If we instead apply a positive voltage to the outside of the left segment, the tube will bend to the left.
By holding the top of the tube in place, and applying proper voltages to all four of the electrodes, the bottom of the tube can be programmed to flex in the X-Y scanning pattern that moves the SPM cantilever tip across the experimental sample.
Note, however, that we have hugely exaggerated the bending: The tube is about 5 cm long but its maximum bend may be only 10-4 cm.
