Human Skin Surface Research Articles

Efficient Wireless Power Transfer System Integrating With Metasurface for Biological Applications

Wireless power transfer (WPT) is a key technique for many existing and emerging applications in biomedical devices. This paper presents a novel implantable magnetic coupling resonate WPT system by integrating with metasurface for biological applications. The receiver element is implanted under the skin surface 3 mm and has the dual-band property for transferring power and data telemetry simultaneously. A conformal strongly coupled magnetic resonator coil is used as the transmitting coil to construct the wireless power link. In addition, we integrate the proposed WPT system with negative permeability (MNG) metasurface over the human skin surface as a miniaturized wearable device to improve the WPT efficiency. The property of the MNG and its effect on the WPT efficiency are analyzed. Considering the special implantable environment, various misalignment tolerances between the metasurface and the receiver are discussed to evaluate the coupling response of the proposed WPT system. Finally, the efficient WPT system integrating with MNG has been verified by the experimental measurements, and the measured result shows that 15.7 dB coupling enhancement can be obtained by integrating with the MNG metasurface.

Thermal Absorptivity Model of Knitted Rib Fabric and its Experimental Verification

Abstract Thermal absorptivity is an indicator of warm and cool feeling of textile materials. An equation based on thermal absorptivity of polyester in solid form, porosity of a fabric, and relative contact area of human skin and fabric surface has been developed to characterize thermal absorptivity of fabric. For verification of suggested model, 15 knitted rib fabrics were produced using 100% polyester yarn and having different surface profile. ALAMBETA semiautomatic non-destructive instrument has been used for measuring the effective thermal absorptivity of knitted rib fabric. It was found that the suggested simple theoretical model exhibits significant agreement with the measured thermal absorptivity values of knitted rib fabric, which endorsed the approach applied.

A Four-Channel Electrical Impedance Spectroscopy Module for Cortisol Biosensing in Sweat-Based Wearable Applications.

A four-channel electrochemical impedance spectroscopy (EIS) analyzer module has been demonstrated on flexible chemi-impedance sensors fabricated with gold electrodes for wearable applications. The module can perform time division multiplexed (TDM) impedance measurements on four sensors at 1 kHz. In this work, we characterize the system for the detection of cortisol in an ultralow volume (1-3 µL) of perspired human sweat, sensor performance, and effects during continuous cortisol dosing and with pH and temperature variations expected on the surface of the skin that would be representative of use conditions as seen by a wearable device. Detection of cortisol was shown for concentrations of 1 pg/mL to 200 ng/mL in both synthetic and perspired human sweat, and output response reported as a change in impedance with varying cortisol concentrations. Continuous dose testing was performed to demonstrate the stability of the sensors over prolonged periods of operation for cortisol concentrations within the physiologically relevant range of 10-200 ng/mL reported in human sweat. Temperature and pH effects testing was performed for pH range 4-8 and in a temperature chamber for the clinical range reported on the surface of human skin: 25-40 °C. The cortisol sensor demonstrated stability of operation with 7.58% variability under these conditions.

Solid Lipid Nanoparticles of Serine Designed by Evaluating Affinity of Solid Lipids to Stratum Corneum for Enhanced Skin Hydration in Combination with Reed Root Extract

The study aimed to assess the skin hydrating effect of hydrogels containing serine‐loaded solid lipid nanoparticles (SLN) prepared with lipids having high affinity to the stratum corneum (SC) and polysaccharide‐rich reed (Phragmites communis) root extract (RRE). To select a lipid with high affinity to the SC, the interaction between the SC obtained by a tape stripping technique and three different lipids such as glycerol mono‐oleate (GMO), lauric acid (LA), and capric acid (CA) was examined by ATR‐FTIR. After choosing GMO as the lipid with the highest affinity to the SC, hydrogel formulations containing serine‐loaded GMO SLN and/or RRE were prepared, and their skin hydrating effect was evaluated after applying the hydrogels to the surface of human skin. The hydrogel containing serine‐loaded GMO SLN and RRE exhibited the greatest skin moisturizing effect, followed by the hydrogels with serine‐loaded GMO SLN, RRE, and blank hydrogel. The results implied that SLN prepared with GMO having high affinity to the SC could be used as an efficacious carrier of serine for the purpose of skin hydration, and synergistic skin hydrating effect could be achieved by different skin moisturizing mechanisms of the serine‐loaded SLN and RRE.

