In the last 30 days

• Open/close Microfluidics-a review

  P Gravesen et al 1993 J. Micromech. Microeng. 3 168 Tag this article

  Article References Full text PDF (1.48 MB)

  An overview is given of research activities in the field of fluid components or systems built with microfabrication technologies. This review focuses on the fluidic behaviour of the various devices, such as valves, pumps and flow sensors as well as the possibilities and pitfalls related to the modelling of these devices using simple flow theory. Finally, a number of microfluidic systems are described and comments on future trends are given.

• Open/close A parametric dynamic compact thermal model of an electrothermally actuated micromirror

  Sagnik Pal and Huikai Xie 2009 J. Micromech. Microeng. 19 065007 Tag this article

  Article References Full text PDF (500 KB)

  A compact thermal model of a one-dimensional (1D) electrothermally actuated micromirror device is reported. Thermal bimorphs with integrated platinum resistors are used for generating angular rotation. A finite element thermal model is built and validated using thermal imaging data. Using a Krylov subspace-based algorithm, a reduced-order model of order 2 is extracted from the finite element model. The reduced model agrees well with finite element results. A lumped element circuit model is used to explain the second-order thermal response.

• Open/close Microelectromechanical flexure PZT actuated optical scanner: static and resonance behavior

  Johannes G Smits et al 2005 J. Micromech. Microeng. 15 1285 Tag this article

  Article References Full text PDF (437 KB)

  An optical, mirror system has been built using MEMS techniques while employing lead zirconate titanate (PZT) thin films as strong piezoelectric material. The system consists of two parallel silicon cantilever beams, on which the PZT was deposited, which were arranged to project inward from a common frame. The beams were laterally offset over a distance appropriate to fit a mirror between them. One end of each beam is fixed to the frame, while the other end is attached to a sideways projected bar, directed to the other beam. To each sideways bar a connector, parallel to the original beam, pointing toward the frame, was attached. Between both connectors a mirror was attached. The application of voltage across the electrodes on top and below the PZT causes the beams to bend as a monomorph, and the mirror between the beams to rotate around an axis through its center. A variety of thicknesses have been chosen to fabricate these devices. The mirror angle at a given voltage is inversely proportional to the square of the beam thickness, while the bandwidth is proportional to the thickness. Beams with thickness of 5 µm were used to achieve optical angles in static mode of up to 40° using voltages up to 13 V. In that case a bandwidth of around 700 Hz was observed. In resonance optical angles of 10° with a driving voltage as low as 100 mV were achieved. For devices with 30 µm thick beams, optical angles of up to 30° were observed in resonance at 17.4 kHz at driving voltages of around 6 V. Due to the proprietary design a figure of merit which may be defined as a product of the resonance frequency and optical angle, is much higher than one of the other PZT scanners.

• Open/close Thermal simulation and design optimization of a thermopile infrared detector with an SU-8 membrane

  C G Mattsson et al 2009 J. Micromech. Microeng. 19 055016 Tag this article

  Article References Full text PDF (1.30 MB)

  Simulation and optimization tools are commonly used in the design phase of advanced electronics devices. In this work, we present a thermal simulation and design optimization tool for infrared thermopile detectors based on a closed membrane structure. The tool can be used to simulate and optimize thermopile detectors with an arbitrary number of design parameters. The optimization utilizes the Nelder–Mead and the adaptive simulated annealing optimization algorithms to maximize the system performance. A thermopile detector with an SU-8-based closed membrane and metal–metal thermocouples has been simulated and optimized. Based on the results generated by the tool, an optimized detector has been fabricated and characterized. The results from the measurements presented are in good agreement with the simulation results.

• Open/close Microsieves made with laser interference lithography for micro-filtration applications

  Cees J M van Rijn et al 1999 J. Micromech. Microeng. 9 170 Tag this article

  Article References Full text PDF (717 KB)

  A microsieve with a very uniform pore size of 260 nm and a pore to pore spacing of 510 nm has been fabricated using multiple exposure interference lithography and (silicon) micro-machining technology.

  The sieve consists of a 0.1 µm thick silicon nitride membrane perforated with sub-micron diameter pores and a macro perforated silicon support. The calculated clean water flux is at least one to two orders higher than that of conventional inorganic membranes.

• Open/close Fabrication of microsieves with sub-micron pore size by laser interference lithography

  Stein Kuiper et al 2001 J. Micromech. Microeng. 11 33 Tag this article

  Article References Full text PDF (1.15 MB)

  Laser interference lithography is a low-cost method for the exposure of large surfaces with regular patterns. Using this method, microsieves with a pore size of 65 nm and a pitch of 200 nm have been fabricated. The pores are formed by inverting a square array of photoresist posts with a chromium lift-off process and by subsequent reactive-ion etching using the chromium as an etch mask. The method has wider process latitude than direct formation of holes in the resist layer and the chromium mask allows for etching of pores with vertical sidewalls.

