Novel Method Of Flow Monitoring In Micro-Fluidic Devices

The monitoring of flow in small volumes is important for many analytical techniques. This has become particularly important in micro-fluidics where microchips are being developed for diagnostic and other analytical purposes. Presently there are no simple non-invasive methods to monitor flow rate or direction in the nanoliter to picoliter volumes that are common for these devices. Just as it would be difficult or impossible to control microelectronic components without voltage and current measurements, it will be problematic to accurately control fluids on micro-instruments and small volume analytical techniques without flow monitoring and control. Just as electrons are moved and monitored in electronics, likewise, fluids will be moved and monitored in fluidic microdevices.Although many techniques have been developed to accomplish the monitoring & control of fluids in micro-devices, none are on-line or non-invasive and could not be applied in complex systems. They typically suffer from accuracy problems and non-trivial output signals. They are therefore not terribly useful and have not found application outside the academic laboratory.Researchers at Arizona State University have developed a method and a device that overcomes these problems. The method has minimal alignment requirements and excellent sensitivity. It is able to operate in small diameter capillaries, which will enable extremely small volume flows to be monitored accurately and easily. The flow measurement information can be fed back into the flow control system to maintain a stable or constant flow, to stop flow or to reverse flow in a dynamic, real time manner.The device can be used with a variety of small volume techniques where flow needs to be monitored and controlled. These techniques include capillary electrophoresis and related techniques; flow injection analysis, microbore liquid chromatography, among others. This system is ideally suited for application on fluidic microchip devices where the movement of fluids is the fundamental process. Fluids, especially in this application, must be monitored and controlled on a non-invasive basis since the materials must remain unaltered for further processing or analysis. This invention provides a simple and non-invasive method for monitoring flow without significant cost or technical complexity.