Artificial Skin Research Articles

Biomimetic bilayer ionic conductive photoelectronic skin based on nano-structured photonic crystal film and flexible adhesive hydrogel for dual-signal motion detection and anti-disturbance temperature monitor

The growing interest in biological skin mimicry has greatly contributed to the creation of high-performance artificial skin. Here, inspired by the optical-electrical signal co-transmission of chameleon skins, a bilayer biomimetic ion-conductive photoelectronic skin (BIPES) was constructed by compositing the mechanochromic nano-structured silica photonic crystal film with an adhesive, flexible hydrogel by a layer-by-layer design strategy. The BIPES has a highly sensitive strain response on electrical and optical signals (GF = 3.27 at 0–100 %, Δλ/Δε = 2.1 nm %–1) and temperature response (TCR = –2.27 % °C–1 at 0–50 °C). Importantly, through the temperature insensitivity of the mechanochromic film, the BIPES not only achieved dual-signal motion detection but also achieved real-time temperature monitoring excluding strain interference. This research provides new inspiration for the construction of multi-signal combined photoelectronic skins and further exploration for advanced accurate smart wearable electronics in applications, especially in health detection for patients with non-spontaneous body-trembling.

Ultrafast readout, crosstalk suppression iontronic array enabled by frequency-coding architecture

The development of iontronic skin (I-skin) capable of ultrafast sensing in a wide pressure range, comparable to human skin, is of paramount importance for intelligent robotics. However, this remains a major challenge due to the lack of iontronic array architectures that can achieve ultrafast readout and crosstalk-free under large capacitance response generated within a wide pressure range. Here, we report a frequency-coding architecture of artificial ion mechanoreceptor skin (AIM-skin) that can provide a universal mode of iontronic array sensing and bypass the dependence of complex integrated back-end interface electronics. Notably, the successful implementation of orthogonal frequency coding in the AIM-skin with high sensitivity and ultrawide pressure range achieve ultrafast parallel readout for the spatiotemporal mechanical stimuli. Furthermore, the parallel zero-potential mechanism (PZPM) of the architecture effectively mitigates electrical crosstalk between sensing units. We have demonstrated that combhination of proposed device and deep learning has a broad application prospect in intelligent human-machine interaction and real-time dynamic robotic manipulation.

Artificial Octopus-Limb-Like Adhesive Patches for Cupping-Driven Transdermal Delivery with Nanoscale Control of Stratum Corneum.

Drug delivery through complex skin is currently being studied using various innovative structural and material strategies due to the low delivery efficiency of the multilayered stratum corneum as a barrier function. Existing microneedle-based or electrical stimulation methods have made considerable advances, but they still have technical limitations to reduce skin discomfort and increase user convenience. This work introduces the design, operation mechanism, and performance of noninvasive transdermal patch with dual-layered suction chamber cluster (d-SCC) mimicking octopus-limb capable of wet adhesion with enhanced adhesion hysteresis and physical stimulation. The d-SCC facilitates cupping-driven drug delivery through the skin with only finger pressure. Our device enables nanoscale deformation control of stratum corneum of the engaged skin, allowing for efficient transport of diverse drugs through the stratum corneum without causing skin discomfort. Compared without the cupping effect of d-SCC, applying negative pressure to the porcine, human cadaver, and artificial skin for 30 min significantly improved the penetration depth of liquid-formulated subnanoscale medicines up to 44, 56, and 139%. After removing the cups, an additional acceleration in delivery to the skin was observed. The feasibility of d-SCC was demonstrated in an atopic dermatitis-induced model with thickened stratum corneum, contributing to the normalization of immune response.

Connective tissue inspired elastomer-based hydrogel for artificial skin via radiation-indued penetrating polymerization

Robust hydrogels offer a candidate for artificial skin of bionic robots, yet few hydrogels have a comprehensive performance comparable to real human skin. Here, we present a general method to convert traditional elastomers into tough hydrogels via a unique radiation-induced penetrating polymerization method. The hydrogel is composed of the original hydrophobic crosslinking network from elastomers and grafted hydrophilic chains, which act as elastic collagen fibers and water-rich substances. Therefore, it successfully combines the advantages of both elastomers and hydrogels and provides similar Young’s modulus and friction coefficients to human skin, as well as better compression and puncture load capacities than double network and polyampholyte hydrogels. Additionally, responsive abilities can be introduced during the preparation process, granting the hybrid hydrogels shape adaptability. With these unique properties, the hybrid hydrogel can be a candidate for artificial skin, fluid flow controller, wound dressing layer and many other bionic application scenarios.

Disentangling Hype from Reality for Artificial Intelligence–Based Skin Cancer Diagnosis: Comment on a Narrative Review

Disentangling Hype from Reality for Artificial Intelligence–Based Skin Cancer Diagnosis: Comment on a Narrative Review

Dual enzymatic preparation of flexible biocomplex with full amino-acid composition

The preparation of highly versatile flexible biomaterials able to adapt to the complex environment of the human body is an important but challenging task. In this study, a flexible biocomplex (AA-FB) was prepared by combining gelatin, polylysine, and skin using a green enzymatic cascade reaction. Interestingly, none of the raw materials used in the preparation of AA-FB introduced any compounds other than amino-acid composition, which can endow AA-FB with low biotoxicity and allergenicity, along with excellent biodegradability. Morever, AA-FB showed good physical properties: its Young's modulus was 30 times higher than that of pure gelatin hydrogel, and its water vapor transmission rate (2480.12 g/m2·24 h) was also significantly improved. AA-FB could also achieve a bacterial inhibition rate of 91.34 % against S. aureus, much higher than that of skin (28.51 %) and gelatin (41.89 %). Tests of artificial skin show that AA-FB can replace skin tissue as a protective barrier for collagen, blood vessels, and cells. As the new skin tissue is reconstructed, it gradually integrates with the normal tissue of the body until is finally metabolized.

