Imec and Holst Centre have
developed very sensitive integrated sensing elements for gas detection. The
polymer-coated microbridges in high-density arrays can detect ppm-level concentrations
of vapors using on-chip integrated read-out techniques. The demonstrated technology
is very suitable for miniaturization of electronic nose devices thanks to the
low power consumption (<1 mW/bridge) and small form factor.
Wireless sensor nodes that can chemically detect gaseous compounds are rapidly
gaining interest from markets such as food monitoring, healthcare and safety.
One of the main gas sensing approaches in uncontrolled environments is the identification
of vapors (“smells”) using multiple sensing elements (“receptors”),
in a system that is often referred to as an “electronic nose” or
“e-nose”. An accurate e-nose requires small, integrated, low-power
detectors with individually tuned chemical coatings. Current solutions, like
chemi-resistors or quartz crystals are however not scalable or power-efficient
enough to build low-power small form factor e-noses.
Imec and Holst Centre have developed a new generation of microbridges with
embedded individual piezoelectric “shakers” in a high-density array
with very high fabrication yield. The novel design allows for rapid coating
of a range of absorbents on individual microbridges using commercial inkjet
printing technology. The suspended structures vibrate individually, and changes
in their modes of vibration (resonances) are monitored as an indication of vapor
absorption in their coatings. Due to the very high length-to-thickness ratio
of the microbridges, imec and Holst Centre’s novel gas sensor chip has
a high sensitivity to low-concentration vapors. Moreover, by implementing integrated
piezoelectric read-out schemes, ultra-low power operation could be demonstrated.
Current work is ongoing to integrate the structures with low-power analog read-out
circuits and to demonstrate simultaneous measurements from multiple structures.
This truly low-power miniaturized implementation of an e-nose technology can
be used in current applications such as wine and cheese monitoring, but could
in the future also help sniff-out human conditions such as asthma, lung cancer,
and kidney diseases.