Fundamentals of Skin Bioimpedances

Area of Science:

• Biomedical Engineering
• Electrical Impedance Tomography
• Skin Physiology

Background:

• Bioimpedance measurements offer clinical insights but are limited by skin's complex structure and the insulating stratum corneum.
• Accurate measurement of viable skin and adipose tissue bioimpedance is challenging due to these factors.

Purpose of the Study:

• To develop a theoretical framework and system design for accurate bioimpedance measurements beyond the stratum corneum.
• To enable non-invasive characterization of viable skin and adipose tissues.

Main Methods:

• Established a theoretical framework for analyzing multilayered tissue impedances, specifically skin.
• Designed electrodes and electronics to minimize measurement errors in the presence of insulating tissues.
• Demonstrated non-invasive measurements despite significantly higher parasitic impedances.

Main Results:

• Successfully enabled non-invasive bioimpedance measurements of living tissues beyond the stratum corneum.
• Measurements remained accurate even with parasitic impedances up to 350 times higher than target bioimpedances.
• Performance was independent of barrier variations (tape stripping) and skin-electrode contact impedance changes (sweat).

Conclusions:

• The developed framework and system design overcome major challenges in skin bioimpedance measurement.
• This advancement facilitates the development of bioimpedance systems for diverse clinical applications.
• Potential applications include transdermal drug delivery, skin cancer assessment, obesity, dehydration, and diabetes monitoring.