A piezoelectric force transducer for single muscle cells.

A cantilevered piezoelectric force transducer is described. The cantilevered element has a 6-mm glass extension that can be projected into a horizontal muscle bath from above. By adjusting the length of the piezoelectric bar from 1 to 4 mm, the sensitivity of the device can be varied between 25 and 100 mV/mN (0.25--1.0 mV/mg) with its resonant frequency varying inversely between 8 and 15 kHz. Although moderately fragile, the sensing elements are inexpensive and easily made. The output of the sensing element is amplified by a small, unity-gain, high-input-resistance amplifier mounted on a support block with the element. Although the arrangement does not provide a DC output, its time constant of over 500 s is sufficiently long for measuring tension during muscle contractions lasting 1--2 s.