Variations of skin thermal diffusivity on different skin regions.

BACKGROUND AND OBJECTIVE: Skin thermal diffusivity plays a crucial role in various applications, including laser therapy and cryogenic skin cooling.This study investigates the correlation between skin thermal diffusivity and two important skin parameters, melanin content and erythema, in a cohort of 102 participants. METHODS: An in-house developed device based on transient temperature measurement was used to assess thermal diffusivity at different body locations. Melanin content and erythema were measured using a colorimeter. Statistical analysis was performed to examine potential correlations. RESULTS: The results showed that the measured thermal diffusivity values were consistent with previous reports, with variations observed among subjects. No significant correlation was found between thermal diffusivity and melanin content or erythema. This suggests that other factors, such as skin hydration or epidermis thickness, may have a more dominant influence on skin thermal properties. CONLCUSION: This research provides valuable insights into the complex interplay between skin thermal properties and physiological parameters, with potential implications for cosmetic and clinical dermatology applications.

Lab-on-a-Fiber Wearable Multi-Sensor for Monitoring Wound Healing.

Chronic wounds are regarded as a silent epidemic, affecting 1-2% of the population and representing 2-4% of healthcare expenses. The current methods used to assess the wound healing process are based on the visual evaluation of physical parameters. This work aims to design a wearable non-invasive device capable of evaluating three parameters simultaneously: the pH and the levels of glucose and matrix metalloproteinase (MMP) present in the wound exudate. The device is composed of three independent polymer optical fibers functionalized with fluorescent-based sensing chemistries specific to the targeted analytes. Each fiber is characterized in terms of detection sensitivity and selectivity confirming their suitability for monitoring the targeted parameters in ranges relevant to the wound environment. The selectivity and robustness of the multi-sensing device are confirmed with analyses using complex solutions with different pH levels (5, 6, and 7), different concentrations of glucose (1.25, 2.5, and 5 mm), and MMP (1.25, 2.5, and 5 µg mL-1 ). Given the simple set-up, the affordability of the materials used and the possibility of detecting additional parameters relevant to wound healing, such multi-sensing fiber-based devices could pave the way for novel non-invasive wearable tools enabling the assessment of wound healing from the molecular perspective.

Functional Fiber Membranes with Antibacterial Properties for Face Masks.

Reusable face masks are an important alternative for minimizing costs of disposable and surgical face masks during pandemics. Often complementary to washing, a prolonged lifetime of face masks relies on the incorporation of self-cleaning materials. The development of self-cleaning face mask materials requires the presence of a durable catalyst to deactivate contaminants and microbes after long-term use without reducing filtration efficiency. Herein, we generate self-cleaning fibers by functionalizing silicone-based (polydimethylsiloxane, PDMS) fibrous membranes with a photocatalyst. Coaxial electrospinning is performed to fabricate fibers with a non-crosslinked silicone core within a supporting shell scaffold, followed by thermal crosslinking and removal of the water-soluble shell. Photocatalytic zinc oxide nanoparticles (ZnO NPs) are immobilized on the PDMS fibers by colloid-electrospinning or post-functionalization procedures. The fibers functionalized with ZnO NPs can degrade a photo-sensitive dye and display antibacterial properties against Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) due to the generation of reactive oxygen species upon irradiation with UV light. Furthermore, a single layer of functionalized fibrous membrane shows an air permeability in the range of 80-180 L/m2s and 65% filtration efficiency against fine particulate matter with a diameter less than 1.0 µm (PM1.0). Supplementary Information: The online version contains supplementary material available at 10.1007/s42765-023-00291-7.

Ibuprofen-loaded electrospun poly(ethylene-co-vinyl alcohol) nanofibers for wound dressing applications.

