Dielectric Models of Blood-Glucose Solutions: A Systematic Literature Review

The characterization of dielectric properties of blood-glucose (or similar) solutions is a tricky and critical element in the design, simulation, evaluation, and prototyping of microwave sensors for non-invasive glucose monitoring. Unfortunately, the extensive literature on dielectric properties of biological tissues-blood-glucose solutions in particular-is sometimes contradictory. The use of different materials, different frequency ranges, different glucose ranges, ad hoc assumptions, simplifications not always justified, different measurement techniques, different tissue models, different fitting algorithms often lead to divergent results and conclusions. This is confusing for those who do bibliographic research on the subject and are looking for experimental data to use in their projects and simulations. Therefore, we systematically reviewed, organized and presented the main knowledge available in the literature about blood-glucose models, to help researchers by providing them relevant information in one place. The systematic review of literature is conducted by applying the well-known and proven Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol, a trustworthy method for establishing the published state of the art of any given topic. After screening, ten models are selected and their main characteristics are summarized. The proposed research questions about the common trends in the results, the current gaps and the future directions of research are addressed. The main outcomes are the absence of any reference model shared by the scientific community and the need to deepen the physical and mathematical modeling of dielectric properties of biological tissues.