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We present the first demonstration of single-walled carbon nanotube transistor operation at microwave frequencies. To measure the sourcedrain ac current and voltage at microwave frequencies, we construct a resonant LC impedance-matching circuit at 2.6 GHz. Both semiconducting and metallic nanotubes are measured. Varying the back-gate voltage for a semiconducting nanotube at dc varies the 2.6-GHz source-drain impedance. In contrast, varying the back-gate voltage on a metallic nanotube at dc has no effect on the microwave source-drain impedance. We find the ac source-drain impedance to be different than the dc source-drain resistance, which may be due to the distributed nature of the capacitive and inductive impedance of the contacts to the nanotube. The dynamical (ac) electrical properties of carbon nanotubes are technologically relevant for both active and passive devices made from carbon nanotubes. At dc, it is known that electrons can move without scattering over many micrometers inside a carbon nanotube. 1 We recently analyzed, from a theoretical point of view, the microwave passive 2,3 and active 4,5 electrical properties of nanotubes in some detail. The successful operation of a multiwalled carbon nanotube rf single-electron transistor was recently reported. 6 In this paper, we present the first measurements of the electrical properties of single-walled nanotubes at gigahertz frequencies. 7 In so doing, we demonstrate, for the first time

This letter reports on the design, fabrication, and testing a new class of low-impedance multiple-frequency micromechanical resonator using piezoelectric transduction mechanism. The resonator is fabricated out of a 3-/spl mu/m-thick silicon layer on a silicon-on-insulator wafer with a low-temperature post-CMOS compatible process. Two types of low-impedance resonators using the same design principle are presented here. The center frequency of the novel resonator is set by the lithographically defined in-plane dimension of the device (width of bar or radius of disk). The 200-/spl mu/m-diameter disk-shaped resonator is measured to have an impedance of 1.6 k/spl Omega/ at the resonant frequency of 45.4 MHz, with a quality factor of 1100. The bar-type resonator is measured to have an impedance of 920 /spl Omega/ at 60 MHz, exhibiting a Q factor of 1400.

This paper presents the fabrication of a silicon based three dimensional intraneural electrode array. The electrode array consists of a 3 by 4 array of needles with a 250 μm center to center distance and 50 μm separation between neighboring needles. The length of each penetrating portion of the needle is defined by the starting silicon material thickness. We present the fabrication details to build 1 mm tall needles with 250 to 400 μm of their height insulated in SU-8. We are able to present a simpler, more elegant, more reproducible, and more scalable process than the current state of the art method that relies on glass insulation and a dicing saw by using deep reactive ion etching to produce needles and SU-8 to electrically isolate them.

We report on the design, fabrication, and test results of a set of microfluidic devices with channels designed to promote fluidic hydrodynamic forces to sort and separate cells based on cell sizes. A set of 14 devices were made from polydimethylsiloxane (PDMS) molded from photolithographically patterned SU-8. The spiral fluidic channels with specific numbers of turns, widths, and outer diameters were designed with branches at strategic locations along the length to divert separated particles into collection chambers. A mixture of polystyrene particles of two different diameters (7 and 20 μm) was used as the test solution to determine the sorting efficiencies. Theoretical analyses of the designed performance were based on previously published equations and were found to be within practical agreement. The optimized performance was consistently close to 90% capture and isolation efficiencies from a mixture of up to 1:100,000 of 20-μm-to-7-μm particles at a flow rate of 4.0 mL·min-1.

This paper presents a novel method for fabricating silicon based planer microelectrodes with SU-8 embedded fluidic channels. A 7 mm long neural probe was fabricated with a 5 mm penetrating shank and a 2 mm × 2 mm base. One surface of the probe consists of eight 160 μm diameter wire bonding pads connected to eight 60 μm diameter electrode sites on 500 μm centers with eight 15 μm wires interconnects. On the opposite surface lies a 200 μm SU-8 embedded fluidic channel. The fluidic channel was constructed by utilizing two wavelengths of ultraviolet light: a higher wavelength (>365 nm) that penetrates the SU-8 completely to construct the fluidic channel walls and a lower wavelength (

A capacitive surface-micromachined sensor suitable for the measurement of liquid and gas pressures was fabricated. The structure consists of a polysilicon stationary electrode suspended 0.7 /spl mu/m above a 20-/spl mu/m-thick lightly doped silicon diaphragm formed by a patterned etch stop. The a priori patterning of the buried etch stop yields diaphragm widths independent of wafer thickness variations with excellent alignment. The design described here has a pressure range of 100 PSI, a nominal capacitance of 3.5 pF with a full scale span of 0.8 pF, and a temperature coefficient of 100 ppm/spl deg/C/sup -1/. Each device, including a matched reference capacitor, occupies 2.9 mm/sup 2/, yielding approximately 2000 devices per 100-mm wafer.

