Parallel integration of aligned carbon strings in polymer composite: Dielectrophoretic preparation, finite element simulation, and electrical characterization

We report on dielectrophoretic alignment of carbon black particles into radially arranged string-like assemblies in oligourethane mixtures followed by photopolymerization. Using finite element modelling and optical microscopy we find significant difference in field distributions depending on the substrate beneath aligned films. On glass, the field is concentrated between the electrode tips leading to string-like assemblies between the tips. On oxide covered silicon, the field is distributed along the electrode circumference leading to more distributed fractal assemblies. Using comprehensive dc resistance measurements and ac-impedance spectroscopy we show that the resistance of the strings varies from 120 kΩ to 5 MΩ with a mean of 1.03 MΩ. Strings on oxide covered silicon show significantly higher resistances than the strings on glass. We also demonstrate the effect of aging and an increase in resistance through elongating aligned strings.