Abstract WP56: Imaging Intra-Carotid Thrombosis Using Near InfraRed Fluorescent-NanoDiamond Particles Bio-engineered With the Disintegrin Bitistatin

Background: Thromboembolism is a major cause of events in carotid artery (CA) disease and predisposes the dissemination of clots to upstream ischemic strokes. Although diagnostic methods are available to define thromboembolic strokes (CT, MRI, etc.), there is no technology to provide ambulatory assessment to ‘content image’ thrombi within the CA bifurcation free of the hospital setting. To address this unmet medical need we bioengineered the joining of the disintegrin bitistatin (Bit) to fluorescent NanoDiamond Particles (F-NDP) in order to bind to and non-invasively image vascular clots. F-NDP-Bit preferentially binds to the human platelet fibrinogen receptor (GPIIB/IIIA). F-NDP-Bit was systematically evaluated for NIR emission capacity in various tissues and demonstrated penetration of NIR fluorescence across distances similar to the distance from the human skin surface to the CA bifurcation. Methods: In vitro studies were conducted to evaluate binding of F-NDP-Bit to purified human GPIIB/IIIA. Also, the ability of the F-NDP-Bit to bind to vascular clots In Vivo was investigated in rat FeCl3-induced internal CA coagulation. Results: Using the specific GPIIB/IIIA antagonist lotrafiban, In Vitro specific and concentration-related F-NDP-Bit binding was demonstrated. In Vivo , intravenous administration of F-NDP-Bit during the evolution of FeCl3-induced internal CA thrombosis resulted in the dose-related clot accumulation of F-NDP-Bit that was cross-validated by three independent methods (all measures were significant as described; p < 0.05): ( 1 ) In Situ whole rat imaging via In Vivo Imaging System (IVIS: using Ex 54 nm; Em 695-770 nm); ( 2 ) Ex Vivo whole vessel/clot imaging (Scanning Confocal Microscopy), and ( 3 ) Extract, isolate and quantitate F-NDP-Bit following internal CA clot dissolution (12N HNO3) and direct counting (hemocytometer). Conclusions: These data indicate that F-NDP-Bit might address the need for fast, safe and highly affordable ambulatory imaging of vascular clot burden. Functionalization of F-NDP with selective ligands that can be pathognomonic for many disease situations also could facilitate risk assessment, earlier intervention and preventative medicine.

Surrogate human sensor for human skin surface temperature measurement in evaluating the impacts of thermal behaviour at outdoor environment

The world is experiencing high rates of urbanisation and it has slowly become an alarming social process, especially in developing countries. This has demanded an urgent investigation on human thermal comfort, especially in tropical climates. In this study, a surrogate human sensor (SHS) was developed to establish a linkage between human skin surface and SHS with the surrounding environments. Black plastic corrugated cardboard was used in the SHS fabrication as its thermal conductivity was close to the thermal conductivity and emissivity of the human epidermal skin layer. The SHS was designed to correlate with human skin surface temperature and a regression model was developed. The regression equation was obtained for the human skin temperature prediction (Th) by using SHS. Statistical analysis of the ANOVA (F = 13,700; ρ < 0.05) was significantly tested to show its reliability. The predicted and measured human skin temperature was compared and the results revealed that both temperature variations was found in range ±0.5 °C in temperature differences. The advantages of SHS as the sensor for the impact of thermal behaviour can be identified by observing the temperature difference as it can directly reflects the influences from the surrounding outdoor environment. Although it is proven valid statistically, however, SHS is only relevant as an initial indicator to investigate the impacts of thermal behaviour and discomfort level. It can further used to measure human thermal comfort by correlating surrounding environment condition with comfort sensation through SHS regression model.

