Skin Adhesion Research Articles

Powdered Medical Adhesive with Long Lasting Adhesion in Water Environment.

Medical adhesives have been used under surgical conditions. However, it is always a big challenge to maintain long-term adhesion in a water environment. Besides, it usually takes a long time to complete the adhesion, and the operation might be complicated. In this study, tannic acid and gelatin solution under acidic conditions were mixed, flocculated, lyophilized, and crushed; thus, a powdered medical adhesive (POWDER) was prepared with long-lasting adhesion in a water environment, convenience, and low price. Tannic acid bound gelatin and maintained adhesive force primarily through hydrogen bonding and reacted with amino sulfhydryl and other amino acid residues after oxidation into aldehyde, exhibiting excellent underwater adhesion. Oxidized dextran (ODex) powder rich in an aldehyde group was introduced to provide covalent binding in the adhesive. In vitro and in vivo studies showed that POWDER could quickly adhere to various tissues in the water environment. In vitro skin adhesion experiments demonstrated that it could achieve effective adhesion in a water environment for up to 60 days. Its blood compatibility, low cytotoxicity, and biodegradability were also verified. The POWDER developed in this study is of great significance for patients who need rapid wound treatments.

Motion-Adaptive Tessellated Skin Patches With Switchable Adhesion for Wearable Electronics.

Skin-interfaced electronics have emerged as a promising frontier in personalized healthcare. However, existing skin-interfaced patches often struggle to simultaneously achieve robust skin adhesion, adaptability to dynamic body motions, seamless integration of bulky devices, and on-demand, damage-free detachment. Here, a hybrid strategy that synergistically combines these critical features within a thin, flexible patch platform is introduced. This design leverages shape memory polymers (SMPs) arranged in a tessellated array, comprising both rigid and compliant SMPs. This configuration enables exceptional deformability, motion adaptability, and ultra-strong, repeatable skin adhesion while offering on-demand adhesion control. Furthermore, the design facilitates the seamless integration of bulky electronics without compromising skin adhesion. By incorporating sizeable electronics including signal acquisition circuits, sensors, and a battery, it is demonstrated that the proposed tessellated patch can be securely mounted on the skin, accommodate dynamic body motions, precisely detect physiological signals with an outstanding signal-to-noise ratio (SNR), wirelessly transmit data, and be effortlessly released from the skin.

Alpha-Tocopherol-Infused Flexible Liposomal Nanocomposite Pressure-Sensitive Adhesive: Enhancing Skin Permeation of Retinaldehyde

Retinaldehyde (RAL), or retinal, is a vitamin A derivative that is widely used for several skin conditions. However, it is light sensitive and has low water solubility, limiting its efficiency in transdermal delivery. This study developed a novel delivery system for retinal (RAL) using flexible liposomes (FLPs) infused with α-tocopherol succinate (α-TS) to improve stability, and enhance skin permeability. The RAL-FLPs were embedded in pressure-sensitive adhesive (PSA) hydrogels, creating a delivery platform that supports prolonged skin residence and efficient permeation of RAL. The stability and skin permeation as well as human skin irritation and adhesion capabilities were assessed to determine the formulation’s safety and efficacy. Our findings suggested that the addition of α-TS could improve liposomal stability and RAL chemical stability. Moreover, the skin permeation and fluorescence microscopic-based studies suggested that the addition of α-TS could enhance skin permeability of RAL through hair follicles. The RAL-FLP was embedded in PSA hydrogels fabricated from 25% GantrezTM S-97 (GT) and 1% hyaluronic acid (Hya) with aluminum as a crosslinker. The PSA hydrogel exhibited desirable peeling and tacking strengths. The developed hydrogels also demonstrated greater skin deposition of RAL compared with its aqueous formulation. Additionally, the RAL-FLP-embedded PSA hydrogels showed no skin irritation and maintained better adhesion for up to 24 h compared to commercial patches. Hence, the developed hydrogels could serve as a beneficial platform for delivering RAL in treating skin conditions.