Chronic wounds are characterized by a prolonged inflammation phase preventing the normal processes of wound healing and natural regeneration of the skin. To tackle this issue, electrospun nanofibers, inherently possessing a high surface-to-volume ratio and high porosity, are promising candidates for the design of anti-inflammatory drug delivery systems. In this study, we evaluated the ability of poly(ethylene-co-vinyl alcohol) nanofibers of various chemical compositions to release ibuprofen for the potential treatment of chronic wounds. First, the electrospinning of poly(ethylene-co-vinyl alcohol) copolymers with different ethylene contents (32, 38 and 44 mol%) was optimized in DMSO. The morphology and surface properties of the membranes were investigated via state-of-the-art techniques and the influence of the ethylene content on the mechanical and thermal properties of each membrane was evaluated. Furthermore, the release kinetics of ibuprofen from the nanofibers in a physiological temperature range revealed that more ibuprofen was released at 37.5 °C than at 25 °C regardless of the ethylene content. Additionally, at 25 °C less drug was released when the ethylene content of the membranes increased. Finally, the scaffolds showed no cytotoxicity to normal human fibroblasts collectively paving the way for the design of electrospun based patches for the treatment of chronic wounds.

Advanced and Smart Textiles during and after the COVID-19 Pandemic: Issues, Challenges, and Innovations.

The COVID-19 pandemic has hugely affected the textile and apparel industry. Besides the negative impact due to supply chain disruptions, drop in demand, liquidity problems, and overstocking, this pandemic was found to be a window of opportunity since it accelerated the ongoing digitalization trends and the use of functional materials in the textile industry. This review paper covers the development of smart and advanced textiles that emerged as a response to the outbreak of SARS-CoV-2. We extensively cover the advancements in developing smart textiles that enable monitoring and sensing through electrospun nanofibers and nanogenerators. Additionally, we focus on improving medical textiles mainly through enhanced antiviral capabilities, which play a crucial role in pandemic prevention, protection, and control. We summarize the challenges that arise from personal protective equipment (PPE) disposal and finally give an overview of new smart textile-based products that emerged in the markets related to the control and spread reduction of SARS-CoV-2.

Assessment of compression forces in a digitally modified short leg cast for pressure injury risk monitoring in healthy children.

Introduction: Casting is an essential treatment for neuro-orthopedic conditions in children with cognitive, sensory, and communicational disabilities. However, a main side-effect is the development of pressure injuries resulting in additional (wound) therapies and prolongation of the hospital stay. The primary aim of our study was to investigate the potential of objective pressure measurements in casts to assess the risk for pressure injury development. Methods: Five pediatric healthy participants were included in this study. We measured the global and the local compression force at body sites prone to pressure injury development for different body positions and the transfer in-between in a cast equipped with pressure sensors. These conditions resulted in partial or full body weight loading. Results and discussion: The global maximum compression force was affected significantly by body postures with partial and full loading of the cast and during transfer. The local compression force significantly correlated with the global compression force at the heel and instep area. In conclusion, the integration of sensing technologies into casts bears a high potential for early recognition of critical conditions inside the cast and inducing preventive measures in the at-risk population.

How long and effective does a mask protect you from an infected person who emits virus-laden particles: By implementing one-dimensional physics-based modeling.

SARS-CoV-2 spreads via droplets, aerosols, and smear infection. From the beginning of the COVID-19 pandemic, using a facemask in different locations was recommended to slow down the spread of the virus. To evaluate facemasks' performance, masks' filtration efficiency is tested for a range of particle sizes. Although such tests quantify the blockage of the mask for a range of particle sizes, the test does not quantify the cumulative amount of virus-laden particles inhaled or exhaled by its wearer. In this study, we quantify the accumulated viruses that the healthy person inhales as a function of time, activity level, type of mask, and room condition using a physics-based model. We considered different types of masks, such as surgical masks and filtering facepieces (FFPs), and different characteristics of public places such as office rooms, buses, trains, and airplanes. To do such quantification, we implemented a physics-based model of the mask. Our results confirm the importance of both people wearing a mask compared to when only one wears the mask. The protection time for light activity in an office room decreases from 7.8 to 1.4 h with surgical mask IIR. The protection time is further reduced by 85 and 99% if the infected person starts to cough or increases the activity level, respectively. Results show the leakage of the mask can considerably affect the performance of the mask. For the surgical mask, the apparent filtration efficiency reduces by 75% with such a leakage, which cannot provide sufficient protection despite the high filtration efficiency of the mask. The facemask model presented provides key input in order to evaluate the protection of masks for different conditions in public places. The physics-based model of the facemask is provided as an online application.

