Skin Application Research Articles

Cell membrane and extracellular vesicle membrane‐coated nanoparticles: An envisaged approach for the management of skin conditions

AbstractCell membrane‐coated biomimetic nanosystems have been recognized as promising drug delivery vehicles in recent years for the management of diverse skin conditions. Nanoparticles (NPs) coated with biomembranes, derived from either cell membranes or subcellular structures (e.g., extracellular vesicles), offer an opportunity to combine the biological interfacial characteristics of the coating alongside with the internal core component at the nanoscale. The biomimetic coating enhances the biocompatibility of NPs and their interaction with the skin, improving skin affinity, contact, and retention. This coating also enables the controlled release of drugs and provides skin‐targeting capabilities, which collectively improve the effectiveness, safety, and stability of topical and transdermal formulations. In this context, the current review delves into the recent progress in using biomimetic NPs for skin therapeutics. Specifically, it examines the various types of coatings, including their origins, heterogeneous functions, and surface molecular repertoires, in great detail. Additionally, this review presents the methods of preparing and characterizing biomimetic‐coated NPs. Furthermore, the potential of bioinspired NPs in treating a range of skin‐related conditions has been meticulously explored. Last, the toxicological aspects of these NPs have been thoroughly examined to provide a thorough summary of the evolution of biomimetic‐coated nanosystems for skin applications.

The effect of using a local skin cooling device on arteriovenous fistula cannulation pain and comfort level of patients on hemodialysis: A single-blind randomized controlled study.

The study aimed to investigate the impact of the using local skin cooling on arteriovenous fistula cannulation pain and the comfort levels of hemodialysis patients. The single-blind randomized controlled trial was formed with 50 patients between June 20, 2023, and July 31, 2023, in the hemodialysis units of two state hospitals in Turkey. Patients were randomly assigned to either the experimental group (n = 25) or the control group (n = 25) using the block randomization method. This data were collected through the use of the CoolSense device, the "Patient Information Form," the "Verbal Category Scale," and the "General Comfort Scale." Patients in the experimental group received the local skin cooling for five seconds during arteriovenous fistula cannulation, while the control group followed the standard hospital protocol. The study was registered on Clinical Trials (NCT06144801). The study revealed that the application of the local skin cooling during arteriovenous fistula cannulation significantly reduced pain and increased patients' comfort levels, demonstrating an anesthetic effect (p < 0.001). Furthermore, it was observed that as pain levels decreased, patient comfort levels increased (p < 0.001). It is concluded that the using lokal skin cooling is an effective tool for reducing pain and enhancing comfort during arteriovenous fistula cannulation in hemodialysis patients.

Biodegradable, Self‐Adhesive, Stretchable, Transparent, and Versatile Electronic Skins Based on Intrinsically Hydrophilic Poly(Caproactone‐Urethane) Elastomer

In biomedical sciences, there is a demand for electronic skins with highly sensitive tactile sensors that have applications in patient monitoring, human–machine interfaces, and on‐body sensors. Sensor fabrication requires high‐performance conductive surfaces that are transparent, breathable, flexible, and easy to fabricate. It is also preferable if the electrodes are easily processable as wastes, for example, are degradable. In this work, the design and fabrication of hydrophilic silanol/amine‐terminated poly(caprolactone‐urethane) (SA‐PCLU) elastomer‐based breathable, stretchable, and biodegradable electrodes are reported. Ag nanowires dispersed in water are sprayed onto the intrinsically hydrophilic electrospun SA‐PCLU that became embedded into the scaffold and formed conformal hydrophilic polyurethane‐based conductive networks (HPCN). The electrodes are used to fabricate capacitive, curvature, and strain sensors, all having monomaterial composition. In addition to displaying particularly good transparencies at low sheet resistances, stretchability, hydrophilicity, and tight and conformal bonding with the target surface, the electrodes also allow the evaporation of perspiration, making them suitable for epidermal sensors for long‐time use. The application of the HPCN electrodes in flexible electronics and bionic skin applications is demonstrated through gesture monitoring experiments and swelling sensors.

