Flexible free-standing SU-8 microfluidic impedance spectroscopy sensor for 3-D molded interconnect devices application

The current contribution reports about the fabrication technology for the development of novel microfluidic impedance spectroscopy sensors that are directly attachable on 3-D molded interconnect devices (3D-MID) that provides an opportunity to create reduced-scale sensor devices for 3-D applications. Advantages of the MID technology in particular for an automotive industry application were recently discussed (Moser and Krause, 2006). An ability to integrate electrical and fluidic parts into the 3D-MID platform brings a sensor device to a new level of the miniaturization. The demonstrated sensor is made of a flexible polymer material featuring a system of electrodes that are structured on and embedded in the SU-8 polymer. The sensor chips can be directly soldered on the MID due to the electroless plated contact pads. A flip chip process based on the opposite electrode design and the implementation of all fluidic and electrical connections at one side of the sensors can be used to assemble the sensor to a three-dimensional substrate. The developed microfluidic sensor demonstrated a predictable impedance spectrum behavior and a sufficient sensitivity to the concentration of ethanol in deionized water. To the best of our knowledge, there is no report regarding such sensor fabrication technology.