Emulsion electrospinning of sodium alginate/poly(ε-caprolactone) core/shell nanofibers for biomedical applications.

Electrospun nanofibers have shown great potential as drug vehicles and tissue engineering scaffolds. However, the successful encapsulation of multiple hydrophilic/hydrophobic therapeutic compounds is still challenging. Herein, sodium alginate/poly(ε-caprolactone) core/shell nanofibers were fabricated via water-in-oil emulsion electrospinning. The sodium alginate concentration, water-to-oil ratio, and surfactant concentration were optimized for the maximum stability of the emulsion. The results demonstrated that an increasing water-to-oil ratio results in more deviation from Newtonian fluid and leads to a broader distribution of the fibers' diameters. Moreover, increasing poly(ε-caprolactone) concentration increases loss and storage moduli and increases the diameter of the resulting fibers. The nanofibers' characteristics were investigated by scanning electron microscopy, transmission electron microscopy, confocal laser scanning microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and water contact angle measurements. It was observed that using an emulsion composition of 10% (w/v) PCL and a water-to-oil ratio of 0.1 results in smooth, cylindrical, and uniform core/shell nanofibers with PCL in the shell and ALG in the core. The in vitro cell culture study demonstrated the favorable biocompatibility of nanofibers. Overall, this study provides a promising and trustworthy material for biomedical applications.

Modeling and Prediction of Thermophysiological Comfort Properties of a Single Layer Fabric System Using Single Sector Sweating Torso.

Thermophysiological comfort is known to play a primary role in maintaining thermal balance, which corresponds to a person's satisfaction with their immediate thermal environment. Among the existing test methods, sweating torsos are one of the best tools to provide a combined measurement of heat and moisture transfer using non-isothermal conditions. This study presents a preliminary numerical model of a single sector sweating torso to predict the thermophysiological comfort properties of fabric systems. The model has been developed using COMSOL Multiphysics, based on the ISO 18640-1 standard test method and a single layer fabric system used in sportswear. A good agreement was observed between the experimental and numeral results over different exposure phases simulated by the torso test (R2 = 0.72 to 0.99). The model enables a systematic investigation of the effect of fabric properties (thickness, porosity, thermal resistance, and evaporative resistance), environmental conditions (relative humidity, air and radiant temperature, and wind speed), and physiological parameters (sweating rate) to gain an enhanced understanding of the thermophysiological comfort properties of the fabric system.

A novel inactivated virus system (InViS) for a fast and inexpensive assessment of viral disintegration.

The COVID-19 pandemic has caused considerable interest worldwide in antiviral surfaces, and there has been a dramatic increase in the research and development of innovative material systems to reduce virus transmission in the past few years. The International Organization for Standardization (ISO) norms 18,184 and 21,702 are two standard methods to characterize the antiviral properties of porous and non-porous surfaces. However, during the last years of the pandemic, a need for faster and inexpensive characterization of antiviral material was identified. Therefore, a complementary method based on an Inactivated Virus System (InViS) was developed to facilitate the early-stage development of antiviral technologies and quality surveillance of the production of antiviral materials safely and efficiently. The InViS is loaded with a self-quenched fluorescent dye that produces a measurable increase in fluorescence when the viral envelope disintegrates. In the present work, the sensitivity of InViS to viral disintegration by known antiviral agents is demonstrated and its potential to characterize novel materials and surfaces is explored. Finally, the InViS is used to determine the fate of viral particles within facemasks layers, rendering it an interesting tool to support the development of antiviral surface systems for technical and medical applications.

Wicking through complex interfaces at interlacing yarns.

