Direct Transfer Printing with Metal Oxide Layers for Fabricating Flexible Nanowire Devices

A direct printing method for fabricating devices by using metal oxide transfer layers instead of conventional transfer media such as polydimethylsiloxane is presented. Metal oxides are not damaged by organic solvents; therefore, electrodes with gaps less than 2 μm can be defined on a metal oxide transfer layer through photolithography. In order to determine a suitable metal oxide for use as transfer layer, the surface energies of various metal oxides are measured, and Au layers deposited on these oxides are transferred onto polyvinylphenol (PVP). To verify the feasibility of our approach, Au source–drain electrodes on transfer layers and Si nanowires (NWs) addressed by the dielectrophoretic (DEP) alignment process are transferred onto rigid and flexible PVP‐coated substrates. Based on transfer test and DEP process, Al₂O₃ is determined to be the best transfer layer. Finally, Si NWs field effect transistors (FETs) are fabricated on a rigid Si substrate and a flexible polyimide film. As the channel length decreases from 3.442 to 1.767 μm, the mobility of FET on the Si substrate increases from 127.61 ± 37.64 to 181.60 ± 23.73 cm² V^?1 s^?1. Furthermore, the flexible Si NWs FETs fabricated through this process show enhanced electrical properties with an increasing number of bending cycles.     

Annealing-induced enhancement of ferromagnetism in SnO2-core/Cu-shell coaxial nanowires

In this study, we have coated tin oxide (SnO₂) nanowires with a Cu shell layer via the sputtering method and subsequently investigated the effects of thermal annealing. The annealing-induced changes in morphologies, microstructures, and compositions of the resulting core-shell nanowires were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energydispersive X-ray spectroscopy (EDX). The Cu shell layers were agglomerated to form clusters, which were mainly comprised of the Cu₂O phase. For the first time, a hysteresis loop indicating weak ferromagnetism was observed from the pure SnO₂ nanowires. Both the coercivity and the retentivity in the hysteresis loop were slightly increased by Cu-sputtering, indicating a very slight enhancement of ferromagnetism. Also, the ferromagnetic behavior was significantly enhanced by thermal annealing. We discuss the possible mechanisms of annealing-induced enhancement of ferromagnetism in the SiO₂/Cu core-shell nanowires, which include the generation of Cu₂O phase, Cu-doping into the SnO₂ lattice, and the generation of oxygen vacancies in SnO₂ core nanowires.     

A high-frequency annular-array transducer using an interdigital bonded 1-3 composite

This paper reports the design, fabrication, and characterization of a 1-3 composite annular-array transducer. An interdigital bonded (IB) 1-3 composite was prepared using two IB operations on a fine-grain piezoelectric ceramic. The final composite had 19-μm-wide posts separated by 6-μm-wide polymer kerfs. A novel method to remove metal electrodes from polymer portions of the 1-3 composite was established to eliminate the need for patterning and aligning the electrode on the composite to the electrodes on a flexible circuit. Unloaded epoxy was used for both the matching and backing layers and a flexible circuit was used for interconnect. A prototype array was successfully fabricated and tested. The results were in reasonable agreement with those predicted by a circuit-analogous model. The average center frequency estimated from the measured pulse-echo responses of array elements was 33.5 MHz and the -6-dB fractional bandwidth was 57%. The average insertion loss recorded was 14.3 dB, and the maximum crosstalk between the nearest-neighbor elements was less than -37 dB. Images of a wire phantom and excised porcine eye were obtained to show the capabilities of the array for high-frequency ultrasound imaging.     

Feasibility of estimating glomerular filtration rate in children using single-sample adult technique

