The interaction of two peptides with the α-hemolysin pore was studied in the presence of a MHz AC field. For an α-helical peptide the proportion of bumping events increased with increasing AC field whereas for a linear peptide with no dipole moment only small changes in the event profiles were observed.

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X-ray lithography shadow projection using silicon nitride-based x-ray masks is used to fabricate sub-micron scale, high-aspect-ratio structures in thick polymer templates for surface acoustic wave (SAW) applications. Interdigital electrode patterns with 380 nm wide, free-standing polymer features are fabricated in 2 μm thick templates, representing an aspect ratio of 5.26:1. The tall and narrow polymer 'ribbons' run laterally in a serpentine arrangement of 114 electrodes over a large area of approximately 30 μm × 250 μm. Aluminum deposition and lift-off using the polymer templates are performed to construct metal electrodes for the verification of SAW resonator performance above 2.5 GHz. Environmental scanning electron microscopy and atomic force microscopy are used to inspect the metal electrode edge and surface topology, and demonstrate the feasibility of metal lift-off with highly vertical sidewall polymer templates for SAW applications. Such precise polymer templates could offer interesting possibilities for acoustic applications requiring thick and/or narrow electrodes and reflectors not only through more traditional metal deposition approaches but also as thick etch masks for metal removal.

A submicron-scale surface acoustic wave (SAW) resonator fabricated by high-aspect-ratio X-ray lithography (XRL) and metal lift-off that operates at microwave frequencies is presented. We demonstrate that XRL is especially well suited for SAW device templating, as long submicron-scale interdigitated transducer structures can be batch patterned with excellent structure quality. 0.4-2.0 lm thick PMMA layers were structured by X-ray lithography shadow projection using silicon nitride-based X-ray masks. Structures with a critical lateral feature size of down to 200-700 nm were processed. The polymer structures served as templates in a subsequent aluminum lift-off process. The metal electrodes were successfully tested as SAW resonators for high frequency applications, e.g. around 1.3 GHz, using calibrated 1-port RF wafer probing measurements. Compared with standard fabrication techniques, the high structure quality of submicronscale polymer templates made of unusually thick PMMA layers offers additional possibilities to fabricate thicker metal transducers.

broadside direction on the radiation pattern, especially at the higher frequency band. However, the overall antenna pattern shows the unidirectional radiation to the desired target direction, which is useful for the high-directive radar imaging applications. It is observed from the simulation results that the gain of the bowtie antenna with a reflector increases from 6.5 to 8.5 dBi, almost double the case without a reflector, which gives more high directional gain to the target direction. CONCLUSIONA novel unidirectional horn-shaped tapered bowtie slot antenna with a pyramidal reflector has been designed and fabricated for ultra high-resolution radar imaging applications. The implemented antenna performance shows very low return loss less than Ϫ10 dB over 3.0 -11.7 GHz and a quasi-unidirectional radiation that shows a high front-to-back ratio over the whole UWB frequency band. This result shows enhanced new performance compared with the previously available antenna design, which will be useful for ultra high-resolution UWB radarimaging applications.