HYPOTHESIS: Wicking flow in the wale direction of knit fabrics is slowed by capillary pressure minima during the transition at yarn contacts. The characteristic pore structure of yarns leads to an unfavorable free energy evolution and is the cause of these minima. EXPERIMENTS: Time-resolved synchrotron tomographic microscopy is employed to study the evolution of water configuration during wicking flow in interlacing yarns. Dynamic pore network modeling is used based on the obtained image data and distributions of delay times for pore intrusion. Good agreement is observed by comparison to the experimental data. FINDINGS: Yarn-to-yarn transition is found to coincide with slow water advance in a thin interface zone at the yarn contact. The pore spaces of the two yarns merge within this interface zone and provide a transition path. A deep capillary pressure minimum occurs while water passes through the center of the interface zone, effectively delaying the wicking flow. A pore network model considering pore intrusion delay times is expanded to include inter-yarn wicking and reproduce the observed wicking dynamics.

Wicking fingering in electrospun membranes.

Pronounced fingering of the waterfront is observed for in-plane wicking in thin, aligned electrospun fibrous membranes. We hypothesize that a perturbation in capillary pressure triggers the onset of fingering, which grows in a non-local manner based on the waterfront gradient. Vertical and horizontal wicking in thin electrospun membranes of poly(ethylene-co-vinyl alcohol) (EVOH) fibers with varying fiber alignment and degree of orientation is studied with backlight photography. A non-local transport model considering the gradient of the waterfront is developed, where fiber orientation is modeled with a correlated random field. The model shows that a transition from straight to highly fingered waterfront occurs during water uptake as observed in the experiment. The size and shape of the fingers depend on fiber orientation. Based on good model agreement, we show that, during wicking in thin electrospun membranes, fingering is initially triggered by a perturbation in capillary pressure caused by the underlying anisotropic and heterogeneous membrane structure which grows in a non-local manner depending on the waterfront gradient.

Wicking dynamics in yarns.

The spontaneous imbibition of a liquid within porous media, known as wicking, can display uncommon features in textiles and yarns. Yarns exhibited step-wise wicking dynamics not captured by current models. HYPOTHESIS: Wicking dynamics in yarns not only depend on inter-fiber pore filling, but are mainly determined by the pore-to-pore transition processes and the structure of the pore network. EXPERIMENTS: Fast X-ray tomographic microscopy is employed to reveal the pore scale processes and neutron radiography for the macroscopic water uptake in yarns. A semi-empirical pore network model is presented that employs the measured pore network topology and pore scale dynamics to reproduce the experimentally observed wicking dynamics in yarns. FINDINGS: The yarn pore system is a sparse network of long and narrow pores that promotes step-wise uptake dynamics. Wicking in yarns displays fast pore filling events in the order of seconds and long waiting times between filling events up to several minutes while navigating the pore network. As main result, we find that a few filling events directly determine the macroscopic behavior of wicking in the sparse pore network of yarns. It is necessary to consider pore-to-pore transition waiting times and the pore network structure to explain the characteristics of wicking dynamics in yarns.

Thioflavin-modified molecularly imprinted hydrogel for fluorescent-based non-enzymatic glucose detection in wound exudate.

The concentration of glucose in the body's fluids is an important parameter that can indicate pathological conditions such as the progress of infected wounds. Several wearables and implantable detection approaches have been developed with high selectivity and sensitivity for glucose. However, all of them have drawbacks such as low stability, limited selectivity, and often require complex technology. In this work, we present a fluorescent-based cost-efficient imprinted hydrogel (MIH_GSH) capable of detecting glucose within 30 â€‹min. The imprinting approach allows us to improve the selectivity for glucose, overcoming the low specificity and limited binding efficiency at neutral pH of boronic acid-based detection mechanisms. The binding affinity determined for glucose-MIH_GSH was indeed 6-fold higher than the one determined for the non-imprinted hydrogel with a calculated imprinting factor of 1.7. The limit of detection of MIH_GSH for glucose in artificial wound exudate was calculated as 0.48 â€‹mM at pH 7.4 proving the suitability of the proposed approach to diagnose chronic wounds (ca. 1 â€‹mM). MIH_GSH was compared with a commercial colorimetric assay for the quantification of glucose in wound exudate specimens collected from hospitalized patients. The results obtained with the two methods were statistically similar confirming the robustness of our approach. Importantly, whereas with the colorimetric assay sample preparation was required to limit the interference of the sample background, the fluorescent signal of MIH_GSH was not affected even when used to measure glucose directly in bloody samples. The sensing mechanism here proposed can pave the way for the development of cost-efficient and wearable point-of-care tools capable of monitoring the glucose level in wound exudate enabling the quick assessment of chronic injuries.