This paper mvestlgates the elcctrostatlc dnve and sense of polynhcon resonators parallel to the substrate, using an mterdlgtated capacitor (electrostatic comb) Three expenmental methods are used nucroscoplc observation mth contmuous or stroboscopic iummatlon, capacltlve sensing using an amphtude-modulation technique and SEM observation The mtnnslc quality factor of the phosphorus-doped low-pressure chemlcal-vapordeposited (LPCVD) polyslhcon resonators is 49 000 + 2000, whereas at atmosphenc pressure, Q < 100 The finger gap IS found to have a more pronounced effect on comb charactenstlcs than finger width or length, as expected from simple theory

This paper demonstrates the substrate dependency of the c-axis zinc oxide growth in radio-frequency sputtering system. Different deposition conditions were designed to study the influences of Si, SiO2/Si, Au/Ti/Si, and Au/Ti/SiO2/Si substrates on the piezoelectric and crystalline qualities of the ZnO thin films. Experimental results showed that the multilayer of Au/Ti/SiO2/Si-coated silicon substrate provided a surface that facilitated the growth of ZnO thin film with the most preferred crystalline orientation. The thermally grown amorphous silicon dioxide layer effectively masked the crystalline surface of the silicon substrate, thus allowing the depositions of high-quality titanium adhesion layer followed by gold thin film. The gold-coated surface allowed deposition of highly columnar ZnO polycrystalline structures. It was also demonstrated that by lowering the deposition rate at the start of sputtering, a fine ZnO seed layer could be created for subsequent higher-rate deposition. This two-step deposition method resulted in substantially enhanced ZnO film quality compared to single-step approach.

A capacitive surface micromachined sensor suitable for the measurement of liquid and gas pressures was fabricated. The structure consists of a polysilicon stationary electrode suspended 0.7 /spl mu/m above a 20 /spl mu/m-thick lightly-doped silicon diaphragm formed by a patterned etch stop. The a-priori patterning of the buried etch stop yields diaphragm widths independent of wafer thickness variations with excellent alignment. The design described here has a pressure range of 100 PSI, a nominal capacitance of 3.5 pF with a full scale span of 0.8 pF and a temperature coefficient of 100 ppm//spl deg/C. Each device, including a matched reference capacitor, occupies 2.9 mm/sup 2/ yielding approximately 2000 devices per 100 mm wafer.

We present the first microwave measurements of the dynamical impedance of an individual, electrically contacted single walled carbon nanotube. Both semiconducting and metallic nanotubes are measured. Using a semiconducting nanotube, we construct an LC nano-resonator at 2 GHz. The Q of the nano-resonator can be tuned by varying the back-gate voltage on the nanotube. In contrast, the Q of a resonator fabricated with a metallic nanotube is insensitive to the back-gate voltage. This represents the first step towards passive microwave signal processing components based on carbon nanotubes.

This paper presents the design, simulation, fabrication and testing of a piezo transduced high frequency micromechanical resonator. The resonator is designed to operate in the wine-glass mode and the anchors are optimized to both suppress spurious modes and minimize the energy loss into the substrate. The resonator is fabricated with a simple 4-mask low temperature process from SOI wafer. The highest temperature during the process is 250°C, allowing post-COMS integration compatibility. A prototype resonator with measured diameter of 100 µ m was tested in air using non-optimized experimental setup, with measured resonant peaks at 44.97 MHz and 138.5 MHz, which match the simulated result from Ansys©. The quality factor of 35 at 138.5 MHz is extracted, and is expected to be substantially higher if measured in vacuum with calibrated RF cables.

Microelectromechanical sensors, ADXL50 and XMMAS40G accelerometers which are fabricated with surface micromachining techniques are characterized for their total dose radiation response. Different failure mechanisms were observed when the sensor element or the whole device was irradiated.

