Mechanical Properties Of Skin Research Articles

Developing biomimetic PVA/PAA hydrogels with cellulose nanocrystals inspired by tree frog structures for superior wearable sensor functionality

This study developed a wearable sensor device featuring biomimetic structures inspired by tree frog toe pads to measure shoulder joint movements effectively. A PVA/PAA double-network hydrogel was formulated by mixing PVA and PAA in a 3:7 ratio, resulting in a Young's modulus of 7.2 kPa, closely matching human skin's mechanical properties. To enhance moisture retention, the hydrogel was supplemented with 20 mL glycerin, increasing its weight retention rate to 95 % after 28 days, a 5.6-fold improvement over glycerin-free hydrogels. Additionally, the incorporation of 0.2 wt% cellulose nanocrystals (CNC) increased the cross-linking density, reducing the swelling ratio from 124 % to 106 % and minimizing the impact of swelling cycles on mechanical properties from 22 % to 4 %. Treefrog-inspired microstructures were fabricated on the sensor surface using laser cutting and casting techniques, significantly enhancing adhesion under humid conditions, with normal, lateral, and peel-off adhesion forces improving by 500, 700, and 700 %, respectively. The sensor demonstrated accurate measurement of shoulder joint movements with an error margin of 6.3 % for polar angles (45°-135°) and 7.8 % for azimuth angles (0°-45°). The accompanying smartphone application provided real-time feedback, helping to prevent exercise injuries and improve user awareness and control of shoulder movements, making it suitable for both rehabilitation and athletic training.

Development and Characterization of Film-Forming Solution Loaded with Syzygium cumini (L.) Skeels for Topical Application in Post-Surgical Therapies.

Considering the antioxidant and antimicrobial properties attributed to compounds in Syzygium cumini extract, this research aimed to advance postoperative therapeutic innovations. Specifically, the study assessed the physicochemical properties of a film-forming solution (FFS) incorporated with S. cumini, evaluating its therapeutic potential for postoperative applications. The S. cumini extract was meticulously characterized to determine its chemical composition, with particular emphasis on the concentration of phenolic compounds. Antioxidant and antimicrobial assays were conducted to assess the extract's efficacy in these domains. Following this, an FFS containing S. cumini was formulated and evaluated comprehensively for skin adhesion, mechanical and barrier properties, and thermal behavior. The antioxidant and antimicrobial activities of the S. cumini extract demonstrated promising results, indicating its potential utility as an adjunct in postoperative care. The developed FFS exhibited favorable physicochemical properties for topical application, including adequate skin adhesion and appropriate pH levels. Moreover, chemical and thermal analyses confirmed the formulation's stability and the retention of the extract's beneficial properties. Overall, the findings suggest that the S. cumini-loaded FFS holds significant potential as a valuable therapeutic tool for post-surgical management.

Dual optical elastography detects -induced alterations in the biomechanical properties of skin scaffolds.

The skin's mechanical properties are tightly regulated. Various pathologies can affect skin stiffness, and understanding these changes is a focus in tissue engineering. Ex vivo skin scaffolds are a robust platform for evaluating the effects of various genetic and molecular interactions on the skin. Transforming growth factor-beta ( ) is a critical signaling molecule in the skin that can regulate the amount of collagen and elastin in the skin and, consequently, its mechanical properties. This study investigates the biomechanical properties of bio-engineered skin scaffolds, focusing on the influence of , a signaling molecule with diverse cellular functions. The receptor I inhibitor, galunisertib, was employed to assess the mechanical changes resulting from dysregulation of . Skin scaffold samples, grouped into three categories (control, -treated, and + galunisertib-treated), were prepared in two distinct culture media-one with aprotinin (AP) and another without. Two optical elastography techniques, namely wave-based optical coherence elastography (OCE) and Brillouin microscopy, were utilized to quantify the biomechanical properties of the tissues. Results showed significantly higher wave speed (with AP, ; without AP, ) and Brillouin frequency shift (with AP, ; without AP, ) in -treated group compared with the control group. The difference in wave speed between the control and + galunisertib with ( ) and without AP ( ) was not significant. Moreover, the + galunisertib-treated group exhibited lower wave speed without and with AP and reduced Brillouin frequency shift than the -treated group without AP, further strengthening the potential role of in regulating the mechanical properties of the samples. These findings offer valuable insights into -induced biomechanical alterations in bio-engineered skin scaffolds, highlighting the potential of OCE and Brillouin microscopy in the development of targeted therapies in conditions involving abnormal tissue remodeling and fibrosis.

