Screen‐printed Tattoo Sensor towards the Non‐invasive Assessment of the Skin Barrier

Abstract

The development and characterisation of a screen‐printed tattoo sensor for the non‐invasive assessment of the skin barrier is presented. A screen‐printed silver tattoo sensor comprising two concentric circle electrodes was fabricated and applied and characterised initially on a soft tissue mimic. It was shown that the tattoo was capable of tracking changes in water content in the soft tissue mimic using impedance spectroscopy. The tattoo sensors were then applied to porcine and human skins and impedance spectroscopy was used to interrogate the skin at the outer stratum corneum (SC). The SC is a layer of great interest from a dermatological point of view since it plays a critical role in the barrier function of the skin by protecting underlying tissue from infection, dehydration, chemical irritants and mechanical stress. Hydration changes were tracked in the skin using the impedance approach and validated against a tissue dielectric constant (TDC) measurement taken with the MoistureMeterD (MMD, Delfin Technologies). The impedimetric results obtained using the tattoo sensor were modelled into proposed circuit models representative of the systems measured. From this study, the potential of using wearable tattoo electrodes coupled with impedance spectroscopy as a transduction technique, to investigate skin barrier status offers considerable promise towards the monitoring and self‐management of skin health.

Non-Invasive Assessment of Skin Barrier Properties: Investigating Emerging Tools for In Vitro and In Vivo Applications

“…The lower frequency range can be attributed to the electrode-skin interface, and the higher frequency range to the skin itself. Figure 3d shows the impedance spectrum for human skin which formed a single semi-circle with a larger diameter to that of Labskin due to the high impedance of the SC in human skin as well as potentially the impedance given by the electrode-skin interface (i.e., due to lower level of conformal contact of the tattoo with human skin) [12]. It is interesting to note that in the human skin spectra, the diameter of the semi-circle is smaller for the male skin when compared to the female skin.…”

“…For example, Jia et al have demonstrated lactate sensing in sweat using a temporary tattoo amperometric sensing approach [10], and Bandodkar et al have demonstrated an enzyme based tattoo amperometric epidermal sensor for glycemic level monitoring during food consumption [11]. Our group has recently reported a screen-printed temporary tattoo sensor for non-invasive skin barrier assessment using impedance spectroscopy [12]. Impedance spectroscopy allows for non-invasive measurements of the overall resistance and reactance of skin using alternating current of various frequencies, where electrical impedance of intact skin is dominated by the SC at low frequencies (≤1 KHz) [13].…”

Coplanar Waveguide Based Sensor Using Paper Superstrate for Non-Invasive Sweat Monitoring

“…CPW lines have demonstrated higher sensitivity in dielectric properties extraction and material characterization compared to microstrip and slot lines [12,18,22,24,[29][30][31][32]. Normally, microstrip-based structures are used in resonance-based sensors due to the sensitivity of the microstrip gap.…”

“…Several sensors have been reported in literature that monitor electrolytes in sweat [11][12][13]. This includes using skin potentiometric sensors [11], impedimetric sensors [12], and multi-biomarker selective patches [13]. However, these devices require continuous contact with the skin during measurements.…”

“…The distinctive dielectric properties of biofluids could help in monitoring kidneys status through urine [22], diabetes through glucose levels [17][18][19][20]25,26], dehydration through sweat [23,24,27] and blood [28]. Among different sensors reported for tracking electrolytes [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], sodium chloride (NaCl) results in the largest recorded variations with changing hydration states [23,24].…”