John Melcher

US Patent:

20110041224, Feb 17, 2011

Filed:

Aug 6, 2010

Appl. No.:

12/852095

Inventors:

Arvind Raman - West Lafayette IN, US
Ronald G. Reifenberger - West Lafayette IN, US
John T. Melcher - West Lafayette IN, US

Assignee:

PURDUE RESEARCH FOUNDATION - West Lafayette IN

International Classification:

G01Q 60/24

US Classification:

850 40

Abstract:

A microcantilever used in Atomic Force Microscopy (AFM) includes an elongated cantilevered body with a probe tip placed preferably near its free end and preferably along the cantilever's axis. Some embodiments of the present invention integrate into the microcantilever body an embedded or etched paddle that rotates rigidly about an axis parallel to that of the cantilever with hinges that connect the paddle to the cantilever body. In one embodiment the resonance frequency of this paddle resonator is higher than the fundamental resonance of the microcantilever so that the paddle rotation is proportional to the vertical microcantilever acceleration at the hinge location. The motion of the paddle can be detected using radiation irradiating the paddle; the reflected beam is centered onto a four quadrant photodiode as commonly found in AFM. The paddle's vertical motion is detected in the usual way by monitoring the vertical channel in the photodiode while its rotation is monitored from the lateral channel in the photodiode. By monitoring the vertical tip acceleration signal from the paddle rotation, it is possible to resolve the history of tip-sample force during oscillation cycles. A calibration method to convert the measured paddle rotation into vertical probe tip acceleration and instantaneous tip-sample force is also disclosed.