Mr. Andrew J. Duncan Profile

Andrew J. Duncan

at Virginia Polytechnic Institute and State Univ

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Author

Publications (5)

Proceedings Article | 6 April 2009 Paper

Electromechanical performance and membrane stability of novel ionic polymer transducers constructed in the presence of ionic liquids

Andrew Duncan, Donald Leo, Timothy Long, Barbar Akle, Jong Park, Robert Moore

Proceedings Volume 7287, 728711 (2009) https://doi.org/10.1117/12.815874

KEYWORDS: Liquids, Polymers, Scattering, Electroactive polymers, Transducers, X-rays, Laser scattering, Glasses, Resistance, Actuators

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Ionic polymer transducers (IPT) are a class of devices that leverage electroactive polymers (EAP), specifically electrolyte-swollen ionomeric membranes, to perform energy conversions. Energy transformation from input to output is referred to as transduction and occurs between the electrical and mechanical domains. The present study expands on IPT investigations with a novel series of sulfonated polysulfones (sBPS), with specific interest in the effect of polymer topology on actuator performance. A hydrophilic ionic liquid was combined with a series of sBPS through a casting method to create hydrated membranes that contained target uptakes (f) of the diluent. The ionic liquid's hydrophilic, yet organic nature raised the issue of its degree of compatibility and miscibility with the microphase separated domains of the host ionomeric membrane. Initial studies of the ionomer - ionic liquid morphology were performed with synchrotron small angle X-ray scattering (SAXS). The effective plasticization of the membranes was identified with dynamic mechanical analysis (DMA) in terms of varied storage modulus and thermal transitions with ionic liquid uptake. Electrical impedance spectroscopy (EIS) was employed to quantify the changes in ionic conductivity for each sBPS ionomer across a range of uptake. Combined results from these techniques implied that the presence of large amounts of ionic liquid swelled the hydrophilic domains of the ionomer and greatly increased the ionic conductivity. Decreases in storage modulus and the glass transition temperature were proportional to one another but of a lesser magnitude than changes in conductivity. The present range of ionic liquid uptake for sBPS was sufficient to identify the critical uptake (f_c) for three of the four ionomers in the series. Future work to construct IPTs with these components will use the critical uptake as a minimum allowable content of ionic liquid to optimize the balance of electrical and mechanical properties for the device components.

Proceedings Article | 6 April 2009 Paper

Forced and free displacement characterization of ionic polymer transducers

Barbar Akle, Andrew Duncan, Etienne Akle, Thomas Wallmersperger, Donald Leo

Proceedings Volume 7287, 72870N (2009) https://doi.org/10.1117/12.815848

KEYWORDS: Transducers, Actuators, Electrodes, Polymers, Temperature metrology, Liquids, Cesium, Lithium, Aluminum, Polymeric actuators

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Ionic polymer transducers (IPT), sometimes referred to as artificial muscles, are known to generate a large bending strain and a moderate stress at low applied voltages (<5V). Recently Akle and Leo[1] reported extensional actuation in ionic polymer transducers. In this study, extensional IPTs are characterized under forced and free displacement boundary condition as a function of transducer architecture. The electrode thickness is varied from 10 μm up to 40 μm while three extensional actuators with Lithium, Cesium, and tetraethylammonium (TEA) mobile cations are characterized. Three fixtures are built in order to characterize the extensional actuation response. The first fixture measures the free displacement of an IPT sample sandwiched between two aluminum plates glued using the electrically conductive silver paste. In the second fixture a spring is compressed against the test sample with variable amounts to generate different levels of pre-stress and prevents the bending of the IPT. In the third fixture dead weights are placed on top of the sample in order to prevent bending. In the spring loaded fixture a thermocouple is placed in the proximity of the actuator and temperature is measured. The different transducers are characterized using a step voltage input and an alternating current (AC) sine wave input. The step input resulted in a logarithmic rise like displacement curve, while the low frequency (<0.1 Hz) AC excitation generated a sine wave displacement response with a strong first harmonic. The high frequency AC excitation generated a response similar to that of the step input. Comparing the measured temperature for step and AC response demonstrated that the sample is heating up when exited with a high frequency signal; which is leading to the expansion of the sample. Initial experimental results demonstrate a strong correlation between electrode architecture and the peak strain response. Strains on the order of 2% are observed with air stable ionic liquid based transducers. A correlation between the strain and charge buildup in the polymer is also characterized. Cesium (Cs) mobile cation outperformed all other tested mobile charges, while Potassium displaced the least. Keywords: Ionic Polymers, Transducer, Actuator, Electroactive Polymer, Extensional Actuator.

Proceedings Article | 10 April 2008 Paper

Optimization of active electrodes for novel ionomer-based ionic polymer transducers

Andrew Duncan, Stephen Sarles, Donald Leo, Timothy Long, Barbar Akle, Matthew Bennett

Proceedings Volume 6927, 69271Q (2008) https://doi.org/10.1117/12.776575

KEYWORDS: Electrodes, Data modeling, Resistance, Particles, Transducers, Circuit switching, Polymers, Liquids, Interfaces, Electromechanical design

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Proceedings Article | 10 April 2008 Paper

A correlation between extensional displacement and architecture of ionic polymer transducers

Barbar Akle, Andrew Duncan, Donald Leo

Proceedings Volume 6927, 69270J (2008) https://doi.org/10.1117/12.776475

KEYWORDS: Transducers, Actuators, Polymers, Electrodes, Liquids, Polymeric actuators, Data modeling, Gold, Aluminum, Electroactive polymers

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Ionic polymer transducers (IPT), sometimes referred to as artificial muscles, are known to generate a large bending strain and a moderate stress at low applied voltages (<5V). Bending actuators have limited engineering applications due to the low forcing capabilities and the need for complicated external devices to convert the bending action into rotating or linear motion desired in most devices. Recently Akle and Leo reported extensional actuation in ionic polymer transducers. In this study, extensional IPTs are characterized as a function of transducer architecture. In this study 2 actuators are built and there extensional displacement response is characterized. The transducers have similar electrodes while the middle membrane in the first is a Nafion / ionic liquid and an aluminum oxide - ionic liquid in the second. The first transducer is characterized for constant current input, voltage step input, and sweep voltage input. The model prediction is in agreement in both shape and magnitude for the constant current experiment. The values of α and β used are within the range of values reported in Akle and Leo. Both experiments and model demonstrate that there is a preferred direction of applying the potential so that the transducer will exhibit large deformations. In step response the model well predicted the negative potential and the early part of the step in the positive potential and failed to predict the displacement after approximately 180s has elapsed. The model well predicted the sweep response, and the observed 1st harmonic in the displacement further confirmed the existence of a quadratic in the charge response. Finally the aluminum oxide based transducer is characterized for a step response and compared to the Nafion based transducer. The second actuator demonstrated electromechanical extensional response faster than that in the Nafion based transducer. The Aluminum oxide based transducer is expected to provide larger forces and hence larger energy density.

Proceedings Article | 10 April 2008 Paper

Plastic Muscles as lightweight, low voltage actuators and sensors

Matthew Bennett, Donald Leo, Andrew Duncan

Proceedings Volume 6927, 69271G (2008) https://doi.org/10.1117/12.776335

KEYWORDS: Transducers, Actuators, Sensors, Liquids, Electrodes, Polymers, Palladium, Capacitance, Platinum, Metals

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