Integrated Sampling Device for Microfluidic Bioanalysis Systems

Application of silicon microfabrication technology to biodiagnostic consumables offers the potential advantages of sub-microliter sample size, immediate test results, and lower cost. Such microelectromechanical systems (MEMS) are limited in achieving their full potential by the present manual methods of drawing a blood sample and using only a small aliquot for the analytical procedure. Our goal is development of a sampling device integrated into the MEMS system which is much less invasive than a finger stick or veinous puncture, draws only the volume needed for the automated analysis, and eliminates the biohazard of disposal of excess blood. During Phase I, MEMS devices having a cuvette with vent and integrated needle will be fabricated and tested. Emphasis will be placed on optimizing the dimensions of the needle, and on surface treatments to improve penetration of the skin, prevent blood clotting, improve wettability, and promote flow. This integrated sampling technique is applicable to complex MEMS systems capable of multi-analyte analyses and assays requiring a complicated series of steps. A MEMS glucose assay system is presented in detail to illustrate that even a relatively simple single cuvette consumable has near-term promise as a commercial product. Design considerations are discussed in sufficient depth to show how this system can be extended to many analytes other than glucose. Biodiagnostic MEMS devices with integrated sampling will reduce the cost, hazards, and inconvenience of blood testing, and bring the benefits of less pain and tissue damage afforded by this minimally invasive technology. Home glucose assays, and testing for exposure to nerve gases, are potential commercial and military applications.