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This article provides measurements of thermal conductivity carried out on a microelectromechanical system (MEMS) structure for the application of selective gas sensing. MEMS thermal conductivity based gas sensors work by measuring the interaction of a heated polysilicon bridge with an ambient gas and sensing temperature changes. The tiny MEMS element provides an ability to measure noble gases and is especially applicable to binary mixtures. In this work we conducted experiments on the KWJ Engineering nano-powered thermal conductivity detector (TCD) elements to investigate the sensitivity of the sensor transient responses to gas composition. Measurements are made at constant power, constant resistance, and constant energy. By introducing feedback to maintain constant sensor temperature, the relative change of gas thermal conductivity with respect to temperature can be estimated and provide information about the concentration as well as insight into the composition of the gas mixture.

This paper describes an ultra-thin, low cost 3D glass sensor packaging platform for near-hermeticity with novel feedthrough and encapsulation technologies. Glass panels of thicknesses ranging from 50 µm to 300 µm are used which limits overall form factor to 10 MPa) and Dow Chemical's Benzocyclobutene (BCB) 14-P005 is found to be the best candidate for panel level glass-glass bonding. Modelling of the proposed three-layer glass packaging platform was performed in COMSOL Multiphysics. Results show a maximum deformation of about 2.3 µm - 2.5 µm in the BCB and GX-92 bonded package and the least average internal stress of 6.40 MPa in the BCB bonded package. The complete manufacturing cycle starting from cavity formation on bare glass to final 3D assembly to form the lidded/open cavity package including singulation is panel based, enabling significant cost reduction (depending on die dimensions and panel size) compared to ceramic and other substrate technologies.