On the durability of surgical masks after simulated handling and wear.

After the spread of COVID-19, surgical masks became highly recommended to the public. They tend to be handled and used multiple times, which may impact their performance. To evaluate this risk, surgical masks of Type IIR were submitted to four simulated treatments: folding, ageing with artificial saliva or sweat and washing cycles. The air permeability, mechanical integrity, electrostatic potential, and filtration efficiency (FE) of the masks were measured to quantify possible degradation. Overall, air permeability and mechanical integrity were not affected, except after washing, which slightly degraded the filtering layers. Electrostatic potential and FE showed a strong correlation, highlighting the role of electrostatic charges on small particle filtration. A slight decrease in FE for 100 nm particles was found, from 74.4% for the reference masks to 70.6% for the mask treated in saliva for 8 h. A strong effect was observed for washed masks, resulting in FE of 46.9% (± 9.5%), comparable to that of a control group with no electrostatic charges. A dry store and reuse strategy could thus be envisaged for the public if safety in terms of viral and bacterial charge is ensured, whereas washing strongly impacts FE and is not recommended.

Understanding multiscale structure-property correlations in PVDF-HFP electrospun fiber membranes by SAXS and WAXS.

Electrospinning is a versatile technique to produce nanofibrous membranes with applications in filtration, biosensing, biomedical and tissue engineering. The structural and therefore physical properties of electrospun fibers can be finely tuned by changing the electrospinning parameters. The large parameter window makes it challenging to optimize the properties of fibers for a specific application. Therefore, a fundamental understanding of the multiscale structure of fibers and its correlation with their macroscopic behaviors is required for the design and production of systems with dedicated applications. In this study, we demonstrate that the properties of poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP) electrospun fibers can be tuned by changing the rotating drum speed used as a collector during electrospinning. Indeed, with the help of multiscale characterization techniques such as scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS), we observe that increasing the rotating drum speed not only aligns the fibers but also induces polymeric chain rearrangements at the molecular scale. Such changes result in enhanced mechanical properties and an increase of the piezoelectric ß-phase of the PVDF-HFP fiber membranes. We detect nanostructural deformation behaviors when the aligned fibrous membrane is uniaxially stretched along the fiber alignment direction, while an increase in the alignment of the fibers is observed for randomly aligned samples. This was analyzed by performing in situ SAXS measurements coupled with uniaxial tensile loading of the fibrous membranes along the fiber alignment direction. The present study shows that fibrous membranes can be produced with varying degrees of fiber orientation, piezoelectric ß-phase content, and mechanical properties by controlling the speed of the rotating drum collector during the fiber production. Such aligned fiber membranes have potential applications for neural or musculoskeletal tissue engineering.

Tailoring Fibre Structure Enabled by X-ray Analytics for Targeted Biomedical Applications.

The rising interest in designing fibres via spinning techniques combining the properties of various polymeric materials into advanced functionalised materials is directed towards targeted biomedical applications such as drug delivery, wearable sensors or tissue engineering. Understanding how these functional polymers exhibit multiscale structures ranging from the molecular level to nano-, micro-and millimetre scale is a key prerequisite for their challenging applications that can be addressed by a non-destructive X-ray based analytical approach. X-ray multimodalities combining X-ray imaging, scattering and diffraction allow the study of morphology, molecular structure, and the analysis of nano-domain size and shape, crystallinity and preferential orientation in 3D arrangements. The incorporation of X-ray analytics in the design process of polymeric fibers via their nanostructure under non-ambient conditions (i.e. temperature, mechanical load, humidity…) allows for efficient optimization of the fabrication process as well as quality control along the product lifetime under operating environmental conditions. Here, we demonstrate the successful collaboration between the laboratory of Biomimetic Textiles and Membranes and the Center of X-ray Analytics at Empa for the design, characterisation and optimisation of advanced functionalised polymeric fibrous material systems.

