KEYWORDS: Biosensing, Microfluidics, Biological and chemical sensing, Atmospheric particles, Weapons of mass destruction, Explosives, Defense technologies, Defense and security
Real-time collection and detection are crucial to mitigate airborne biothreats as evidenced during the COVID-19 pandemic. Herein, we numerically and experimentally demonstrate the collection and enrichment of aerosolized polystyrene microparticles using stratified air-water flow in U-shaped and spiral microchannels. Collection efficiencies calculated from multiphase flow simulations show good agreement with the experiment data. The U-shaped channel demonstrates poor particle capture efficiency for submicron particles. To aid this, a two-stage spiral microchannel is designed and fabricated, which shows a 60% higher average particle capture efficiency for submicron particles. Thus, the microchannels enable enrichment and capture of microparticles in sensing-ready solutions.
Monitoring electrochemical impedance changes due to aptamer/ligand binding on nanochannel surface provides an attractive sensing mechanism for chemical and biological species. We report a surface charge modulation based sensing mechanism for the detection of small molecules – amodiaquine and homoserine lactone with their respective specifically binding aptamers. The change in charge distribution due to aptamer/ligand binding modifies ionic transport across the nanochannel, results in transmembrane impedance changes proportional to the amount of target present, providing a quantitative response. A sensor reader based on an analog devices chip ADuCM355 was developed and used to monitor the nanoporous membrane's impedance changes over the desired frequency range. These results show that the combination of a low cost sensor reader and aptamer functionalized membrane will enable the development of a portable and inexpensive sensor system.
A miniature differential surface stress sensor consisting of two adjacent micromachined cantilevers (a
sensing/reference pair) is developed for detection of chemical and biological species. Presence of analyte species is
detected by measuring the differential surface stress associated with adsorption/absorption of chemical species on
sensing cantilever. A novel interferometric technique is utilized to measure the differential surface stress induced
bending of sensing cantilever with respect to reference cantilever. Sensor performance is characterized through
measurement of surface stress associated with formation of alkanethiol self-assembled monolayers (SAMs) on gold
coated sensing cantilever. Chemisorptions and self-assembly of alkanethiol molecules onto the gold-coated cantilever
surface leads to development of compressive surface stress. Magnitude of measured surface stress compares well with
data reported in literature.
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