Lateral mode resonators for in liquid biosensing applications with a second harmonic based read out method

Aydın, Eren
This thesis presents design and implementation of lateral mode electrostatic resonators for in liquid biosensing applications and a novel read-out approach for eliminating parasitic feedthrough current and enhance Q of the resonating system at the same time. The main objective of this thesis is to make resonators operating under when the microchannel is filled with liquid. Liquid injection inside the microchannel of resonators brings lots of mechanical and electrical problems together. These problems are categorized as damping and feedthrough current. In the scope of this thesis, new resonators are designed suitable for operation under liquid flow optimizing their damping. Calculations show that all types of the designed resonators have Q higher than 45 on liquid. The designed devices are fabricated using silicon-glass anodic bonding process and coated with 500 nm parylene layer. One type of the tested devices without parylene coating has 590 Q and 330 kHz resonance frequency in air and after parylene coating Q has decreased to 93 and resonance frequency increased to 407 kHz. After liquid injection inside the microchannel Q of the resonator has vi decreased to 54 and the resonance frequency of the resonator has increased to 480 kHz. This is the first time illustration of resonance of a lateral mode electrostatic resonator on liquid without postprocessing. Moreover a new resonance characterization method based on sensing second harmonic component of the resonators is developed. Utilizing this method, feedthrough current is eliminated and resonance peak was increased from 1 dB to 35 dB. Moreover it is shown that this method is suitable for eliminating both capacitive and resistive feedthrough current without using complex resonator design and circuitry. Furthermore this method also improves Q of the resonating system 66%. 
Citation Formats
E. Aydın, “Lateral mode resonators for in liquid biosensing applications with a second harmonic based read out method,” M.S. - Master of Science, Middle East Technical University, 2017.