Progress in the state of the art of nanofabrication now allows devices that may enable the experimental sensing of bubble nucleation in nanochannels, and the direct measurement of the bubble nucleation rate in nanoconfined water and other fluids. In this paper we report on two aspects in achieving this goal: 1) new molecular dynamics simulations of nanobubble formation in nanoconfined argon and water model systems and 2) an ultrasensitive nanofluidic device architecture potentially able to detect individual nanobubble nucleation events.

Minimizing risk is an important factor in new product planning because high volume breakthrough products require tens of millions of dollars to develop and bring to market. Sometimes risk can be minimized by following the IC model: build new devices on an existing process – just change the mask set. This approach obviously has limits. Adoption of new materials and processes greatly expands the horizon for “disruptive” products. This paper uses a case study approach to examine how changes in masks, materials and unit processes were used, and will continue to be used, to produce MEMS products for high volume applications.

Bond strength between three dimensional micro-sized cylindrical patterns and Si substrate has been evaluated to clarify the effects of the cylinder length vs. diameter ratio, i.e. the aspect ratio, on the bond strength. Cylindrical shape was employed for avoiding ambiguity of loading point under bend conditions. Multiple cylindrical specimens of an epoxy type photoresist, SU-8 with various lengths were fabricated on a silicon substrate under the same photolithographic condition. Bond strength between micro-sized SU-8 and Si substrate under bend loading mode was measured by a mechanical testing machine for micro-sized materials. The maximum bend moment is 9.6 × 10−6 Nm in average and lineally increases with increasing the aspect ratio. On the other hand, the maximum load, i.e. maximum shear load is 106 mN in average and almost constant with increasing aspect ratio. This result suggests that the shear stress near the interface may cause the initiation of delamination. This phenomenon is discussed with three dimensional fracture observation and quantitative analysis of the line profile around the initiation site by AFM.

In this work a novel technique to create nanometer sized air gaps for high frequency (HF) mechanical resonators will be presented. The technique is based on the narrowing of initially wide gaps with a conformal “narrowing” layer. The novelty of this technique is that it enables the creation of narrow high-aspect ratio gaps (e.g. 100nm gaps in 10μm thick layers) without the need for complex lithography or high aspect ratio etching. Furthermore, the electrodes and the resonator itself can be patterned in a single processing step. The process methodology will be explained and validation experiments in a silicon-germanium (SiGe) based technology will be shown. This technology uses low temperature (∼450°C) poly silicon-germanium (SiGe) as the structural layer, which can be processed above CMOS, and therefore allows the fabrication of MEM devices above CMOS.

The emergence of BioMEMS fabrication technologies such as soft lithography, micromolding and assembly of 3D structures, and biodegradable microfluidics, are already making significant contributions to the field of regenerative medicine. Over the past decade, BioMEMS have evolved from early silicon laboratory devices to polymer-based structures and even biodegradable constructs suitable for a range of ex vivo and in vivo applications. These systems are still in the early stages of development, but the long-term potential of the technology promises to enable breakthroughs in health care challenges ranging from the systemic toxicity of drugs to the organ shortage. Ex vivo systems for organ assist applications are emerging for the liver, kidney and lung, and the precision and scalability of BioMEMS fabrication techniques offer the promise of dramatic improvements in device performance and patient outcomes.

Ultimately, the greatest benefit from BioMEMS technologies will be realized in applications for implantable devices and systems. Principal advantages include the extreme levels of achievable miniaturization, integration of multiple functions such as delivery, sensing and closed loop control, and the ability of precision microscale and nanoscale features to reproduce the cellular microenvironment to sustain long-term functionality of engineered tissues. Drug delivery systems based on BioMEMS technologies are enabling local, programmable control over drug concentrations and pharmacokinetics for a broad spectrum of conditions and target organs. BioMEMS fabrication methods are also being applied to the development of engineered tissues for applications such as wound healing, microvascular networks and bioartificial organs. Here we review recent progress in BioMEMS-based drug delivery systems, engineered tissue constructs and organ assist devices for a range of ex vivo and in vivo applications in regenerative medicine.

