Alataş, Yağmur CerenTefek, UzayKüçükoğlu, BerkBardakçı, NazSalehin, SayedusHanay, M. Selim2025-02-202025-02-202024-06-151530-437Xhttps://hdl.handle.net/11693/116482Microwave sensors integrated with microfluidic platforms can provide the size and permittivity of single cells and microparticles. Among the microwave sensor topologies, the planar arrangement of electrodes is a popular choice owing to the ease of fabrication. Unfortunately, planar electrodes generate a nonuniform electric field, which causes the responsivity of the sensor to depend on the vertical position of a microparticle in the microfluidic channel. To overcome this problem, we fabricated 3-D electrodes at the coplanar sensing region of an underlying microwave resonator. The 3-D electrodes are based on SU8 polymer, which is then metallized by sputter coating. With this system, we readily characterized a mixture composed of 12- and 20 $\mu \text{m}$ polystyrene particles and demonstrated separation without any position-related calibration. The ratio of the electronic response of the two particle types is approximately equal to the ratio of the particle volumes, which indicates the generation of a uniform electric field at the sensing region. This work obviates the need for using multiple coplanar electrodes and extensive processing of the data for the calibration of particle height in a microfluidic channel: as such, it enables the fabrication of more sophisticated microwave resonators for environmental and biological applications.EnglishCC BY-NC-ND (Attribution-NonCommercial-NoDerivs 4.0 International)https://creativecommons.org/licenses/by-nc-nd/4.0/deed.enCapacitive sensorsImpedance spectroscopyMicrofluidicsMicroparticle sensingMicrowave devicesArticle10.1109/JSEN.2024.33849841558-1748