A MEMS based device for active focus control is presented. The concept has been developed using coupled field FEM simulation. The focus length is adjusted by a reflective membrane which is electro-statically deformed. Using a special ring shaped counter electrode and an optimized weak membrane suspension, a perfect parabolic shape of the deformed membrane is obtained over a very large diameter at reasonable low driving voltages. The counter electrode is part of the chip package which simplifies the fabrication process. Using SOI-technology, the realization of stress free membranes with a diameter up to 10 mm has been proven. The device can be used in active optical applications where large numerical apertures are needed. Potential applications are e.g. confocal microscopy or scanning applications for focus control. In this paper, detailed results of the design optimization process are presented.
In the paper the new concept of fully integrated scanning confocal optical microscope on-chip is proposed. The operation of this microscope combines the 3-D transmissive scanning of VCSEL laser beam by use of two MOEMS scanners, and active signal detection, based on the optical feedback in the VCSEL laser cavity. The silicon-based electrostatically driven scanners provide controlled movement of two convex microlenses, working as an objective lens of microscope. Glass microlenses are monolithically integrated on movable silicon tables of scanners. The first results of technological investigation on the microscope components are presented.
A 2D MEMS platform for a microlens scanner application is reported. The platform is fabricated on an SOI wafer with 50 μm thick device layer. Entire device is defined with a single etching step on the same layer. Through four S-shaped beams, the device is capable of producing nonlinear 2D motion from linear 1D translation of two pairs of comb actuator sets. The device has a clear aperture of 2mm by 2mm, which is hallowed from the backside for micro-optics assembly. In this paper, a numerical device model and its
validation via experimental characterization results are presented. Integration of the micro-optical components with the stage is also discussed. Additionally, a new driving scheme to minimize the settling time of the device in DC operation is explored.
A novel translational micro mirror with a circular shape of 3 mm diameter and oscillation frequencies of 500 Hz and 1000 Hz is presented including a design study based on analytical and numerical calculations. The study takes mechanical limits like stress and shock resistivity into account as well as fabrication issues resulting in the design points presented. Considerations and results of this study including stress limits for single crystalline silicon and a FE analysis of the main oscillation mode of the resonant structure will be illustrated. Based on an SOI process with 30 μm thick and highly doped single crystalline silicon several devices were fabricated. For the characterization of the devices a Michelson interferometer set-up was used which allows determining the voltage-deflection curves as a function of the air pressure. Deflections of more than ± 50 μm for the 500 Hz device and ± 85 μm for the 1000 Hz have been achieved at a pressure of 10 Pa. The target is at ± 250 μm and ± 180 μm amplitude. In the outlook packaging requirements and approaches will be shown.
MEMS based microdisplays have been given a lot of attention recently since the DLP based products have started to generate substantial revenues for Texas Instrument. Other companies are trying to enter this promising market with similar or alternative concepts. How will he MEMS-based microdisplay market develop until the end of the decade? May other mass markets emerge such as displays for cell phones? Is anyone in the position to challenge TI? This paper
presents the results of the analysis of MEMS microdisplay applications and markets in the NEXUS III study.
A triangulation distance sensor is constructed bending the wafer with metal hinges. On the Si wafer, elements are pre-aligned at the planer condition using the photolithography. The position sensitive detector (PSD), mirror, and alignment pit for a ball lens are prepared. 3-sensor array is integrated in 20x17x10 mm3 size. Compared with our previous study using polymer, the metal hinge stabilizes the long-term performance and the process. Optical
elements including LD chip are all included on the wafer. The demonstrated measurement range is 18-40 mm.
