Smart fluids: Current and future developments

A smart fluid comprises a suspension of micrometre-sized particles in a dielectric carrier liquid. The application of a suitable stimulus – either electrical or magnetic – causes a significant increase in the resistance to flow of the fluid. Current and future developments in smart fluids are reviewed, paying particular attention to electro-rheological (ER) and magneto-rheological (MR) fluids. ER fluids have been the focus of intense academic interest over several decades. However, not until the re-discovery of MR fluids did commercial exploitation finally occur. Both microscopic and macroscopic models of smart fluids will be described. The link with industrial applications is established by introducing the three modes of operation through which smart fluids are harnessed. Insight into the behaviour of smart fluids is obtained through the development of relatively simple quasi-steady and dynamic models. A concise summary of the latest industrial applications is provided. Future trends are then considered under the headings of smart fluid technology, modelling of smart fluids and, finally, engineering devices.