A quantitative approach to the dielectric properties of the skin

Raicu, Valerică; Kitagawa, Nobuko; Irimajiri, Akihiko

doi:10.1088/0031-9155/45/2/101

Cited by 76 publications

(67 citation statements)

References 10 publications

(10 reference statements)

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“…Furthermore, at a fixed hydration level of 90, the impedance amplitude decreases from 558 kX at 15 kHz to 332 kX at 95 kHz, while the phase increases by 0.36 rad over this same RF range. These trends arise from the frequency dependence of the conductivity and permittivity of the skin due mostly to expected effects in aqueous electrolyte solutions [31][32][33][34]. The result is increased changes in impedance with hydration levels at low measurement frequencies (e.g.…”

Section: Frequency-dependent Impedance Changes With Hydration Levelsmentioning

confidence: 99%

Epidermal Differential Impedance Sensor for Conformal Skin Hydration Monitoring

et al. 2012

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We present the design and use of an ultrathin, stretchable sensor system capable of conformal lamination onto the skin, for precision measurement and spatial mapping of levels of hydration. This device, which we refer to as a class of ‘epidermal electronics’ due to its ‘skin-like’ construction and mode of intimate integration with the body, contains miniaturized arrays of impedance-measurement electrodes arranged in a differential configuration to compensate for common-mode disturbances. Experimental results obtained with different frequencies and sensor geometries demonstrate excellent precision and accuracy, as benchmarked against conventional, commercial devices. The reversible, non-invasive soft contact of this device with the skin makes its operation appealing for applications ranging from skin care, to athletic monitoring to health/wellness assessment.

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Section: Frequency-dependent Impedance Changes With Hydration Levelsmentioning

confidence: 99%

Epidermal Differential Impedance Sensor for Conformal Skin Hydration Monitoring

et al. 2012

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“…The results of reflection measurements performed with a coaxial probe of reduced size were used to calculate the complex permittivity of skin at microwave frequencies [Grant et al, 1988;Gabriel et al, 1996a;Lahtinen et al, 1997;Alanen et al, 1998;Raicu et al, 2000]. Skin reflection measurements in the mm-wave frequency range were performed at the open ends of standard waveguides either at one selected frequency [Kuznetsov et al, 2003] or over a wide frequency range [Kislyakov, 1994].…”

Section: Introductionmentioning

confidence: 99%

Human skin permittivity determined by millimeter wave reflection measurements

Алексеев

Ziskin

2007

Bioelectromagnetics

169

156

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Millimeter wave reflection from the human skin was studied in the frequency range of 37-74 GHz in steps of 1 GHz. The forearm and palm data were used to model the skin with thin and thick stratum corneum (SC), respectively. To fit the reflection data, a homogeneous unilayer and three multilayer skin models were tested. Skin permittivity in the mm-wave frequency range resulted from the permittivity of cutaneous free water which was described by the Debye equation. The permittivity increment found from fitting to the experimental data was used for determination of the complex permittivity and water content of skin layers. Our approach, first tested in pure water and gelatin gels with different water contents, gave good agreement with literature data. The homogeneous skin model fitted the forearm data well. Permittivity of the forearm skin obtained with this model was close to the skin permittivity reported by others. To fit reflection from the palmar skin with a thick SC, a skin model containing at least two layers was required. Multilayer models provided better fitting to both the forearm and palmar skin reflection data. The fitting parameters obtained with different models were consistent with each other.

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“…We assume that the dielectric properties of the skin and the underlying tissue including blood (hereafter referred to as skin) are characterized by a vector S. Elements of this vector could for instance be the bulk permittivity e b 0 and bulk conductivity r b of the skin [14,15,33] or the resonance point (f res , |Z res |) of a fringing field RLC circuit [7,9,38], where |Z| res = |Z(f res )| is the magnitude of the complex impedance at the resonance frequency (f res ) For convenience, we refer to this vector S as the skin vector and to its elements as the skin parameters s k , (k = 1,...,N).…”

Section: Compensation Of Perturbing Factors: General Conceptmentioning

confidence: 99%

The compensation of perturbing temperature fluctuation in glucose monitoring technologies based on impedance spectroscopy

et al. 2007

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Non-invasive glucose monitoring techniques based on impedance spectroscopy are affected by a variety of perturbing effects. In order to use the impedance as a glucose measure, these perturbing effects need to be quantified and compensated. Since effects induced by temperature fluctuations certainly rank among the severest perturbations, a clinical study was carried out to establish whether temperature, as a perturbing factor, could be compensated for in impedance spectroscopy. The results as well as a concept allowing for the compensation of perturbing temperature fluctuations are presented here. The compensation technique described is a generic approach that, in principle, can be applied to compensate most perturbation effects provided that there are now multiplicative interactions between the variable of interest (in our case the glucose) and the perturbations. The results allow for the determination of the minimum required sensitivity of an impedance spectrometer to glucose in order to be operational in home-use conditions. Furthermore, the data can be used to estimate if a universal temperature compensation can be applied or if an individual calibration is necessary. For instance, applying a universal temperature compensation and requiring an application range of +/-5 degrees C, the minimum required sensitivity of the minimum impedance and frequency in a sensor-skin RLC circuit to resolve glucose variations equivalent to 10 mg/dl is 0.85 Omega/mg/dl and 0.14 MHz/mg/dl, respectively. The sensitivity requirements reduce by about a factor 1.6, if for each subject an individual calibration is carried out. Depending on the measure and the calibration procedure, the required sensitivities are a factor 3-50 greater than those reported in the literature. Thus, in order to be operational in home-use conditions, the signal-to-noise ratio (S/N) of existing impedance-based monitoring platforms using RLC circuits need to be improved by about one order of magnitude. In order to make non-invasive glucose monitoring possible we, therefore, suggest some measures that may improve the S/N by the required factor.

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A quantitative approach to the dielectric properties of the skin

Cited by 76 publications

References 10 publications

Epidermal Differential Impedance Sensor for Conformal Skin Hydration Monitoring

Epidermal Differential Impedance Sensor for Conformal Skin Hydration Monitoring

Human skin permittivity determined by millimeter wave reflection measurements

The compensation of perturbing temperature fluctuation in glucose monitoring technologies based on impedance spectroscopy

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