Butt coupled optical waveguides are well known in integrated optics by high sensitivity of energy transfer to their misalignment with respect to each other. This might be detrimental if efficient and firm coupling from one light guide to another is needed, for example, coupling from a fiber to a waveguide on chip. However, this phenomena is efficiently used for sensing applications, where small misalignment between two objects provided with the waveguides can be detected. In this work we studied the abilities of this method to detection of ultrasmall displacements of microcantilevers frequently used in biological research. In the proposed design the cantilever itself acts as a waveguide operated in visible range. The simulations demonstrated ability to detect cantilever deflections with sensitivity of 18 fm/Hz1/2. The capability of detection with subangstrom resolution in the dynamic mode was demonstrated experimentally in air. The preliminary experiments in liquids are presented. The technique can be considered as an alternative to the known methods used for read-out of response of microcantilevers to external nanomechanical forces exerted on them.
In this article the design, fabrication and characterization of micro-Fabry-Perot filters operating in the mid-wavelength infrared range is presented. Using surface micromachining techniques, low temperature silicon nitride based structures with distributed Bragg mirrors made of Ge/SiO/Ge layers have been fabricated and tested, both mechanically and optically. The membrane/mirror deflection has been measured using an optical profilometer and is estimated to be of the order of 800nm with voltage bias up to 17V while still preserving good mirror parallelism. The respective optical transmission peak shifted from 4.5μm to 3.6μm. Without antireflection coating at the back of the silicon substrate ~50% maximum transmission has been measured at the resonance peaks. The FWHM was measured to be 210+/-20nm, which is ~20% larger than estimated theoretically. In agreement with theoretical modeling, after crossing 1/3 of the cavity length, the membrane/mirror structure has been found to enter into an unstable region followed by snap-down to the bottom mirror surface. In order to prevent this detrimental effect, membranes with anti-stiction bumps have been fabricated demonstrating repeatable structure recovery from the stage of full collapse.
We present a Fourier-transform infrared (FTIR) spectrometer where a micro-electro-opto-mechanical system (MOEMS) replaces the macroscopic mirror drive enabling a miniaturized, robust and low cost system. The MOEMS devices are manufactured in a CMOS compatible process on a Silicon on insulator (SOI) substrate. The device consists of a metallized actuator plate with an area of 1.65 mm2 acting as mirror, bearing springs and electrodes for the electrostatic drive. Due to the driving principle based on in-plane electrode combs, 200 μm translatory displacement can be achieved with comparatively low voltages (<40 V) at an ambient pressure below 500 Pa. The actuator operates at a resonant frequency of 5 kHz. Consequently this yields a maximum spectral resolution of 25 cm-1 and an acquisition time of 200 μs per spectrum. Based on a Michelson setup the infrared optical bench of the presented FTIR system is designed to account for the mirror aperture and the desired spectral bandwidth of 2 μm to 5μm. The integrated signal processing electronics has to cope with a bandwidth of 8 MHz as a result of the mirror motion. A digital signal processor manages system control and data processing. Furthermore, high-level analysis algorithms can be applied without the need of an external PC. The high acquisition rate and integration level of the system makes it appropriate for applications like process control and surveillance of fast reactions. First results of transmission and absorbance measurements are shown.
An MgB2 thin film was grown on a SiN-Si substrate, with a superconducting transition temperature, Tc, near 39K. At the mid-point of the transition (T= 38.24K) and at 10Hz a noise spectral density SV = 0.34nV/ √Hz was measured. The temperature noise, Kn, of the MgB2 film at different frequencies is compared to that of cuprate high temperature superconducting (HTS) thin films (with Tc ~ 90 K) used currently in transition-edge bolometers. Κn values predict that high performance far-IR thermal detectors (i.e bolometers) can be developed using MgB2 as a thermistor.
