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

TL;DR

This study integrates microwave and optical sensing in microfluidic devices to differentiate and track single cells and microparticles based on dielectric properties, offering a new approach for biophysical analysis.

Contribution

The paper introduces combined microwave and optical sensors with novel design for single-cell dielectric characterization and size tracking in microfluidic channels.

Findings

Microwave sensors achieved high signal-to-noise ratios (~100 for CPW, ~70 for SRR) in detecting 20-micron particles.

Microwave sensing can differentiate cells based on dielectric properties.

Standalone microwave sensors can monitor cellular size changes in real-time.

Abstract

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.