This PDF file contains the front matter associated with SPIE Proceedings Volume 8248, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Battery life is huge problem for today's CE devices and every year the problem gets worse. That is a painful consequence of the explosion in capability and applications in modern wireless electronics of all types, and is particularly acute in advanced smartphones. Fuel cells have long been touted as the solution to the battery problem, and significant programs have been funded at large companies, start-ups, and within academia. Thus far, none of those efforts have resulted in a commercially successful product for consumer electronics. Lilliputian Systems has taken a unique approach by leveraging MEMS fabrication methods to enable the use of a fuel cell known as a solid oxide fuel cell (SOFC). SOFCs provide high efficiency and reliable operation in a very compact Silicon Power Cell™, and allow the use of high energy density fuels, such as butane. This combination overcomes the barriers which have prevented other fuel cell efforts from being commercialized. But in order to use SOFCs, the MEMS structure must operate at elevated temperatures, typically above 600°C, must do so very efficiently, and must be effectively integrated into a complete system. By overcoming these unusual challenges, Lilliputian has developed a solution with a run-time 5-10X longer than existing batteries and with instant recharge by inserting a new cartridge. The absolute safety of the approach is supported by world-wide approval for carry-on and use on airplanes. Over the past several years, Lilliputian Systems has created the many innovations required to bring this complex system to high-volume manufacturing. We will discuss the unique challenges in system architecture and high-temperature MEMS design which have been overcome, enabling Lilliputian to provide long-lasting portable power for consumer electronics devices.

This paper aims to describe the device operation, microfabrication and measurement results of an array of optically transparent, pressure sensors which exhibit high capacitance-to-pressure sensitivity and reliable operation.

Rotary comb-drive electrostatic actuators with smooth vertical sidewalls were designed and fabricated for photonic applications. Silicon on insulator (SOI) wafers with device layer thicknesses of up to 100 μm and oxide layers of 1-2 μm were used. Structures were fabricated through bulk micromachining of the handle layer followed by removal of the buried oxide. Deep reactive ion etching (DRIE) of the device layer defined the comb structure with simultaneous release of the moving arm. Thick photoresist and oxide masking layers were used for the high aspect ratio deep etches. Notching effects or depth variations of device layers were not observed. Etch/ passivation cycles in DRIE were optimized to obtain smooth sidewalls. Traces of etch scallops were confined only to the first few microns of the top and bottom edges of the reflecting sidewall. A movable arm length of 2 mm with a maximum rotation of 2.8 degrees was achieved. The edge deflection was over 100 μm at 100 volts. The fabricated structure provides a long reflecting sidewall that is accessible for hybrid integration in three dimensional space. The fabricated structures can be reliably operated in the kilohertz range.

We have designed and fabricated a silicon photodiode array for use as a subretinal prosthesis aimed at restoring sight to patients who lost photoreceptors due to retinal degeneration. The device operates in photovoltaic mode. Each pixel in the two-dimensional array independently converts pulsed infrared light into biphasic electric current to stimulate remaining retinal neurons without a wired power connection. To enhance the maximum voltage and charge injection levels, each pixel contains three photodiodes connected in series. An active and return electrode in each pixel ensure localized current flow and are sputter coated with iridium oxide to provide high charge injection. The fabrication process consists of eight mask layers and includes deep reactive ion etching, oxidation, and a polysilicon trench refill for in-pixel photodiode separation and isolation of adjacent pixels. Simulation of design parameters included TSUPREM4 computation of doping profiles for n⁺ and p⁺ doped regions and MATLAB computation of the anti-reflection coating layers thicknesses. The main process steps are illustrated in detail, and problems encountered are discussed. The IV characterization of the device shows that the dark reverse current is on the order of 10-100 pA-negligible compared to the stimulation current; the reverse breakdown voltage is higher than 20 V. The measured photo-responsivity per photodiode is about 0.33A/W at 880 nm.

Edge-lit backlighting has been used extensively for a variety of small and medium-sized liquid crystal displays (LCDs). The shape, density and spatial distribution pattern of the micro-optical elements imprinted on the surface of the flat light-guide panel (LGP) are often "optimized" to improve the overall brightness and luminance uniformity. A similar concept can be used to develop interior convenience lighting panels and exterior tail lamps for automotive applications. However, costly diffusive sheeting and brightness enhancement films are not be considered for these applications because absolute luminance uniformity and the minimization of Moiré fringe effects are not significant factors in assessing quality of automotive lighting. A new design concept that involves micromilling cylindrical micro-optical elements on optically transparent plastic substrates is described in this paper. The variable parameter that controls illumination over the active regions of the panel is the depth of the individual cylindrical micro-optical elements. LightTools™ is the optical simulation tool used to explore how changing the micro-optical element depth can alter the local and global luminance. Numerical simulation and microfabrication experiments are performed on several (100mmx100mmx6mm) polymethylmethacrylate (PMMA) test samples in order to verify the illumination behavior.

