Axial Light-force Sensor

Tech ID: 17318 / UC Case 2004-011-0


Commercially available optical tweezers can move objects using laser light, but they are generally not used to measure forces exerted on those objects, since accurate force calibration is difficult. Research in the field of optical trapping has led to the development of optical tweezers that measure forces (transverse to optic axis) by changes in light-momentum. Force calibration is greatly simplified by using this method. However, in measuring the light force on a trapped object, it is also desirable to obtain all three vector components of that force.

Representing an improvement on the light-momentum force-sensor, researchers at the University of California, Berkeley have developed an axial light-force sensor. A system incorporating the Berkeley improvement permits simultaneous measurements of the axial and transverse forces acting on a trapped particle. Like the transverse sensor, the axial force sensor is calibrated from measured constant values: the speed of light, the objective focal length, and the power sensitivity of the planar photo-diode. Thus calibration is not affected by particle shape, laser power, particle refractive index, or sharpness of the trap focus. In addition, a highly-miniaturized, ultra stable, optical trap system has been developed that should permit a low cost instrument with force-measuring capabilities for use in normal lab environments.


Force analysis on single cells, viruses, DNA, RNA, and other Nanomolecules
Biophysics, enzymology research, and possibly drug discovery
Measurement of the elastic, viscous, and structural properties of nanomolecules
Nanomaterial structural research and molecular motor mechanics


Lower cost and smaller than present research devices
Environmental effects are minimized which would lower the facility costs. Users would no longer need a vibration-free environment

Patent Status

Country Type Number Dated Case
United States Of America Issued Patent 7,133,132 11/07/2006 2004-011


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Other Information


lasers, instrumentation, optics, equipment, atomic probe, atomic probe: microscopy, sensors, Nanotech, imaging, materials

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