In situtime response measurement of the microspheres dispersed in electrorheological fluids

The aggregations of different kinds of microspheres suspended in electrorheological fluids have been observed in situ upon application of time-regulated electric field. It is found that both the initial response time and the chain’s formation time depend on the conductivity of the microspheres. Water free, watered, and metal-coated glass microspheres together with ${\mathrm{SrTiO}}_3$ and Cu microspheres were studied. Among them, the water-free glass particle shows the longest initial response (chain formation) time of 16.7 ms (117.6 ms) under an electric pulse strength $V_{p-p}$ of 2.6 kV, while the metal-coated microsphere has the shortest initial response (chain formation) time of 0.5 ms (25.4 ms). The overall trend is that the higher the microsphere’s conductivity, the shorter the response time and the stronger the particles’ interaction under the same external electric field. Moreover, it is found that the aggregation of the microspheres becomes faster if the applied field strength is increased.