Percolation network study of highly sensitive buckled elastomeric piezoresistive sensors

Abstract Flexible pressure sensors are needed for future artificial electronic skin applications. Carbon black (CB)-enhanced elastomers are known for their unique conductivity, allowing for special uses in sensor technology. This research analyzes the sensitivity of elastomeric sensors reinforced with CB, under a pre-strained buckle, using a modified percolation network model to enhance performance in sensing applications. The finite element method is employed to analyze the piezoresistive characteristics of the sensors across various thicknesses. The research involves analyzing the strain patterns of buckled piezoresistive sensors when an indenter applies a load, and how this influences the sensors’ resistivity. The mechanical parameter is directly correlated to the sensor sensitivity through the maximum principal strain. The model shows a good agreement with the experimental data. The pressure sensitivity resulting from indenter compressive contact is 0.03 and 0.0061 kPa−1 in the pressure range of 0–1 and 0–5 kPa for wavy and straight 1000 μm buckled sensors, respectively. The results show that the film with 50% taller waves has a 40%–60% narrower pressure sensing ranges. Moreover, results indicate that adding waves to the geometry of the sensor improves the piezoresistive behavior by increasing the relative displacements of edges. Results also reveal more stable performance from fewer waves and a higher working range by thicker sensors.

Thymol-Loaded Polymeric Nanocapsules’ Repellent Activity on Nymphs of Rhipicephalus sanguineus Sensu Lato

Thymol-loaded polymeric nanocapsules were developed in this study to control volatilization and drug release for repellent application on Rhipicephalus sanguineus nymphs. Policaprolactone-loaded nanocapsules were prepared and characterized by diameter, PdI, zeta potential, pH, entrapment efficiency, and thymol content. Moreover, drug release, skin permeation profile, and repellent activity were evaluated. Nanocapsules showed a mean diameter of 195.7 ± 0.5 nm, a PdI of 0.20 ± 0.01, a zeta potential of −20.6 ± 0.3 mV, a pH of 4.7 ± 0.1, and an entrapment efficiency and a thymol content of 80.1 ± 0.1% and 97.9 ± 0.2%, respectively. The nanosystem progressively released 68.6 ± 2.3% of the thymol over 24 h, demonstrating that it can control drug release. Thymol-loaded nanocapsules showed less epidermis penetration upon skin application than pure thymol (control). Moreover, nanocapsules showed 60–70% repellency for 2 h against Rhipicephalus sanguineus nymphs. Thus, the nanocapsules proved to be a promising alternative for use as an arthropod repellent.

A skin-inspired anisotropic multidimensional sensor based on low hysteresis organohydrogel with linear sensitivity and excellent robustness for directional perception

Human skin has complex sensors to perceive three-dimensional stimuli from the environment. Skin-inspired flexible sensors with multidimensional and directional perception are desirable for applications in intelligent robots and human–machine interaction. Herein, wearable multidimensional sensors have been fabricated by macroscopically assembling 3D-printed microstructured anisotropic organohydrogel sensory units through robust interfacial adhesion. The organohydrogel is crosslinked using microgels and starch microparticles through non-covalent interactions, and composited with short carbon fibers as conductive fillers. The physical network exhibits low hysteresis against 5000 cyclic loadings, which demonstrates excellent robustness in both mechanical properties and sensory performance. The organohydrogel precursor is printed into a cone-shaped sensor with a pressure sensitivity 50 times higher than that of its bulk counterpart. A sea cucumber epidermis-like microstructured sensor with abundant highly sensitive cone array is assembled with 3D-printed anisotropic gels with highly aligned carbon fibers inside, generating a multidimensional sensor capable of perceiving stimuli along X-, Y-, and Z-axis. The assembled sensor can directionally distinguish external forces and identify human motions. This study demonstrates a promising strategy to fabricate well-structured organohydrogel sensors for applications in electronic skin, biomimetic flexible electronics, and artificial intelligence.

