Chemiresitor Gas Sensors:
A large array of chemical sensors with responses interpreted using a pattern-recognition algorithm can discriminate a variety of chemicals. Chemiresistors, which change resistance when exposed to a gas or vapor, are low-cost devices that can be easily implemented in a sensor array. These devices consist of interdigitated electrodes coated with a conducting polymer film. We are examining a number of polymer/conductive particle combinations as chemiresistor materials.

Further information:
Chemiresistor

Micromachined Filament Combustible Gas Sensor:
The combustible gas sensor consists of a conductive filament, coated with a catalytic layer, that is heated by an electrical current. Micromachining technology allows the filament to be made very small and suspended above the substrate for thermal isolation, resulting in low-power operation. Combustible gases react on the catalytic surface, releasing heat that changes the filament resistance. This device is proposed for use in exhaust gas analysis and to indicate combustible gas hazards.

Further information:
Micromachined Filament

FET-Based Hydrogen Sensor:
The integrated hydrogen sensor consists of an FET and chemiresistor, both using Pd-Ni metallization, that together measure hydrogen concentrations from 1 ppm to 100%. These sensors are integrated with electronic circuitry for signal processing and temperature control. Applications include detecting hydrogen leaks in rocket engines and refineries, and monitoring corrosion in high-value equipment. As hydrogen cells become more common, hydrogen sensors will be needed in all parts of the fuel cycle from safety to fuel cell performance.

Further information:
Hydrogen Sensor

Fiber Optic-Based Chemical Sensors:
Micromirror chemical sensors are constructed by coating the end of an optical fiber waveguide with a chemically-sensitive film that changes reflectivity upon exposure to a chemical of interest. This device enables remote monitoring of chemical concentration, operates in electrically-noisy environments, and does not constitute an ignition hazard. Applications include monitoring hydrogen levels in transformer oil to indicate breakdown and detecting oxidizing compounds in the Martian soil and atmosphere.

Further information:
Fiber Optic Chemical

Further information:
Fiber Optic Polymer

Further information:
Flexural Plate

High Temp Acoustic:
Sensors based on surface acoustic wave (SAW) devices are being developed to detect a wide range of chemicals. The SAW device is an extremely sensitive gravimetric detector that can be coated with a film to collect chemical species of interest. Based on these devices, sensor systems have been developed that can detect trace (ppm to ppb) levels of airborne contaminants. Applications include weapon state-of-health, environmental, and non-proliferation monitoring.

Further information:
High Temp Acoustic

Hot Plate Based Technology:
The microhotplate, used as a basis for the microcombustor, is fabricated by through-wafer silicon etching. It consists of a silicon nitride membrane suspended from a frame of Si using either the Bosch etching or KOH etching to release the membrane, with no discernable operational differences between the completed devices made by either method.

Further information:
Hot Plate Based Technology & BTU Monitors

Integrated SAWs using GaAs:
One approach to realizing a miniaturized, low-cost sensor system is to construct on-chip acoustic sensors--providing high gravimetric sensitivity--and combine these with on-chip control electronics. The piezoelectric and semiconducting properties of gallium arsenide (GaAs) substrates enable surface acoustic wave sensors to be constructed with on-chip control electronics. Working with Sandia's Compound Semiconductor Research Laboratory (CSRL), we have constructed SAW sensors on GaAs that operate between 100 and 450 MHz. Development of the on-chip control electronics is currently underway.

Further information:
Integrated SAWs using GaAs

Ion Mobility Spectrometry (IMS):
Ion mobility spectrometry (IMS) drift tubes fabricated from low-temperature co-fired ceramic (LTCC) materials and LIGA control structures hold promise for inexpensive mass-production of IMS-based sensor systems. Sandia National Laboratories has produced a hand-held explosives detection system based on these miniature drift tubes for “First Responder” applications. Adequate sensor performance has been demonstrated while virtually eliminating the assembly and deployment complexity of traditional “stacked” IMS designs.

Further information:
Ion Mobility Spectrometry (IMS)

Microcalibrator Chip:
Sandia has developed a microfabricated source array for controlled release of pairs of marker compounds into the analytical streams of microsensor systems to obtain calibrations of analyte separation (when appropriate) and mass response of the sensor.

Further information:
Microcalibrator Chip

Micro Ion Traps:
Sandia has designed and built an ion trap mass analyzer consisting of 1 x 10 6 micron-sized cylindrical ion traps. Sandia has microfabricated massive parallel ion trap arrays consisting of traps with r 0 = 1, 2, 5 and 10 µm. The instrument is the result of a conceptually radical change in the scaling of both size and number of ion traps and in the fabrication approach compared to previous embodiments.

Further information:
Micro Ion Traps and Mass Analysis

Electrochemically-based Chemical Sensors:
Sensors responsive to electrochemical reactions are being developed to detect a wide range of chemicals in water. These sensors consist of highly ordered arrays of nanometer sized dots (electrodes) that detect trace (ppm to ppb) levels of waterborne contaminates. The design of the arrays takes advantage of diffusion phenomenons at the surface of 10's of millions of tiny electrodes that would be lost using larger designed electrodes. Applications include environmental, industrial, and domestic monitoring for surety and safety of water resources.

Further information:
Nano Electrode Arrays

Nanoparticles:
Thin films composed of nanoparticles have emerged as useful chemical sensor platforms. These detection sensors have demonstrated the ability to sense various chemical agents with sensitivity in the sub part per million volume range. Nanoparticle based sensors provide a simple signal transduction scheme based on changes in resistance. They also consume less energy and are easier to integrate into an embedded single chip platform.

Further information:
Nanoparticle Based Detection

Polychrometer - Programmable Diffraction Grating:
Chemical species can be detected optically using optical correlation spectroscopy: broadband light passing through an unknown gas sample picks up spectral features of the sample; by correlating the light with known spectra, species in the sample can be identified. Work is underway to develop programmable diffraction gratings that can synthesize molecular spectra for use in an optical correlation spectrometer. These consist of micromachined diffraction elements whose "weighting" can be varied. When broadband light is incident on the array, light reflected from the individual elements interferes to produce a desired spectrum.

Further information:
Synthetic Spectra

Quartz Resonator Fluid Monitor:
Sensors based on bulk quartz resonators are being developed to monitor fluid properties such as density and viscosity and to act as in situ chemical sensors for liquids. The device is electrically excited into a shear mode of vibration that probes the mechanical properties of a contacting fluid. The small, rugged device can be operated inside engines or pipelines to monitor properties of critical fluids such as lubricant.

Further information:
TSM Fluid Monitors
QCM Chemical Sensors
Cloud Point Detectors

SAW-Based Chemical Sensors:
Sensors based on surface acoustic wave (SAW) devices are being developed to detect a wide range of chemicals. The SAW device is an extremely sensitive gravimetric detector that can be coated with a film to collect chemical species of interest. Based on these devices, sensor systems have been developed that can detect trace (ppm to ppb) levels of airborne contaminants. Applications include weapon state-of-health, environmental, and non-proliferation monitoring.

Further information:
SAW Arrays

Smart SAND:
(Distributed Chemical Sensor Particles)
Smart Sand uses a distributed chemical particle with a fluorescent signature and LIDAR detection.

For more information, select from the following categories below or download the brochure pdf):

Further information:
Protocol sequence
How it works