Comparing microstructure and mechanical properties of AlSi10 alloy produced by powder bed fusion-laser beam and high pressure die casting

PurposePowder bed fusion-laser beam (PBF-LB) is a rapidly growing manufacturing technology for producing Al-Si alloys. This technology can be used to produce high-pressure die-casting (HPDC) prototypes. The purpose of this paper is to understand the similarities and differences in the microstructures and properties of PBF-LB and HPDC alloys.Design/methodology/approachPBF-LB AlSi10Mg and HPDC AlSi10Mn plates with different thicknesses were manufactured. Iso-thermal heat treatment was conducted on PBF-LB bending plates. A detailed meso-micro-nanostructure analysis was performed. Tensile, bending and microhardness tests were conducted on both alloys.FindingsThe PBF-LB skin was highly textured and softer than its core, opposite to what is observed in the HPDC alloy. Increasing sample thickness increased the bulk strength for the PBF-LB alloy, contrasting with the decrease for the HPDC alloy. In addition, the tolerance to fracture initiation during bending deformation is greater for the HPDC material, probably due to its stronger skin region.Practical implicationsThis knowledge is crucial to understand how geometry of parts may affect the properties of PBF-LB components. In particular, understanding the role of geometry is important when using PBF-LB as a HPDC prototype.Originality/valueThis is the first comprehensive meso-micro-nanostructure comparison of both PBF-LB and HPDC alloys from the millimetre to nanometre scale reported to date that also considers variations in the skin versus core microstructure and mechanical properties.

Design and validation of a DMA-inspired device for in-vivo measurement of human skin mechanics: a finite element analysis approach

Abstract This study introduces a novel method for measuring the mechanical properties of human skin in-vivo, inspired by dynamic mechanical analysis (DMA). We designed and applied a DMA-like device to living human skin and validated its functionality through finite element analysis (FEA) on an ideally elastic skin model. The device features multiple testing modes, including horizontal movement in both same and opposite directions with optional pre-stretching. Stress-strain behaviours obtained from FEA align with initial setup parameters, serving as powerful tools for further research into the mechanical properties of skin. This method is expected to have potential significance in biomechanical theory, clinical, and healthcare applications.

Dynamic Responses of Human Skin and Fascia to an Innovative Stimulation Device-Shear Wave Stimulation.

Exposure to mechanical stimuli such as pressure and stretching prompts the skin to undergo physiological adaptations to accommodate and distribute applied forces, a process known as mechanotransduction. Mechanotherapy, which leverages mechanotransduction, shows significant promise across various medical disciplines. Traditional methods, such as massage and compression therapy, effectively promote skin healing by utilizing this mechanism, although they require direct skin contact. This study introduces a novel contactless modality, Shear Wave Stimulation (SWS), and evaluates its efficacy compared to traditional massage in eliciting responses from human skin and fascia. Fifteen healthy volunteers received SWS, while another fifteen volunteers received massage. Tests of skin mechanical properties revealed significant enhancements in skin shear modulus for both methods, showing an increase of approximately 20%. Additionally, deformation analysis of ultrasound images showed distinct responses of the skin and fascia to the two stimuli. SWS induced extension in the dermis (∼18%), hypodermis (∼16%), and fascia (∼22%) along the X and Y axes. In contrast, massage compressed the skin layers, reducing the dermis by around 15% and the hypodermis by about 8%, while simultaneously stretching the superficial fascia by approximately 8%. The observed extension across the entire skin with SWS highlights its potential as a groundbreaking contactless approach for promoting skin healing. Furthermore, the differing responses in blood flow reaffirm the distinct stimulation modes of SWS and massage. These findings establish a foundation for future innovative skin therapy modalities.

Skin mechanical properties measured with skin elasticity measurement device in patients with lymphedema: Scoping review.

