'Middle East Technical University, Faculty of Architecture'
Abstract
This thesis reports development of a parylene bonding based fabrication method for MEMS gravimetric resonant based mass sensors that are integrated with microfluidics for real-time detection when there is a liquid flow through the microfluidic channels. Parylene bonding has been optimized by conducting several bare bonding experiments. The optimized bonding takes place at 250ºC, in vacuum (1 mTorr) and with 2000 N of vertical piston force for 1 hour. The average shear bonding strength is 15.58 MPa for the optimized bonding recipe. Based on the optimized recipe, a novel method for fabricating lateral gravimetric resonators located on top of a microfluidic channel has been proposed. A previous resonator design has been selected as benchmark, and has been fabricated using the method. The measurements show close agreement with the analytical and FEM results, proving the applicability of the fabrication method. The mass sensitivity of one of the fabricated resonators has been calculated as 5.89 pg/Hz. Attachment of a µ-bead has caused a shift of 150 Hz in the resonance frequency. The mass of the attached µ-bead has been measured as 883.5 pg. Liquid flow tests has shown that there is no liquid leakage neither around the bonding interface nor through the resonator gaps. However, the liquid inside the microfluidic channel has introduced additional feedthrough suppressing the sensing current of the sensor. The resonance characteristics when there is liquid inside the channel could not be extracted by using the differential characterization technique. The models and experimental results prove the potential of the proposed fabrication method for fabricating gravimetric resonant based mass sensors and low temperature integration with microfluidics. M.S. - Master of Scienc
