Control of fluid flows by micro transducers

Emerging micromachining technology enables us to fabricate micron size mechanical parts which provide us with sensors and actuators with very small time constants and fine spatial resolution. Furthermore, these miniature transducers can be integrated with microelectronics to form a system which will be able to carry out sensing, information processing and actuation. This type of system enables us to perform real-time control of time varying events which are common in fluid dynamics. For example, the flow structures responsible for viscous shear stress increase in wall-bounded shear flow are very small in size, typically several hundred microns in width and several mm in length. Their life time is short, in the millisecond range or less. Great difficulties arise by the fact that they are randomly distributed in time and space. In the past, direct manipulation of these structures was very difficult because the traditional transducers are typically one order of magnitude larger than the structures. The miniature size of the micro transducers and the real-time information process capability of the micro system make this task possible, though still very challenging.