This work was undertaken to verify whether a single-sample adult technique, when applied using body surface-corrected plasma concentration, can be used in place of specific pediatric method to estimate 51Cr-EDTA renal clearance in children. METHODS: In a series of 90 children (aged 0.1 to 15 yr). 51Cr-EDTA renal clearance was calculated using for different approaches. The first approach used specific pediatric single-sample methods; three techniques were chosen and they all used 120-min plasma concentration. The second approach used the same three specific pediatric methods, but they were applied using 120-min plasma concentration prescaled for 1.73 m2 body surface area. The third approach used single-sample methods designed for adults; three methods were again chosen. They all used 240-min plasma concentration. The fourth approach used the same adults algorithms, but they were applied using 240-min plasma concentration prescaled for 1.73 m2 body surface area. RESULTS: Clearances calculated using the three specific pediatric methods were all closely cross-correlated regardless of whether or not the plasma concentration was prescaled. The use of classical adult methods produced in some cases obviously erroneous clearance values. Improvements were observed when the same adult methods were applied using prescaled plasma concentration. Nonetheless, the clearance values obtained only fairly correlated with those obtained using specific pediatric methods. CONCLUSION: The single-sample adult technique using plasma concentration prescaled for 1.73 m2 body surface area cannot be used in place of a specific pediatric single-sample method to estimate 51Cr-EDTA renal clearance in children.     

IC/microfluidic hybrid system for magnetic manipulation of biological cells

This paper introduces an integrated circuit (IC)/microfluidic hybrid system for magnetic manipulation of biological cells. The hybrid system consists of an IC and a microfluidic system fabricated on top. Biological cells attached to magnetic beads are suspended inside the microfluidic system that maintains biocompatibility. The IC contains a microcoil array circuit that produces spatially-patterned microscopic magnetic fields. Programmable, rapid reconfiguration of the field pattern made possible by the IC allows an efficient simultaneous manipulation of multiple individual bead-bound cells with precise position control. Two prototypes, SiGe/microfluidic and CMOS/microfluidic hybrid systems, validate the proposed approach.     

Measurement of Power Frequency Fluctuations Using the FFT

A new method for detecting fluctuations in the fundamental frequency component of a power system, by relating it to a leakage coefficient in the FFT, is presented. The phenomenon of leakage in the FFT is used advantageously to increase spectral resolution. The leakage coefficient is a quantitative measure of the deviation from the fundamental frequency component with respect to the sampling frequency. Theoretical aspects are considered along with a method for on-line implementation.     

Scanning electron microscopy of central nervous system cerebrospinal-fluid-contacting surfaces: a bibliography (1963-1995)

This bibliography is compiled to assist in locating papers related to the application of scanning electron microscopy (SEM) to cerebrospinal-fluid-contacting surfaces in vertebrates. The use of SEM by neuroscientists has continued apace since the publication of the first bibliography in 1980. SEM studies now include more than 50 species of vertebrates and range from cyclostomes to humans; they encompass development from embryo to senescence and concern both normal and pathologic morphology. Although remarkable strides have been made toward a greater understanding of many aspects of the structure and function of cerebrospinal-fluid-contacting surfaces, many significant problems await the judicious application of scanning electron microscopy.     

Nylon 4,I: an amorphous polyamide

The melt polymerization of nylon 4, I was studied, starting with nylon-salt and nylon prepolymers (η_inh=0.25). With nylon-salt only low molecular polymers were obtained, while with prepolymers the inherent viscosity could be raised to 0.77 (3h, 270°, vac.). The cyclization of tetra methylene diamine to pyrrolidine seem to be the major disturbing factor. The polymer is glassy and could easily be melt pressed. The torsion modulus of the material at 20°C was high (1.8 10⁹ Pa) and remained high to near its T_g (138°C).     

Reproducibility of simplified techniques for the measurement of 51Cr-EDTA clearance

The aim of this study was to assess the reproducibility of a number of simplified clearance methods using chromium-51 ethylenediamine tetraacetic acid (51Cr-EDTA) and to compare these with the multiple blood sample technique. Twenty-four healthy volunteers were enrolled into the study. The test was performed twice, 1 week apart and under similar physiological conditions. After intravenous injection of the tracer, 13 blood samples were taken between 5 and 240 min. The reference clearance was calculated after adapting a bi-exponential fit on the whole plasma disappearance curve. Simplified methods included the slope intercept method using different combinations of blood samples (2 and 4 h; 2, 3 and 4 h; 1.5, 2, 3 and 4 h; 1.5, 2 and 3 h) and several single clearance methods (Constable 3 h; Groth 3 h; Groth 4 h). The standard deviation of the differences between the first and second measurements were similar for all methods, confirming the comparable reproducibility of these methods.