Skin conditions in patients with lymphedema have been identified according to changes in skin mechanical properties. The skin elasticity meter is a non-invasive tool for measuring the mechanical properties of the skin; however, its potential use in patients with lymphedema has received little attention. This review aimed to provide an overview of studies measuring the skin mechanical properties of patients with lymphedema using a skin elasticity meter. Search terms and synonyms related to lymphedema and skin mechanical property measurement using a skin elasticity meter were identified, and electronic databases containing articles in English were searched. A total of 621 articles were retrieved, and four articles were analyzed after screening. Despite this research subject receiving increasing attention, no consensus has been reached regarding the best methods. Measurement methods are expected to be standardized in the future to elucidate the skin mechanical properties of patients with lymphedema.

Assessment of Intraday Variations in Skin Indentation Resistance.

Information about the mechanical properties of skin and their changes with age and other conditions is important to help characterize skin physiology and pathological changes. One method to obtain this information is to measure the force required to indent the skin to a specified indentation depth (FORCE). This process measures the tissue's resistance to indentation or its compressibility and is related to the tissue's elastic modulus. Since such measurements are made in clinical and other settings at various times of day (TOD), it is useful to estimate the extent of intraday variations in FORCE that may be expected. This report focuses on this issue. FORCE was self-measured on the volar forearm, 5 cm distal to the antecubital fossa, every two hours from 08:00 to 24:00 hours on two consecutive days by 12 medical students (six females and six males) who were trained in the measurement process using an indentation device (SkinFibroMeter). Variability in FORCE versus TOD was analyzed using the nonparametric Friedman test and differences between genders by the nonparametric Wilcoxon test. Differences between the first day (day 1) and the second day (day 2) were tested at each TOD. The whole-body fat percentage (FAT%) and water percentage (H2O%) were determined for each participant via bioimpedance measurements at 50 KHz. The age and BMI of the combined group (mean ± SD) were 24.5 ± 1.5 years and 23.2 ± 3.3 kg/m2.The overall average FORCE (mean ± SD) for the day over the 16 hours was 84.1 ± 22.7 mN and for day 2, it was 83.4 ± 28.5 mN with no significant difference between day 1 and day 2. For females, the overall two-day average FORCE (mean ± SD) over the 16 hours was 81.8 ± 20.3 mN and for males, it was 85.7 ± 30.1 mN with no significant difference between them (p = 0.271). Overall, there was no statistically significant difference in FORCE among TOD (p = 0.568). FORCE was not correlated with either FAT%, HTO%, or BMI. The findings indicate no statistically significant variation in indentation force in females, males, or combined concerning the TODof the measurement or differences between consecutive days at corresponding times. This suggests that whether such measurements are done in a research setting or within a clinic, they can be done at various TODwith minimal expected variation for a given subject. However, an extension of these findings to persons with skin conditions or ages not herein evaluated must await further study.

Effects of spironolactone on skin biophysical properties in women with acne treated with oral spironolactone.

Spironolactone (SPL) is an effective treatment for women acne, but other effects on skin biophysical properties remain to be investigated. The aim of the current study was to explore the effects of oral SPL used to treat women acne on skin biophysical properties, including hydration, transepidermal water loss (TEWL), skin surface lipid (SSL) levels, mechanical properties, color, pH, and pore size. Twenty-five Thai women with acne treated with oral SPL were followed for 6 months. Skin hydration, TEWL, SSL levels, mechanical properties, color, pH, and pore size of the forehead, chest, and inner arm were evaluated at baseline and 2, 4, and 6 months after treatment with oral SPL. Facial and upper back pore size were also assessed. Clinical outcomes were changes in these skin biophysical properties at each visit compared with baseline. Skin hydration, TEWL, SSL levels, color, pH, and pore size remained stable throughout the study. Facial skin parameters at 6 months demonstrated the following changes: hydration levels, 7.60 (95% confidence interval [CI], -59.74 to 74.94); TEWL, -2.36 (95% CI, -5.77 to 1.06); L* value, 0.51 (95% CI, -0.70 to 1.72); individual typology angle, 1.65 (95% CI -2.27 to 5.57); pH, 0.01 (95% CI -0.43 to 0.46); pore size, -0.24 (95% CI, -1.21 to 0.73); and SSL levels, 7.60 (95% CI -59.74 to 74.94). Improvement of facial mechanical properties was observed. R0 (indicating skin tightness) and R1 (indicating elasticity) showed significant decreases (-0.076 [95% CI, -0.141 to -0.010] and -0.016 [95% CI, -0.033 to -0.001]). R3 and R4 (representing tiring effects) were also improved (-0.091 [95% CI, -0.158 to -0.025] and -0.022 [95% CI, -0.044 to -0.001]). Parameters in the truncal and inner arm areas remained stable, except for skin elasticity and tiring effects, which exhibited a similar trend of improvement as the facial area. The changes were notable as early as 4 months. Oral SPL used for acne did not impair the skin barrier. Moreover, the skin mechanical properties were improved at 4 to 6 months.

