arXiv subjects

Uzay Tefek

Publications and source records attributed to Uzay Tefek.

5 recordsLinked to original sources

arXiv2025

Microwave Cytometry with Machine Learning for Shape-Resolved Microplastic Detection

Microplastics are increasingly recognized as a global environmental health threat, yet their detection and characterization remain constrained by the cost, form factor, and throughput of existing analytical tools. Portable micro/nanotechnology-based sensors are emerging to address this need, but most rely on the assumption of spherical particle geometry in their operating principle, limiting their relevance for environmental analysis. Here, we overcome this limitation by advancing microwave cytometry with machine learning-enabled shape recognition. Microwave cytometry is a flow-through electronic platform that integrates microwave resonator responses with low-frequency impedance signals to capture the dielectric signatures of individual particles. Using microscopy-derived shape measurements as ground truth, we trained a random forest model to decode these information-rich waveforms. Once trained, the system operates without optical input, enabling electronic-only determination of particle geometry. We demonstrate extraction of the major and minor axes of ellipsoidal microparticles with <8% relative error on average and use these predictions to derive the dielectric permittivity of ellipsoid particles. This approach removes long-standing shape assumptions in microplastic sensing and establishes a pathway toward portable, high-throughput, morphology-aware detection technologies.

physics.app-ph↗

arXiv2024

Rapid Differentiation between Microplastic Particles Using Integrated Microwave Cytometry with 3D Electrodes

Rapid identification of microparticles in liquid is an important problem in environmental and biomedical applications such as for microplastic detection in water sources and physiological fluids. Existing spectro-scopic techniques are usually slow and not compatible with flow-through systems. Here we analyze single microparticles in the 14 - 20 micrometer range using a combination of two electronic sensors in the same microfluidic system: a microwave capacitive sensor and a resistive pulse sensor. Together, this integrated sen-sor system yields the effective electrical permittivity of the analyte particles. To simplify data analysis, 3D electrode arrangements were used instead of planar electrodes, so that the generated signal is unaffected by the height of the particle in the microfluidic channel. With this platform, we were able to distinguish between polystyrene (PS) and polyethylene (PE) microparticles. We showcase the sensitivity and speed of this tech-nique and discuss the implications for the future application of microwave cytometry technology in the en-vironmental and biomedical fields.

physics.app-ph↗

arXiv2024

Three-Dimensional Electrode Integration with Microwave Sensors for Precise Microparticle Detection in Microfluidics

Microwave sensors integrated with microfluidic platforms can provide the size and permittivity of single cells and microparticles. Amongst the microwave sensor topologies, the planar arrangement of electrodes is a popular choice owing to the ease of fabrication. Unfortunately, planar electrodes generate a non-uniform 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 three-dimensional (3D) electrodes at the coplanar sensing region of an underlying microwave resonator. The 3D electrodes are based on SU8 polymer which is then metallized by sputter coating. With this system, we readily characterized a mixture composed of 12 um and 20 um 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. The current 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.

physics.app-ph↗

arXiv2023

Dielectric Detection of Single Nanoparticles Using a Microwave Resonator Integrated with a Nanopore

The characterization of individual nanoparticles in a liquid constitutes a critical challenge for environmental, material, and biological sciences. To detect nanoparticles, electronic approaches are especially desirable owing to their compactness and lower costs. Indeed, for single-molecule and single-nanoparticle detection, resistive pulse sensing has advanced significantly during the last two decades. While resistive pulse sensing was widely used to obtain the geometric size information, impedimetric measurements to obtain dielectric signatures of nanoparticles have scarcely been reported. To explore this orthogonal sensing modality, we developed an impedimetric sensor based on a microwave resonator with a nanoscale sensing gap surrounding a nanopore. The approach of single nanoparticles near the sensing region and their translocation through the nanopore induced sudden changes in the impedance of the structure. The impedance changes in turn were picked up by the phase response of the microwave resonator. We worked with 100 nm and 50 nm polystyrene nanoparticles to observe single-particle events. Our current implementation was limited by the non-uniform electric field at the sensing region. The work provides a complementary sensing modality for nanoparticle characterization where the dielectric response, rather than the ionic current, determines the signal.

physics.app-ph↗

arXiv2023

High Resolution Dielectric Characterization of Single Cells and Microparticles Using Integrated Microfluidic Microwave Sensors

Microwave sensors can probe intrinsic material properties of analytes in a microfluidic channel at physiologically relevant ion concentrations. While microwave sensors have been used to detect single cells and microparticles in earlier studies, the synergistic use and comparative analysis of microwave sensors with optical microscopy for material classification and size tracking applications have been scarcely investigated so far. Here we combined microwave and optical sensing to differentiate microscale objects based on their dielectric properties. We designed and fabricated two types of planar sensor: a Coplanar Waveguide Resonator (CPW) and a Split-Ring Resonator (SRR). Both sensors possessed sensing electrodes with a narrow gap to detect single cells passing through a microfluidic channel integrated on the same chip. We also show that standalone microwave sensors can track the relative changes in cellular size in real-time. In sensing single 20-micron diameter polystyrene particles, Signal-to-Noise ratio values of approximately 100 for CPW and 70 for SRR sensors were obtained. These findings demonstrate that microwave sensing technology can serve as a complementary technique for single-cell biophysical experiments and microscale pollutant screening.

cond-mat.soft↗