Joseph M. Bauer

A monolithically-integrated μGC chemical sensor system.

Gas chromatography (GC) is used for organic and inorganic gas detection with a range of applications including screening for chemical warfare agents (CWA), breath analysis for diagnostics or law enforcement purposes, and air pollutants/indoor air quality monitoring of homes and commercial buildings. A field-portable, light weight, low power, rapid response, micro-gas chromatography (μGC) system is essential for such applications. We describe the design, fabrication and packaging of μGC on monolithically-integrated Si dies, comprised of a preconcentrator (PC), μGC column, detector and coatings for each of these components. An important feature of our system is that the same mechanical micro resonator design is used for the PC and detector. We demonstrate system performance by detecting four different CWA simulants within 2 min. We present theoretical analyses for cost/power comparisons of monolithic versus hybrid μGC systems. We discuss thermal isolation in monolithic systems to improve overall performance. Our monolithically-integrated μGC, relative to its hybrid cousin, will afford equal or slightly lower cost, a footprint that is 1/2 to 1/3 the size and an improved resolution of 4 to 25%.

Recent advancements in the gas-phase MicroChemLab

Sandias hand-held MicroChemLabTM system uses a micromachined preconcentrator (PC), a gas chromatography channel (GC) and a quartz surface acoustic wave array (SAW) detector for sensitive/selective detection of gas-phase chemical analytes. Requisite system size, performance, power budget and time response mandate microfabrication of the key analytical system components. In the fielded system hybrid integration has been employed, permitting optimization of the individual components. Recent improvements in the hybrid-integrated system, using plastic, metal or silicon/glass manifolds, is described, as is system performance against semivolatile compounds and toxic industrial chemicals. The design and performance of a new three-dimensional micropreconcentrator is also introduced. To further reduce system dead volume, eliminate unheated transfer lines and simplify assembly, there is an effort to monolithically integrate the silicon PC and GC with a suitable silicon-based detector, such as a magnetically-actuated flexural plate wave sensor (magFPW) or a magnetically-actuated pivot plate resonator (PPR).

Incorporation of bioactive materials into integrated systems

Sandia is exploring two classes of integrated systems involving bioactive materials: 1) microfluidic systems that can be used to manipulate biomolecules for applications ranging from counter-terrorism to drug delivery systems, and 2) fluidic systems in which active biomolecules such as motor proteins provide specific functions such as active transport. An example of the first class involves the development of a reversible protein trap based on the integration of the thermally-switchable polymer poly(N-isopropylacrylamide)(PNIPAM) into a micro-hotplate device. To exemplify the second class, we describe the technical challenges associated with integrating microtubules and motor proteins into microfluidic systems for: 1) the active transport of nanoparticle cargo, or 2) templated growth of high-aspect ratio nanowires. These examples illustrate the functions of bioactive materials, synthesis and fabrication issues, mechanisms for switching surface chemistry and active transport, and new techniques such as the interfacial force microscope (IFM) that can be used to characterize bioactive surfaces.