Community Masks - from an Emergency Solution to an Innovation Booster for the Textile Industry.

The COVID-19 pandemic resulted in shortages of personal protective equipment and medical devices in the initial phase. Agile small and medium-sized enterprises from regional textile industries reacted quickly. They delivered alternative products such as textile-based community masks in collaboration with industrial partners and research institutes from various sectors. The current mask materials and designs were further improved by integrating textiles with antiviral and antimicrobial properties and enhanced protection and comfort by novel textile/membrane combinations, key factors to increase the acceptance and compliance of mask wearing. The innocuity and sustainability of masks, as well as taking into account particular needs of vulnerable persons in our society, are new fields for textile-based innovations. These innovations developed for the next generation of facemasks have a high adaptability to other product segments, which make textiles an attractive material for hygienic applications and beyond.

Fabrication of a Wearable Flexible Sweat pH Sensor Based on SERS-Active Au/TPU Electrospun Nanofibers.

Development of wearable sensing platforms is essential for the advancement of continuous health monitoring and point-of-care testing. Eccrine sweat pH is an analyte that can be noninvasively measured and used to diagnose and aid in monitoring a wide range of physiological conditions. Surface-enhanced Raman scattering (SERS) offers a rapid, optical technique for fingerprinting of biomarkers present in sweat. In this paper, a mechanically flexible, nanofibrous, SERS-active substrate was fabricated by a combination of electrospinning of thermoplastic polyurethane (TPU) and Au sputter coating. This substrate was then investigated for suitability toward wearable sweat pH sensing after functionalization with two commonly used pH-responsive molecules, 4-mercaptobenzoic acid (4-MBA), and 4-mercaptopyridine (4-MPy). The developed SERS pH sensor was found to have good resolution (0.14 pH units for 4-MBA; 0.51 pH units for 4-MPy), with only 1 µL of sweat required for a measurement, and displayed no statistically significant difference in performance after 35 days (p = 0.361). Additionally, the Au/TPU nanofibrous SERS pH sensors showed fast sweat-absorbing ability as well as good repeatability and reversibility. The proposed methodology offers a facile route for the fabrication of SERS substrates which could also be used to measure a wide range of health biomarkers beyond sweat pH.

Tailoring the multiscale architecture of electrospun membranes to promote 3D cellular infiltration.

Controlling the architecture of engineered scaffolds is of outmost importance to induce a targeted cell response and ultimately achieve successful tissue regeneration upon implantation. Robust, reliable and reproducible methods to control scaffold properties at different levels are timely and highly important. However, the multiscale architectural properties of electrospun membranes are very complex, in particular the role of fiber-to-fiber interactions on mechanical properties, and their effect on cell response remain largely unexplored. The work reported here reveals that the macroscopic membrane stiffness, observed by stress-strain curves, cannot be predicted solely based on the Young's moduli of the constituting fibers but is rather influenced by interactions on the microscale, namely the number of fiber-to-fiber bonds. To specifically control the formation of these bonds, solvent systems of the electrospinning solution were fine-tuned, affecting the membrane properties at every length-scale investigated. In contrast to dichloromethane that is characterized by a high vapor pressure, the use of trifluoroacetic acid, a solvent with a lower vapor pressure, favors the generation of fiber-to-fiber bonds. This ultimately led to an overall increased Young's modulus and yield stress of the membrane despite a lower stiffness of the constituting fibers. With respect to tissue engineering applications, an experimental setup was developed to investigate the effect of architectural parameters on the ability of cells to infiltrate and migrate within the scaffold. The results reveal that differences in fiber-to-fiber bonds significantly affect the infiltration of normal human dermal fibroblasts into the membranes. Membranes of loose fibers with low numbers of fiber-to-fiber bonds, as obtained from spinning solutions using dichloromethane, promote cellular infiltration and are thus promising candidates for the formation of a 3D tissue.