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Title: Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ∼4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ∼5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.
Authors:
; ;  [1] ;  [2] ; ;  [3] ;  [2]
  1. Department of Materials, Imperial College London, SW7 2AZ London (United Kingdom)
  2. (United Kingdom)
  3. Centre for Terahertz Science and Engineering, Imperial College London, SW7 2AZ London (United Kingdom)
Publication Date:
OSTI Identifier:
22486349
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 3; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BLOOD CELLS; CRYSTALS; DIELECTRIC MATERIALS; DISTURBANCES; ELECTRIC FIELDS; ELECTROMAGNETIC FIELDS; ETHANOL; EXPLOSIVES; GHZ RANGE; LIQUIDS; LOSSES; MONITORING; PERMITTIVITY; RESONATORS; SILICON; SIMULATION; SLABS; SUSPENSIONS; TOXICITY; TUBES