In the face and neck, keloid scar distribution is related to skin thickness and stiffness changes associated with movement.

Keloid scars tend to occur in high-tension sites due to mechanical stimuli that are involved in their development. To date, a detailed analysis of keloid distribution focused specifically on facial and neck areas has not been reported, and limited literature exists as to the related mechanical factors. To rectify this deficiency of knowledge, we first quantified the facial and neck keloid distribution observed clinically in 113 patients. Subsequently, we performed a rigorous investigation into the mechanical factors and their associated changes at these anatomic sites in healthy volunteers without a history of pathologic scarring. The association between keloid-predilection sites and sebaceous gland-dense and acne-prone sites was also examined. To assess skin stretch, thickness and stiffness, VECTRA, ultrasound and indentometer were utilised. Baseline skin stiffness and thickness were measured, as well as the magnitude of change in these values associated with facial expression and postural changes. Within the face and neck, keloids were most common near the mandibular angle (41.3%) and lateral submental (20.0%) regions. These areas of increased keloid incidence were not associated with areas more dense in sebaceous glands, nor linked consistently with acne-susceptible regions. Binomial logistic regression revealed that changes in skin stiffness and thickness related to postural changes significantly predicted keloid distribution. Skin stiffness and thickness changes related to prolonged mechanical forces (postural changes) are most pronounced at sites of high keloid predilection. This finding further elucidates the means by which skin stretch and tension are related to keloid development. As a more detailed analysis of mechanical forces on facial and neck skin, this study evaluates the nuances of multiple skin-mechanical properties, and their changes in a three-dimensional framework. Such factors may be critical to better understanding keloid progression and development in the face and neck.

Water-compatible cross-linked pyrrolidone acrylate pressure-sensitive adhesives with persistent adhesion for transdermal delivery: Synergistic effect of hydrogen bonding and electrostatic force

Poor skin adhesion and mechanical properties are common problems of pressure-sensitive adhesive (PSA) in transdermal drug delivery system (TDDS). Its poor water compatibility also causes the patch to fall off after sweating or soaking in the application site. To solve this problem, poly (2-Ethylhexyl acrylate-co-N-Vinyl-2-pyrrolidone-co-N-(2-Hydroxyethyl)acrylamide) (PENH), a cross-linked pyrrolidone polyacrylate PSA, was designed to improve the adhesion and water resistance of PSA through electrostatic force and hydrogen bonding system. The structure of PENH was characterized by 1H NMR, FTIR, DSC, and other methods. The mechanism was studied by FTIR, rheological test, and molecular simulation. The results showed that the PENH patch could adhere to human skin for more than 10 days without cold flow, and it could still adhere after sweating or water contact. In contrast, the commercial PSA Duro-Tak® 87-4098 and Duro-Tak® 87-2852 fell off completely on the 3rd and 6th day, respectively, and Duro-Tak® 87-2510 showed a significant dark ring on the second day. Mechanism studies have shown that the hydrogen bond formed by 2-ethylhexyl acrylate (2-EHA), N-vinyl-2-pyrrolidinone (NVP), and N-(2-Hydroxyethyl)acrylamide (HEAA) enhances cohesion, the interaction with skin improves skin adhesion, and the electrostatic interaction with water or drug molecules enhances the ability of water absorption and drug loading. Due to the synergistic effect of hydrogen bonds and electrostatic force, PENH can maintain high cohesion after drug loading or water absorption. PENH provides a choice for the development of water-compatible patches with long-lasting adhesion. Statement of significanceBased on the synergistic effect of hydrogen bonding and electrostatic force, a hydrogen-bonded, cross-linked pyrrolidone acrylate pressure-sensitive adhesive for transdermal drug delivery was designed and synthesized, which has high adhesion and cohesive strength and is non-irritating to the skin. The patch can be applied on the skin surface continuously for more than 10 days without the phenomenon of “dark ring”, and the patch can remain adherent after the patient sweats or bathes. This provides a good strategy for choosing a matrix for patches that require prolonged administration.

