Electromagnetic Excitation Wireless Acoustic QCM Sensor

QCM, short for quartz crystal microbalance, is a high precision acoustic sensor that turns tiny surface mass change into resonant frequency change using quartz crystal as transducer. With advantages such as high precision, simple structure and low price, it is very popular among researchers. The crystal is driven by electromagnetic field and so is the decay signal received wirelessly. With efforts on theoretical analysis, detection device and experimental method, we can detect pH and glucose concentration using polymer as the sensitive film.A wireless liquid detection system was build based on homemade liquid micro-cavity and ferromagnetic coil and the detection system was proved to be useful both in gas environment and liquid environment. The detection of pH was achieved combing a hydroxylethyl methacrylate co methacrylic acid poly on the surface of the crystal by UV light polymerization. As the pH of the liquid in contact with QCM sensor increases, the poly film swells resulting in the decrease of the resonant frequency and the increase of dissipation factor. The more the poly film swells, the more the output characters change. The response curve was s-shaped and the most sensitive response was achieved with the buffer pH in the range from5.0to6.0. With the sensitive as high as669Hz/pH, we can achieve mpH accuracy. A acrylamide co3-acrylamidophenylbonic acid film was polymerized on the surface of a quartz crystal. The swelling and shrinking of the polymer film caused by the binding between glucose and phenylboronate changes resonant frequency and dissipation factor. The response is linear in the range0-20mM both for resonant frequency and dissipation factor. The response is almost identical under the influence of different flow rate conditions.