constructing a relatively complete map of the somatosensory homunculus in a single
experiment. With this in mind I designed and built an automated multichannel tactile
stimulator utilizing piezoelectric bending actuators that is safe to use in an MRI
environment and does not interfere with MR image acquisition.
PiezoelectricBendingActuators
The Vibrotactile stimulus is delivered by piezoelectric bending actuators (Fig. 1)
purchased from Piezo Systems (www.piezo.com). Piezoelectric materials deform when
exposed to a voltage; either stretching and becoming longer and thinner, or contracting
and becoming shorter and thicker, depending on the polarity of the voltage. The
piezoelectric bending actuators used in this system consist of two stacked piezoelectric
plates with wires attached in such a way that the two plates are in opposing polarity.
When a voltage is applied one plate expands and the other contracts, causing the
actuator to bend. If an alternating voltage is applied the actuator will bend back and
forth, causing it to vibrate at the frequency of the applied signal.
Two different sizes of bending actuators were used, a larger one is capable of
large displacements and strong stimulation (Fig. 1A), and a smaller thinner actuator that
is small enough to be placed on a finger (Fig. IB). Before the actuators could be used
safely in an MRl environment they had to first be modified for safety and durability
(Figs. 2.1.1C and D). (1) The lead wires were encased in rubber-coated fiberglass tubing
to prevent burns in the event that the lead wires heat up from the rapidly switching