Immortelle Essential-Oil-Enriched Hydrogel for Diabetic Wound Repair: Development, Characterization, and In Vivo Efficacy Assessment

Background: Alarming data revealed that 19% to 34% of adults with diabetes mellitus develop chronic wounds, which are characterized by impaired healing and a higher risk of infections. Inspired by the traditional use of immortelle for wound healing and the lack of scientific evidence regarding how it thoroughly influences tissue regeneration, we aimed to formulate a hydrogel loaded with immortelle essential oil and assess its effectiveness on diabetic excision wounds. Methods: The rheological properties of the hydrogel, an in vivo safety test, as well as wound healing capacity, were determined in rats with induced diabetes and excision wounds. Diabetic rats were divided into four groups: untreated, treated with 1% silver sulfadiazine ointment, treated with a gel base, and treated with the immortelle essential oil-based hydrogel. Results: It was revealed that the hydrogel exerts pseudoplastic behavior and has no potential to act as an irritant, thus highlighting its suitability for skin application. Moreover, analysis of macroscopic, biochemical, and histopathological data revealed that the immortelle essential oil-based hydrogel significantly improves wound repair. Superior re-epithelialization, scar maturation, and increased collagen fiber density were achieved after immortelle essential oil-based gel application. Conclusions: These findings suggest that the immortelle essential oil-based hydrogel could be a natural, safe, and effective wound-healing dressing.

Biomaterials for reliable wearable health monitoring: Applications in skin and eye integration

Recent advancements in biomaterials have significantly impacted wearable health monitoring, creating opportunities for personalized and non-invasive health assessments. These developments address the growing demand for customized healthcare solutions. Durability is a critical factor for biomaterials in wearable applications, as they must withstand diverse wearing conditions effectively. Therefore, there is a heightened focus on developing biomaterials that maintain robust and stable functionalities, essential for advancing wearable sensing technologies. This review examines the biomaterials used in wearable sensors, specifically those interfaced with human skin and eyes, highlighting essential strategies for achieving long-lasting and stable performance. We specifically discuss three main categories of biomaterials—hydrogels, fibers, and hybrid materials—each offering distinct properties ideal for use in durable wearable health monitoring systems. Moreover, we delve into the latest advancements in biomaterial-based sensors, which hold the potential to facilitate early disease detection, preventative interventions, and tailored healthcare approaches. We also address ongoing challenges and suggest future directions for research on material-based wearable sensors to encourage continuous innovation in this dynamic field.

An Experimental Study of Morphofunctional Features of Hair Follicles Early Response in Cyclophosphamide-Induced Alopecia

The aim of the study was to determine the effect of 3-β-methoxy-Δ18-oleanene (miliacin) on the structural and functional reorganization of hair follicles at the early response stage in the simulated cyclophosphamide-induced alopecia. Material and methods. The study involved 30 male C57BL/6 mice with the anagen stage induced by depilation of hair shafts from the skin of the back. The animals were divided into five groups: I and II – control groups, III, IV and V groups – experimental ones. The animals of group I were exposed to depilation only. The animals of group IV was daily exposed to topical skin applications of 3-β-methoxy-Δ18- oleanene (miliacin) diluted in polyoxyethylated (20) sorbitan oleate in the area of depilation. The animals of group V were only exposed to polyoxyethylated (20) sorbitan oleate. In 9 days after depilation, the animals of the experimental groups received a single injection of cyclophosphamide solution, dosage 125 mg/kg, intraperitoneally; the animals of the control group II received the same volume of 0.9% sodium chloride solution. All animals were withdrawn from the experiment on day 15. The skin of the back in the depilation zone was studied using light microscopy, morphometry and statistics. Results. In 15 days after anagen induction, all hair follicles were synchronized at the anagen VI stage in the skin of mice in the control groups. Exclusively dystrophic forms of hair follicles were detected in the skin of mice of groups III and V. In the skin of animals of group IV, hair follicles predominated in the early and middle anagen stages without signs of dystrophy; the portion of hair follicles in the late dystrophic catagen stage accounted for only 9.2±3.27% of the total number of hair follicles. Conclusion. Topical use of a composition with 3-β-methoxy-Δ18-oleanene (miliacin) leads to an accelerated transition of chemically damaged hair follicles from the anagen VI stage to the dystrophic catagen and a shortening of the telogen stage, which resulted in the entry of the overwhelming majority of hair follicles of mice in this group into the next new cycle of hair follicle development (anagen stages I, II, III).

