Microwaving Blood as a Non‐Destructive Technique for Haemoglobin Measurements on Microlitre Samples

Abstract

The non-destructive ex vivo determination of haemoglobin (Hgb) concentration offers the capability to conduct multiple red blood cell haematological measurements on a single sample, an advantage that current optical techniques are unable to offer. Here, a microwave method and device for the accurate and non-destructive determination of Hgb concentration in microlitre blood samples are described. Using broadband microwave spectroscopy, a relationship is established between the dielectric properties of murine blood and Hgb concentration that is utilized to create a technique for the determination of Hgb concentration. Subsequently, a microwave dielectric resonator-microfluidic system is implemented in the analysis of 52 murine samples with microlitre volumes and Hgb concentrations ranging from 0 to 17 g dL(-1) . Using the characterized relationship, independent and minimally invasive Hgb measurements are made on nine healthy mice as well as seven with mutations in the Adenomatous polyposis coli (APC) gene that leads to colorectal cancer and consequently anaemia.

Non-invasive assessment of leaf water status using a dual-mode microwave resonator

“…As a possible explanation for the enhanced loss tangent measured at 2.4 GHz, it is likely that higher dielectric relaxation losses than assumed for free water may occur due to a high abundance of surface water, which has a significantly higher loss tangent than bulk water at 2.4 GHz [ 25 , 26 ]. The observed slight increase of IQS / FRS at 2.4 GHz with increasing weight loss is likely due to an increase of the ratio of surface to bulk water as result of faster evaporation of bulk water.…”

Microwave-to-terahertz dielectric resonators for liquid sensing in microfluidic systems

“…Fig. 1 from our previous work [4] shows a whispering gallery mode resonator of low azimuthal index (6) embedded in a semi-open metal shielded cavity. The liquid under test flows through a linear channel which intersects the field maxima of the WG resonance in the ceramic dielectric disc placed underneath the plastic microfluidic chip.…”

“…The microwave-to-terahertz range is quite unique for this purpose because of fundamental physical facts: the cell membrane relaxation at MHz frequencies makes a cell quite transparent for frequencies above 1 -5 GHz, which enables the determination of the average complex permittivity within an effective medium approach [4]. At the same time, the wavelength is still large in comparison to the cell size of 1-30 microns, which diminishes scattering effects and enables absorption measurements.…”

Micro- and millimetre wave measurements of nanolitre biological liquids by dielectric resonators

“…In Ref. 3 we describe a ceramic DR of permittivity 28, excited in a low-order WGM of n=6 @10 GHz, the Q was about 10,000. The FOM value of this cavity comes out to be 0.037, still high enough for measurements on sample volumes of less than one microlitre, which is ideal for blood diagnostics.…”