Influence of nanocarrier additives on biomechanical response of a rat skin.

Skin health monitoring focuses on identifying diseases through the assessment of the mechanical properties of the skin. These properties may degrade with time, which can alter the skin's natural frequencies and the form of the modes associated with those frequencies. Exploring the skin's mechanical properties can enhance our understanding of its dynamics, improving clinical trials and diagnostics. In this work, the dynamics of the skin were measured using a laser-based non-invasive optical sensor experiment. We measured the skin's mechanical properties over time by analyzing its resonant frequencies and mode shapes. A nanocarrier gel and ketoconazole cream were topically applied to keep the skin hydrated and facilitate deeper penetration of the additives in the skin. Time-based research was used to assess the effect of different formulations on skin elasticity. Experimental results for the modulus of elasticity were compared with those obtained using Finite Element Analysis (FEA) simulations. We observed a reduction in frequencies of cream and gel-treated skin by 29.98% and 44.029% respectively compared to normal skin (frequency: 263.3 ± 1.18 Hz and Modulus of elasticity: 7.56 ± 2.60 MPa). A decrease in stiffness (function of frequency) attributed to increased water content, was observed in cream- and nanocarrier gel-treated skin compared to normal skin. Experimental and numerical results are found to be consistent with one another. This optical sensor-based approach has the potential for studying diseased skin mechanics and its response to gel and cream treatments, aiming to reduce skin disorder morbidity and severity.

Peeling mechanism of tomato induced by HHAIB: Microscopic, ultrastructure, chemical, physical and mechanical properties perspectives

In order to better manage the peeling degree and avoid unnecessary losses, the current work aimed to explore the peeling mechanism of a novel peeling technology, high-humidity hot air impingement blanching (HHAIB). The relationships between HHAIB peeling performance and the changes in skin temperature, skin structure, water state, pectin fractions content, and skin mechanical properties of tomatoes were analyzed. Results showed, after HHAIB treatment, the epicuticular wax was disrupted, the skin exhibited more and longer random cracks, the degradation of inner skin tissue was observed by transmission electron microscopy, the free water percentage increased resulting in water loss in the whole tomato, the water-soluble pectin contents decreased in tomato fleshes, while the contents of chelate-soluble pectin and sodium-carbonate-soluble pectin increased. HHAIB heating reduced the elongation at break, and increased Young's Modulus of tomato peel. This study revealed the HHAIB peeling mechanism and provided new insights for developing HHAIB peeling technology.

Intra- and inter-rater reliabilities of skin mechanical properties measured in healthy individuals using skin elasticity meter

Purpose The aim of this study is to establish a standardized measurement method and to examine the intra- and inter-reliabilities and absolute reliability of measuring skin mechanical properties using a skin elasticity meter (Cutometer®). Methods Ten healthy participated in the study. Skin mechanical properties were measured at four sites: upper arm, lower arm, upper leg and lower leg on both sides in supine position using a non-invasive skin elasticity meter by two trained different raters. The measurements include quantitative indices of the maximal distensibility (R0), elasticity (R2, R5, R7), and viscoelasticity (R6). Intra- and inter- relative reliabilities were determined using the intraclass correlation coefficient (ICC) (1,1) and ICC (2,1) methods, respectively. The absolute reliability was assessed via the Bland-Altman analysis. Moreover, we evaluated the minimal detectable change at a 95% confidence level (MDC95). Results At each site, the ICC (1,1) values were >0.90, and the ICC (2,1) values were >0.50. The Bland–Altman analysis did not reveal any fixed errors, and several sites and parameters have proportional errors. Conclusions In this study, intra- and inter-reliabilities were measured at “excellent” and more than “moderate” levels, respectively. However, because some proportional errors were observed, the limits of reliability agreement should be considered when using the proposed methods. We believe that the results of this study can be applied to clinical research in field of rehabilitation treatment.

