Environmental Engineering Reference
In-Depth Information
Chapter 6
Needle-Type Multi-Analyte MEMS Sensor
Arrays for In Situ Measurements in Biofilms
Jin-Hwan Lee, Youngwoo Seo, Woo Hyoung Lee, Paul Bishop,
and Ian Papautsky
Abstract Biofilms are colonies of microbial cells in a polymeric matrix. Formation
of biofilms has been associated with a broad range of industrial problems at the
annual cost of billions of dollars. For example, biofilms are ubiquitous in water dis-
tribution systems and control of their growth have been a great challenge, with many
water utilities in the US reporting biofilm survival in water distribution systems
despite the continuing presence of disinfectants. In addition to being a nuisance,
biofilms may also harbor various types of microorganisms including opportunis-
tic pathogens and thus can threaten public health. The conventional methods
for studying biofilms include microelectrode sensors fabricated from pulled glass
micropipettes. However, fragility, difficulty to manufacture and operate, and sus-
ceptibility to electrical interference limit their use to specialized laboratories under
highly controlled conditions. Thus, there is a critical need for robust microelectrode
sensors that can be used In Situ to study biofilms.
This chapter describes the use of microelectromechanical systems (MEMS) tech-
nologies to develop needle-type sensors for In Situ measurements in biofilms. The
individual needle-type sensors for measuring oxidation reduction potential (ORP),
dissolved oxygen (DO), and phosphate were integrated into a single multi-analyte
sensor array. All three sensors were extensively characterized, exhibiting higher
sensitivity, faster response time, and higher stability with smaller tip size than
the conventional sensors. The multi-analyte sensor was successfully applied to In
Situ evaluation of microprofiles in multi-species biofilms. The major advantages of
these new MEMS sensors include the ability to penetrate samples to perform mea-
surements, the small tip size for In Situ measurements, array structure for higher
robustness, and possibility of multi-analyte detection. The sensors demonstrated
monitoring of local concentration changes in small structures with a high spatial
resolution, and offer the versatility of the microelectrode technique as well as the
capability for repetitive measurements. Ultimately, this research will enable in situ
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