During the last decade, it was discovered that the mechanical properties and interactions of cells and their surrounding extra-cellular matrix play important roles in cellular activities. Substantial efforts have been made to develop various methodologies and tools to study cell mechanics. In this paper, we report an ongoing study on integrating the concept of a smart structure with a microfabricated thin film piezoelectric transducer for characterizing the various changes in mechanical properties associated with cellular events. A microbridge sensor integrated with a thin film piezoelectric transducer was created from silicon dioxide and zinc oxide sandwiched between two gold electrodes. The cells to be tested were cultured on the microbridge surface. The surface tractions exerted by the cells on the microbridge directly modulated the selected resonant behaviors, which were detected with the custom designed effective surface electrode. Our theory and simulation results showed, for the first time, that the application and changes in these surface tractions resulted in resonant and anti-resonant frequency shifts in the impedance response of the piezoelectric transducer. Both spatial and temporal information of dynamic cellular activities could be inferred from the changes in the impedance spectra. The design, theory, finite-element simulation, microfabrication techniques, and preliminary test results are discussed.

An experimental study of the levitation force, normal to the substrate, associated with interdigital capacitor electrostatic comb lateral actuators is reported. For compliant suspensions, normal displacements of over 2 mu m for a comb bias of 30 V were observed. This phenomenon is due to electrostatic repulsion by image charges mirrored in the ground plane beneath the suspended structure. By electrically isolating alternating drive-comb fingers and applying voltages of equal magnitude and opposite sign, levitation can be reduced by an order of magnitude while reducing the lateral drive force by less than a factor of two. >

This letter introduces a resonant mass sensor that is based on a lateral extensional mode piezoelectric resonator and has a minimum detectable mass of 10−15g at room temperature and atmospheric pressure. The resonator with size of about 200×50×1μm3 has a quality factor (Q) of >1400 at 60MHz, and as small as 0.1ppm shift of its resonant frequency can be detected. The 0.1ppm detection capability corresponds to a mass uncertainty of only about 4.6fg. We have experimentally demonstrated a minimum detectable frequency shift of ∼1.6ppm due to absorption of isopropanol vapor (73fg) on the sidewalls of the parylene-coated lateral extensional mode piezoelectric resonator.

This letter presents the design, fabrication, and testing results of a piezoelectrically transduced UHF micromechanical resonator. The resonator is designed to vibrate in the (2, i) in-plane mode, and thin-film zinc oxide is used for piezoelectric transduction. A four-mask process is developed to fabricate the resonator on silicon on insulator wafer, and the maximum processing temperature is kept below 250°C. Prototypes with various diameters are fabricated, with a measured resonant frequencies span from 44.97 MHz to 1.14 GHz. Quality factors around 200 are obtained on different devices. Motional impedance in the range of several hundred ohms is demonstrated.

This paper presents the design, simulation, fabrication, and test results of a new type of piezoelectrically transduced micromechanical disk resonator approaching UHF frequencies. The resonators were fabricated from silicon-on-insulator (SOI) wafers with a 4-mask low-temperature process. The highest processing temperature was 250/spl deg/C, allowing post-CMOS integration compatibility. Several prototype resonators with measured diameter of 100 /spl mu/m and 60 /spl mu/m were tested in air, with the highest resonant peak observed at 208 MHz, which matched well with simulation results from finite-element analysis. A quality factor of 15 at 208 MHz was extracted, and is expected to be significantly higher with an optimized design and vacuum testing.

Proof-of-concept testing of a microfabricated vaporizing liquid thruster was performed. In this liquid-fed thruster concept, propellant vaporization is achieved in a microfabricated thin film heater arrangement. Chip temperatures of 100, 150 and 200 C were achieved at power levels of 3.5, 5.5 and 7.5 W. Voltage requirements were below 5 V for these temperature values. A substantial fraction of the heat was believed to have been conducted into the packaging material. Thermal characterization tests of chips placed onto insulating Pyrex blocks resulted in temperatures of about 90 and 150 C for power levels of 1.2 and 2.5 W, respectively, thus cutting thermal losses by more than half. One thruster chip was tested using water as a liquid propellant and vaporization was achieved at 7 W electric input power.

The paper presents the design, simulation, fabrication, and preliminary test results of a novel micromechanical filter based on coupled piezoelectrically transduced resonators. This is the first report of two identical microfabricated free-free beam resonators coupled with two torsional beams forming a second-order mechanical filter. Piezoelectric transducers from thin-film ZnO were used to drive anti sense resonance, eliminating the need for precision fabrication of nanometer-scale gaps in contrast to electrostatic transduction. Fabrication was done with a four-mask process on SOI wafers with maximum temperature capped at 250/spl deg/C, allowing post-CMOS integration. Preliminary tests showed a resonant peak of 10.83 MHz and a quality factor of 41 under atmospheric pressure.