Here we demonstrate design, fabrication, and testing of electronic sensor array based on single-walled carbon nanotubes (SWNTs). Multiple sensor elements consisting of isolated networks of SWNTs were integrated into Si chips by chemical vapor deposition (CVD) and photolithography processes. For chemical selectivity, SWNTs were decorated with metal nanoparticles. The differences in catalytic activity of 18 catalytic metals for detection of H(2), CH(4), CO, and H(2)S gases were observed. Furthermore, a sensor array was fabricated by site-selective electroplating of Pd, Pt, Rh, and Au metals on isolated SWNT networks located on a single chip. The resulting electronic sensor array, which was comprised of several functional SWNT network sensors, was exposed to a randomized series of toxic/combustible gases. Electronic responses of all sensor elements were recorded and the sensor array data was analyzed using pattern-recognition analysis tools. Applications of these small-size, low-power, electronic sensor arrays are in the detection and identification of toxic/combustible gases for personal safety and air pollution monitoring.

of the filter were measured using condensation particle counters (TSI Inc. model 3022A). Submicrometer particles entering the counters are grown into micrometer sized droplets by condensation of a supersaturated vapor of 1-butanol onto the particles, then counted by laser light scattering. The particle concentrations were averaged over ten measurements at each particle size. Filter experiments were repeated at least twice to ensure reproducibility. The pressure drop after filtration was also measured using previously described methods.

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We have fabricated a series of highly sensitive spin valve sensors on a micron scale that successfully detected the presence of a single superparamagnetic bead (Dynabeads M-280, 2.8 μm in diameter), and thus showed suitability for identifying biomolecules labeled by such magnetic beads. By polarizing the magnetic microbead on a spin valve sensor with a dc magnetic field and modulating its magnetization with an orthogonal ac magnetic field, we observed a magnetoresistance (MR) signal reduction caused by the magnetic dipole field from the bead that partially cancelled the applied fields to the spin valve. A lock-in technique was used to measure a voltage signal due to the MR reduction. A signal of 1.2 mV rms or 5.2 mΩ of resistance reduction was obtained from a 3 μm wide sensor and a signal of 3.8 mV rms or 11.9 mΩ from a 2.5 μm wide sensor. Micromagnetic simulations were also performed for the spin valve sensors with a single bead and gave results consistent with experiments. Further experiments and simulations suggested that these sensors or their variations can detect 1–10 Co nanoparticles with a diameter of ∼11 nm, and are suitable for DNA fragment detection.

Scaling of the ferroelectric and piezoelectric properties in Pt/SrBi2Ta2O9/Pt thin films was studied. Focused ion beam milling was used to fabricate submicron devices (1×1, 0.5×0.5, 0.25×0.25, 0.09×0.09, and 0.07×0.07 μm2) and scanning force microscopy was used to examine their piezoelectric response. It was found that capacitors as small as 0.09×0.09 μm2 exhibit good piezoelectric/ferroelectric properties and that submicron (0.25×0.25 μm2) capacitors show resistance to bipolar fatigue with up to at least 109 cycles. The results were compared with similar capacitor structures milled in the Pb1.0(Nb0.04Zr0.28Ti0.68)O3 system where structures as small as 0.07×0.07 μm2 were analyzed.