We report on an array of atomic force microscopes (AFM) based on a simple optical set-up using heterodyne detection. The deflection of AFM cantilevers is given by the path differences between the reference and the measuring wave in a Michelson interferometer. A matrix of micro-lenses is placed just above the cantilevers, in such a way that the deflected light from each cantilever is collected by one micro-lens. Both the micro-lenses and the cantilever chips are previously glued to increase the robustness of the system. The interference between the light from each micro-lenses and the
reference light is selected by a diaphragm and subsequently detected by a photodetector. This procedure is repeated for each cantilever. In order to validate our instrument we measure the profile of a binary grating having a step height of 19.66 nm. By a piezoelectric platform a lateral range of 10 μm was scanned with a speed of 1 μm/s and an integration time of 10 ms, which leads to a lateral resolution of 10 nm. The profiles measured by the cantilevers are in good agreement with the profile of the sample grating.
Design, fabrication and characterization of a novel out-of-plane vertical comb-drive actuator based Fourier transform microspectrometer (FTS) is presented. The spectrometer utilizes resonant mode vertical comb actuators as a variable-depth diffraction grating and a single photodetector to monitor the 0th order of the diffraction pattern. The spectrum of the source illuminating the gratings is computed by Fourier transforming the
0th order intensity as a function of the optical path difference. The vertical comb actuators have a travel range of 100 μm under atmospheric pressure with 28V excitation, which yields a theoretical spectral resolution of 0.5nm in the visible and better than 5nm in the telecom wavelengths.
This presentation will address some of the latest market and technology developments for components using MST/MEMS such as portable consumer products, data storage devices etc. The impacts of these developments on the supply chain for MST/MEMS will be discussed. A MST/MEMS mantra is "there is no Moore's law in MEMS". This presentation will demonstrate that elements of MEMS roadmaps are appearing. Although the MEMS industry is highly diverse, sometimes trends can be identified which affect the industry as a whole. To identify and understand these trends is of the utmost importance for the service and equipment suppliers in the MNT/MEMS supply chain. These facilities have to invest in new technologies to be able to sustain their competitive position.
Biological applications require more and more compact, sensitive and reliable microsystems. We will present solutions in order to realize a "microspectroscopy" up to Terahertz frequencies of various biological entities (living cell, neurons, proteins...). We investigate these entities in liquid phase. In a recent work, we have demonstrated a solution to excite efficiently a single wire transmission line . The propagation mode is similar to a surface
plasmon and known as a Goubau-mode . The wire we used is extremely thin compared to other recent solutions at terahertz frequencies. There are three orders of magnitude in the size of the wire used by K. Wang and D.M. Mittleman. Typically the wire's width is 1μm compared to the 900μm diameter metal wire in . Moreover our solution is in a planar configuration which is more suitable for microfluidic applications. We benefit from the high confinement of the electromagnetic field around this very thin gold wire to optimize the sensitivity of these Terahertz BioMEMS. Microfluidic channels are placed below the strip in a perpendicular direction. We will first present some properties of the Planar Goubau-Line (PGL)  and the measurements results obtained with structures fabricated on glass and quartz substrates. In a last part resonant structures and Mach-Zehnder type interferometers will also be presented.
Proton beam writing is a lithographic technique that can be used to fabricate microstructures in a variety of materials including PMMA, SU-8 and FoturanTM. The technique utilizes a highly focused mega-electron volt beam of protons to direct write latent images into a material which are subsequently developed to form
structures. Furthermore, the energetic protons can also be used to modify the refractive index of the material at a precise depth by using the end of range damage. In this paper we apply the proton beam writing technique to the fabrication of a lab-on-a-chip device that integrates buried waveguides with microfluidic channels. We have chosen to use FoturanTM photostructurable glass for the device because both direct patterning and refractive index modification is possible with MeV protons.
Medical applications often require the detection of specific peptides that are indicators of patients' specific medical conditions. The identification of such peptides is to some extent cumbersome and requires specialized equipment, specialized personnel and the results of the test may come as false negative or false positive. This paper presents the experimental results that directed towards the developments of a device and measurement system that is precisely detecting the reaction time between a peptide and a corresponding reaction match. A series of reaction signatures are identified and presented in the paper. Besides, SEM analysis of the peptides after the reaction confirms the existence of the signatures as the ones recorded by the authors. The proposed device could be miniaturized and a potential solution of the optical-based measurement system is presented and discussed. Serious challenges such as packaging or peptide manipulation are also discussed. The configuration of the sensing element is essential in producing the desired sensitivity of the device. A sensitivity analysis is carried out to prove that concentrations of fraction of ppm are detectable through this method.
