OPTICAL NANOPARTICLE TRAPPING SENSOR

Darryl BenallyTeam member: ChEng Graduate Student Christopher KillingsworthSupervisor: 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 coliImage from National Institute of Allergy and Infectious Diseases

http://www3.niaid.nih.gov/topics/BiodefenseRelated/Biodefense/PublicMedia/image_library.htm

Project GoalsStrategy 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 TMRadiation

ReflectedRadiation

X

Z

EvanescentField Decay

Gaussian BeamShape

PolarizableParticle

FZ

FX

Total Internal Reflection (TIR)

Trapping force

Brownian motion

Trapping force scales with r3

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]

10 [mm]

14 [mm]

Using Prism for TIR

Using the prism dimension to cause Total Internal Reflection (TIR)

Gaussian BeamShape

Light Source forAbsorption Spectrum

(Not to Scale)

Incident TMRadiation

ReflectedRadiation

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 ViewTop 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

Fg

Fdx

Fdz

Laminar FlowVelocity

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

Questions

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