Development of an acousto-electric biochemical sensor (AEBS) for monitoring biological and chemical processes

Demands exist for rapid, sensitive, selective and portable biosensors for monitoring a variety of biochemical and biological processes in medicine, pharmaceutical, health care and a variety of environmental conditions. Attractive and promising solutions to these needs are emerging as concepts of a low cost and easy to use analytical system such as a BioChemLab-on-Chip (Biochip). These types of devices represent a large-scale integration of various biological, mechanical, and electrical functionalized components and require the integration of several transducers with different sensing interfaces, and sample delivery systems. In addition it is envisioned that integrated signal processing and control functions are to be implemented on the same substrate. The major challenges in making these devices are mostly related to the development of novel fabrication processes that need to combine complex bio-opto-mechanical electronic working environments. This thesis is focused on the development and testing of processes and performance of a "Biochip" based on piezoelectric thickness shear mode (TSM) sensing technology.;The device consists of an array of acousto-electronic (i.e., piezoelectric) sensors fabricated on a quartz wafer or substrate, which is applicable for piezoelectric modalities. A micro-fluidic line is constructed on the same substrate to deliver the measurands onto the electrodes of the arrays of sensors operating at one or different frequencies. Three different processes [Wet-Photolithography-Deposition (WPD) - Plasma WPD (PWPD) and Implant PWPD (IPWPD)], to fabricate this multi-frequency biochip are detailed. The biochip design layout allows someone to perform studies on how to improve the design rules and enhance performance while streamlining fabrication steps of devices in the future. The multi-sensor device is applicable to both gaseous and liquid phase measurements of chemical samples. We demonstrate the application of this device to measure different measurands and interfacial processes simultaneously under a broad range of experimental conditions and how it be used in new applications, new market, and accurately monitor interfacial properties with higher temporal and spatial resolution. Experimental studies have shown several interesting features of piezo-arrays, for example, by decreasing their electrode diameter by 25%, the frequency shift from air to Di water increases by 47%. A new design structure based on placing small electrodes in form of clusters and connecting them together in parallel is developed to improve the amplitude, as well as increase the sensitivity and dynamic range of the AEBS (Acousto-Electric Biochemical Sensor). Moreover, new design procedures that allow further decrease of the biochip are demonstrated for the first time. The obtained results provide a foundation for the development of a fully integrated piezo-biochip.