SLNs and NLCs for Skin Applications: Enhancing the Bioavailability of Natural Bioactives.

Natural bioactives are mixtures of compounds extracted from plants with physicochemical properties that are usually not favorable for penetrating the skin's complex barrier. Nanoparticles have important advantages both in dermatology and cosmetology: improved solubility and stability of encapsulated phytocompounds, controlled and sustained skin delivery, and enhanced skin permeation, leading to an improved bioavailability. This review focuses on two generations of lipid-based nanoparticles: solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs). An extensive overview on the recent studies on SLNs and NLCs entrapping essential oils, oils, herbal extracts, and phytocompounds for topical applications is presented, emphasizing their composition, physicochemical characterization, efficacy, and methodologies used to evaluate them. This review also summarizes topical systems containing natural bioactives incorporated into SLNs and NLCs, commercially available products and registered patents in the field. SLNs and NLCs turn out to be effective nanocarriers for skin applications, offering significantly improved encapsulation efficiency, stability, and bioactives delivery. However, their full potential is underexplored. Future applications should study the encapsulation potential of new natural bioactives and show more specialized solutions that address specific requirements; an improved product performance and a pleasant sensory profile could lead to increased customer compliance with the product use.

Environmentally stable, Adhesive, Self-healing, Stretchable and Transparent Gelatin based Eutectogels for Self-Powered Humidity Sensors

Intrinsic environmental and stability limitations of hydrogels have inhibited their practical applications as a flexible wearable device due to water evaporation or freezing in complex environments such as low temperatures and arid environments. In this work, a multifunctional gelatin based ionic conductive eutectogel with double network structure is designed via ternary deep eutectic solvent (DES) (acrylic acid (AA), choline chloride (ChCl) and ethylene glycol (EG)). In this system, the introduction of ethylene glycol (EG) can be used to dissolve gelatin. The resulting DESG eutectogel exhibited excellent adhesion, mechanical robustness, anti-freeze, anti-drying, and self-healing. Interestingly, the DESG gels showed high humidity sensitivity in a wide humidity detection range (11 %–83 %), which can be assembled as a self-powdered humidity sensor to monitor human mouth and nose breathing. This work is expected to bring new prospect to construct high performance humidity sensors using gelatin based humidity-responsive materials for a wide range of potential applications in respiratory diagnostics, sleep monitoring, electronic skin and wearable electronics.

Myelin Sheath-Inspired Hydrogel Electrode for Artificial Skin and Physiological Monitoring.

Significant advancements in hydrogel-based epidermal electrodes have been made in recent years. However, inherent limitations, such as adaptability, adhesion, and conductivity, have presented challenges, thereby limiting the sensitivity, signal-to-noise ratio (SNR), and stability of the physiological-electrode interface. In this study, we propose the concept of myelin sheath-inspired hydrogel epidermal electronics by incorporating numerous interpenetrating core-sheath-structured conductive nanofibers within a physically cross-linked polyelectrolyte network. Poly(3,4-ethylenedioxythiophene)-coated sulfonated cellulose nanofibers (PEDOT:SCNFs) are synthesized through a simple solvent-catalyzed sulfonation process, followed by oxidative self-polymerization and ionic liquid (IL) shielding steps, achieving a low electrochemical impedance of 42 Ω. The physical associations within the composite hydrogel network include complexation, electrostatic forces, hydrogen bonding, π-π stacking, hydrophobic interaction, and weak entanglements. These properties confer the hydrogel with high stretchability (770%), superconformability, self-adhesion (28 kPa on pigskin), and self-healing capabilities. By simulating the saltatory propagation effect of the nodes of Ranvier in the nervous system, the biomimetic hydrogel establishes high-fidelity epidermal electronic interfaces, offering benefits such as low interfacial contact impedance, significantly increased SNR (30 dB), as well as large-scale sensor array integration. The advanced biomimetic hydrogel holds tremendous potential for applications in electronic skin (e-skin), human-machine interfaces (HMIs), and healthcare assessment devices.