Dynamic behavior of multilayered skin structure: A preliminary numerical and analytical microscopic analysis

High-velocity micro-particle impact on multilayered skin structure is of interest in the framework of transdermal drug delivery system. The understanding of the physical impact process in this phenomenon is complex and lack of experimental investigations in the literature. This work aims to investigate the impact responses of multilayered skin structure impacted by high-velocity micro-scale particle utilizing numerical and analytical analysis. Numerical and analytical analysis were conducted based on Smoothed Particle Hydrodynamics (SPH) method and Poncelet model, respectively. A good agreement exits between analytical and numerical penetration trajectories and velocity-penetration relationships with an initial impact velocity of 200 m/s, while the discrepancies increase with a higher velocity of 600 m/s. The comparison between analytical and numerical results reveals that the developed numerical model is able to reasonably predict the impact responses of different skin layers under micro-particle impact. The present work is a first step to study high-velocity micro-particle impact responses applying real multilayered skin structures and mechanical properties, which could be further investigated to interpret and guide the design of transdermal drug delivery equipment.

Layer-by-Layer Analysis of In Vitro Skin Models.

In vitro human skin models are evolving into versatile platforms for the study of skin biology and disorders. These models have many potential applications in the fields of drug testing and safety assessment, as well as cosmetic and new treatment development. The development of in vitro skin models that accurately mimic native human skin can reduce reliance on animal models and also allow for more precise, clinically relevant testing. Recent advances in biofabrication techniques and biomaterials have led to the creation of increasingly complex, multilayered skin models that incorporate important functional components of skin, such as the skin barrier, mechanical properties, pigmentation, vasculature, hair follicles, glands, and subcutaneous layer. This improved ability to recapitulate the functional aspects of native skin enhances the ability to model the behavior and response of native human skin, as the complex interplay of cell-to-cell and cell-to-material interactions are incorporated. In this review, we summarize the recent developments in in vitro skin models, with a focus on their applications, limitations, and future directions.

Constructing epidermal rete ridges using a composite hydrogel to enhance multiple signaling pathways for the maintenance of epidermal stem cell niche.

The undulating microstructure rete ridge (RR) located at the junction between the dermis and epidermis plays a crucial role in improving skin mechanical properties and maintaining skin homeostasis. However, the investigation of RR microstructures is usually neglected in current tissue engineering for skin regeneration. Here, to create an epidermal model with RR microstructures, keratinocytes were cultured on a patterned GelMA-PEGDA hydrogel constructed using molding technology. Furthermore, grafting acryloylated Arg-Gly-Asp (RGD) peptides on the hydrogel surface significantly improved cell adhesion, fusion, and development. RT-PCR, Western blot, and immunofluorescence staining confirmed that cells on RR microstructures exhibited higher gene and protein expression associated with epidermal stem cells. RNA sequencing analysis of cells on RR microstructure showed higher gene expression profiles related to stem cell maintenance, basement membrane formation, and epidermal development. Furthermore, RT-PCR analysis of epidermal models of various dimensions demonstrated that smaller microstructures were more conducive to epidermal stem cell marker gene expression, which is analogous to human skin. Overall, we have successfully developed a method for integrating RR microstructures into an epidermal model that mimics natural skin to maintain epidermal stem cell niche, providing a valuable reference for researching skin regeneration within the fields of tissue engineering and regenerative medicine. STATEMENT OF SIGNIFICANCE: This study presents a method for precisely fabricating microstructures of skin rete ridges using composite hydrogels, thereby creating a skin model that mimics natural human skin. The findings reveal that this microstructure provides a stem cell niche that regulates the pathways and promotes the expression of proteins related to epidermal stem cells. This work advances the functional properties of tissue engineered skin and holds promise for improving the therapeutic efficacy of artificial skin grafts for the skin wounds.

