Microwave dielectric sensing of free-flowing, single, living cells in aqueous suspension

Clare Watts, Stephen Hanham, James Armstrong, Munir Ahmad, Molly Stevens, Norbert Klein

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
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Dielectric measurements offer the possibility of highly sensitive detection of physical cell properties, and are of interest for clinical applications due to their non-destructive nature and the lack of need for cell labelling. Here we report sensitive measurements on single, living, free-flowing cells (not electrostatically or dielectrophoretically trapped, cultured or fixed directly on sensing elements) in aqueous medium at ~9.8 GHz taken using a coupled dielectric-split ring resonator assembly. Inductive coupling between the two resonators enabled separation of microfluidic chips from RF connectors and allowed for time-resolved continuous-wave measurements on flowing single cells via the coaxial ports of a dielectric-loaded microwave cavity. Analysis via an equivalent circuit model showed that the novel resonator assembly maintained the permittivity-dependent sensitivity of a split ring resonator while operating at quality factors >1000 with lossy aqueous media (typically ~1900). Using a microfluidic channel with a 300 x 300 μm cross section, at a water-loaded resonant amplitude of ~-22 dB at 0 dBm input power level, shifts in amplitude due to individual cells passing through the sensing region of up to -0.0015 dB were observed. Correlations between averaged amplitude shifts and cell size as well as material properties demonstrate the diagnostic potential of this technique.


  • Biological cells
  • biosensors
  • Cells (biology)
  • dielectric
  • Dielectric measurement
  • Dielectrics
  • microfluidics
  • Microwave measurement
  • microwave sensors
  • Microwave theory and techniques
  • permittivity
  • resonators
  • Sensitivity
  • Sensors

ASJC Scopus subject areas

  • Radiation
  • Radiology Nuclear Medicine and imaging
  • Instrumentation


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