Does cannula's size alter rheological properties of hyaluronic acid filler?

This study evaluated the rheological properties of various hyaluronic acid (HA) gels after passing through different-sized cannulas (22-G and 25-G). Five commercial brands of highly crosslinked HA fillers were analyzed: (A) Rennova® Ultra Deep, (B) Restylane® Lyft, (C) Hialurox® - Ultra Lift, (D) Belotero® Volume, and (E) E.P.T.Q S500. Rheological characterization was conducted using an automated controlled stress rheometer. The rheological properties of the fillers were assessed both before and after passing through the cannulas. Each filler brand and cannula size was tested three times by a researcher who was blinded to the commercial brands. For data analysis, frequencies of 0.1, 0.5, and 2 Hz were employed. The rheological properties (storage modulus [G'] and loss modulus [G"]) of the high-crosslink HA fillers did not change after being passed through cannulas of different sizes (22-G and 25-G) (p > 0.109) compared to baseline measurements (no cannula). Furthermore, all fillers displayed desirable solid-like, volumizing behavior at low frequencies and strain amplitudes (<10 %). Under physiologically relevant conditions for skin and facial applications, the cannula size did not alter the rheological properties of high crosslink HA fillers.

General Criterion for Non-Hermitian Skin Effects and Application: Fock Space Skin Effects in Many-Body Systems.

Non-Hermiticity enables macroscopic accumulation of bulk states, named non-Hermitian skin effects. The non-Hermitian skin effects are well established for single-particle systems, but their proper characterization for general systems is elusive. Here, we propose a general criterion of non-Hermitian skin effects, which works for any finite-dimensional system evolved by a linear operator. The applicable systems include many-body systems and network systems. A system meeting the criterion exhibits enhanced non-normality of the evolution operator, accompanied by exceptional characteristics intrinsic to non-Hermitian systems. Applying the criterion, we discover a new type of non-Hermitian skin effect in many-body systems, which we dub the Fock space skin effect. We also discuss the Fock space skin effect-induced slow dynamics, which gives an experimental signal for the Fock space skin effect.

Synthesis and characterization of chitosan-pectin fabricated nanoemulsion for ethylhexyl triazone topical delivery

This study aimed to investigate the stability of nanoemulsions for the UVB filter, ethylhexyl triazone (EHT) encapsulation followed by fabrication with chitosan and pectin. Four formulations were developed to assess the influence of hydrophile-lipophile balance (HLB) values on nanoemulsion stability for EHT encapsulation, targeting high Sun Protection Factor (SPF) values. The selected nanoemulsion was then subjected to fabrication with chitosan and pectin, followed by physical characterization and rheological behaviour study. Results indicated that all nanoemulsions exhibited particle sizes ranging from 137.7 nm to 206.0 nm and high entrapment efficiency from 88.76 % to 91.98 %. Sample N3, containing 1 % Tween 20 and 2 % polyethylene glycol (PEG) 400 with HLB of 12, demonstrated the highest stability, yielding a significantly elevated SPF value (10.33). Moreover, polymer-coated nanoemulsions with a low concentration of chitosan (0.1 %) showed enhanced stability when combined with different percentages of pectin. Polymer-coated nanoemulsions indicated shear-thinning behaviour at lower shear rates to Newtonian flow at higher shear rate. Furthermore, both polymer-coated and uncoated nanoemulsions exhibited decreased viscosity with increasing temperature. Also, polymer-coated nanoemulsions was found to enhance the sustainable release of EHT. These findings demonstrated the potential of polymer-coated nanoemulsions for skin application, offering enhanced stability and improved flow behaviour. The design of polymer-coated nanoemulsions could potentially minimize the risks of accumulation and toxicity of UV filters by providing a sustainable release behaviour.

