simultaneously enabling light to be delivered and collected. This unique capability allows extensive optical characterization of the structure being held such as transmission, reflection, or fluorescence. The microgrippers require external actuation which was accomplished by two methods: initially with a micrometer screw, and later with a piezoelectric actuator. Thanks to a novel actuation mechanism, the “fishbone”, the gripping facets remain parallel within 1 degree. The design, simulation, fabrication, and characterization are systematically presented. The devices mechanical operation was verified by means of 3D finite element analysis simulations. Also, the optical performance and losses were simulated by the 3D-to-2D effective index (finite difference time domain FDTD) method as well as 3D Beam Propagation Method (3D-BPM). The microgrippers were designed to manipulate structures from submicron dimensions up to approximately 100 µm. The devices were implemented in SU-8 due to its suitable optical and mechanical properties. This work demonstrates two practical applications: the manipulation of single SKOV-3 human ovarian carcinoma cells, and the detection and identification of microparts tagged with a fluorescent “barcode” implemented with quantum dots. The novel devices presented open up new possibilities in the field of micromanipulation at the microscale, scalable to the nano-domain.

Polymer based microelectromechanical systems (MEMS) micromachining is finding more interest in research and applications. This is due to its low cost and less time processing compared with silicon MEMS. SU-8 is a photo-patternable polymer that is used as a structural layer for MEMS and microfluidic devices. In addition to being processed with low cost, it is a biocompatible material with good mechanical properties. Also, amorphous silicon (α-Si) has found use as a sacrificial layer in silicon MEMS applications. α-Si can be deposited at large thicknesses for MEMS applications and also can be released in a dry method using XeF2 which can solve stiction problems related to MEMS applications. In this thesis, an SU-8 MEMS process is developed using amorphous silicon (α-Si) as a sacrificial layer. Electrostatic actuation and sensing is used in many MEMS applications. SU-8 is a dielectric material which limits its direct use in electrostatic actuation. This thesis provides a MEMS process with two conductive metal electrodes that can be used for out-of-plane electrostatic applications like MEMS switches and variable capacitors. The process provides the fabrication of dimples that can be conductive or non-conductive to facilitate more flexibility for MEMS designers. This SU-8 process can fabricate SU-8 MEMS structures of a single layer of two different thicknesses. Process parameters were tuned for two sets of thicknesses which are thin (5-10μm) and thick (130μm). Chevron bent-beam structures and different suspended beams (cantilevers and bridges) were fabricated to characterize the SU-8 process through extracting the density, Young’s Modulus and the Coefficient of Thermal Expansion (CTE) of SU-8. Also, the process was tested and used as an educational tool through which different MEMS structures were fabricated including MEMS switches, variable capacitors and thermal actuators.