Devices based on SOI technology are subject to bow due to residual stress induced by the buried oxide. We have designed and fabricated a compact tunable piston tip-tilt mirror device in which the shape and the arrangement of the suspension beams result in both a reduced stress in the suspension beams and an optically flat mirror. The piston tip-tilt mirror is characterized by an accurate vertical displacement of up to 18 μm @ 80 V with good repeatability, and a tip-tilt of up to 2 mrad @ 50 V.
We describe the design and fabrication of novel Fabry-Perot tunable filters based on a deformable structure composed of surface micromachined indium phosphide (InP) / Air Distributed Bragg Reflectors (DBRs). As compared to conventional designs, superior spectral selectivity has been achieved by displacing the resonant cavity into the high index material (InP) rather than in air. This configuration is expected to reduce significantly the lateral losses of the cavity. The filters feature also a novel doping structure for bi-directional electrostatic actuation. We present simulations
and experimental results that demonstrate the effectiveness of this high index cavity concept for improving the selectivity of small dimension tunable MOEMS filters. The devices are fabricated using a multiple InP-air-gap MOEMS technology based on the sacrificial etching of an InP / InGaAs stack A spectral linewidth better than 0.15 nm over a tuning range of 40 nm is experimentally demonstrated. Design improvements for doubling the tuning range are also proposed.
Electrothermal actuation provides the long displacement required by an increasing number ofMEMS applications. However, its high power consumption is a limiting factor, especially for applications in which multiple actuators are required. An iris type variable optical attenuator (VOA),5 which was recently introduced by our group, is an example of such an application. In this paper we introduce an improved single sided electrothermal design, which
reduces the power consumption by a factor of 70%, while at the same time removing an undesired mechanical resonance. The optical performance is also improved by the introduction of a novel aperture shape which provides higher extinction, independent of the process technology.
The electromechanical response of piezoelectrically-actuated AlN micromachined bridge resonators has been characterized using laser interferometry and electrical admittance measurements. We compare the response of microbridges with different dimensions and buckling (induced by the initial residual stress of the layers). The resonance frequencies are in good agreement with numerical simulations of the electromechanical behavior of the structures. We
show that it is possible to perform a rough tuning of the resonance frequencies by allowing a determined amount of built-in stress in the microbridge during its fabrication. Once the resonator is made, a DC bias added to the AC excitation signal allows to fine-tune the frequency. Our microbridges yield a tuning factor of around 88 Hz/V for a 500 μm-long microbridge.
Optical techniques are finding more and more use in the domain of nanoelectromechanical systems (NEMS). In particular, Michelson interferometry and Fabry-Perot interferometry have been employed to transduce high frequency motion of NEMS resonators. Here, we review our recent accomplishments in optical probing of NEMS. We discuss
the effectiveness of the above-mentioned optical techniques as the relevant NEMS dimensions are reduced beyond the optical probing wavelength.
Digital Holographic Microscopes (DHM) enables recording the whole information necessary to provide real time nanometric vertical displacement measurements with a single image acquisition. The use of fast acquisition camera or stroboscopic acquisition mode makes these new systems ideal tools for investigating the topography and dynamical behavior of MEMS and MOEMS. This is illustrated by the investigation of resonant frequencies of a dual axis micromirror.
This enables the definition of the linear, non-linear, and modal resonance zones of its dynamical response.