• Open/close Analysis and wafer-level design of a high-order silicon vibration isolator for resonating MEMS devices

  Sang Won Yoon et al 2011 J. Micromech. Microeng. 21 015017 Tag this article

  Article References Full text PDF (1.13 MB)

  This paper presents the analysis and preliminary design, fabrication, and measurement for mechanical vibration-isolation platforms especially designed for resonating MEMS devices including gyroscopes. Important parameters for designing isolation platforms are specified and the first platform (in designs with cascaded multiple platforms) is crucial for improving vibration-isolation performance and minimizing side-effects on integrated gyroscopes. This isolation platform, made from a thick silicon wafer substrate for an environment-resistant MEMS package, incorporates the functionalities of a previous design including vacuum packaging and thermal resistance with no additional resources. This platform consists of platform mass, isolation beams, vertical feedthroughs, and bonding pads. Two isolation platform designs follow from two isolation beam designs: lateral clamped–clamped beams and vertical torsion beams. The beams function simultaneously as mechanical springs and electrical interconnects. The vibration-isolation platform can yield a multi-dimensional, high-order mechanical low pass filter. The isolation platform possesses eight interconnects within a 12.2 × 12.2 mm ² footprint. The contact resistance ranges from 4–11 Ω depending on the beam design. Vibration measurements using a laser-Doppler vibrometer demonstrate that the lateral vibration-isolation platform suppresses external vibration having frequencies exceeding 2.1 kHz.

• Open/close Fabrication of high-aspect-ratio microstructures using dielectrophoresis-electrocapillary force-driven UV-imprinting

  Xiangming Li et al 2011 J. Micromech. Microeng. 21 065010 Tag this article

  Article References Full text PDF (1.26 MB)

  We propose a novel method for fabricating high-aspect-ratio micro-/nano-structures by dielectrophoresis-electrocapillary force (DEP-ECF)-driven UV-imprinting. The force of DEP-ECF, acting on an air–liquid interface and an air–liquid–solid three-phase contact line, is generated by applying voltage between an electrically conductive mold and a substrate, and tends to pull the dielectric liquid (a UV-curable pre-polymer) into the mold micro-cavities. The existence of DEP-ECF is explained theoretically and demonstrated experimentally by the electrically induced reduction of the contact angle. Furthermore, DEP-ECF is proven to play a critical role in forcing the polymer to fill into the mold cavities by the real-time observation of the dynamic filling process. Using the DEP-ECF-driven UV-imprinting process, high-aspect-ratio polymer micro-/nano-structures (more than 10:1) are fabricated with high consistency. This patterning method can overcome the drawbacks of the mechanically induced mold deformation and position shift in conventional imprinting lithography and maximize the pattern uniformity which is usually poor in capillary force lithography.

• Open/close The mechanical properties of the rubber elastic polymer polydimethylsiloxane for sensor applications

  J C Lötters et al 1997 J. Micromech. Microeng. 7 145 Tag this article

  Article References Full text PDF (62 KB)

  Polydimethylsiloxane (PDMS) is a commercially available physically and chemically stable silicone rubber. It has a unique flexibility with a shear elastic modulus due to one of the lowest glass transition temperatures of any polymer . Further properties of PDMS are a low change in the shear elastic modulus versus temperature , virtually no change in G versus frequency and a high compressibility. Because of its clean room processability, its low curing temperature, its high flexibility, the possibility to change its functional groups and the very low drift of its properties with time and temperature, PDMS is very well suited for micromachined mechanical and chemical sensors, such as accelerometers (as the spring material) and ISFETs (as the ion selective membrane). It can also be used as an adhesive in wafer bonding, as a cover material in tactile sensors and as the mechanical decoupling zone in sensor packagings.

• Open/close Three-dimensional etching of silicon substrates using a modified deep reactive ion etching technique

  S Azimi et al 2011 J. Micromech. Microeng. 21 074005 Tag this article

  Article References Full text PDF (1.78 MB)

  We report realization of highly featured three-dimensional micro- and nano-structures on silicon substrates with a single masking layer using a hydrogen-assisted deep reactive ion etching process. Three gases of oxygen, hydrogen and SF ₆ are used in a sequential passivation and etching process to achieve high aspect ratio features. By controlling the flows of these gases and the power and timing of each subsequence, it is possible to achieve desired deep vertical etching with controlled underetching and recovery, yielding three-dimensional features directly on silicon substrates. Etch rates up to 0.75 µm min ⁻¹ have been obtained with a low plasma power density of 1 W cm ⁻². Also features with a controllable underetching with more than 8 µm in sidewall recession have been achieved. The three-dimensional structures can be used as a mold for polymers as well as a holding substrate for projection display applications where an electro-chromic material (WO ₃) has been used.