Soft hydrogels obtained by photothermal curing of poly(vinylpyrrolidone)/gold nanoparticles dispersions showing anisotropic swelling and photo-activated antimicrobial properties

Poly(vinylpyrrolidone) (PVP) hydrogels were obtained by green light irradiation of aqueous PVP/ammonium persulfate solutions modified with gold nanoparticles (AuNPs). The increase in temperature produced through the activation of the photothermal effect of AuNPs triggers the decomposition of ammonium persulfate producing radicals that, by attacking the polymer main chain and generating macro-radicals, induce the crosslinking of the polymer via recombination paths. Irradiation from the top of the solutions in an open configuration produced water evaporation and a concomitant increase in temperature during curing, giving rise to dry materials with high aspect ratio and moderate swelling anisotropy. Pads that reversibly adhere to different substrates, including human skin, were produced by simple contact of the final materials with water. Impregnation of gauze wound dressings with PVP-Au-ammonium persulfate dispersions, followed by direct “in situ” photothermal crosslinking, enabled the fabrication of supported functional pads with potential applications as reversible adhesive skin wound dressings. Infusion of the hydrogels with Rose Bengal (RB) provides the materials with photosensitizing properties useful for the photodynamic inactivation of Staphylococcus aureus. A decrease in cell viability of 99.9% was attained after 30 min of irradiation with a low-power green LED source, which demonstrates the efficient singlet oxygen production by RB in the hydrogels and paves the way towards the design of new stimulus-activated bactericidal supplies for biomedical uses.

Rapid Photoinduced Self-Healing, Controllable Drug Release, Skin Adhesion Ability, and Mechanical Stability of Hydrogels Incorporating Linker-Modified Gold Nanoparticles and Nanogels.

Appropriately modified thermoresponsive hydrogels, such as poly(N-isopropylacrylamide) hydrogels, bring an opportunity for a variety of biomedical applications. Incorporating compounds with different properties into poly(N-isopropylacrylamide) hydrogels offers opportunities to enhance their mechanical, self-healing ability, adhesiveness, thermal responsiveness, and drug release capabilities. In this study, we investigated the influence of Au-sulfur interactions on the properties of the poly(N-isopropylacrylamide) hydrogels after introducing N,N'-bis(acryloyl)cystine (a newly synthesized cross-linker), modified gold nanoparticles, and a p(NIPAm-BISS) nanogel into the hydrogel matrix. Our findings demonstrated that poly(N-isopropylacrylamide) hydrogels with these compounds exhibited higher mechanical strength (65% tensile stress and 25% elongation), faster thermal responsiveness, controllable self-healing [85% recovery after 2 min, using a NIR laser (800 nm, 0.75 W)], skin adhesiveness, and enhanced drug release (0.08 mg·mL-1, a 93% improvement). These results may contribute to advancements in the design of temperature-responsive hydrogels tailored for specific biomedical needs, such as targeted drug delivery with the use of a NIR laser and tissue engineering.

Skin adhesion of a newly developed, bioequivalent rotigotine patch formulation in comparison to the originator product: Results of a multi-center, randomized, crossover trial in patients with Parkinson's disease.

To demonstrate adequate skin adhesion of a new once-daily rotigotine transdermal patch (ROT-TDS) compared to the originator product (reference) in patients with Parkinson's disease (PD). Pharmacokinetic bioequivalence (PK BE) was assessed with the 4 mg/24h patches in healthy adults in a single-/multiple-dose, crossover trial. The trial investigating skin adhesion in PD patients (stable dose ≥ 8 mg/day rotigotine) was performed with the 8 mg/24h patches as a multiple-dose, crossover trial (4 alternating once-daily patch applications). Skin status (seborrhea, sweating) was characterized at screening. Adhesion was assessed 5 minutes after application and 5 minutes before removal of each patch. Systemic safety and skin irritation/sensitization were monitored. ROT-TDS was bioequivalent to the reference product in the PK BE trial in 48 randomized healthy subjects. In the skin adhesion trial in 43 randomized PD patients, the cumulative mean percentage of adhesion (90% CI) at the end-of-dosing interval was 92.948% (90.156 - 95.740%) for ROT-TDS and 90.471% (87.574 - 93.367%) for the reference. For ROT-TDS, 80.23% of patches were ≥ 90% adhered at the end-of-dosing interval, while this was the case for 67.44% of the reference patches. Safety and skin tolerability of both products were comparable; the most frequent treatment-related adverse event was application-site pruritus for both treatments at comparable extent. ROT-TDS - with shown BE to the originator reference product - displayed similar safety and local tolerability as the reference product in patients with PD. The results show a trend to improved skin adhesion of the new patch compared to the reference in the target population.

