A micromachined fluidic structure for capillary-based sample introduction into a microbead array chemical sensor

The development of a micromachined fluidic structure for the introduction of liquid samples into a chip-based sensor composed of an array of polymeric microbeads is presented. The micromachined structure consists of micromachined storage cavities combined with a covering glass layer that confines the microbeads and fluidic channels. In our sensor array, transduction occurs via optical changes to receptors or/ and indicator molecules that are attached to the polymeric microbeads. Hence, the confining structures must also allow optical access to the microbeads. The fabrication process has been selected to protect receptors or/and indicator molecules that may be sensitive to the normal processes used in chip fabrication. One of the key parts of the structure is a passive fluid introduction system driven only by capillary force. This simple means of fluid introduction realizes a compact device. The capillary flow on the inlet channel has been studied, and the responses of the microbeads to the liquid sample have been characterized. The test results show that this system may be useful in a micro-total-analysis-system (μ-TAS) and biomedical applications.