Mr. Scott T. McGovern Profile

Scott T. McGovern

at Univ of Wollongong

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Author

Publications (4)

Proceedings Article | 10 April 2008 Paper

Fast bender actuators for fish-like aquatic robots

S. McGovern, G. Spinks, B. Xi, G. Alici, V. Truong, G. Wallace

Proceedings Volume 6927, 69271L (2008) https://doi.org/10.1117/12.784977

KEYWORDS: Actuators, Robots, Polymers, Liquids, Robotics, Polymeric actuators, Ferroelectric polymers, Carbonates, Artificial muscles, Control systems

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Small, highly-mobile "swimming" robots are desired for underwater monitoring operations, including pollution detection, video mapping and other tasks. Actuator materials of all types are of interest for any application where space is limited. This constraint certainly applies to the small-scale swimming robot, where multiple small actuators are needed for forward/backward propulsion, steering and diving/surfacing. A number of previous studies have demonstrated propulsion of floating objects using IPMC type polymer actuators [1-3] or piezoceramic actuators [4, 5]. Here, we show how propulsion is also possible using a multi-layer polypyrrole bimorph actuator. The actuator is based on our previously published work showing very fast resonance actuation in polypyrrole bending-type actuators [6]. The bending actuator is a tri-layer structure, in which the gold-PVDF (porous poly(vinylidene fluoride) membrane) substrate was coated on both sides with polypyrrole layers to form an electrochemical cell. Polypyrrole films on gold coated PVDF were grown galvanostatically at a current density of 0.10 mA/cm2 for 12 hours from propylene carbonate (PC) solution containing 0.1 M Li+TFSI-, 0.1 M pyrrole and 1% (w/w) water. The polypyrrole deposited PVDF was thoroughly rinsed with acetone and stored in 0.1 M Li+TFSI- / PC solution. The edges of the bulk film were trimmed off and the bending actuators were prepared as rectangular strips typically 2mm wide and 25 mm long. These actuators gave fast operation in air (to 90 Hz), and were utilised as active flexural joints on the tail fin of a fishshaped floating "boat". The actuators were attached to a simple truncated shaped fin and the deflection angle was analysed in both air and liquid for excitation with +/- 1V square wave at a range of frequencies. The mechanical resonance of the fin was seen to be 4.5 Hz in air and 0.45 Hz in PC, which gave deflection angles of approximately 60° and 55° respectively. The boat contained a battery, receiver unit and electronic circuit attached to the actuator fin assembly. Thus, the boat could be operated by remote control, and by varying the frequency and duty cycle applied to the actuator, the speed and direction of the boat could be controlled. The boat had a turning circle as small as 15 cm in radius and a maximum speed of 2m/min when operating with a tail frequency of approximately 0.7 Hz. The efficiency of the flapping tail fin was analysed and it was seen that operation at this frequency corresponded with a Strouhal number in the optimal range.

Proceedings Article | 5 April 2007 Paper

Tri-layer conducting polymer actuators with variable dimensions

Rick Minato, Gürsel Alici, Scott McGovern, Geoffrey Spinks

Proceedings Volume 6524, 65241J (2007) https://doi.org/10.1117/12.715456

KEYWORDS: Actuators, Polymers, Polymeric actuators, Electrodes, Ferroelectric polymers, Ions, Mathematical modeling, Data modeling, Thermal modeling, Finite element methods

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Proceedings Article | 9 May 2005 Paper

The use of embedded sensors for the monitoring of adhesive joints in marine environments

Scott McGovern, Geoffrey Spinks, Gordon Wallace

Proceedings Volume 5770, (2005) https://doi.org/10.1117/12.599515

KEYWORDS: Sensors, Adhesives, Resistance, Humidity, Polymers, Water, Calibration, Electrodes, Coating, Polymeric sensors

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A copolymer incorporating polyaniline was used as a sensing medium in the construction of a resistance based humidity sensor. Aniline monomer was polymerised in the presence of poly (butyl acrylate / vinyl acetate) and a copolymer containing polyaniline emeraldine salt was obtained. The sensing medium was then developed by redissolving 1-2 w/w% of the resulting polymer residue in dichloromethane to produce a processable polymer blend solution. Some of this polymer residue was also de-doped in a solution of ammonia, and then washed with distilled water until the waste water had a neutral pH. This residue was then redissolved at 1-2 w/w% in dichloromethane to produce a second processable polymer blend this time containing polyaniline emeraldine base. The final sensor design utilised 125μm polyester insulated platinum wire as conducting electrodes that were dip coated in the emeraldine salt copolymer solution and allowed to dry in a desiccator. The sensor was then dip-coated in a protective barrier layer of the emeraldine base copolymer to prevent over-oxidation and/or de-protonation of the emeraldine salt sensing medium under this coating. The sensors had an overall final thickness of less than 150μm and showed high sensitivity to humidity, low resistance, and good reversibility without hysteresis. Sensors were monitored for 2-probe resistance changes when in contact with water. Calibration curves for each sensor were produced to convert the resistance reading to mass uptake of water. Individual sensors were embedded within Aluminium 5083 / Araldite 2015 adhesive joints to monitor mass uptake of water when exposed to marine environments. Correlations between mass uptake of water and joint strength were made. There are various advantages of such a sensor design. Polymer based thin film humidity sensors have the advantage that the high processability of the material allows for simple fabrication of a range of geometries including smaller sensor designs. The ease of processing gives a low cost sensor, whilst the small size and good mechanical properties gives a robust sensor which has the flexibility to be able to be used in applications where dynamic stresses and strains are encountered. Such sensors may find uses in a number of areas including electronic textiles, food/ electronics packaging and corrosion detection.

Proceedings Article | 28 February 2005 Paper

Highly processable method for the construction of miniature conducting polymer moisture sensors

Scott McGovern, Geoffrey Spinks, Gordon Wallace

Proceedings Volume 5649, (2005) https://doi.org/10.1117/12.582241

KEYWORDS: Sensors, Polymers, Resistance, Humidity, Polymeric sensors, Coating, Epoxies, Electrodes, Calibration, Platinum

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