In this work, we report the post-growth investigation of the microstructure and stress in the AlN films grown on patterned amorphous dielectrics through micro-Raman spectroscopy. The surface texture of AlN/SiO2 structures was characterized by randomly oriented crystallites typical of polycrystalline films. Post growth analysis of the AlN/SiO2 structures using micro Raman spectroscopy did not reveal phonon modes corresponding to wurtzite AlN. The presence of randomly oriented crystallites with a possibility of oxidized Al phase in the AlN film could have suppressed the appearance of wurtzite AlN phonon peaks in the Raman spectrum. Profiling the stress and the microstructure of AlN/SiO2 structures across the width of the bridges is thus limited by these factors. AlN structures on SiO2 when subjected to wet etching in buffered HF (10:1) showed a clear change in texture. Micro-raman spectroscopy on the etched areas revealed wurtzite AlN like phonon modes. The appearance of wurtzite AlN modes can be attributed to the removal of oxidized Al phase in the AlN film after wet etching.

Accurate mechanical property measurement of films on substrates by instrumented indentation requires a solution describing the effective modulus of the film/substrate system. Here, a first-order elastic perturbation solution for spherical punch indentation on a film/substrate system is presented. Finite element method (FEM) simulations were conducted for comparison with the analytic solution. FEM results indicate that the new solution is valid for a practical range of modulus mismatch, especially for a stiff film on a compliant substrate.

Epitaxaially-grown KNbO3 thick films over 8 μm in thickness were successfully grown at 220 °C for 6 h on (100)cSrRuO3//SrTiO3 substrates by a hydrothermal method. Epitaxial SrRuO3 layers grown on (100)cSrTiO3 substrates by sputter method were used as bottom electrode layers. Relative dielectric constant and the dielectric loss were 530 and 0.11, respectively. Clear hysteresis loops originated to the ferreoelectricity were observed and a remanent polarization was 25 μC/cm2 at a maximum applied electric field of 540 kV/cm. In addition, the hydrothermal KNbO3 thick film was able to transmitting and receiving of ultrasonic waves over 50MHz.

Metal layers can be used as bonding layers at wafer-level in MEMS manufacturing processes for device assembly as well as just for electrical integration of different levels. One has to distinguish between two main types of processes: metal diffusion bonding and bonding with formation of an interface eutectic alloy layer or an intermetallic compound. The different process principles determine also the applications area for each. From electrical interconnections to wafer-level packaging (with emphasis on vacuum packaging) metal wafer bonding is a very important technology in MEMS manufacturing processes.

A new X-ray diffraction technique to determine elastic moduli of polycrystalline thin films deposited on monocrystalline substrates is demonstrated. The technique is based on the combination of sin2ψ and X-ray diffraction wafer curvature techniques which are used to characterize X-ray elastic strains and macroscopic stress in thin film. The strain measurements must be performed for various hkl reflections. The stresses are determined from the substrate curvature applying the Stoney's equation. The stress and strain values are used to calculate hkl reflection dependent X-ray elastic moduli. The mechanical elastic moduli can be then extrapolated from X-ray elastic moduli considering film macroscopic elastic anisotropy. The derived approach shows for which reflection and corresponding value of the X-ray anisotropic factor Γ the X-ray elastic moduli are equal to their mechanical counterparts in the case of fibre textured cubic polycrystalline aggregates. The approach is independent of the crystal elastic anisotropy and depends on the fibre texture type, the texture sharpness, the amount of randomly oriented crystallites and on the supposed grain interaction model. The new method is demonstrated on a fiber textured Cu thin film deposited on monocrystalline Si(100) substrate. The advantage of the new technique remains in the fact that moduli are determined non-destructively, using a static diffraction experiment and represent volume averaged quantities.

Nanofluidic devices are finding growing interest for a variety of applications. An initial report is presented here on a wide range of parameters influencing transport of ionic species as they translocate across solid-state nanopores. AC electrical bias at low ionic concentration with overlapping electric double layers provides an enhancement of ionic flux over pure DC bias. Furthermore, results also indicate that concentration and pH gradients can be maintained across solid-state nanopores for extended periods of time that can last for several hours in the absence of driving forces such as electric fields.

