Low-cost microfluidic device micromachining and sequential integration with SAW sensor intended for biomedical applications

The paper reports on fabrication processes related to low-cost manufacturing and integration of microfluidic biomedical detection systems fabricated without a cleanroom. First, we developed and demonstrated a process for manufacturing a microfluidic device. Second, we demonstrated a low temperature assembly technique for the packaging of the surface acoustic wave (SAW) sensor die. Sequentially, we demonstrated a low temperature process for the integration of the microfluidic device with a SAW sensor to form a fully functional biomedical detection system. The microfluidic device was manufactured by mechanical micromilling technology that is rapid, conceptually simple and a low-cost process. It is suitable for both prototyping and for a low and a medium scale production to address a niche market that is typical for the intended application. That technology has no specific requirement for a certified clean room environment. Unlikely other technology, such as molding and photolithography, for example, it has a shorter lead-time from design to manufacturing. The assembly technique for a SAW sensor is a carefully selected combination of known and matured processing steps causing no damage to a sensitive biofunctionalization on the sensor. The developed and demonstrated integration process for the in-house manufactured microfluidic device and the SAW sensor is a purely low temperature process that prevents a biological material deposited on the SAW sensor from degradation. Biocompatibility issues were also addressed during the study reported. Finally, we performed an ultrasonic (US) impedance characterization of the fully assembled system and demonstrated that neither the microfluidic system integrated on the sensor nor the integration process itself have an impact on the US impedance of the SAW sensor. That means that it does not affect the sensor performance.