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Nanoparticle Manipulation Metrology

Summary:

We are advancing the measurement of dimension and function of engineered nanoparticles for biomedical research, manufacturing, and environmental health & safety impact studies through the development of validated physical measurement and particle manipulation methods.

Description:

Engineered nanoparticles are a key component of biomedical research, advanced manufacturing, and a major issue for environmental health & safety impact studies. The size and shape of nanoparticles provide the basis of their functional properties, so dimensional measurements of nanoparticles (NP) and complex NP assemblies are required to understand their behavior in changing environments. The primary goal of this project is to develop the necessary, sufficient, and validated physico-chemical measurement and particle manipulation methods that will enable nanoparticle-based applications to move forward.

Atomic force microscopy images of nanoparticle reference materials. Gold nanoparticles (left) and polystyrene latex spheres (right).

Atomic force microscopy images of nanoparticle reference materials. Gold nanoparticles (left) and polystyrene latex spheres (right).

Trapping single particles allows particle properties and interactions to be precisely measured and enables the assembly of complex nanoparticle structures for applications in sensing, computation, and photonics. The ability to fully manipulate a particle’s position and orientation in three dimensions also offers new routes to test and fabricate nanodevices that may have no other path to manufacturing.


A 20 µm silica sphere levitated by a laser beam
A 20 µm silica sphere levitated by a laser beam.

Levitating particles in air or vacuum provides nearly perfect isolation from environmental disturbance and allows precision measurement of dimension, shape, surface chemistry and optical properties of particles. These measurements can be made extremely sensitive by using surface resonances (whispering gallery modes or plasmons) of the light interacting with the particle.

We have recently demonstrated accurate particle tracking in three dimensions without the ambiguities included in traditional instruments. This has allowed us to show for the first time that an optical levitation trap in air can be simultaneously in the underdamped and overdamped regimes, and to explain historically controversial results.

One of the next steps for this work will be to support precision acceleration measurements in the Nanoscale Metrology Group by using a particle as an ideally supported test mass and monitoring seismic accelerations of the test chamber.

 

Laser trapping of a 100-nm gold nanoparticle is improved by a factor of 20 under controlled conditions.

Laser trapping of a 100 nm gold nanoparticle is improved by a factor of 20 under controlled conditions.

Trapping in water allows more effective manipulation of nanoparticles and intrinsic compatibility with the most highly developed methods of particle preparation, storage and transport. This also provides a natural interface to biological systems.

We have focused on extending optical trapping to nanoparticles, and demonstrated a range of techniques that improve the ability to trap nanoparticles by orders of magnitude. Controlling the intensity and position of the trapping has enhanced the precision in positioning particles, but more importantly has extended the trapping time for nanoparticles by more than a factor of twenty. This controlled trapping allows particles to be trapped long enough for practical test and assembly operations.

Cross polarized components of a linearly polarized beam. All linearly polarized Gaussian beams include similar components, but they are frequently neglected.
Cross polarized components of a linearly polarized beam. All linearly polarized Gaussian beams include similar components, but they are frequently neglected.

We have recently developed counter propagating beam-based traps to balance the optical scattering forces that destabilize particles in traps. This also improves trapping performance significantly, and may be used simultaneously with both the controlled trapping developed here, and ultra-resolution microscopy techniques developed in other labs.

This technique will be used to assemble and test nanophotonic devices that can not be made by other means, and to examine the emergence of quantum phenomena in plasmonic devices. This work also allows measurement of particle-beam interactions and metrology of the beam itself. The results highlight important aspects of the beams that are frequently neglected (such as the existence and behavior of cross-polarized components in linearly-polarized Gaussian beams) and are highly relevant to areas such ultra-resolution microscopy.

Major Accomplishments:

  • Developed methods for quantifying size, stability, and functionality of a targeted nanoparticle delivery system.
  • Initiated efforts to re-establish Division leadership in calibration services and production of reference materials for nanoparticle characterization.
  • Demonstrated more than an order of magnitude improvement in the ability to trap and manipulate nanoparticles while enhancing positioning precision and reducing heating-induced damage.
  • Developed complete measurement of particle position and velocity in three dimensions to demonstrate that a levitated single particle can be simultaneously in both the under and overdamped regimes. 

Start Date:

January 29, 2010

Lead Organizational Unit:

pml

Staff:

John Dagata, Project Leader
Thomas W. LeBrun

 


Physicist Dr. Thomas W. LeBrun uses a special joystick to manipulate nanowires with

Physicist Dr. Thomas W. LeBrun uses a special joystick to manipulate nanowires with "optical tweezers."

Contact

John Dagata
301-975-3597

100 Bureau Drive, M/S 8212
Gaithersburg, Maryland 20899-8212