Abstract: A method and apparatus for identifying and analyzing vapor elements, using a preconcentrator collector. The preconcentrator collector collects and preconcentrates chemical vapors to be detected and identified before chromatographic analysis using surface acoustic wave gas chromatograph (SAW/GC) technology. The preconcentrator collector is used in conjunction with a sensor in an SAW/GC detector in the apparatus. A physical parameter associated with the sensor changes in a defined manner upon exposure of the sensor to an unknown vapor, permitting identification of the individual vapor elements. The preconcentrator collector of the invention includes a body portion having an inlet and an outlet, and a stack of collector plates disposed in the body portion. The collector plates are made of a material that is easily micromachinable and easily cleanable, such as silicon, silica or fused quartz.

Abstract: A method of electronically displaying a closed-figure image in order to identify a time-varying parameter, in which a predetermined time period is established for purpose of analysis, the parameter is sampled at spaced intervals throughout the predetermined time period, corresponding circumferentially spaced data points are placed in a polar diagram to represent the samples, and connecting lines are then provided between each two adjacent data points to produce the closed-figure image.

Abstract: A process whereby the olfactory response of a gas chromatograph, equipped with a focused surface acoustic wave interferometer integrating detector is converted to a visual image for the purpose of performing pattern recognition. As volatile analytes exit a gas chromatography column a Surface Acoustic Wave Interferometer is used to monitor the condensation and re-evaporation of these analytes by periodically measuring the resonant frequency of the interferometer. A time varying output parameter is then converted to a polar display. This form of electronic nose provides a recognizable visual image of specific vapor mixtures (fragrances) containing possibly hundreds of different chemical species. Because the method provides a means of adapting and learning to recognize new vapors using these images, it is a useful method for testing chemical compositions as well as the vapors associated with bacteria and human disease.

Abstract: A method and apparatus for identifying and analyzing vapor elements, using a preconcentrator collector. The preconcentrator collector collects and preconcentrates chemical vapors to be detected and identified before chromatographic analysis using surface acoustic wave gas chromatograph (SAW/GC) technology. The preconcentrator collector is used in conjunction with a sensor in an SAW/GC detector in the apparatus. A physical parameter associated with the sensor changes in a defined manner upon exposure of the sensor to an unknown vapor, permitting identification of the individual vapor elements. The preconcentrator collector of the invention includes a body portion having an inlet and an outlet, and a stack of collector plates disposed in the body portion. The collector plates are made of a material that is easily micromachinable and easily cleanable, such as silicon, silica or fused quartz.

Abstract: A detector and method for identifying a chemical vapor and determining its concentration in the ambient atmosphere. The chemical detector apparatus preferably includes a means of collecting vapors in one atmosphere and transferring the vapors by injection into a chromatographic separation column. The exit of the separation column is confined by a nozzle which causes the vapors to be focused into a specific area of an acoustic wave interferometer wherein standing waves are created by constructive interference of waves reflected from a plurality of reflecting elements. Identification of vapor species is by a combination of timed adsorption rate peaks and temperature programmed desorption rates of the individual vapor species.

Abstract: Selective etching of microelectronic devices comprising crystal substrates s achieved by electrically masking conductive areas thereon which are not to be etched by ionic bombardment. The electrical masking is accomplished by biasing the selected areas with a bias voltage which will repel the ions, which are attracted to all of the unbiased portions of the microelectronic device.

Abstract: Disclosed is a surface acoustic wave interferometer, including a substrate on which are disposed a first reflector and a second reflector so as to define a multimode resonant cavity therebetween. A third reflector is positioned on the substrate so that a single mode resonant cavity is defined between the second and third reflectors. An input transducer generates surface acoustic waves in the single mode cavity, while an output transducer detects the interference between surface acoustic waves in the multimode and single mode cavities. A base is rigidly affixed to the substrate in the region of the single mode cavity so that a force applied to the substrate will alter the surface acoustic wave propagation characteristics within the multimode cavity.

Abstract: Disclosed is a surface acoustic wave filter based on a ferroelectric crystal having a plurality of ordered domains of alternating polarity. An output interdigital transducer, with at least one pair of electrodes, is deposited on a surface of the crystal so that each of the electrode pairs corresponds to one of the ordered domains, and an input interdigital transducer is oriented on the surface to direct a surface acoustic wave toward the output transducer. In addition, sources of both positive and negative electrical potential may be provided, with a switch for each output electrode pair to selectably apply either the positive or the negative potential to that pair.

Abstract: Disclosed is an acoustic wave sensor, including an acoustic wave oscillator having a resonant frequency which is modulated according to changes in a physical variable and a broadcast amplifier for directly transmitting the modulated frequency as a radio frequency signal. As a surface acoustic wave pressure sensor, the sensor includes a housing defining a cavity therein, an opening in the housing communicating with the cavity, a surface acoustic wave transducer attached to the housing to close the opening and adapted to deflect in response to a pressure differential across the transducer, an amplifier coupled to the transducer in a feedback loop, the transducer thereby being adapted to modulate the resonant frequency of the loop in response to the deflection, and a broadcast amplifier for directly transmitting the modulated frequency as a radio frequency signal.

Abstract: A method and apparatus for the replication of thin film patterns. A stencil is fabricated of a material such as silicon by etching or epitaxially growing on the silicon wafer. The stencil is used as a shadow mask in molecular beam deposition of the thin film pattern. The technique provides high yields in the formation of relatively large scale thin film patterns.