design of our actuators is based on microfabricated torsional resonators.
They consist of rectangular grids suspended by two rods that act as
torsional springs. They are fabricated in a SCREAM process (Single Crystal
Silicon Reactive Etching And Metallization). When an AC voltage is applied
between the grid and adjacent electrodes, the grid oscillates at resonance
frequencies in the high kHz range. The edges of the grid reach deflections
of several micrometers out of the substrate plane.
By introducing asymmetries into the resonator grid (such as placing the torsional rods off the center of the grid, or adding poles on one side of the grid) anisotropic lateral forces are generated, thus achieving a motion bias for the object on top of the actuator.
Each actuator can generate motion in one specific direction if it is activated; otherwise it acts as a passive frictional contact. The combination and selective activation of several actuators with different motion bias allows us to generate various motions in the plane.