Potential predictive effect of mechanical properties of the plantar skin and superficial soft tissue, and vibration perception on plantar loading during gait in individuals with diabetes

BackgroundThis exploratory study aimed to investigate the extent to which mechanical properties of the plantar skin and superficial soft tissue (hardness, stiffness, and thickness) and vibration perception thresholds (VPTs) predict plantar pressure loading during gait in people with diabetes compared to healthy controls.MethodsMechanical properties, VPTs, and plantar loadings during gait at the heel and first metatarsal head (MTH) of 20 subjects with diabetes, 13 with DPN, and 33 healthy controls were acquired. Multiple regression analyses were used to predict plantar pressure peaks and pressure-time integrals at both locations based on the mechanical properties of the skin and superficial soft tissues and VPTs.ResultsIn the diabetes group at the MTH, skin hardness associated with 30-Hz (R2 = 0.343) and 200-Hz (R2 = 0.314) VPTs predicted peak pressure at the forefoot. In the controls at the heel, peak pressure was predicted by the skin thickness, hardness, and stiffness associated with 30-Hz (R2 = 0.269, 0.268, and 0.267, respectively) and 200-Hz (R2 = 0.214, 0.247, and 0.265, respectively) VPTs.ConclusionThe forefoot loading of people with diabetes can be predicted by the hardness of the skin when combined with loss of vibration perception at low (30-Hz) and high (200-Hz) frequencies. Further data from larger sample sizes are needed to confirm the current findings.

Use of a novel indentometer to evaluate skin stiffness in healthy and diseased human skin.

Mechanical behavior of the skin can be evaluated by different non-invasive methods. In this study, we applied a new measurement device based on indentometry to determine the skin mechanical properties in healthy individuals and in patients with systemic sclerosis (SSc). Three studies were performed. Study 1 included 100 healthy individuals (46 male and 54 female) divided into four age groups with mean ages of 21.5, 28.9, 51.2, and 69.3 years, respectively. Test sites were located on the center of the forehead and the middle of both volar forearms. Study 2 included 16 healthy individuals (two males and 14 females). Test sites were on both volar forearms. Measurements were made before and after the application of Vaseline and emulsion with 12% urea. Study 3 included 20 patients (one male and 19 females) with SSc and 60 age-matched healthy individuals (23 males and 37 females). Test sites were on the center of the forehead and the middle of both volar forearms. Skin stiffness was measured with skin Indentometer IDM 800 (Courage + Khazaka, Cologne, Germany) equipped with two probes with pin diameters of 3 and 5mm, respectively. The stiffer the skin, the less deep the displacement by the indenter. The smaller the diameter, the deeper the pin will go into the skin when using the same force. In addition, the Corneometer CM 820 (Courage + Khazaka) was used to determine epidermal water content in study 2. Indentometric (IDM) values of healthy subjects measured with both probes were lower on the forehead compared to volar forearms. There was no significant difference between both forearms. In all age groups, the IDM values on the male forearms were lower than on the female forearms whereas there was no significant difference on the forehead. In both sex and on all test locations a significant positive correlation between age and IDM values measured with both probes was observed. There was a significant positive correlation between IDM values measured with both probes. The application of moisturizers induced significant changes in epidermal water content whereas the IDM values remained unchanged. At both the forehead and volar forearms, the IDM values in patients with SSc were significantly lower compared to the healthy control skin. The non-invasive indentometric method used can successfully distinguish the changes in normal skin mechanical properties related to age, sex, and anatomical location, as well as in patients with SSc. The method is not appropriate to study the changes related to epidermal hydration.

Smart epidermal electrophysiological electrodes: Materials, structures, and algorithms

Epidermal electrophysiological monitoring has garnered significant attention for its potential in medical diagnosis and healthcare, particularly in continuous signal recording. However, simultaneously satisfying skin compliance, mechanical properties, environmental adaptation, and biocompatibility to avoid signal attenuation and motion artifacts is challenging, and accurate physiological feature extraction necessitates effective signal-processing algorithms. This review presents the latest advancements in smart electrodes for epidermal electrophysiological monitoring, focusing on materials, structures, and algorithms. First, smart materials incorporating self-adhesion, self-healing, and self-sensing functions offer promising solutions for long-term monitoring. Second, smart meso-structures, together with micro/nanostructures endowed the electrodes with self-adaption and multifunctionality. Third, intelligent algorithms give smart electrodes a “soul,” facilitating faster and more-accurate identification of required information via automatic processing of collected electrical signals. Finally, the existing challenges and future opportunities for developing smart electrodes are discussed. Recognized as a crucial direction for next-generation epidermal electrodes, intelligence holds the potential for extensive, effective, and transformative applications in the future.