A highly stretchable and self-adhesive cellulose complex hydrogels based on PDA@Fe3+ mediated redox reaction for strain sensor

As the application of conductive hydrogels in the field of wearable smart devices is gradually deepening, a variety of hydrogel sensors with high mechanical properties, strong adhesion, fast self-healing, and excellent conductivity are emerging. However, it is still a great challenge to manufacture hydrogel sensors combining multiple properties. Herein, we leveraged the dynamic redox reaction occurring between polydopamine (PDA) and Fe3+ to induce ammonium persulfate (APS) to generate free radicals, thereby initiating the copolymerization of hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) monomers. Then, polypyrrole-encapsulated cellulose nanofibers (PPy@CNF) and carboxymethylcellulose (CMC) were incorporated as conductive reinforced nanofillers and interpenetrating network skeleton. The obtained hydrogel cross-linked through reversible metal-ligand bonds, π-π stacking and abundant hydrogen bonding demonstrated great mechanical properties (strength 240.4 kPa, strain 1175 %) and self-healing ability (88.96 %). Particularly, the gel displayed ultrahigh durability and skin adhesive ability (75 kPa after 10 cycles), surpassing previous skin adhesion hydrogels. Furthermore, through the synergistic conductive effect of PPy@CNF and Fe3+, the prepared hydrogel sensor possessed high sensitivity (GF = 1.89) with a wide sensing range (~1000 %), which could realize the human body's daily motion detection, and had a promising application in flexible wearable electronics.

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.

Design and in vitro/in vivo evaluation of chitosan-polyvinyl alcohol copolymer material cross-linked by dynamic borate ester covalent for pregabalin film-forming delivery system

This research introduced a novel polymer synthesized by combining chitosan and modified polyvinyl alcohol, cross-linked with boric acid using dynamic covalent bonds. The polymer was developed to formulate a pregabalin Film-forming system (FFS) for treating postherpetic neuralgia via topical application, showcasing notable skin adhesion and drug delivery properites. The chitosan-boric acid-modified polyvinyl alcohol polymer was analyzed using NMR, FTIR. The exceptional features of the optimized FFS were evaluated through rheometer, Differential scanning calorimetry (Tg = 45.98 °C), contact angle (θ = 78.62°). The elongation (60.05 ± 3.67 %), cohesion (56.94 ± 4.65 MPa) and skin adhesion (58.12 ± 2.99 kPa) of chitosan-boric acid-modified polyvinyl alcohol were found to be 5.2, 6.8, and 8.3 times higher than those of the pure chitosan film, attributed to the double network structure formed by the cross-linked reversible dynamic covalent bond. The optimized pregabalin FFS exhibited increased in vitro (86.25 ± 1.87 μg/g) and in vivo (100.42 ± 7.44 μg/g) skin retention amounts compared to in vivo oral administration (28.43 ± 4.61 μg/g). In summary, the utilization of borate ester dynamic covalent bonds in developing chitosan-based film-forming polymer proved beneficial in improving skin adhesion and topical therapeutic effectiveness, thereby mitigating the risk of systemic side effects associated with oral administration.

Advancements in the Transdermal Drug Delivery Systems Utilizing Microemulsion-based Gels.

Microemulsion gel, as a promising transdermal nanoparticle delivery system, addresses the limitations of microemulsions and enhances their performance in drug delivery and release. This article aims to discuss the advantages of microemulsion gel, including improved drug bioavailability, reduced drug irritation, enhanced drug penetration and skin adhesion, and increased antimicrobial properties. It explores the methods for selecting microemulsion formulations and the general processes of microemulsion preparation, as well as commonly used oil phases, surfactants, and co-surfactants. Additionally, the biomedical applications of microemulsion gel in treating conditions, such as acne and psoriasis, are also discussed. Overall, this article elucidates the significant potential of microemulsion gel in topical drug delivery, providing insights into future development and clinical applications.

Sticky Science: Using Complex Coacervate Adhesives for Biomedical Applications.

Tissue adhesives are used for various medical applications, including wound closure, bleeding control, and bone healing. Currently available options often show weak adhesion or cause adverse effects. Recently, there has been an increasing interest in complex coacervates as medical adhesives. Complex coacervates are formed by mixing oppositely charged macromolecules that associate and undergo liquid-liquid phase separation, in which the dense bottom phase is the complex coacervate. Complex coacervates are strong and often biocompatible, and show strong underwater adhesion. The properties of the resulting materials are tunable by intrinsic factors such as polymer chemistry, molecular weight, charge density, and topology of the macromolecules, as well as extrinsic factors such as temperature, pH, and salt concentration. Therefore, complex coacervates are interesting new candidates for medical adhesives. In this review, it is described how complex coacervates form and how different factors influence their behavior. Next, an overview of recent studies on complex coacervates in the context of medical adhesives is presented. The application of complex coacervates as hemostatic or embolic agents, skin or bone repair adhesives, and soft tissue sealants is discussed. Lastly, additional possibilities for utilizing these materials in the future are discussed.