In this paper, we report the results of a rapid and room temperature integration approach for the selective and structured deposition of carbon nanotubes (CNTs) into three-dimensional microstructures. The approach exploits electrophoretic deposition (EPD) from an aqueous suspension of CNTs, together with suitably patterned and electrically-energized microstructure-bearing substrates. Uniform 2-D and 3-D micropatterns of CNTs on wafer scale have been achieved in less than 4 minutes with controllable thicknesses ranging from 133nm to several micrometers. Orientation of the deposited CNTs was observed in microstructures with certain dimensions. Surface hydrophobicity of the microstructures was found to be critical in achieving well-defined micropatterning of CNTs. A hydrophobic microstructure surface leads to the selective patterning profiles of CNTs, while a hydrophilic surface induces CNTs assembly over the entire microstructure, with resultant loss of selectivity. This approach can be further extended to fabricate 3-D micropatterns with multilayer materials on flexible substrate through the aid of transfer micromolding techniques.

We report a highly selective technique for the rapid and label-free analysis of nucleic acid sample using Metal Oxide Semiconductor (MOS) capacitive sensors. The binding of charged macromolecules such as DNA on the surface of these Field Effect Devices modifies the charge distribution in the Semiconductor (Si) region of the sensor. These changes are manifested as a significant shift in the Capacitance-Voltage (C-V) characteristics measured across the device. The speed and selectivity of the detection process is enhanced by the use of external electric field of controlled intensity. This simple and high-throughput sensing technique holds promises for the future electronic DNA arrays and Lab-on-a chip devices

The results of micromechanical tensile experiments performed on thin aluminum samples are presented and discussed. The micro tensile test system and the design of the samples, based on finite element modeling (FEM), and their production by micromachining are briefly described. Some examples of the stress strain curves are presented. The Young's modulus and critical parameters (flow and rupture stress and strains) are reported. The micro structural changes induced by the tensile experiment were observed during and after the testing by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The results of micromechanical tensile experiments performed on thin aluminum samples are presented and discussed. The micro tensile test system and the design of the samples, based on finite element modeling (FEM), and their production by micromachining are briefly described. Some examples of the stress strain curves are presented. The Young's modulus and critical parameters (flow and rupture stress and strains) are reported. The micro structural changes induced by the tensile experiment were observed during and after the testing by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

As Microelectromechanical Systems (MEMS) continue to mature and increase in design complexity, the need to exploit rotation in MEMS devices has become more apparent. An in-plane piezoelectric rotational actuator is proposed that provides free deflections on the order of 1.5° with applied biases of less than 35V and nanoampere currents. Moments up to 6×10−8 N·m, corresponding to forces of 125 μN, were measured using MEMS cantilever springs. The actuator utilizes the low-power, high-force characteristics of lead zirconate titanate and a coupled, dual offset-beam design to provide efficient rotational displacement. The resulting power consumption is three orders of magnitude less than current electrothermal rotational designs.

Fatigue properties of thin film materials are extremely important to design durable and reliable microelectromechanical systems (MEMS) devices. However, it is rather difficult to apply conventional fatigue testing method of bulk materials to thin films. Therefore, a fatigue testing method fitted to thin film materials is required. In this investigation, we have developed a fatigue testing method that uses a resonance of cantilever type specimen prepared from thin films. Cantilever beam specimens with dimensions of 1(W) × 3(L) × 0.01(t) mm3 were prepared from Ni-P amorphous alloy thin films and gold foils. In addition, cantilever beam specimens with dimension of 3(L) × 0.3(W) × 0.005(t) mm3 were also prepared from single crystalline silicon thin films. These specimens were fixed to a holder that is connected to an golddio speaker used as an actuator, and were resonated in bending mode. In order to check the validity of this testing method, Young's moduli of these specimens were measured from resonant frequencies. The average Young's modulus of Ni-P was 108 GPa and that of gold foil specimen was 63 GPa, and these values were comparable with those measured by other techniques. This indicates that the resonance occurred theoretically-predicted manner and this testing method is valid for measuring the fatigue properties of thin films. Resonant fatigue tests were carried out for these specimens by changing amplitude range of resonance, and S-N curves were successfully obtained.

