Patent ID: 7635420

Claim:
A method for testing for presence of particles of a selected species in a liquid or fluid, the method comprising: providing an array of at least first and second spaced apart nanostructure (“NS”) electrodes that are part of a first electrode surface; providing a second electrode, spaced apart from the first electrode surface by a distance in a selected distance range, to thereby form a channel between the first electrode surface and the second electrode; impressing a time varying electrical field E(t) between the NS electrodes and the second electrode to provide a root-mean-square electrical filed intensity E 2 rms with non-zero gradient in a direction (z) substantially perpendicular to the first electrode surface; allowing a liquid or fluid, which may contain particles of a selected species and includes at least one of a general medium and non-selected particles, to flow in the channel; allowing the selected species particles, when present, to move, by dielectrophoresis forces, toward, and to thereby increase concentration of the selected species particles adjacent to, the NS electrodes; providing an electrically insulating material, having an insulating material surface, in an interstitial space between said at least first and second NS electrodes, where a portion of at least one of said NS electrodes is exposed at or adjacent to the insulating material surface; providing a first functionalizing substance on a first region of the insulating material surface, which promotes attachment of said selected species particles, when present, to the first region; allowing at least one of the selected species particles, when present, to approach and become attached to the first region; providing a measured value Z(meas) of a selected electrical property of at least one of the first and second NS electrodes, providing a reference value Z(ref) for the selected electrical property, and providing a value ΔZ(meas) based on a difference between Z(ref) and Z(meas); when |ΔZ(meas)|≧ΔZ(thr) is satisfied, where Z(thr) is a selected threshold value, interpreting this condition as indicating that the selected species particle is present in the liquid or fluid; and when |ΔZ(meas)|<ΔZ(thr), interpreting this condition as indicating that the selected species particles are not present, or are present below a selected threshold concentration, in the liquid or fluid.