An in Vitro Evaluation of the 14-Day Microbial Barrier Property of Exofin High Viscosity Topical Skin Adhesive.

Background: Wound closure is a critical aspect of medical care, and the choice of closure methods plays a pivotal role in preventing infections. Traditional sutures and staples can introduce foreign material into the wound, increasing the risk of infection. Adhesives offer a potential alternative by providing a physical barrier against microorganisms. Objective: To assess the microbial barrier properties of Exofin High Viscosity Topical Skin Adhesive (HVTSA), a novel adhesive system, against a range of challenge organisms. Methods: This study, conducted by the independent research organization NAMSA (North American Science Associates, LLC), aimed to evaluate the effectiveness of Exofin HVTSA as a microbial barrier. This study was carried out by an independent research organization NAMSA. Challenge organisms, including Staphylococcus aureus, Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Escherichia coli, Candida albicans, and Aspergillus brasiliensis, were used to evaluate the adhesive's effectiveness. Inocula of each organism were placed on cured Exofin HVTSA test articles and observed for 14 days. Positive and negative control plates were included to validate the effectiveness of the challenge organisms and assess the absence of contamination. Results: Exofin HVTSA demonstrated effective microbial barrier properties against all challenge organisms, except Pseudomonas aeruginosa. No growth or color change was observed for Staphylococcus aureus, Staphylococcus epidermidis, MRSA, Escherichia coli, Candida albicans, and Aspergillus brasiliensis over the 14-day observation period. Pseudomonas aeruginosa exhibited no growth, but showed a color change in two out of five replicates on day 14. Conclusion: Exofin HVTSA demonstrated effective microbial barrier properties for 14 days against a range of common wound pathogens, suggesting its potential as a safe and effective alternative to traditional wound closure methods. Further research is warranted to investigate its efficacy in clinical settings.

Comparison of the safety and efficacy of three superficial skin closure methods for multi-layer wound closure in total knee arthroplasty: a multicenter, prospective, randomized controlled trial

BackgroundGood wound healing is critical to infection prophylaxis and satisfactory rehabilitation in Total Knee Arthroplasty (TKA). Currently, two techniques, i.e., barbed continuous subcuticular suture without skin adhesive or combined use skin adhesive (n-butyl-2) are being used for superficial wound closure of TKA. While a new skin adhesive (2-octyl) with self-adhesive mesh has been employed as an alternative to conventional surgical skin closure in TKA, its superiority, especially in reducing wound complications and improving wound cosmetic outcomes has not been investigated. This study aimed to compare 2-octyl, n-butyl-2, and no skin adhesive in terms of safety and efficacy in TKA superficial wound closure.MethodsWe conducted a multicenter, prospective, randomized controlled study in 105 patients undergoing primary TKA between May 2022 and October 2023. Each patient’s knee was randomized to receive 2-octyl, n-butyl-2, or no skin adhesive skin closure with all using barbed continuous sutures in deep tissue. Wounds were followed 1, 3, 5 days, 2, 6 weeks, and 3 months after surgery. Wound discharge, complications, cosmetic outcomes, patient satisfaction, and wound-related costs were compared among these three methods.ResultsWound discharge was less in 2-octyl group and n-butyl-2 group than in non-adhesive group at 1 day, with the discharge only being less in 2-octyl group than in the non-adhesive group at day 3 and day 5 days (P < 0.05). There was no statistical difference in the incidence of other wound complications among the groups (P > 0.05). The 2-octyl group achieved better cosmetic effects than the other two groups in 6 weeks and 3 months (P < 0.05). Compared to the non-adhesive group, 2-octyl group scored higher in overall patient satisfaction score in 2 weeks and incurred lower costs (P < 0.05).ConclusionsSkin closure in TKA using 2-octyl adhesive material showed superiority when compared to no skin adhesive or n-butyl-2, in reducing wound discharge, improving the cosmetic outcomes, without increasing wound complications. In addition, the use of 2-octyl yielded better patient satisfaction and also was less costly compared to no skin adhesive. Our study exhibited that 2-octyl was a safe and effective wound closure technique for patients undergoing TKA.Trial registrationThis study has been registered at Clinical Trials. Gov (No. ChiCTR210046442).

