Development of a Transfer Function for a Personal, Thermophoretic Nanoparticle Sampler

Abstract

Effective assessment of nanoparticle exposures requires accurate characterization of the aerosol. Of increasing concern is personal exposure to engineered nanoparticles that are specifically designed for use in the nanotechnology sector. This manuscript describes the operation and use of a personal sampler that utilizes thermophoretic force to collect nanoparticles onto a standard TEM (transmission electron microscope) grid. After collection, nanoparticles on the TEM grid are analyzed with an electron microscope, and the resultant data used to determine the characteristics of the nanoparticle aerosol sampled. Laboratory experiments were conducted to determine the inlet losses and collection efficiency of the thermophoretic sampler for particles between 20 and 600 nm in diameter. These results are used together with theory for thermophoretic velocity to form a transfer function that relates the properties of the collected particles to the properties of the sampled aerosol. The transfer function utilizes a normalization factor, F(d), which is larger than unity for very small particles but approaches unity for particles larger than about 70 nm.

Physical properties of secondary photochemical aerosol from OH oxidation of a cyclic siloxane

“…Compressed air (3.5 or 5 L min −1 ) was passed through activated carbon and HEPA filters, and humidified to 25 %-40 % relative humidity (RH) (Sigma-Aldrich Optima or Barnstead Nanopure filtered ultrapure reagent grade water). All experiments were performed under ambient conditions of 22 • C, but the chamber was likely warmer (∼ 24 • C, Li et al, 2015) due to the lamps. No temperature correction due to potential OFR heating was employed in this work however.…”

“…However, the personal care concentrations could be up to 20 times greater than the D 5 concentrations used and still fall in the OH-favored regime. Chamber conditions for the 12 scenarios had a water mixing ratio of 0.81 %-1.5 % (25 %-45 % RH), OHR ext 0.5-26 s −1 , and 185 nm photon flux as estimated from Li et al (2015) 6.5-8.6 × 10 13 photons cm −2 s −1 .…”

“…3.1. A likely source of uncertainty in the predicted OH exposure is UV light intensity which was estimated from the intensity output from a similar OFR reported in Li et al (2015). Despite using the same lamp model, light intensity likely varies due to agerelated reduction or production differences.…”

NIOSH field studies team assessment: Worker exposure to aerosolized metal oxide nanoparticles in a semiconductor fabrication facility

“…Another alternative is to sample directly onto the TEM grid using an electrostatic precipitator (ESP) or thermophoretic sampler (TPS). (31–33) …”

Perspectives on the design of safer nanomaterials and manufacturing processes

“…In development is a new personal nano sampler that uses thermal precipitation technology for collection of ENMs. This technique would allow for non-destructive collection of particles directly onto an EM grid used as a collection substrate (Leith et al , 2013). Analytical techniques are also being developed that will use dark-field hyperspectral microscopy imaging to determine a ENM presence in biologic material (Ma et al , 2012).…”