Measurement of Vibration Frequency on Human Skin Surface with Optical Interferometer

Measurement of Vibration Frequency on Human Skin Surface with Optical Interferometer

Over a Decade of recA and tly Gene Sequence Typing of the Skin Bacterium Propionibacterium acnes: What Have We Learnt?

The Gram-positive, anaerobic bacterium Propionibacterium acnes forms part of the normal microbiota on human skin and mucosal surfaces. While normally associated with skin health, P. acnes is also an opportunistic pathogen linked with a range of human infections and clinical conditions. Over the last decade, our knowledge of the intraspecies phylogenetics and taxonomy of this bacterium has increased tremendously due to the introduction of DNA typing schemes based on single and multiple gene loci, as well as whole genomes. Furthermore, this work has led to the identification of specific lineages associated with skin health and human disease. In this review we will look back at the introduction of DNA sequence typing of P. acnes based on recA and tly loci, and then describe how these methods provided a basic understanding of the population genetic structure of the bacterium, and even helped characterize the grapevine-associated lineage of P. acnes, known as P. acnes type Zappe, which appears to have undergone a host switch from humans-to-plants. Particular limitations of recA and tly sequence typing will also be presented, as well as a detailed discussion of more recent, higher resolution, DNA-based methods to type P. acnes and investigate its evolutionary history in greater detail.

Preparation of Artificial Skin that Mimics Human Skin Surface and Mechanical Properties.

We have developed an artificial skin that mimics the morphological and mechanical properties of human skin. The artificial skin comprises a polyurethane block possessing a microscopically rough surface. We evaluated the tactile sensations when skin-care cream was applied to the artificial skin. Many subjects perceived smooth, moist, and soft feels during the application process. Cluster analysis showed that these characteristic tactile feels are similar to those when skin-care cream is applied to real human skin. Contact angle analysis showed that an oil droplet spread smoothly on the artificial skin surface, which occurred because there were many grooves several hundred micrometers in width on the skin surface. In addition, when the skin-care cream was applied, the change in frictional force during the dynamic friction process increased. These wetting and frictional properties are important factors controlling the similarity of artificial skin to real human skin.

Influence of probe pressure on diffuse reflectance spectra of human skin measured in vivo.

Mechanical pressure superficially applied on the human skin surface by a fiber-optic probe influences the spatial distribution of blood within the cutaneous tissues. Upon gradual load of weight on the probe, a stepwise increase in the skin reflectance spectra is observed. The decrease in the load follows the similar inverse staircase-like tendency. The observed stepwise reflectance spectra changes are due to, respectively, sequential extrusion of blood from the topical cutaneous vascular beds and their filling afterward. The obtained results are confirmed by Monte Carlo modeling. This implies that pressure-induced influence during the human skin diffuse reflectance spectra measurements in vivo should be taken into consideration, in particular, in the rapidly developing area of wearable gadgets for real-time monitoring of various human body parameters.

Contactless physiological signals extraction based on skin color magnification

Although the human visual system is not sufficiently sensitive to perceive blood circulation, blood flow caused by cardiac activity makes slight changes on human skin surfaces. With advances in imaging technology, it has become possible to capture these changes through digital cameras. However, it is difficult to obtain clear physiological signals from such changes due to its fineness and noise factors, such as motion artifacts and camera sensing disturbances. We propose a method for extracting physiological signals with improved quality from skin colored-videos recorded with a remote RGB camera. The results showed that our skin color magnification method reveals the hidden physiological components remarkably in the time-series signal. A Korea Food and Drug Administration-approved heart rate monitor was used for verifying the resulting signal synchronized with the actual cardiac pulse, and comparisons of signal peaks showed correlation coefficients of almost 1.0. In particular, our method can be an effective preprocessing before applying additional postfiltering techniques to improve accuracy in image-based physiological signal extractions.