Scanning white light interferometry (SWLI) is now an established technique for the measurement of surface topography. It has the capability of combining sub-nanometre interferometric resolution with a range limited only by the z-traverse, typically at least 100μm. A very useful extension to its capability is the ability to measure thin films on a local scale. For films with thicknesses in excess of ~2μm (depending on refractive index), the SWLI interaction with the film leads simply the formation of two localised fringe bunches, each corresponding to a surface interface. It is evidently relatively trivial to locate the positions of these two envelope maxima and therefore determine the film thickness, assuming the refractive index is known. For thin films (with thicknesses ~20nm to
~2μm, again depending on the index), the SWLI interaction leads to the formation of a single interference maxima. In this context, it is appropriate to describe the thin film structure in terms of optical admittances; it is this regime that is addressed through the introduction of a new function, the 'helical conjugate field' (HCF) function. This function may be considered as providing a 'signature' of the multilayer measured so that through optimization, the thin film multilayer may be determined on a local scale. Following the derivation of the HCF function, examples of extracted multilayer structures are presented. This is followed by a discussion of the limits of the approach.
The goal of this study is to perform a complement of the existing Telcordia standard in order to assess the reliability of commercial optical microswitches in a space environment. A standard qualification (Telcordia / Bellcore) already exists for ground applications, but some topics (in particular radiation and in vacuo operation), which are a specificity of the space environment, are not covered. To this purpose, a specific test battery (γ-ray, neutrons, protons and in vacuo life tests) has been developed in order to assess the switch behavior in space environment and to achieve a complete evaluation of these optical microswitches for space applications. Little effect has been observed on such devices that may be considered as possible candidates for space applications, at least concerning the mission constraints detailed in this study.
Diffractive Fresnel Lenses (FL) were designed, fabricated and tested. The lens aims for increasing the sensitivity of a Non-Dispersive InfraRed (NDIR) silicon based optical gas system, focusing as much radiation as possible onto the detector. The studied wavelengths are 10.6μm and 3.4μm, which are the main absorption lines for ethylene and ethanol respectively. The lens diameter (5mm) and the focal length (4mm) are fixed by the detector package. Those diffractive lenses are compatible with the planar nature of silicon microtechnology. A theoretical study about the global lens efficiency as a function of the technological constrains and the process complexity has been carried out. Using only three photolithographic masks, eight quantization steps can be etched and a theoretical lens efficiency of 95% can be achieved. Once the devices were fabricated, the focal length and the spot size have been measured.
In MEMS design many different fabrication techniques and materials are involved and the strong dependency between microstructure and fabrication process leads to application specific fabrication processes. A comprehensive management of process knowledge is required to take into account the various interdependencies and constraints occurring within a MEMS fabrication process. This paper presents an environment for the management of process knowledge and provides support for the design and verification of application specific fabrication processes.
The microfabrication and performance of a micro direct methanol fuel cell (μDMFC) by silicon processes are presented in this paper. Using the silicon micromachining techniques, including thermal oxidation, optical lithography, wet etching, silicon anodization, physical vapor deposition, electroless plating, laser beams cauterization, and anodic bonding, we have successfully made single μDMFC as small as 10mmx8mmx3mm. The main reason for the use of MEMS technology is the prospective potential for miniaturization and economical mass production of micro direct methanol fuel cells. The double side of silicon wafer deep wet etching was employed for the gas channels and fuel chamber preparation. The formation of porous silicon (PS) layers for electrode supports by electrochemical process is the key technologies to improve the MEMS-based μDMFC. The method of catalyst deposition reported here differs from previous work in the specific method of electroless plating Pt-deposition and platinum with ruthenium (Pt-Ru) co-deposition on the porous silicon substrates. The power density of the single cell reached only 2.5mW/cm2 lower than that single cell with traditional MEA (4.9mW/cm2) at the same operation conditions, but further improved performance of the μDMFC with the electro-catalytic electrodes is expectant. Moreover, using the MEMS technology makes the batch fabrication of μDMFC much easier and can reduce the usage of rare metals.