Impact of Nanoethosomes Loaded with Polyherbal Extracts on the Mechanisms Involved in Wound Healing In-vitro Research.

This study focuses on formulating and optimizing Polyherbal Nanoethosomes for controlled drug delivery, utilizing a polyherbal extract comprising Basella alba L., Portulaca oleracea L., Lawsonia inermis L., Trigonella foenum L., and Peristrophe paniculata L. Comprehensive characterization revealed a variety of secondary metabolites within the extract. The primary goal was to create poly herbal extract-entrapped ethosomes that could be integrated into a sustained-release transdermal gel dosage. We prepared nanoethosomes using phosphatidylcholine, ethanol, Tween 80, and SLS, and optimized them using Design Expert software. The characteristics included size (particle size: 121 ± 2.60 nm) and entrapment efficiency (81.91 ± 1.92%), followed by incorporation into a carbopol gel for skin application. We performed in-vitro permeation studies and cytotoxic assays on L-929 cells, which revealed favorable outcomes. Optimized nanoethosomes displayed desirable particle characteristics, highlighting their potential for controlled drug delivery. The nano vesicular gels had good rheological and physical properties (polydispersity index: 0.41 ± 0.04, zeta potential: -8.12 ± 1.25 mV), which meant they could be used topically. This research underscores the compatibility of plant extracts with formulation components, offering a foundation for Polyherbal Nanoethosomes in pharmaceutical formulations. The study emphasizes precise control over particle attributes and suggests potential applications in enhancing drug release and bioavailability.

Study of the Effect of Phosvitin as a Potential Carrier on the Permeation Process of Somatotropin (STH) and Corticotropin (ACTH) from Biodegradable Polymers Used as Vehicles for STH and ACTH in Semi-Solid Formulations for Skin Application.

Phosvitin shows chelating abilities, an affinity for ACTH (corticotropin), growth factors, antioxidant properties, and acidic nature. An attempt was made to use this protein in hydrogels as a transporter of other protein substances: somatotropin (STH) and (ACTH). The aim of the study was to evaluate the effect of phosvitin on the permeation of ACTH and STH from semi-solid forms of the drug applied to the skin. Four hydrogel substrates were prepared using natural polymers: sodium alginate, methylcellulose, and starch. Based on the evaluation of physicochemical parameters, the hydrogel with the most favorable properties was selected and loaded with the active substances STH and ACTH, followed by the addition of phosvitin. A study of the permeation of STH and ACTH through the artificial cellulose membrane and through porcine skin was carried out without and with the addition of phosvitin. The effect of protein substances on rheological and textural parameters was studied. The evaluation of physicochemical parameters showed a favorable effect of STH and Phosvitin on the stability of the hydrogel with 4% methylcellulose and no effect of ACTH. All prepared formulations showed a reaction close to the natural pH of human skin. In the porcine skin permeation study, the addition of Phosvitin to the hydrogel with STH caused a slight increase in the amount of STH permeated and an increase in the time for STH to permeate porcine skin by 30 min. Phosvitin caused an increase in the amount of ACTH permeated through porcine skin almost twofold. Phosvitin may prove to be a promising permeation promoter for model protein-peptide substances when applied to the skin surface.

Polymeric silk fibroin hydrogel as a conductive and multifunctional adhesive for durable skin and epidermal electronics.

