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Darryl Benally Team member: ChEng Graduate Student Christopher Killingsworth Supervisor: Professor Randy Bartels. Optical Nanoparticle Trapping Sensor. Outline. Project Goals Prior Research Current Progress Budget Plans for next semester. Project Goals.

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Presentation Transcript
Darryl Benally

Team member: ChEng Graduate Student Christopher Killingsworth

Supervisor: Professor Randy Bartels

Optical Nanoparticle Trapping Sensor

  • Project Goals
  • Prior Research
  • Current Progress
  • Budget
  • Plans for next semester
project goals
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 goals1
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]
collect nanoparticles for detection
Collect Nanoparticles for Detection

Gaussian Beam



Field Decay






Total Internal Reflection (TIR)


Incident TM




collect nanoparticles for detection1
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
prior research
Prior Research
  • Research done in past summer on developing techniques on making the gold nanoparticles and attaching anti-bodies
assignment to project
Assignment to Project
  • Build Prism Mounts and Prism Holder
  • Theoretical Calculations for Particle Dynamics
coating prism mount
Coating Prism Mount
  • Coating the prism with gold
  • No mount commercially available

14 [mm]

10 [mm]

10 [mm]

using prism for tir
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


  • 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




(Not to Scale)

prism holder design
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 design1
Prism Holder Design

1 in

  • Second design
  • The holder can be placed within an optical mount

Side view

Corner View

Top view

theoretical calculations
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
Derivation of Differential Equation
  • Assuming uniform gradient force
  • Assuming laminar flow
  • Assuming gradient force is much greater than scattering forces





Laminar Flow




x distance

Prism Gold Coated Surface

  • 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
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