Research On Microfluidic Biological Detection Technology Based On Surface Acoustic Wave Device

Surface acoustic wave (SAW) biosensors, possessing the advantages of simple structure, high sensitivity, label-free, real-time measurements, hold great potential in the application of clinical early diagnosis. Currently, there are some drawbacks which limit the application of SAW biosensors. One of the limitations is the lack of a rapid, sensitive and stable detection platform. In this paper, a complete SAW biosensor detection experimental platform was built, taking advantage of microfluidic detection technology and SAW devices.Combined with the relevant literatures, we reviewed the Love wave theory, including the frequency dispersion theory, sensing principle and temperature effect. According to these theories, there are some key factors in the design of the device, including the substrate material, waveguide material and interdigital transducer (IDT) parameters. After careful consideration, SAW devices were designed with the following parts:LiTaO3 substrate with SiO2 film as wave guide layer, two set of IDTs, gold film for biorecogniton modification. Then, the device was fabricated by using micro-nano manufacture technology. In order to realize real-time detection, we designed an oscillation detection circuit and direct digital frequency synthesis (DDS) sweeping frequency detection circuit. Both of the circuits were investigated to test their validity. Furthermore, a point frequency excitating phase detection circuit was designed based on the DDS detection circuit. A polydimethylsiloxane (PDMS) microfluidic chip was designed and manufactured to achieve trace, quantitative and reliable sample injection. Before the biosensing experiments, the insertion loss and frequency temperature sensitivity of devices were interrogated by varying the thickness of SiO2 waveguide layer. It is demonstrated that the results were consistent with this theory. At the end, with biological modification method, two label-free and selective aptamer beacon based Love-wave biosensing devices were developed for prostate specific antigen (PSA) and Carcinoembryonic Antigen (CEA) detection, and tested by oscillation and phase detection circuit, respectively. The established system showed good performance for PSA and CEA detection between 10 ng/mL to 1 μg/mL, with a low detection limit of 10 ng/mL, which verified the correctness of the design of SAW biological sensing and testing platform.