Darryl Benally Team member: ChEng Graduate Student Christopher Killingsworth Supervisor: Professor Randy Bartels

Outline  Project Goals  Prior Research  Current Progress  Budget  Plans for next semester

Project Goals  Pathogen detection of food borne illnesses at very low concentration  Detection time to less than 24 hours Scanning electron microscope image of E coli Image from National Institute of Allergy and Infectious Diseases Related/Biodefense/PublicMedia/image_library.htm

Project Goals Strategy of binding pathogens to gold nanoparticles 1. A dissolved sample containing pathogens (red dots). 2. Gold nanoparticles with attached anti-bodies (gold/blue dots) are added. 3. Nanoparticles will fill a large volume and attach to pathogens. 4. The attached pathogens to nanoparticles are selectively concentrated in the trap volume (broken line) for subsequent detection. [a]

Collect Nanoparticles for Detection Incident TM Radiation Reflected Radiation X Z Evanescent Field Decay Gaussian Beam Shape Polarizable Particle FZFZ FXFX Total Internal Reflection (TIR)

Trapping force Brownian motion Trapping force scales with r 3 Brownian motion scales with 1/r Trapping force Brownian motion Collect Nanoparticles for Detection  Concept behind for selective concentration of different sized nanoparticles  As radius increases trapping forces increase and Brownian motion decreases  Nanoparticle in Rayleigh regime causing the particle to behave as an inducible point dipole

Prior Research  Research done in past summer on developing techniques on making the gold nanoparticles and attaching anti-bodies

Assignment to Project  Build Prism Mounts and Prism Holder  Theoretical Calculations for Particle Dynamics

Coating Prism Mount  Coating the prism with gold  No mount commercially available 10 [mm] 14 [mm]

Using Prism for TIR  Using the prism dimension to cause Total Internal Reflection (TIR) Gaussian Beam Shape Light Source for Absorption Spectrum (Not to Scale) Incident TM Radiation Reflected Radiation  A light beam will enter on the sides and refracted to appropriate angles  Particles will move into the center of the evanescent field  A second light source will be directed from the top to perform establish absorption spectrum  The detection of the gold nanoparticles will come from differential absorption spectroscopy

Prism Holder Design  The first design that was made  The idea was to bring the beam through the sides to cause TIR  The top piece used to securing place the prism sealing the sample  The opening for the second light source the differential absorption spectroscopy  However, prove to be unstable and difficult to mount  A second design was need

Prism Holder Design  Second design  The holder can be placed within an optical mount Side view Corner View Top view 1 in

Theoretical Calculations  These calculations are used to evaluate the particle dynamics in fluidic chamber  The theoretical calculations will help predict how far the particle will fall once under the optical forces  These predictions will help in determining how fast the fluid in the chamber will need to be

Derivation of Differential Equation  Assuming uniform gradient force  Assuming laminar flow  Assuming gradient force is much greater than scattering forces z x FgFg F dx F dz Laminar Flow Velocity Prism Gold Coated Surface Coordinates x distance

Budget  Budgeted 50 dollars from ECE department  Have not spent any of this money  The Project is funded through the Infectious Disease Supercluster here at CSU

Plans for Next Semester  Design and build new prism mount with more stability  Perform test and evaluate  Put together new setup for more sensitive detection using thermal modulation of nanoparticles

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