Chronic Biosymbiotic Electrophysiology

AbstractContinuous monitoring of electrophysiological biosignals such as electrocardiogram (ECG) and bioimpedance (BioZ) rely on gel‐based electrodes and adhesive skin interfaces requiring active patient interaction inherently restricting chronic use. Current solutions aimed at addressing seamless, comfortable, and reliable recordings with dry electrodes use battery power and are limited to days of operation with clinical‐grade fidelity. Here, current limitations are overcome by uniting at‐distance wirelessly powered wearable electronics with carbon‐doped filament deposition modeling (FDM) printed dry electrodes that overcome impedance degradation by seamless integration into textile and biosymbiotic systems, allowing for high‐fidelity operation over indefinite timescales. These capabilities are demonstrated with ECG during work, activity, and sleep and BioZ recordings documenting gains in forearm training over weeks.

Dual‐Modal Stretchable Sensing Patches for In Situ Monitoring of Electromyography and Acoustic Myography

AbstractElectromyography (EMG) and acoustic myography (AMG) play crucial roles in assessing muscle function, providing valuable insights into neural control, muscle activation, and fatigue levels. However, the current landscape reveals a gap in dual‐modal stretchable sensing patches, highlighting the need for comfortable and wearable solutions in the field of in situ monitoring of synchronous EMG and AMG sensing. In this work, a dual‐modal stretchable patch (DMSP) is developed that fully integrates a multi‐channel EMG electrode with AMG sensors. It possesses stable electromechanical properties even at strains exceeding 200%. With an overall modulus of under 40 kPa and a skin adhesion force surpassing 30 N m−1, the DMSP exhibits exceptional durability, enduring 1000 stretching cycles. The DMSP enables in situ simultaneous monitoring of EMG and AMG signals from sternocleidomastoid muscle during neck rotation where the mechanical strain reaches up to 30%. The DMSP proves instrumental in characterizing muscle activity, facilitating in‐depth research on muscle movement, and thus enhancing clinical outcomes in rehabilitation medicine and physical therapy.

A Self-Powered, Skin Adhesive, and Flexible Human-Machine Interface Based on Triboelectric Nanogenerator.

Human-machine interactions (HMIs) have penetrated into various academic and industrial fields, such as robotics, virtual reality, and wearable electronics. However, the practical application of most human-machine interfaces faces notable obstacles due to their complex structure and materials, high power consumption, limited effective skin adhesion, and high cost. Herein, we report a self-powered, skin adhesive, and flexible human-machine interface based on a triboelectric nanogenerator (SSFHMI). Characterized by its simple structure and low cost, the SSFHMI can easily convert touch stimuli into a stable electrical signal at the trigger pressure from a finger touch, without requiring an external power supply. A skeleton spacer has been specially designed in order to increase the stability and homogeneity of the output signals of each TENG unit and prevent crosstalk between them. Moreover, we constructed a hydrogel adhesive interface with skin-adhesive properties to adapt to easy wear on complex human body surfaces. By integrating the SSFHMI with a microcontroller, a programmable touch operation platform has been constructed that is capable of multiple interactions. These include medical calling, music media playback, security unlocking, and electronic piano playing. This self-powered, cost-effective SSFHMI holds potential relevance for the next generation of highly integrated and sustainable portable smart electronic products and applications.

Abstract Mo051: Phototherapy to stimulate carnosine activity and enhance global heart function: A promising adjunctive therapy for congestive heart failure (CHF)

Background: The emerging field of cardiac optogenetics uses pulses of light to stimulate optically-sensitive proteins in the heart, influencing cellular physiology with unprecedented spatiotemporal resolution. Effects include increased glutathione and carnosine activity, and promotion of ATP synthesis. Clinical benefits include improved functional capacity, heart rhythm stability, and relief form congestive heart failure (CHF). Transcutaneous phototherapy devices are now available (LifeWave Inc, San Diego, USA), which may provide these benefits without the requirement for an external power source. Objective: To investigate whether upregulation of carnosine activity using a wearable cutaneous phototherapy device may improve echocardiographic measures of global heart function, cardiac contractility, and hemodynamics. Methods: The Carnosine ® adhesive skin patch (34 mm outside diameter) contain an organic crystalline material that reflects back specific frequencies of infra-red light known to activate carnosine dipeptides throughout the body. These function as a high-energy phosphate system known to enhance muscle function. Study participants (n=12 healthy volunteers (7 male, 5 female), 40-66 years of age) underwent a focused baseline echocardiogram, which included atrial (A) and early (E) mitral valve inflow, peak tissue velocity (E’) at both the lateral and septal mitral annulus, and left ventricular ejection fraction (LVEF). 10-14 patches were then applied along the sternum and across the left thorax (3 rd -5 th interspace), incorporating the anterior axilla. The echocardiogram was repeated 20-30 minutes after patch application. Results: LVEF was improved following application of the phototherapy device, increasing from 59.8±6.3% to 66.65±5.8% (Δ 6.3%, p&lt;0.05), indicating an improvement in overall cardiac function. Septal E’ also increased, from 7.3±0.7 cm/s to 8.2±0.6 cm/s (Δ 0.89 cm/s, p&lt;0.05), indicating a direct effect on contractility. E and A wave velocities increased from 63.7 cm/s to 66.1 cm/s (Δ 2.5±0.4 cm/s, p&lt;0.08) and from 56.8 cm/s to 62.6 cm/s (Δ 5.7±0.7 cm/s, p&lt;0.1), indicating augmented hemodynamics trending towards significance. Conclusion: Self-powered wearable phototherapy devices may enhance myocardial contractility and overall cardiac function. Such technologies represent a promising therapy for CHF.