The fabrication of microstructures with continuous surface profiles and very large sag heights by a laser lithographic process on a commercially available laser lithography system is presented. The fabricated structures possess sag heights up to 60 μm with a pitch of 400 μm. Fabrication imperfections due to nonlinearities in the photoresist response and the isotropy of the development process have been compensated in the exposure data to minimize profile deviations. Therefore, an empirical process model is proposed based on experimentally determined development rates. The achievable accuracy of the data pre shape and exposure method as well as their limitations are discussed.

The following paper describes a design of experiments investigation of the deep reactive of pillar structures on a silicon wafer. The etched wafers would subsequently be used as masters for the fabrication of nickel mould inserts for micro-injection moulding. Undercuts occur when the pillar base has a smaller cross-section than the apex of the pillar. They therefore affect tolerances of the subsequent nickel mould, its strength and its de-mouldability from the silicon form. The response measured in these experiments was the degree of undercut of micro-scale (10 μm x 10 μm x 40 μm, 5 μm x 5 μm x 40 μm and 2 μm x 2 μm x 40 μm) The literature suggests that gas pressure, platen power, gas flow rate, phase switching times and mask size can all affect the degree of undercut. After examination of this literature, and of manufacturers guidelines, three parameters were selected for experimental testing: platen power, C₄F₈ gas flow rate during the passivation phase and switching times. Switching times was found to be the only statistically significant parameter for both 10x10 μm and 5x5 μm pillars. The 2x2 μm pillars were not successfully replicated and could therefore not undergo statistical evaluation.

Laser micro-polishing (LμP) is a new laser-based microfabrication technology for improving surface quality during a finishing operation and for producing parts and surfaces with near-optical surface quality. The LμP process uses low power laser energy to melt a thin layer of material on the previously machined surface. The polishing effect is achieved as the molten material in the laser-material interaction zone flows from the elevated regions to the local minimum due to surface tension. This flow of molten material then forms a thin ultra-smooth layer on the top surface. The LμP is a complex thermo-dynamic process where the melting, flow and redistribution of molten material is significantly influenced by a variety of process parameters related to the laser, the travel motions and the material. The goal of this study is to analyze the impact of initial surface parameters on the final surface quality. Ball-end micromilling was used for preparing initial surface of samples from H13 tool steel that were polished using a Q-switched Nd:YAG laser. The height and width of micromilled scallops (waviness) were identified as dominant parameter affecting the quality of the LμPed surface. By adjusting process parameters, the Ra value of a surface, having a waviness period of 33 μm and a peak-to-valley value of 5.9 μm, was reduced from 499 nm to 301 nm, improving the final surface quality by 39.7%.

Surface texturing of metallic surfaces is studied in mixed regimes of ablation and melting, by adjusting time and energy distribution of infrared lasers, for textures combining ablated and elevated topography in relation to the original surface. This can allow for higher productivities and a wider range of geometries than purely ablative micromachining LST. A methodology is presented for producing regular patterns of micron sized features on metals. By adjusting scanning patterns, features well under the beam size can be obtained, resulting from the displacement of the molten bath by the intense recoil pressure generated by the ablated metal. By engineering the flow of the bath and the position of the recast material, very high aspect ratio structures can be obtained, with limits very dependent on the characteristics (viscosity, temperature, ...) of the molten bath. 2-5 microns sized walls, 40 microns high, were obtained with nanosecond laser of 50 microns beam diameter on titanium. Sub-nanosecond laser pulses were also studied: passively q-switched lasers with 400-500 ps pulse length provide very precise control of molten pool displacement and fine feature generation. Ni-Cr and Ni-Cu coated steel was textured in the form of two dimensional square textures and ribletted surfaces, in order to evaluate the molten metal flow, the progressive shaping of the textures and the redistribution of the layer components during the process.

