Optical Nanoparticle Trapping Sensor

1. Darryl Benally Team member: ChEng Graduate Student Christopher Killingsworth Supervisor: Professor Randy Bartels Optical Nanoparticle Trapping Sensor

2. Outline • Project Goals • Prior Research • Current Progress • Budget • Plans for next semester

3. 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 • http://www3.niaid.nih.gov/topics/Biodefense • Related/Biodefense/PublicMedia/image_library.htm

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

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

6. Collect Nanoparticles for Detection • Trapping force scales with r3 • Brownian motion scales with 1/r • 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 • Brownian motion • Brownian motion • Trapping force • Trapping force

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

8. Assignment to Project • Build Prism Mounts and Prism Holder • Theoretical Calculations for Particle Dynamics

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

10. Using Prism for TIR Light Source for Absorption Spectrum • Using the prism dimension to cause Total Internal Reflection (TIR) • A light beam will enter on the sides and refracted to appropriate angles Gaussian Beam Shape • 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 Incident TM Radiation Reflected Radiation (Not to Scale)

11. 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

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

13. 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

14. Derivation of Differential Equation • Assuming uniform gradient force • Assuming laminar flow • Assuming gradient force is much greater than scattering forces Fdz z Coordinates Fdx Laminar Flow Velocity x Fg x distance Prism Gold Coated Surface

15. 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

16. 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

17. Questions ?????????