Mechanical stimulation and micromanipulation with piezoelectric bimorph elements

Piezoelectric bimorph elements are versatile and inexpensive electromechanical transducers which may be used to construct fast mechanical stimulators and finely controlled micromanipulators. The mechanical stimulators described provide continuously graded displacements ranging from nanometers to about a millimeter, or forces equivalent to 0-7 g. Appropriately designed units can produce small step displacements complete within 100 microseconds. Micromanipulators are described which generate 3-dimensional motion under remote electrical control and which enable positioning within a few tenths of a micrometer. They are sufficiently stable to hold glass microelectrodes for cell penetration or probes for microdissection. The two significant drawbacks of bimorph elements are mechanical resonance and continued movement following displacement, or 'creep", but methods have been developed to compensate for these. A number of methods are available to measure motion of bimorphs with spatial resolution of 10 nm and temporal resolution of 2 microseconds in favorable situations.