Surface micromachined polysilicon heart cell force transducer

A microelectromechanical systems (MEMS) force transducer system, with a volume less than 1 mm/sup 3/ millimeter, has been developed to measure forces generated by living heart muscle cells. Cell attachment and measurement of contractile forces have been demonstrated with a commercially fabricated surface-micromachined hinged polysilicon device. Two freestanding polysilicon clamps, each suspended by a pair of microbeams, hold each end of a heart cell. When the cell contracts, the beam bend and force is determined from the measured deflection and the spring constant in the beams. The average maximal force over seven contractile experiments using a calcium solution stimulus was F/sub max/=12.6/spl plusmn/4.66 /spl mu/N. Normalizing to a cross-sectional area, F/sub max//area was 23.7/spl plusmn/8.6 mN/mm/sup 2/. These force data were also correlated to optically imaged striation pattern periodicity. Intermediate forces were also measured in response to a calcium solution gradient and showed similar behavior to those measured in other laboratories. This MEMS force transducer demonstrates the feasibility of higher fidelity measurements from muscle cells and, thus, an improved understanding of the mechanisms of muscle contraction.