The integration of multiple measurement modalities into a single chip or chip-based package would enable accurate, multi-parameter data to be obtained on a wide variety of complex fluids. The choice of sensors, and the ability to integrate such sensors with stable and controllable flow and temperature, can depend on the details of the specific fluid system under investigation.
Eventually, many kinds of microfluidic sensors will be embedded in the same sorts of compact and robust packages for deployment by users. To encourage comparisons of measurements between devices by different manufacturers, and to enable interoperability of components, NIST is creating prototypes for a common microfluidic platform.
The platform will accommodate a variety of sensors as well as providing a dimensional model for sensor designers and fabricators to use so that their devices will be able to work with successive iterations of the common platform. A common platform will also be essential in order to test the reliability, interchangeability, and long-term stability of sensors.
Our initial version of an integrated platform for optical and electrical microfluidics (Poem-1) is realized with a microfluidic chip bonded to a printed-circuit board, and contains 4 fluidic input-outputs, 4 high-frequency (40 GHz) electronic input-outputs, and optical microscope access. It features integrated thermal control and integrated direct-current leads for additional measurements. The platform is intended to be used in order to quantify sensitive dielectric measurements of fluids, based on microwave interferometry, for studying protein and DNA interactions as a function of temperature. Quantifying stability and accuracy of the dielectric measurements, and correlating dielectric results with optical observations, are goals for the first implementation of packaged, high-frequency devices.
NIST scientists are also active in efforts to standardize the fluidic, electrical, and optical interfaces between the microfluidic devices and the macroscale. With standardized connections, one can foresee chip-scale modules that measure individual physical parameters (flow, density, viscosity, pressure, etc.) that can be plugged in to each other in various combinations to address different applications.