Experimental analysis of metal coated dielectric waveguides

This paper concerns the experimental characteristics of metal coated dielectric waveguides with a rectangular surface corrugation. Waveguide are designed to operate at a second Bragg frequency of 90 GHz. The period, height and the duty cycle of a rectangular grating were calculated using the chosen frequency. A metallic layer of aluminum is sputtered on one side of the slab waveguide. The purpose of the metallic layer is to simulate a layer of high density plasma on the surface of the waveguide similar to that obtained by optical excitation of semiconductor structures. Experiments were performed to examine the far field radiation pattern, attenuation constant and the dispersion relation. Due to the presence of the plasma layer there will be an angular shift in the far field radiation pattern. We have observed angular shifts of about 20 in the radiation pattern of the waveguide before and after coating. Measurements are made in the frequency range of 88–95 GHz. This waveguide structure can be used to design an electronically steerable antenna and an electronic phase shifter operating in the millimeter-wave frequency band.Supported in part by the Army Research Office.     

Writing with DNA and protein using a nanopipet for controlled delivery

We present a new, general method for the controlled deposition of biological molecules on surfaces, based on a nanopipet operating in ionic solution. The potential applied to the pipet tip controls the flux of biological molecules from the pipet, allowing fine control of the delivery rate. We used the ion current to control the distance of the pipet from the surface of a glass slide and deposited the fluorescently labeled DNA or protein G at a defined location onto the surface. Features of 830 nm size were obtained by depositing the biotinylated DNA onto a streptavidin surface; 1.3 mum size spots were obtained by depositing protein G onto a positively charged glass surface.