Definitive rheology studies under electrical stimulation
How do your materials change when exposed to electric charge?
The ARES-G2 and ARES-G3 rheometer’s electrorheology (ER) accessory provides the ability to investigate the novel rheology of materials in response to external electrical stimuli. The accessory can apply up to 4,000 volts during the course of an experiment and is compatible with both parallel plate and concentric cylinder geometries. The test voltage is applied to the sample via a Trek Amplifier through a high voltage cable – both AC and DC voltage profiles are supported. A specially designed insulator block between the transducer hub and the upper geometry isolates the applied voltage from the ARES-G2 rheometer’s electrical circuits. Even at high electric field, operator safety is of utmost concern, with specifically designed ARES-G2 and ARES-G3 rheometer protective polycarbonate shields with interlock triggers to protect from electrical shocks. Upon removal of the shield, the electric field is immediately turned off.
Features and Benefits
- Compatible with Advanced Peltier System (APS) over a temperature range from -10 °C to 150 °C
- Choice of 25 mm and 50 mm stainless steel parallel plates and 28 mm diameter concentric cylinder geometries
- Wide voltage range: 4000 VDC, 400 VAC (8000 V peak-to-peak)
- Fully programmable from TRIOS software
- Integrated with interlock triggers for safe operation
Step Voltage on Starch Suspension under Steady Shear
A 10% starch solution in silicone oil demonstrates dramatic and reversible changes in structure under the application of high voltage. The figure shows time-dependent viscosity with varying DC voltage, from 500 to 4000 V, applied for 100 s. The underlying rheological test is a constant rate at 1 s-1, which minimizes the disturbance to the structuring process. When an electrical field is applied, polarization of the starch particles in the non-conducting silicone oil leads to stringing of the starch particles, which align between the electrode plates. This orientation is responsible for the strong viscosity increase.
The time to align the particles depends on the viscosity of the suspending fluid and the strength of the electrical field. Because under the applied shear rate, deformation of the structuring process is not completely eliminated, a maximum viscosity is observed when the dynamic equilibrium between forming and breaking of strings of aligned particles is achieved.
