Christopher D Hahn

20020106308, Aug 8, 2002

Feb 2, 2001

09/776427

Ronald Zweifel - Naperville IL, US
Christopher Hahn - Downers Grove IL, US

B01L003/02

422/100000, 422/067000, 073/863010, 073/864010, 073/864240, 073/864250

A method and apparatus for preventing or limiting damage to capillaries used to dispense microdrops measures the voltage produced by a piezoelectric transducer when the capillary contacts a solid surface or the phase shift occurring when the piezoelectric transducer is operated at its resonant frequency. After distinguishing the voltage created from such contact from the voltage produced from unrelated random sources, corrective action is taken, in one aspect by stopping the relative movement of the capillary and the surface being contacted. The method and apparatus may also be employed to determine the position of a solid or liquid surface.

20040185569, Sep 23, 2004

Dec 23, 2003

10/746039

Ronald Zweifel - Naperville IL, US
Christopher Hahn - Decatur IL, US

G01N035/00

436/043000, 422/100000

A method and apparatus for preventing or limiting damage to capillaries used to dispense microdrops measures the voltage produced by a piezoelectric transducer when the capillary contacts a solid surface or the phase shift occurring when the piezoelectric transducer is operated at its resonant frequency. After distinguishing the voltage created from such contact from the voltage produced from unrelated random sources, corrective action is taken, in one aspect by stopping the relative movement of the capillary and the surface being contacted. The method and apparatus may also be employed to determine the position of a solid or liquid surface. In one embodiment, the method and apparatus of the invention is used to detect contact of the capillary with very small liquid droplets.