Low Cost Optoelectronic Sensors for Gas Monitoring in Diverse Environments
Abstract: Gas sensors are
used extensively in monitoring of the environment. Many volatile organic compound gases
found in the environment severely impact the health of an individual. Volatile organic
compounds are also present in food odors (i.e. fruits, coffee, poultry) and we believe
sensing them using gas sensors may provide an effective indicator of food freshness. For
these sensors to ... read morebe used en masse, they need to be affordable, sensitive, user-friendly,
easy to fabricate, and ecofriendly. Thus the objective is design, fabricate, test and
validate low-cost optoelectronic sensor arrays for some targeted application in medical
diagnostics and food quality monitoring. Towards this goal, cellulosic paper is among
the most promising substrates, since it is inexpensive, flexible, lightweight, portable
and biodegradable. Several paper-based gas sensor platforms functionalized with
different gas sensitive elements (e.g. chemo-responsive dyes, conductive nanomaterials)
have been presented for gas detection in diverse environments. In one work, a
paper-based microfluidic platform functionalized with an array of chemo-responsive dyes
is built. Selective sensing of dissolved ammonia and carbon dioxide is achieved with ppm
level sensitivity. In another work, a disposable food sensor is made on paper substrate
with colorimetric microbeads arrays arranged as a geometric barcode to monitor the food
spoilage. The sensor is fabricated through a stamping process, which is easy and highly
reproducible. This barcode sensor can distinguish hourly change of food freshness at
room temperature. Another paper based optoelectronic platform with combined optical and
electrical chemi-resistive sensor arrays is used for sensing and discriminating several
volatile gases and mixtures. By combining the optical and electrical approaches, a
unique optoelectronic signature is generated for each gas analyte and its mixtures.
Using support vector machine (SVM) based machine learning approach enables accurate
classification of these gases from the combined use of both optical and electrical
sensor responses. Another part of work includes a couple of sensor platforms with
dye-contained colorimetric microbeads as the core sensing element. These works include
an optical fiber sensor functionalized with colorimetric beads for the detection of
gastric gas at ppm level; a microfluidic sensing platform incorporating colorimetric
beads for detection of ammonia concentration in saliva with sub-ppm sensitivity; the
colorimetric beads embedded hydrogel fiber used to monitor the pH of the skin for wound
healing. In summary, several optoelectronic sensor platforms have been developed, which
combine the advantages of clean room free fabrication, low-cost paper-based substrate
material with highly sensitive sensing materials such as chemoresponsive dyes. These
as-fabricated cost-effective and highly reproducible sensor platforms have been used to
realize gas sensing in diverse environments.
Thesis (Ph.D.)--Tufts University, 2017.
Submitted to the Dept. of Electrical Engineering.
Advisor: Sameer Sonkusale.
Committee: Eric Miller, John Durant, and Mehmet Dokmeci.
Keywords: Optics, and Electrical engineering.read less