| Abstrak/Abstract |
Assessing dermis sodium concentration in skin is essential since an excessive amount of sodium
is associated with vascular function disorders. In this research, dermis sodium concentration c
has been quantified by the power spectral density drop ∆P of square-wave electrical impedance
spectroscopy (PSDd-sEIS). PSDd-sEIS is composed of three stages: (1) dermis voltage
measurement, (2) PSDd calculation, and (3) dermis sodium quantification. In the 1st stage, three
electrodes are arranged to measure voltage v under the constant current I of square-wave. In the
2nd stage, ∆P is evaluated by the first and third harmonic frequency from v. In the 3rd stage, c
is quantified by the developed linear regression. To obtain the highest sensitivity between c and
∆P, four measurement factors (square-wave frequency f sw, duty-cycle γ, electrode distance d,
and electrode diameter ø) were optimized using numerical simulations of a skin model.
Experiments on multi-layered skin under various c in the range of 5 nM–50 mM were
conducted by PSDd-sEIS hardware with optimized measurement factors of fsw∗ = 100 kHz,
γ∗ = 50%, d∗ = 2 mm, and φ ∗ = 0.8 mm. As the results, the quantification of c has a good
accuracy with the normalized sensitivity ⟨S⟩ = 0.87 and determination coefficient R2 = 0.92.
The measurement factors of f sw and γ affect the power of square-wave excitation to pass
through the high resistivity barrier of the stratum corneum, while the measurement factors of d
and ø affect the stability of current flow in the dermis. |
