Assembly of skeletal muscle cells on a Si-MEMS device and their generative force measurement.

We have fabricated a simple Si-MEMS device consisting of a microcantilever and a base to measure active tension generated by skeletal muscle myotubes derived from murine myoblast cell line C2C12. We have developed a fabrication process for integration of myotubes onto the device. To position myotubes over the gap between the cantilever and the base without damage due to mechanical peeling or the use of an enzymatic reaction, we cultured myotubes on poly-N-isopropylacrylamide (PNIPAAm) as a sacrifice layer. By means of immune staining of alpha-actinin, it was confirmed that a myotube micropatterned onto the device bridged the gap between the cantilever and the base. After 7d differentiation, the myotube was actuated by electrical stimulation. The active tension generated by the myotube was evaluated by measuring the bending of the cantilever using image processing. On twitch stimulation, the myotube on the device contracted and generated active tension in response to the electrical signals. On tetanus tension measurement, approximately 1.0 microN per single myotube was obtained. The device developed here can be used in wide area of in vitro skeletal muscle studies, such as drug screening, physiology, regenerative medicine, etc.

Crystallographic contributions to piezoelectric properties in PZT thin films.

We report on the correlated investigation between macroscopic piezoelectric properties and the microscopic deformation of crystal structures of both epitaxial and polycrystalline Pb(Zr,Ti)O3 (PZT) thin films grown on MgO and Si substrates, respectively. We observed the reversible elongation and contraction of lattice parameter under an applied electric field using synchrotron X-ray diffraction. The effective piezoelectric coefficients were estimated from the relationship between electric field and field-induced strain, and compared with those characterized by the macroscopic cantilever method. The electric field dependences of the piezoelectric coefficients obtained from both characterization were in good agreement with each other. The results also revealed large and nonlinear piezoelectric properties for the polycrystalline PZT thin film. The comparative discussion in this study provides valuable insights of crystallographic contributions and opens the way to improve the piezoelectricity in thin-film based piezoelectric devices.