Impact of a pH 5 Oil-in-Water Emulsion on Skin Surface pH

Background: Human skin surface has a physiologically acidic pH (pH_ss). In cases of increased pH_ss, the acidity of the skin can be restored by topical formulations. We tested a pH 5 oil-in-water (O/W) emulsion for pH_ss regeneration and stabilization. Methods: We performed 2 experiments with 10 female study subjects in each. In both experiments, 2D imaging with luminescent sensor foils was used to determine pH_ss. Alkalization was reached by washing the volar forearm with a soap bar and warm running tap water for 20 min. Experiment 1: after defining the baseline pH_ss, we alkalized the respective area and measured pH_ss over a duration of 5 h, while applying emulsion every hour. Experiment 2: study subjects used the emulsion twice daily for 1 week. Then, pH_ss was measured before and after 5 min of washing a treated and an untreated area on the volar forearm. Results: (1) 5 h after alkalization, the treated arm showed a significantly lower pH_ss than the untreated one (5.87 ± 0.03 vs. 6.05 ± 0.03); (2) after washing, the treated area had a significantly lower pH_ss than controls (6.13 ± 0.03 vs. 6.27 ± 0.05). Conclusions: The tested pH 5 O/W emulsion seems to improve regeneration and stabilization of pH_ss.

Study of skin and nail Candida species as a normal flora based on age groups in healthy persons in Tehran-Iran

The skin is the body's largest organ that hosts heterogeneous inhabitants. Until now, the diversity of the cutaneous microbiome was mainly investigated for bacteria and there is a little information about the skin fungal flora. Also, among skin fungal flora, Candida is found as a main member whose distribution is affected by sex, age, climate. In this study, differences in Candida community structure associated with 9 different skin sites of 238 healthy people during 10 months from July to March 2016, are described. These subjects were divided by age into 4 groups: infants, children, adults and geriatrics. The collected samples were examined by culture on Sabouraud Chloramphenicol Agar and CHROM-agar Candida. For precise identification of species ITS1-5. 8S-ITS2 rDNA regions were sequenced where needed. The frequency of Candida species was significantly different between age groups. The most Candida isolations were related to the elderly age group and the fewest in the infants. C.parapsilosis virtually, was the predominant isolated species in all age groups. This study showed no statistically significant effect of the subject's sex on Candida population resident on human skin surface.

The identification of Meyerozyma guilliermondii from blood cultures and surveillance samples in a university hospital in Northeast Turkey: A ten-year survey

Meyerozyma (Pichia) guilliermondii exists in human skin and mucosal surface microflora. It can cause severe fungal infections like candidemia, which is an opportunistic pathogen. One hundred and forty-one M.guilliermondii isolates, consisting of 122 blood culture isolates, belonging to 126 patients; 13 total parenteral nutrition solution isolates; and two rectal swab isolates were identified according to carbohydrate assimilation reactions in a university hospital in Turkey between January 2006 and December 2015. Following Candida albicans (34.0%) and C.parapsilosis (21.2%), the third yeast species most commonly isolated from blood cultures in the Farabi Hospital was M.guilliermondii (20.6%). The patients were hospitalised in 27 different departments. A total of 50% of the patients were in pediatric departments, 49.2% were in intensive care units, and 17.2% were in haematology-oncology departments. Molecular identification of the isolates was performed using DNA sequence analysis of ribosomal ITS gene regions and IGS amplification-AluI fingerprinting (IGSAF). With molecular identification, 140 isolates were identified as M.guilliermondii and one isolate was identified as Candida membranifaciens. It was observed that the ITS1 region specifically helps in identifying these species. It was demonstrated that biochemical and molecular methods were 99.3% consistent in identifying M.guilliermondii. The Wild-Type (WT) Minimum Inhibitory Concentrations (MICs) distribution of fluconazole, voriconazole, itraconazole, and flucytosine were determined using the Sensititre YeastOne YO2V system after 24h of incubation. One M.guilliermondii strain was determined to be non-WT for fluconazole, voriconazole, itraconazole and flucytosine. In total, three M.guilliermondii strains, for fluconazole, were determined to be non-WT in this study.

