Fabrication and Optimization of Magnetomotive Gravimetric MEMs Sensors

• Author / Creator

  Cherkawski, Breanna D

• Reducing device size in sensing technology allows for greater measurable responses, and easier integration into smaller testing environments. This work details the fabrication of high sensitivity magnetomotive gravimetric MEMS cantilevers for eventual use in gas detection. The devices are doubly clamped
  beams, and “U”-shaped variations of singly clamped resonant beams. When placed in a magnetic field, the current flowing through the devices generates a Lorentz force, driving the cantilevers into resonance. As analyte adsorbs to the surface of the device, the added mass will lead to a detectable shift in resonant frequency. Higher quality factor devices can be scaled down to the sub-micron scale. The dimension of the cantilever determines the resonant frequency, and cantilevers have been fabricated that range from 2.5 μm to 6.5 μm in length, but only 500 nm wide, and 174 nm thick. As size of the sensor decreases, the greater the effect adsorbed mass will have on the resonant frequency. Optimization of the fabrication process flow led to a substantial increase in yield of
  functional devices. Developments in vapour-phase HF etching to remove the sacrificial layer of the devices has eliminated stiction and also increased the yield. First measurements of these devices have shown resonant frequencies in expected ranges, agreeing reasonably well with mathematical modelling of both shapes of cantilever devices. This work also serves to prove the efficacy of the low-cost easy-to-use magnetomotive apparatus and balancing circuit developed by the Engineered Nanomaterials Laboratory. The configuration of these sensors, and ease of fabrication open the possibility for further functionalization by other groups by using the low-cost apparatus demonstrated in this work.

• Subjects / Keywords

  • MEMs
  • Gravimetric
  • Magnetomotive
  • Microfabrication
  • Sensors

• Graduation date

  Fall 2024

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-2eg4-0268

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.