The Piezo-Sensory arm is the answer to our prosthetic needs. What makes
this arm unique is that it provides a range of feelings yet it is durable
and the idea is simple. In the future, the Piezo-Sensory arm will replace
other arm prosthetics. In addition, this arm will be superior because
it does not depend entirely on electronics to function.
The range of feelings provided by the Piezo-Sensory arm is possible because
of the piezoelectric effect. The piezoelectric effect occurs in piezoelectric
crystals (generally these crystals are nonmetallic minerals) such as tourmaline.
However, there are many types of piezoelectric crystals, and some are
fairly rare or it may be hard to produce the sufficient quantities or
properties. Use of the Piezo- Sensory arm requires an abundant and easy
to synthesize piezoelectric crystal. Rochelle Salt is an example of a
piezoelectric crystal that can be easily synthesized.
The piezoelectric effect is caused when piezoelectric crystals develop
an electric charge on its surface. This electric charge is produced when
any type of pressure is applied to the crystal. This includes being warped,
twisted or compressed. Piezoelectric crystals also resonate at a narrow
frequency range when an electric voltage is applied to it. Many electronics,
such as radios, already use piezoelectric material. In radios the piezoelectric
material is cut so only certain frequencies can pass through it. Other
examples are microphones or other electronics that change sound waves
into electric signals.
The piezoelectric effect can be fully utilized in the Piezo-Sensory arm. There is
a processor located inside the arm, which is necessary to relay the signals
between the body and the prosthetic. In today's prosthetics the arm responds
to signals coming from the upper arm. The processor in the Piezo-Sensory arm,
however, responds to the nerve signals sent from the brain and interprets these
signals causing the arm to act accordingly. The revolutionary concept of this
arm is that the user's body responds to the signal generated by the mechanical
motion of the arm. The piezoelectric crystals are the key players in giving
feedback to the body. The crystals will be made into strips and be laid all over
the perimeter of the arm, almost like another skin. The crystals will be
connected to a processor. When the arm twists, warps or is compressed, the
crystals get twisted, warped or compressed as well. The crystals then generate
an electric pulse due to the piezoelectric effect. These signals are sent to the
processor. The processor regulates the signals so the brain is aware of
movement and pressure in the arm. The person wearing the prosthetic will then
begin to feel. However, if there is too little twisting, warping or pressure, than
the signal will not be sent because there may be too little movement in the
piezoelectric crystals to produce a pulse. The arm will probably be unable to duplicate the exact same signal as the nervous system, therefore conditioning is necessary for the user to fully utilize the arm's feedback function.
Wires and nerves are also connected the to processor. The nerves are
connected to the processor so the brain can give signals to the arm and
the arm can give signals back. The wires are connected to the motor functions
of the arm as well as the processor. The brain can now send signals to
the arm to command it to move.
To control the motor functions of the arm, there will be five electrical
motors placed in the arm. One in the wrist to allow it to twist, two in
the hand to control the four fingers, and one motor will be placed in
the middle finger joints of the two fingers closest to the thumb, and
one in the thumb joint. Each finger cannot be controlled individually,
instead, they are controlled in pairs. The top two fingers can bend up
and down together while the bottom two fingers can bend in the middle
joint and move up and down. This system will better simulate the grasping
motions of the hand and allow it to conform to odd shaped objects.
When the brain sends a signal to command the arm to move, the processor
will take in the signal and interpret what the signal means and what it
wants the arm to do. The processor will than send a signal to the motor
functions of the arm to move according to what is interpreted. Again,
the people wearing the prosthetic must be conditioned to know how to send
the proper signals to command the arm to move.
MORE PICTRUES OF THE PIEZO-SENSORY ARM