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Several researchers are actively studying Ionomeric polymer transducers (IPT) as a large strain low voltage Electro-
Active Polymer (EAP) actuator. EAPs are devices that do not contain any moving parts leading to a potential large life
time. Furthermore, they are light weight and flexible. IPT have the ability to generate bending strains on the order 5%
when +2V potential is applied across its thickness. As sensors however, IPTs are proven to be superior compared to any
other EAP material when a charge amplifier is used as a signal conditioner. Furthermore, researchers has developed
miniature sensors from IPTs that could be flush mounted to a surface and measure shear stresses due to fluid flow at
even low Reynolds numbers. Sensor resolution is on the order of 10 mPa enables it to be useful as a wall shear stress
sensor for several aero/hydrodynamic and biomedical applications. In this paper a new signal conditioning circuit is
designed with superior sensing capabilities compared to the old circuit. In the new circuit the IPT is biased with a small
voltage on the order of 5mV to 25 mV. Initial experimental results demonstrated 30% enhancement in signal to noise
ratio compared to the old circuit. Furthermore, this circuit enables the use of IPT polymers with larger capacitance
compared to the previous circuits. Akle et al. demonstrated that the capacitance of an ionic polymer transducer is
proportional to transducer performance. Ionic polymers are generally made of an ion exchange membrane, typically
Nafion, coated with a flexible electrode. In this study the Direct Assembly Process (DAP) is used for the fabrication of
IPT. The DAP consists of mixing a metal particulate with an ionomer solution and spraying it directly on a diluent
saturated ion conducting membrane. The thickness of the electrode is controlled by altering the amount of the
ionomer/metal mix sprayed on the membrane. Thicker electrodes provide IPT with a larger capacitance, and hence larger
sensitivity is obtained using the new circuit. It was impossible to use the previous signal conditioning circuit for high
capacitance sensors. Finally an attempt to model these sensors along with the circuit is provided. By understanding the
interaction between the IPT and the signal conditioning circuit we can create devices with even higher sensitivity. The
presented circuit will help in modeling and predicting the response of the sensor.
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