Evaluation of a robotic transfer replicator: machine parameters that affect measurements of transfer of particulates from carpet surfaces to human skin versus human skin-like surfaces

We have designed and built a robotic machine (robotic transfer replicator) to replicate the process by which various particulates are transferred from carpet surfaces to human skin. The particulates tested included bovine serum albumin, dust mites, paint dust, pesticides, and pollen. We have investigated the effect of time of transfer, applied pressure, skin-like receptor materials, particulate size, carpet composition and construction, and motion of the receptors on the percent transfer. The amount transferred was determined to be directly proportional to the amount of particulate applied to the carpet surface. The percent transfer values ranged from 0.05% to 28% for different combinations of particulates, carpet types, and method of transfer. The percent transfer was shown to be independent of receptor size or applied pressure. To explain the variations in the percent transfer, a three-zone model for particulate penetration into carpets is proposed. While the robotic transfer replicator was not capable of reproducing exactly the results from human finger transfer, it does provide a controlled and reproducible approach to the transfer process and the ability to use toxic or pathogenic materials that could not be used with human subjects.

Temperature-responsive nanogel multilayers of poly(N-vinylcaprolactam) for topical drug delivery

We report nanothin temperature-responsive hydrogel films of poly(N-vinylcaprolactam) nanoparticles (νPVCL) with remarkably high loading capacity for topical drug delivery. Highly swollen (νPVCL)n multilayer hydrogels, where n denotes the number of nanoparticle layers, are produced by layer-by-layer hydrogen-bonded assembly of core-shell PVCL-co-acrylic acid nanoparticles with linear PVPON followed by cross-linking of the acrylic acid shell with either ethylene diamine (EDA) or adipic acid dihydrazide (AAD). We demonstrate that a (νPVCL)5 film undergoes dramatic and reversible swelling up to 9 times its dry thickness at pH = 7.5, indicating 89v/v % of water inside the network. These hydrogels exhibit highly reversible ∼3-fold thickness changes with temperature variations from 25 to 50°C at pH = 5, the average pH of human skin. We also show that a (νPVCL)30 hydrogel loaded with ∼120µgcm−2 sodium diclofenac, a non-steroidal anti-inflammatory drug used for osteoarthritis pain management, provides sustained permeation of this drug through an artificial skin membrane for up to 24h at 32°C (the average human skin surface temperature). The cumulative amount of diclofenac transported at 32°C from the (νPVCL)30 hydrogel after 24h is 12 times higher than that from the (νPVCL)30 hydrogel at 22°C. Finally, we demonstrate that the (νPVCL) hydrogels can be used for multiple drug delivery by inclusion of Nile red, fluorescein and DAPI dyes within the νPVCL nanoparticles prior to hydrogel assembly. Using confocal microscopy we observed the presence of separate dye-loaded νPVCL compartments within the hydrogel matrix with all three dyes confined to the nanogel particles without intermixing between the dyes. Our study provides opportunity for development of temperature-responsive multilayer hydrogel coatings made via the assembly of core-shell nanogel particles which can be used for skin-sensitive materials for topical drug delivery.

Evaluation of a human skin surface temperature for the protective clothing – Skin system based on the protective clothing–skin imitating material results

Experimental studies used for evaluation of quality of the fire-fighters protective clothing are based on irradiation of the clothing sample by an external pulse of a given duration. The other side of the clothing sample is in contact with a material imitating the human skin, which has properties different than these of the skin. Therefore the problem considered in this paper was: what conditions should be satisfied to convert the experimental results, carried out on the stand with a skin-imitating material, to the case of the real human skin with different properties for which the experiments are not made? This will allow for better evaluation of the clothing protecting properties and estimation of the possible burns. Due to multilayer structure of the protective clothing and skin as well as complex phenomena involved in energy transfer through them the problem is very complicated. Therefore at the first attempt to solve the problem a simplified two-layer, clothing-skin system irradiated from external heat source was considered in the present paper. Temperature variation in the system was initially determined using the in-house 1D numerical code accounting for heat conduction in the skin and clothing, non-grey thermal radiation absorption, scattering and emission together with the water vapour diffusion and phase transformations of bound water to the gaseous phase in the protective clothing. Then the analytical model for temperature variation in the considered system was proposed and solved using the Laplace transform approach. In the latter model water vapour diffusion with its phase transformations were excluded and radiation emission was neglected. The analytical model allowed for deriving a formula which can be applied for converting the skin surface temperature obtained from the experiments carried out using the skin-imitating material to the material having skin properties. In order to verify the range of validity of the formula the analytical predictions were compared to the results of numerical simulations of temperature in the protective clothing-skin system considering cases in which different phenomena were included. For the majority of the cases studied good matching between analytical and numerical results was obtained for time corresponding to the heating and cooling processes of the protective clothing-skin system.