Silk fibroin (SF)-based hydrogels are promising multifunctional adhesive candidates for real-world applications in tissue engineering, implantable bioelectronics, artificial muscles, and artificial skin. However, developing conductive SF-based hydrogels that are suitable for the micro-physiological environment and maintain their physical and chemical properties over long periods of use remains challenging. Herein, we developed an ion-conductive SF hydrogel composed of glycidyl methacrylate silk fibroin (SilMA) and bioionic liquid choline acylate (ChoA) polymer chains, together with the modification of acrylated thymine (ThyA) and adenine (AdeA) functional groups. The resulting polymeric ion-conductive SF composite hydrogel demonstrated high bioactivity, strong adhesion strength, good mechanical compliance, and stretchability. The formed hydrogel network of ChoA chains can coordinate with the ionic strength in the micro-physiological environment while maintaining the adaptive coefficient of expansion and stable mechanical properties. These features help to form a stable ion-conducting channel for the hydrogel. Additionally, the hydrogel network modified with AdeA and ThyA, can provide a strong adhesion to the surface of a variety of substrates, including wet tissue through abundant hydrogen bonding. The biocompatible and ionic conductive SF composite hydrogels can be easily prepared and incorporated into flexible skin or epidermal sensing devices. Therefore, our polymeric SF-based hydrogel has great potential and wide application to be an important component of many flexible electronic devices for personalized healthcare.

Hierarchically structured hollow PVDF nanofibers for flexible piezoelectric sensor

The emergence of flexible sensors addresses the limitations of traditional detection equipment, such as large size, high cost, and inconvenient portability. These sensors have significantly advanced the development of wearable electronic devices for applications in electronic skin, energy harvesting, and energy storage. To enhance the sensitivity of flexible sensors, we developed a hierarchical polyvinylidene fluoride (PVDF) nanofiber-based piezoelectric sensor. By utilizing coaxial electrospinning, we fabricated nanofibers with hollow interiors and porous outer walls. Additionally, microstructures were constructed on the fiber membrane surface by modifying the collector’s shape. The resulting microstructured hollow PVDF nanofiber membrane exhibited high β-phase content (91.31 %), excellent flexibility (maximum strain 56.9 %), and high porosity (88.94 %). The sensor demonstrated a sensitivity of 2.7 V/N (1.08 V/kPa) and a maximum output voltage of 10.1 V, approximately three times higher than that of solid PVDF nanofibers without microstructures. Even after 14,400 cycles of impact, the sensor maintained stable output. The sensor was successfully applied to human activity monitoring and gesture recognition, showcasing its ability to monitor various human activities, respond rapidly (60.4 ms), and synchronously control a mechanical palm to perform different gestures. This work highlights the potential of hierarchically structured hollow PVDF nanofibers in advancing the performance and application scope of flexible piezoelectric sensors.

A high sensing performance piezoresistive sensor based on TPU/c-MWCNTs/ V2CTX-MXene electrospun film for human motion detection

Since wearable pressure sensors have promising applications in the fields of human physiological signal detection and bionic robots, there is an urgent need for wearable pressure sensors with comprehensive attributes such as high sensitivity and wide detection range. Here, we introduce a facile electrospinning process to fabricate a film composed of thermoplastic polyurethane/carboxyl multiwalled carbon nanotube/V2CTX-MXene (TPU/c-MWCNTs/V2C). This film has high sensitivity and great linearity, designed for flexible piezoresistive sensors. To further enhance sensor performance, we applied a spin-coating of polydimethylsiloxane (PDMS) on the sandpaper surface to create a top substrate with intermittent spinosum structures. Additionally, a layer of TPU fibers was electrospun between the conductive film and the interdigitated electrodes. The assembled components form a flexible piezoresistive sensor with a wide detection range of 0–200 kPa, a high sensitivity of 545.2 kPa−1, a low detection limit of 5 Pa, a short response time of 48 ms, and excellent long-term durability after 7000 loading/unloading cycles, making the piezoresistive sensor highly discriminating for detecting complex human movements. Thanks to the great sensing performance and stable structure, we conducted various demonstrations to capture human physiological signals, including signals of muscle activity and pulse. These findings indicate the potential of the designed flexible pressure sensor for applications in electronic skin and smart devices.