Nanomaterial based detection and degradation of biological and chemical contaminants in a  microfluidic system
Creators: name: Jayamohan, Harikrishnan
Publisher: name: University of Utah
Year: 2016
Subjects: subject: Biosensors
subject: Electrochemical Detection
subject: Lab-on-a-chip
subject: Microfluidics
subject: Nanotechnology
subject: FOS: Nanotechnology
subject: Pathogen

description: Monitoring  and  remediation  of environmental  contaminants  (biological  and  chemical)  form  the  crux of global  water  resource  management.  There  is  an  extant  need  to  develop  point-of-use,  low-power,  low-cost  tools that  can address this  problem effectively with min­ imal  environmental  impact.  Nanotechnology  and  microfluidics  have  made  enormous  ad­ vances during the past decade in the area of biosensing and environmental remediation.  The  "marriage"  of these two technologies  can  effectively  address  some  of the  above-mentioned  needs  [1].  In  this  dissertation,  nanomaterials  were  used  in  conjunction  with  microfluidic  techniques to detect and degrade biological and chemical pollutants. In the first project, a point-of-use sensor was developed for detection of trichloroethylene  (TCE)  from water.  A self-organizing nanotubular titanium dioxide  (TNA)  synthesized  by  electrochemical anodization and functionalized with photocatalytically deposited platinum  (Pt/TNA)  was applied to the detection.  The morphology and crystallinity of the Pt/TNA  sensor  was  characterized  using  field  emission  scanning  electron  microscope,  energy  dis­ persive  x-ray  spectroscopy,  and  X-ray  diffraction.  The  sensor  could  detect  TCE  in  the  concentrations  ranging from  10 to  1000  ppm.  The  room-temperature operation capability  of  the  sensor  makes  it  less  power  intensive  and  can  potentially  be  incorporated  into  a  field-based  sensor.  In the  second  part,  TNA synthesized  on  a foil was  incorporated  into a  flow-based microfluidic format and applied to degradation of a model pollutant,  methylene  blue.  The system was demonstrated to have enhanced photocatalytic performance at higher  flow  rates  (50-200  ^L/min)  over  the  same  microfluidic  format  with  TiO2  nanoparticulate  (commercial P25) catalyst.  The microfluidic format with TNA catalyst was able to achieve  82%  fractional  conversion  of  18  mM  methylene  blue  in  comparison  to  55%  in  the  case  of  the  TiO2  nanoparticulate  layer  at  a flow  rate  of 200  L/min.  The  microfluidic  device  was  fabricated using non-cleanroom-based methods, making it suitable for economical large-scale  manufacture.  A computational model of the microfluidic format was developed in COMSOL  Multiphysics®  finite  element  software  to  evaluate  the  effect  of  diffusion  coefficient  and  rate  constant  on  the  photocatalytic  performance.  To  further  enhance  the  photocatalytic  performance of the microfluidic device, TNA synthesized on a mesh was used as the catalyst. The  new  system  was  shown  to  have  enhanced  photocatalytic  performance  in  comparison  to TNA on a foil.  The device was then employed  in the inactivation of E.  coli  O157:H7 at  different flow rates and light  intensities  (100,  50,  20,  10 mW/cm2). In  the  second  project,  a  protocol  for  ultra-sensitive  indirect  electrochemical  detection  of  E.  coli   O157:H7  was  reported.   The  protocol  uses  antibody  functionalized  primary  (magnetic)  beads  for capture  and  polyguanine  (polyG)  oligonucleotide  functionalized  sec­ ondary  (polystyrene)  beads  as  an  electrochemical  tag.  The  method  was  able  to  detect  concentrations of  E.  coli  O157:H7  down to 3  CFU/100 mL  (S/N=3).  We also demonstrate  the  use  of  the  protocol  for  detection  of  E.  coli   O157:H7  seeded  in  wastewater  effluent  samples.