Biomedical Engineering Reference
In-Depth Information
7
Sensing, Transduction,
Feedback Control, and
Robotic Applications
of Polymeric Artificial
Muscles
7.1
INTRODUCTION
This chapter covers sensing, transduction, feedback control, and robotic actuation
capabilities and issues related to these topics. Ionic polymer-metal nanocomposites
(IPMNCs) and ionic polymer conductor nanocomposites (IPCNCs) are amazing
tools for soft robotic actuation and built-in sensing and transduction in a distributed
manner. One can even see the distributed biomimetic, noiseless nanosensing, nano-
transduction, and nanoactuation capabilities of IPMNCs and IPCNCs.
7.2
SENSING CAPABILITIES OF IPMNCS
This section presents a brief description and testing results of ionic polymer-metal
composites (IPMNCs) as dynamic sensors. As previously noted, a strip of IPMNC
can exhibit large dynamic deformation if placed in a time-varying electric field.
Conversely, dynamic deformation of such ionic polymers produces dynamic electric
fields. The underlying principle of such a mechanoelectric effect in IPMNCs can be
explained by the linear irreversible thermodynamics in which ion and solvent trans-
port are the fluxes and electric field and solvent pressure gradient are the forces, as
described in chapter 6. Important parameters include the material capacitance, con-
ductance, and stiffness, which are related to material permeability.
The dynamic sensing response of a strip of IPMNC under an impact type of
loading is also discussed. A damped electric response is observed that is highly
repeatable with a broad bandwidth to megahertz frequencies. Such direct mechano-
electric behaviors are related to the endo-ionic mobility due to imposed stresses.
This means that, if one imposes a finite solvent flux without allowing a current flux,
the material creates a certain conjugate electric field that can be dynamically mon-
itored. IPMNCs are observed to be highly capacitive at low frequencies and highly
resistive under high-frequency excitations. Current efforts are to study the low- and
the high-frequency responses and sensitivity of IPMNCs that might conceivably
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