AJP - Cell Physiology, Vol 263, Issue 3 C700-C707, Copyright © 1992 by American Physiological Society
A novel remote-sensing isometric force transducer for micromechanics studies
W. H. Guilford and R. W. Gore
Department of Physiology, College of Medicine, University of Arizona, Tucson 85724.
We have developed an innovative transducer for measuring force with
femtonewton-to-micronewton resolution in biological systems. A magnetic
microsphere is attached to the specimen being studied and is positioned
between two electromagnets. Video microscopy and edge detection are used to
monitor small movements of the microsphere that occur when the specimen
generates force. An automatic control system adjusts the current through
the electromagnets to keep the microsphere stationary. Measured force is a
linear function of this current. This transducer is unique in its
combination of sensitivity and isometric properties and its ability to
measure force without direct connections to the specimen. That is, the
transducer is "remote sensing" and can measure force through intervening
membrane or tissue. The transducer is isometric at steady state to the
limit at which displacement of the microsphere can be resolved, which can
be as low as 19 nm. The completed system is being used to study the
mechanics of interstitial connective tissue but may also be used to study
molecular generation of force.
