Browsing by Author "Salehin, Sayedus"
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Item Open Access Three-dimensional electrode integration with microwave sensors for precise microparticle detection in microfluidics(IEEE, 2024-05-15) Alataş, Yağmur Ceren; Tefek, Uzay; Küçükoğlu, Berk; Bardakçı, Naz; Salehin, Sayedus; Hanay, M. SelimMicrowave 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.