Surface acoustic wave (SAW) technology for microfluidic lab-on-chips (LoCs) and biosensors

In the middle of the fourth industry revolution the necessity of intelligent manufacturing and sensors plays an important role and pulls the research activity of these days. In particular, smart objects able to sense, act, and behave within smart environments are suitable tools to make this revolution evolve even further. More efficient devices (in terms of costs, time and results) and data generated at all levels, from industry production processes to people health monitoring, are desirable to improve life quality. This goal would not be achieved without smart lab-on-chips (LoCs) and sensors. Over the last decades surface acoustic wave (SAW) technology has been studied and exploited to realize such smart devices. Main advantages over standard microfluidic fluids manipulators and sensors are the high portability of these devices, their all-electrical readout systems, their fabrication scalability and their application versatility. In this context I developed my Ph.D. research activity, by designing, fabricating, characterizing and testing new SAW-based devices for LoC and sensing applications. I exploited both Rayleigh and Love SAWs for this purpose, exploring different designs and working frequencies and obtaining several encouraging results. With these SAW devices I demonstrated for the first time that it is possible to enhance cells proliferation or gold functionalization kinetics and efficiency. One of the main advantages of these devices is that they are totally integrable with other ones and compatible with standard laboratories protocols. Moving for the first time to ultra-high frequency (UHF), I realized SAW biosensors with lower limit of detection than standard commercial acoustic sensors and higher sensitivity and dynamic range than low-frequency SAW sensors. The devices were tested with benchmark analytes and cells after being characterized in details with microscopes, a laser Doppler vibrometer, a vector network analyzer, an infrared camera and by means of micro-particle image velocimetry. Given these results, the devices here presented are promising in the light of the development of versatile, portable, and sensitive SAW-based devices for more efficient production of functionalized materials and cells, smart diagnostics and monitoring of diseases, food and air quality. They have the potential to contribute to the improvement of daily life in the vision of the internet of things devices, for a smarter and more efficient “future” world.