Sensing Capabilities of Ionic Polymer-Metal Composites

摘要

This paper presents a brief description and testing results of Ionic Polymer-Metal Composites (IPMC's) as dynamic sensors. As previously noted a strip of IPMC 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 IPMC can be explained by the linear irreversible thermodynamics in which ion and solvent transport are the fluxes and electric field and solvent pressure gradient are the forces. Important parameters include the material conductance and the permeability. The dynamic sensing response of a strip of IPMC under an impact type loading is also discussed. A damped electric response is observed which is highly repeatable with a broad frequency range above 10~4 Hz. Such direct mechanoelectric 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 monitored. IPMC's are observed to be highly capacitive at low frequencies while they are highly resisitive under high frequency excitations. Current efforts are to study the low and the high frequency responses of IPMC's and sensitivity of IPMC that might conceivably replace piezoresistive and piezoelectric sensors with just one sensor for a broad frequency range.