In reference to the patent: US8726746

Does this 2002 journal article, "An integrated piezo-acoustic shear-force distance sensor with nanometer resolution for a micropipette tool" (pdf), demonstrate prior art? The authors document a sensing system comprised of two piezo-electric elements coupled to a pipette:

"One of the piezos excites the pipette at the mechanical resonance of its tapered tip while the other piezo is used for detection of the vibration."

The inventors of the '746 patent claim a method comprising:

"coupling an ultrasonic signal into the wall of the suction tube, wherein said ultrasonic signal is generated by a piezo actuator disposed between said wall of said suction tube and an additional mass, said piezo actuator mounted on said wall of said suction tube, said piezo actuator in contact with said additional mass on a side facing away from said suction tube;"

  • Note that the inventors claim the use of only one piezo element (which they suggest can be used to both generate vibrations and sense them), whereas the prior work used two piezo elements;
  • the inventors claim their invention is useful for determining the volume of fluid inside the pipette tip, while the prior work documented using the piezo system for sensing the distance of the tip from a fluid sample;
  • the inventors claim the use of a "plurality of frequencies" although the prior work also involved a plurality of frequencies.

Prior work:

"The outer electrode of one of the piezos is connected to a frequency generator (model 8550, Tabor Electronics Inc., USA) and excites the pipette at its mechanical resonance in the frequency range of 10± 150 kHz and at amplitudes between 50 mVpp and 5 Vpp. The second piezo-element serves as piezo-acoustic detector and is connected to a lock-in amplifier (model 5302, EG&G Inc., USA) to measure magnitude and phase shift of the system response."


"measuring the frequency-dependent damping of the ultrasonic signal in the wall of the suction tube in a predefined frequency range comprising a plurality of frequencies as a function of the frequency;"

1 Answer 1


As to the specific question "is this prior art?", the 2002 article is, on its face, prior in time, and appears to be germane to the subject matter of the '746 patent. Thus, yes, it appears to be prior art with respect to '746. However, that doesn't in itself tell us much. Is the article sufficient to anticipate (under Pre-AIA 35 USC 102) each and every element, arranged identically as in the claims of '746? Probably not, based on your explanation alone, and thus insufficient alone to invalidate the '746 patent. But it may well be tht the article could be applied in combination with another reference, or in view of common sense, or in view of well-known features, as rendering the claims of '746 obvious (under Pre-AIA 35 USC 103), as might be identified and argued in a reexamination, post grant review proceeding, or in court.

  • Thanks for your analysis! It's a shame the USPTO missed the research article when reviewing this patent.
    – Mac Cowell
    Jan 23, 2015 at 5:23

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