Universal and one-step visualization of latent fingermarks on various surfaces using hydrophilic cellulose membrane and dye aqueous solution

A high-resolution and universal method for the rapid visualization of latent fingermarks on a broad variety of surfaces has been achieved by simply combining hydrophilic cellulose membrane with dye aqueous solution. In this approach, the relatively hydrophobic characteristic of fingermark residue enable the deposit act as a “mask”, directing dye absorption processes to regions of both furrows without the ridge residues and bare cellulose membrane substrate. This effect during the spatially selective dye absorption generates a negative pattern of the fingermark within a few seconds to minutes depending on the properties of the substrates and fingermark types. It provides observation of latent fingermarks on cellulose membrane surface with high definition of level 2 and level 3 details used for personal identification purposes. It is also highly-efficient for visualizing the latent fingermarks lifted from various common (glass, carton, ceramic cup) and problematic (banknote, human skin and leather) surfaces by using transparent adhesive tape. To examine the generality of the proposed method, eight different kinds of dye aqueous solutions have been tested for developing latent fingermarks and they all provide very good results as expected. Moreover, this approach is easily used for aged fingermarks and natural fingermarks as well. Imaging may be accomplished visibly (by dye color) and topographically (using a microscope or a camera). This approach is a simple, rapid, non-destructive, safe, low-cost, universal and high resolution method compared with conventional approaches, so it demonstrates good potentiality in individual identity validation related applications.

Simultaneous and multi-point measurement of ammonia emanating from human skin surface for the estimation of whole body dermal emission rate.

Ammonia is one of the members of odor gases and a possible source of odor in indoor environment. However, little has been known on the actual emission rate of ammonia from the human skin surface. Then, this study aimed to estimate the whole-body dermal emission rate of ammonia by simultaneous and multi-point measurement of emission fluxes of ammonia employing a passive flux sampler - ion chromatography system. Firstly, the emission fluxes of ammonia were non-invasively measured for ten volunteers at 13 sampling positions set in 13 anatomical regions classified by Kurazumi et al. The measured emission fluxes were then converted to partial emission rates using the surface body areas estimated by weights and heights of volunteers and partial rates of 13 body regions. Subsequent summation of the partial emission rates provided the whole body dermal emission rate of ammonia. The results ranged from 2.9 to 12mgh-1 with an average of 5.9±3.2mgh-1 per person for the ten healthy young volunteers. The values were much greater than those from human breath, and thus the dermal emission of ammonia was found more significant odor source than the breath exhalation in indoor environment.

A Flexible PMN‐PT Ribbon‐Based Piezoelectric‐Pyroelectric Hybrid Generator for Human‐Activity Energy Harvesting and Monitoring

The rapid advancements of wearable electronics require continued innovation in sustainable power sources and human interactive sensors. An abundance of energy in various forms, such as mechanical, thermal, optical, and sound, are ubiquitous in the environment and human activities. Hybrid generators using piezoelectric polymers with relatively low piezoelectric and pyroelectric constants have been fabricated to simultaneously scavenge mechanical and thermal energies. In this work, micropatterned single‐crystal (1−x)Pb(Mg,Nb)O3‐xPbTiO3 (PMN‐PT) ribbons, which possess excellent piezoelectric and pyroelectric properties, are utilized to build human activities energy harvesting and monitoring systems. The flexible PMN‐PT ribbon‐based sensor conformally attached on the surface of human skin enables high sensitivity for human body motions and can detect acoustic sounds precisely. The sensor has been used for monitoring temperature‐related activities, caused for instance by warm water flow and even light illumination. The multifunctional performance of the PMN‐PT ribbon‐based hybrid generator shows great potential for self‐powered wearable and human activities monitoring devices.