Femtosecond laser interference is a promising tool for micro-fabrication and micromachining of periodical structures on the surface of samples or inside transparent materials, but femtosecond laser pulses are very hard to interfere due to their spectrum widths may reach to several tens of nanometers, and their spectrum widths will be stretched by shorting the duration according to the Fourier transform. We realized two 25 fs pulses interference and encoded micro-gratings on Au-Cr thin films using this interference pattern. The interference patterns of two laser pulses with different pulse durations in sub-hundred femtosecond time domain were calculated to explore the influence of pulse durations on processing qualities of encoded micro-gratings. The results show that, the shorter pulses are preferable to fabricate micro-gratings with fine resolution on intractable materials, and longer pulses are helpful to improve encoding efficiency and contrast ratio of bright & dark interfered fringes. The differences between encoded micro-gratings on Au-Cr thin film using these interference patterns validated our analysis, which are hardly observed when pulse duration is longer than 100 fs mainly because the size of interfered area is larger than the focal spots. Moreover, the distance between two focal spots also has been chosen to identify our calculations, and the experimental results are agreement with the calculations.

This paper presents a method for etching millimetre-deep trenches in commercial grade PMMA using deep-UV at 254 nm. The method is based on consecutive cycles of irradiation and development of the exposed areas, respectively. The exposure segment is performed using an inexpensive, in-house built irradiation box while the development part is accomplished using an isopropyl alcohol (IPA):H₂O developer. The method was tested and characterized by etching various dimension square test structures in commercial grade, mirrored acrylic. The undercut of the sidewalls due to the uncollimated nature of the irradiation light was dramatically alleviated by using a honeycomb metallic grid in between the irradiation source and the acrylic substrate and by rotating the latter using a direct current (DC) motor-driven stage. By using an extremely affordable set-up and non-toxic, environmentally friendly materials and substances, this process represents an excellent alternative to microfabricating microfluidic devices in particular and high aspect ratio structures in general using PMMA as substrate.

In this paper we describe a process for creating thin SU-8 2002 films between 1.5 μm and 3.0 μm thick that are hardbaked and can withstand a release etch in either aqueous or plasma silicon etchants. Resulting films are characterized using both wafer bow and membrane bulge tests to monitor in-plane stress and Young's modulus. We explore the influence on final film stress of several process variables including hard bake temperature, exposure dose, film thickness, and various temperature profiles. We observe resultant film stress in the range of 13.8 to 32 MPa, and Young's modulus in the range of 2.1 to 5.2 GPa for free-standing membranes. Illustrative process recipes are described for both patterned and un-patterned SU-8 2002 membrane devices.

The aim of this paper was to create finite element model of the hot imprint process for analysis of the heating, imprinting and demolding steps. Polycarbonate was modeled as elasto-plastic material, because it was analyzed below glassing temperature. In general, the simulation model and numerical results provide a useful understanding of the fundamental formation mechanism during the hot imprint process and serve as a useful guide for specifying the optimal processing conditions for variety of hot imprint applications.

Additive direct writing has many advantages compared with the subtractive conventional MEMS fabrication process. With its reduced manufacturing steps, the processing time is shortened and the overall process costs less. Also, the process is non-toxic and its flexibility in the manufacturing gives the capability to alter printing patterns promptly. Among many direct writing methods, electro-hydrodynamic (EHD) printing is also receiving a huge interest due to its capability of high resolution printing. However, there are still many issues to be resolved for the high volume fabrication process, such as the realization of multi-nozzle drop on demand system, etc. In this work, EHD printing was demonstrated using a hole-type electrode with stainless steel nozzle to which the liquid is supplied from a constant pressure reservoir. With varying square voltage pulses between the nozzle and the electrode, three types of jet emission modes are observed; continuous mode, fine jet pulsating mode and droplet pulsating mode. Among these modes, the droplet pulsating mode and the fine jet pulsating mode were optimized to print relatively large patterns and high resolution patterns, respectively. In addition, to demonstrate near field printing for high position accuracy, EHD printing was carried out with a nozzle penetrating the hole-type electrode, so that the distance between nozzle tip and the substrate could be shortened.

Since frictional interactions in microscopically small components are becoming increasingly important for the development of new products for all modern technology, we present a laser-based technique for micro-patterning surfaces of materials using low-cost microlens arrays. The microlens used were fabricated on soda-lime glass using a laser direct-write technique, followed by a thermal treatment into an oven. By combining laser direct-write and the thermal treatment it was possible to obtain high quality elements using a low cost infrared laser widely implemented in industry which makes this technique attractive in comparison with other more expensive methods. The main advantage of using microlens arrays for micropatterning surfaces is the possibility of fabricating a large number of identical structures simultaneously, leading to a highly efficient process. In order to study the capabilities of the microlens fabricated for microstructuring materials, identical structures and arrays of holes were fabricated over a variety of materials, such us, stainless steel, polymer and ceramic. The minimum diameter of the individual microstructure generated at surface is 5 μm. Different nanosecond lasers operating at Infrared, Green and UV were used. The topography and morphology of the elements obtained were determined using a confocal microscope SENSOFAR 2300 Plμ.