A proposed simple, portable, robust apparatus, capable of automated operation, has been proposed for collecting samples of selected biological or chemical species in harsh environments. The sampled species could range in size from molecules to nanoparticles (that is, particles with dimensions of the order of nanometers). The apparatus would select a biological or chemical species of interest for sampling by utilizing a combination of (1) electrostatic or electrodynamic fields and (2) a sieve containing holes of predetermined size.
The apparatus (see figure) would include an ionizing grid, the sieve, an electric- ally insulating capture vessel, and a back electrode at the far end (the right end in the figure) of the capture vessel. The sieve would consist of a porous disk of silicon carbide on silicon, supported by an electrically insulating ceramic ring that would be sealed to the left end of the capture vessel. The sieve would contain an array of nanopores formed by a photoelectrochemical etching process. The nanopores would be made to taper toward narrower openings on the capture-vessel side. A metallic film could be deposited on a surface of the SiC sieve for electrical contact.
In operation, entering particles would be ionized by use of static or pulse discharges in the ionizing grid. An electric potential would be applied to the sieve, causing the ionized particles to accelerate toward and through the sieve. The opposite potential would be applied to the back electrode. Particles would be selected for passage according to their sizes and the sizes of pores in the sieve. After passing through the sieve, the particles would be decelerated by the electric field between the sieve and the back electrode. Condensable molecules would be collected on the inner surface of the capture vessel. Data sampling can be accomplished remotely by spectrographically imaging a thin-film silicon carbide port incorporated into the middle of the backplane.
This work was done by Margaret Ryan, Virgil Shields, and Roger Williams of Caltech for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
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Refer to NPO-30182, volume and number of this NASA Tech Briefs issue, and the page number.