Smart-Adhesive, Breathable and Waterproof Fibrous Electronic Skins.

For the need of direct contact with the skin, electronic skins (E-skins)should not only fulfill electric functions, but also ensure comfort during wearing, including permeability, waterproofness, and easy removal. Herein, the study has developed a self-adhesive, detach-on-demand, breathable, and waterproof E-skin (PDSC) for motion sensing and wearable comfort by electrospinning styrene-isoprene block copolymer rubber with carbon black nanosheets as the sensing layer and liner copolymers of N, N-dimethylacrylamide, n-octadecyl acrylate and lauryl methacrylate as the adhesive layer. The high elasticity and microfiber network structure endow the PDSC with good sensitivity and high linearity for strain sensing. The hydrophobic and crystallizable adhesive layer ensures robust, waterproof, and detaching-on-demand skin adhesion. Meanwhile, the fiber structure enables the PDSC good air and water permeability. The integration of electric and wearable functions endows the PDSC with great potential for motion sensing during human activities as both the sensing and wearable performances.

Recurrent evolution of adhesive defence systems in amphibians by parallel shifts in gene expression

Natural selection can drive organisms to strikingly similar adaptive solutions, but the underlying molecular mechanisms often remain unknown. Several amphibians have independently evolved highly adhesive skin secretions (glues) that support a highly effective antipredator defence mechanism. Here we demonstrate that the glue of the Madagascan tomato frog, Dyscophus guineti, relies on two interacting proteins: a highly derived member of a widespread glycoprotein family and a galectin. Identification of homologous proteins in other amphibians reveals that these proteins attained a function in skin long before glues evolved. Yet, major elevations in their expression, besides structural changes in the glycoprotein (increasing its structural disorder and glycosylation), caused the independent rise of glues in at least two frog lineages. Besides providing a model for the chemical functioning of animal adhesive secretions, our findings highlight how recruiting ancient molecular templates may facilitate the recurrent evolution of functional innovations.

Hybrid 3D Printing of a Nature‐Inspired Flexible Self‐Adhesive Biopatch for Multi‐Biosignal Sensing

AbstractBioinspired skin adhesives are promising alternatives to traditional glue‐based skin patches for use in various skin‐attachable devices. However, the typical nano‐/microfabrication of these bioinspired microstructures provides limited manufacturing freedom over their performance, constraining their versatility and customization for widespread use. In this study, a hybrid 3D printing approach for fabricating a permeable skin patch is developed with adhesive miniaturized octopus‐like suckers (AMOS) for biosignal monitoring. The design and geometrical influences are investigated on the adhesion strength under different skin conditions (i.e., dry, wet, and hairy), permeability, and durability as well as proposed a biocompatible, stretchable, highly permeable, reusable, and conformable biopatch. Unlike commercially available biopatches that use chemical adhesives, the adhesion strength of an AMOS patch is customizable, does not cause skin irritation, and is comfortable for the wearer when worn for extended durations. The biopatch is tested in electromyogram, electrooculogram, and electrocardiogram signal measurement during a hand‐cycling experiment over extended durations that confirms its potential in extreme sport events. In addition to biosignal monitoring, 3D‐printed AMOS patches have broad applicability across various skin‐interfacing devices, including glucose and sweat monitoring, drug delivery, and wound healing. This approach offers a promising and highly customizable manufacturing solution for unlocking next‐generation skin‐attachable technologies.