The design and fabrication for a novel silicon-based micro direct methanol fuel cell (μ-DMFC) of 0.64cm2 active area on <100> silicon wafer are described in this paper. The novelty of the DMFC structure is that the anodic micro channels arranged in the asymmetric mesh have been fabricated, and the first objective of the experimental trials is to verify the feasibility of the novel structure on the basis of MEMS technology. The effect of different operating parameters on μ-DMFC performances is experimentally studied for two different flow field configurations (grid and spiral). Preliminary testing results show that this novel μ-DMFC demonstrates the better performances using 2M methanol feed at room
temperature, and the output characteristics of μ-DMFC with the grid flow field exceed the one with the spiral flow field. Results have demonstrated a maximum output power density of about 2.3mW/cm2 using 2M methanol solution.
Experiments show that the gauge factor of poly-Si film is biggish when its thickness is in the range of nano scale, which cannot be explained reasonably by existing piezoresistive theories. This paper focuses on how gauge factor varies with film thickness, analyzes the origin of poly-Si piezoresistive properties under the circumstance of small grain size, and indicates that tunneling current going through grain boundary barrier is influenced by the strain, which makes the enhancement of piezoresistive effect at gain boundary. Based on these, a modified model on poly-Si piezoresistive properties is proposed, and it fits the experimental results well.
Microfluidic components are basic tools in microanalysis systems. A simple structure PDMS micro valve is described. Driven by the PZT piezoelectric actuator, this microvalve could realize to control the liquid flow rate in the microliter or submilliliter scale. The fabrication method about the PZT piezoelectric thick film with the screening printing technique and the Polydimethylsiloxane (PDMS) valve body with the soft lithography technique are presented. The optimal PZT film processing annealing temperature parameter at 800°C in 60 min could be observed, the PZT grain size is about 1μm or more. Then the silicone substrate and the drilled PDMS top substrate are bonded together with the oxygen plasm to form the chamber. The overall dimensions of the valve are 10mm x 10mm x 2mm. While the dead volume is 0.1 ml, and the inner diameter of the valve seat is 6 mm. Finally, the performance of the PDMS valve is tested.
Microchip electrophoresis technique have been developed fully these years, especially the detection methods have been the research focuses. With the help of MEMS technique, the system integrating function are more and more. This paper presented a novel design and fabrication method about this electrophoresis chip with the detection electrodes. The two-layer structure, one is PDMS
substrate to fabricate the electrophoresis microchannel, the other is the glass substrate with the Pt electrodes, are bonded together. The soft lithography with the two molds is developed to accommodate
the PDMS curing and peeling off. Then the inorganic cation Cu2+ is introduced and tested the project feasibility. All these works are laid a stable foundation for the chip appliance.
Tunable wavelength selective and band pass filters are widely used nowadays in transmission technology and light processing, with setups based on Acustooptic modulators, Fabry Perot filters, Mach Zehnder and Sagnac interferometers and fiber Bragg gratings (FBGs) with electro-optical, mechanical or thermal tuning mechanism. Multilayer structures like FBGs are used in the design of e.g. broad-band terminations of transmission lines1, narrow-band transmission filters for wavelength-division multiplexing (WDM)2 and in other fiber optics systems for signal processing3. One of the biggest advantages of dielectric mirrors is that they are characterized with very small losses, as compared with normal metallic mirrors. Apart from that, with the use of Bragg mirrors one can control bandwidth of the reflected light beam, as well as the angles for which the reflection is obtained. This opens up a possibility of building setups sensitive to such parameters as the lighting angle and the wavelength. Additionally, Bragg mirrors can be used for a wide spectrum of the electromagnetic waves from UV to FIR. In this paper we propose a new concept of MOEMS-based free-space tunable Bragg grating as a wavelength selective and band pass filter. The use of MEMS allows obtaining fast and reliable tuning with respect to other methods.