Liquid metal microscale switches, often using mercury, are sometimes used in place of solid-solid contact switches because of the ability to minimize damage from switching and the ability to make good contacts for electrical and thermal conductivity. However, mercury has potential health and safety problems, and is difficult to use at high frequency (kHz) operation due to poor adhesion between the liquid-solid contacts. One alternative to the mechanical and chemical problems of a liquid mercury switch is using soft metals, such as gallium or tin, as a solid metal sphere for switches that can melt at moderate temperatures. Ga micro-spheres for switching operations were deposited on a substrate consisting of photolithographically patterned W films on SiO2 and Si substrates by electroplating, and the applicability for use in a microscale switch was investigated by characterizing the macro structure, hardness, and electrical performance during switching. The resistivity of the electroplated Ga droplets was similar to the theoretical value for pure Ga, and suggests that the electrodeposited Ga will be suitable for a solid MEMS switch. The hardness of the Ga sphere was 5.7 MPa. This suggests a maximum of ∼40 micron-Newton can be applied to each 50 micron-meter radius Ga contact in the current configuration for switching applications. When the Ga spheres were investigated for electrical performance during hot switching, the resistance increased over six switching cycles, but the original lower resistivity was recovered after a 393 K thermal reflow process.

Hydrophobic property of PDMS surface was improved by the 400 W UV-Vis lamp light irradiation in the atmospheric condition for several ten minutes. As a result of this surface treatment, the surface became to hydrophilic character for one month long. This surface treatment technique applied to PDMS micro-fluidic device and verified valve-less switching. The UV-Vis light irradiated to PDMS micro fluidic pattern with partly covered by aluminum foil. Finally inlet and outlets were connected 0.5 mm diameter tubes. The syringe pumps injected the distilled water into the inlet of the PDMS micro channel at the flow rates of 0.5, 5.0, and 50 μl/min for the both width channel. As results of water injection water flowed only the UV-Vis treated channel at the flow rates of 0.5 and 5.0 μl/min. On the other hand, the water flowed for all channels at the flow rate of 50 μl/min. This result was observed from 5.0 μl/min flow again for both width devices which dried by air. These results were occurred by the difference of the flow conductance and wettability. The mechanism of this hyrophilicity of PDMS was reported to form Si-O in the surface by means of glassy surface. From the IR spectra, the Si-O-Si peak shifted to higher wave number for UV-Vis irradiated PDMS than the untreated PDMS comparing with the other IR peaks. This result showed that the Si-O-Si network bonding of PDMS changed to the O-Si-O bonding around the surface.

Among different MEMS wafer level bonding processes glass frit bonding provides reliable vacuum tight seals in volume production. The quality of the seal is a function of both seal glass materials and the processing parameters used in glass frit bonding. Therefore, in this study Taguchi L18 screening Design of Experiment (DOE) was used to study the effect of materials and process variables on the quality of the glass seal in 6” silicon wafers bonded in EVG520IS bonder. Six bonding process variables at three levels and two types of sealing glass pastes were considered. The seals were characterized by Scanning Acoustic Microscopy (SAM), cross sectional Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX). The results were quantified into four responses for DOE analysis. Key results are a) peak temperature has the strongest influence on seal properties, b) hot melt paste has significantly lower defects compared to liquid paste, and c) peak firing temperatures can be as low as 400°C under certain conditions.

The design of microresonators with high natural frequencies (1 MHz to 1 GHz) and low structural damping is essential for devices used for applications in communications. Here, we report experimental measurements of damping at low pressure and ambient temperature in electrostatically-actuated, metallized silicon carbide microresonators. Comparison of the measured values with the predictions of a model for thermoelastic damping indicates that the contribution of this mechanism to the measured damping ranges from 10% to 50% over a broad frequency range (3 MHz to 30 MHz).