Journal of Microelectromechanical Systems

This paper reports theoretical analysis and experimental results on a new class of rectangular plate and ring-shaped contour-mode piezoelectric aluminum nitride radio-frequency microelectromechanical systems resonators that span a frequency range from 19 to 656 MHz showing high-quality factors in air (Qmax=4300 at 229.9 MHz), low motional resistance (ranging from 50 to 700 Omega), and c... View full abstract»

Substantial reductions in vibrating micromechanical resonator series motional resistance Rx have been attained by mechanically coupling and exciting a parallel array of corner-coupled polysilicon square plate resonators. Using this technique with seven resonators, an effective Rx of 480 Omega has been attained at 70 MHz, which is more than 5.9X smaller than the 2.82 kOmega ex... View full abstract»

This paper presents two approaches to analyzing and calculating thermoelastic damping in micromechanical resonators. The first approach solves the fully coupled thermomechanical equations that capture the physics of thermoelastic damping in both two and three dimensions for arbitrary structures. The second approach uses the eigenvalues and eigenvectors of the uncoupled thermal and mechanical dynam... View full abstract»

We have developed a single-wafer vacuum encapsulation for microelectromechanical systems (MEMS), using a thick (20-mum) polysilicon encapsulation to package micromechanical resonators in a pressure <1 Pa. The encapsulation is robust enough to withstand standard back-end processing steps, such as wafer dicing, die handling, and injection molding of plastic. We have continuously monitored the pre... View full abstract»

A microtechnology for synthetic biodegradable polymers has been developed to fabricate three-dimensionally (3-D) shaped and microstructured multilayer constructs for biomedical applications. A unique micromolding method is proposed to create deep and interconnecting microstructures which facilitate cellular scale interconnection across the layers for cell-to-cell communication and the supply of nu... View full abstract»

There is a great need in experimental biology for tools to study interactions between biological molecules and to profile expression levels of large numbers of proteins. This paper describes the fabrication, packaging and testing of a resonant mass sensor for the detection of biomolecules in a microfluidic format. The transducer employs a suspended microchannel as the resonating element, thereby a... View full abstract»

This paper describes the fabrication technology and characterization of Parylene neural probes containing fluidic channels for delivery of small amounts of drugs into biological tissue as well as neural recording. We present a first attempt to realize such neural probes by micromolding and thermal bonding of Parylene. Compared to the common fabrication method, where a sacrificial photoresist layer... View full abstract»

Recently, the ability to create engineered heart tissues with a preferential cell orientation has gained much interest. Here, we present a novel method to construct a cardiac myocyte tissue-like structure using a combination of dielectrophoresis and electro-orientation via a microfluidic chip. The device includes a top home-made silicone chamber containing microfluidic channels and bottom integrat... View full abstract»

Monodispersed emulsions are of great significance for a variety of applications. The current study reports a new microfluidic system capable of formation of microdroplets in liquids for emulsification applications. This new emulsion chip can precisely generate uniform droplets using a novel combination of hydrodynamic-focusing and liquid-chopping techniques. Experimental data show that microdrople... View full abstract»

This paper describes the design, fabrication, and force analysis of a pneumatically driven microcage. Pneumatic actuation, suitable to function in a wide range of environments, is especially useful for operation in a small liquid space. The capture of single motile microbes (Volvox and Stentor ~400 mum) in aqueous environments is demonstrated with the microcage. The setup for the capture experimen... View full abstract»

This paper presents the design, fabrication and testing of a new structure of dielectrophoresis (DEP) chip having a three-dimensional (3-D) electric field gradient and an asymmetric distribution of the electric field in the vertical plane. This achievement was possible due to the special configuration of the electrodes: a bulk silicon electrode and a thin amorphous silicon electrode. The thick ele... View full abstract»

An experimental investigation is presented on flow boiling of deionized water in 227-mum hydraulic diameter microchannels with reentrant type cavities. Key features of nucleate boiling are discussed. Active nucleation site density, bubble frequency and departure diameter, and flow patterns over mass velocities ranging from 41 kg/m2-s to 302 kg/m2-s and heat fluxes ranging fro... View full abstract»

The Agilent all-optical bubble switch uses bubbles in an organic fluid index matched to a silica planar lightwave circuit. The bubble is created and sustained by heaters that are deposited on an attached silicon substrate. Testing of the bubble shows how heater power and ambient pressure affect bubble shape, size, and optical reflection characteristics. Heat and fluid flow in the bubble were model... View full abstract»

This paper describes the design, fabrication and testing of a quasi-static electromagnetic cavity resonator fabricated using potassium-hydroxide (KOH) etching, shallow reactive-ion etching (RIE), metalization and wafer bonding. The resonator is distinguished by its simultaneous high-Q near 200, and wide high-frequency tuning range, 2.5-4.0 GHz for the experimental resonator presented here. When co... View full abstract»

Thin, planar, radio frequency microelectromechanical systems (MEMS) resonators have been shown to self-oscillate in the absence of external forcing when illuminated by a direct current (dc) laser of sufficient amplitude. In the presence of external forcing of sufficient strength and close enough in frequency to that of the unforced oscillation, the device will become frequency locked, or entrained... View full abstract»

In this paper, we have demonstrated an addressable array (5-by-5) of high-quality microlenses suitable for application in a Shack-Hartmann (SH) sensor in a microoptical system. Specific lenses in the array can be addressed using a new selection scheme (that we have designed, built, and tested) in which the mechanical resonant frequencies of individual lens-support carriages are varied. Thus, by ch... View full abstract»

In this paper, we have developed a new micromirror with a compact footprint which can be rapidly tilted to large angles. The micromirror is supported by a liquid-metal drop (LMD) with low vapor pressure and is rotated by an electrostatic torque. A torsional spring model is proposed to predict the equivalent torsional constant of the LMD and the resonant frequency of the mirror. Micromirrors (1 mmt... View full abstract»

A self-latched micromachined mechanism with large displacement ratio is presented in this paper. The large output displacement is obtained by amplifying the small input motion through the elastic deformation of the compliant configuration, which realizes the self-latched output by local bifurcation effect. The design theory and synthesis of compliant microstructures are analyzed. The numerical and... View full abstract»

A soft-landing actuation waveform was designed to reduce the bounce of a single-pole single-throw (SPST) ohmic radio frequency (RF) microelectromechanical systems (MEMS) switch during actuation. The waveform consisted of an actuation voltage pulse, a coast time, and a hold voltage. The actuation voltage pulse had a short duration relative to the transition time of the switch and imparted the kinet... View full abstract»

This paper presents radio frequency microelectromechanical systems (RF-MEMS) capacitive switches fabricated using printed circuit processing techniques. The key feature of this approach is the use of most commonly used flexible circuit film, Kapton E polyimide film, as the movable switch membrane. The physical dimensions of these switches are in the mesoscale range. For example, electrode area of ... View full abstract»

"Both the authors and the Editor-in-Chief of Volume 15, number 6 of the IEEE/ASME JMEMS (December 2006, pp.1606-1611) of the paper numbered JMEMS 1743 have agreed that this paper, "An RF MEMS Switch with Low Actuation Voltage and High Reliability," should not have been published. The paper would have been withdrawn had this fact been discovered before the IEEE/ASME JMEMS print date for December 20... View full abstract»

Static friction between sidewall contact surfaces of polycrystalline silicon micromachines was investigated under different contact pressures, vacuum conditions, relative humidity levels, and temperatures. The static coefficient of friction exhibited a nonlinear dependence on the external contact pressure. A difference between in-contact and pull-out adhesion forces was observed due to the elastic... View full abstract»