Biomedical Engineering Reference
In-Depth Information
2.4
ELECTRIC DEFORMATION MEMORY EFFECTS,
MAGNETIC IPMNCS, AND SELF-OSCILLATORY
PHENOMENA IN IONIC POLYMERS
The preceding novel phenomena have been observed and established recently in our
laboratories at the University of New Mexico and the University of Nevada-Reno.
The novel electric deformation memory effect in connection with ionic polymer
conductor composites (IPCNCs) and, in particular, IPMNCs, is first reported here.
An IPMNC sample is capable of storing geometric shape and deformation
information for a given step voltage or imposed electric field, even when the field
is turned off—provided the sample is completely isolated form any electric discharg-
ing systems. In this case, IPMNCs do not need to be trained for a given shape
memory effect such as shape memory alloys (SMAs) or ferromagnetic shape memory
materials. Rather, they have an infinite set of possibilities of deformation shapes
versus voltage that can be memorized even when the electric field is removed. This
creates, for the first time, potential for building “geometric computers” that store
information in geometrical forms containing infinite amounts of information for a
given voltage signal or electric field. The data presented here will establish that,
from a neutral position and charge-free state, for any given voltage, a cantilever
sample of IPMNC bends to a shape; if one removes the voltage, the shape will not
change and the material remembers the shape permanently, provided the sample is
completely isolated form any electric discharging systems.
The process is highly reversible. Any change in shape is due to environmental
changes such as humidity or temperature and, in a controlled environment, we
observe that after the voltage is removed, having allowed the sample to stabilize its
shape, the shape stays almost permanently. Upon shorting out the electrodes on the
two sides of the sample, the sample moves back to its initial configuration before
the application of the step voltage.
The data enclosed here show that, from a neutral position and charge-free state
(this is important because IPMNCs are such sensitive and large-capacity charge
capacitors, and most anomalies are because we do not initially discharge the sample),
for any given voltage, the cantilever sample bends to a shape. If the voltage is
removed, the shape will not change, provided the sample is prevented from being
electrically discharged by completely isolating it from any electric discharging
systems. Typical observations are depicted in figure 2.43 (a, b, c, d, and e), in which
the sample is shorted out first and then reactivated and consequently completely
detached from its fixtures and left on a table to show that the shape is memorized
and is permanent.
In general, important observations are:
The electric deformation memory effect is due to rearrangement of immobi-
lized charges (double layer interactions) after the voltage is removed. Thus,
in a way, the electric deformation shape memory effect is due to a kind of
ionic solid phase transformation, which is capacitively induced.
The direction of the IPMNC motion is always consistent with the direction
of charges.