Antibiotics against Pseudomonas aeruginosa on Human Skin Cell Lines: Determination of the Highest Non-Cytotoxic Concentrations with Antibiofilm Capacity for Wound Healing Strategies.

Pseudomonas aeruginosa is one of the most common microorganisms causing infections of severe skin wounds. Antibiotic or antiseptic treatments are crucial to prevent and curb these infections. Antiseptics have been reported to be cytotoxic to skin cells and few studies evaluate the impact of commonly used antibiotics. This study evaluates how clinical antibiotics affect skin cells' viability, proliferation, migration, and cytokine secretion and defines the highest non-cytotoxic concentrations that maintain antibacterial activity. Cell proliferation, viability, and migration were evaluated on cell monolayers. Cytokines related to the wound healing process were determined. The minimum inhibitory concentrations and the impact on bacterial biofilm were assessed. Results showed that 0.02 mg/mL ciprofloxacin and 1 mg/mL meropenem are the highest non-cytotoxic concentrations for fibroblasts and keratinocytes while 1.25 mg/mL amikacin and 0.034 mg/mL colistin do not affect fibroblasts' viability and cytokine secretion but have an impact on keratinocytes. These concentrations are above the minimum inhibitory concentration but only amikacin could eradicate the biofilm. For the other antibiotics, cytotoxic concentrations are needed to eradicate the biofilm. Combinations with colistin at non-cytotoxic concentrations effectively eliminate the biofilm. These results provide information about the concentrations required when administering topical antibiotic treatments on skin lesions, and how these antibiotics affect wound management therapies. This study set the basis for the development of novel antibacterial wound healing strategies such as antibiotic artificial skin substitutes.

3D bioprinting of Salvianolic acid B-sodium alginate-gelatin skin scaffolds promotes diabetic wound repair via antioxidant, anti-inflammatory, and proangiogenic effects

In patients with diabetic wounds, wound healing is impaired due to the presence of persistent oxidative stress, an altered inflammatory response, and impaired angiogenesis and epithelization. Salvianolic acid B (SAB), which is derived from the Chinese medicinal plant Salvia miltiorrhiza, has been found to exhibit antioxidant, anti-inflammatory, and proangiogenic effects. Previous studies have used 3D bioprinting technology incorporating sodium alginate (SA) and gelatin (Gel) as basic biomaterials to successfully produce artificial skin. In the current study, 3D bioprinting technology was used to incorporate SAB into SA-Gel to form a novel SAB-SA-Gel composite porous scaffold. The morphological characteristics, physicochemical characteristics, biocompatibility, and SAB release profile of the SAB-SA-Gel scaffolds were evaluated in vitro. In addition, the antioxidant, anti-inflammatory, and proangiogenic abilities of the SAB-SA-Gel scaffolds were evaluated in cells and in a rat model. Analysis demonstrated that 1.0 wt% (the percentage of SAB in the total weight of the solution containing SA and Gel) SAB-SA-Gel scaffolds had strong antioxidant, anti-inflammatory, and proangiogenic properties both in cells and in the rat model. The 1.0% SAB-SA-Gel scaffold reduced the expression of tumor necrosis factor-α, interleukin-6, and interluekin-1β and increased the expression of transforming growth factor-β. In addition, this scaffold removed excessive reactive oxygen species by increasing the expression of superoxide dismutase, thereby protecting fibroblasts from injury. The scaffold increased the expression of vascular endothelial growth factor and platelet/endothelial cell adhesion molecule-1, accelerated granulation tissue regeneration and collagen deposition, and promoted wound healing. These findings suggest that this innovative scaffold may have promise as a simple and efficient approach to managing diabetic wound repair.

A multimodal magnetoelastic artificial skin for underwater haptic sensing.

Future exploitation of marine resources in a sustainable and eco-friendly way requires autonomous underwater robotics with human-like perception. However, the development of such intelligent robots is now impeded by the lack of adequate underwater haptic sensing technology. Inspired by the populational coding strategy of the human tactile system, we harness the giant magnetoelasticity in soft polymer systems as an innovative platform technology to construct a multimodal underwater robotic skin for marine object recognition with intrinsic waterproofness and a simple configuration. The bioinspired magnetoelastic artificial skin enables multiplexed tactile modality in each single taxel and obtains an impressive classification rate of 95% in identifying seven types of marine creatures and marine litter. By introducing another degree of freedom in underwater haptic sensing, this work represents a milestone toward sustainable marine resource exploitation.

Near‐Infrared‐Sensing Flexible Organic Synaptic Transistors with Water‐Processable Charge‐Trapping Polymers for Potential Neuromorphic Computing/Skin Applications

Neuromorphic devices, which can mimic the human body's neural system, are rising as an essential technology for artificial intelligence. Here, two types of organic synaptic transistors (OSTRs), OSTR‐A and OSTR‐B, are fabricated on either glass or polymer film using water‐processable charge‐trapping gate‐insulating layers that are prepared by reacting ethylenediamine (EDA) and poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPSA). OSTR‐A is designed to function as a basic artificial synapse by gate pulse stimulation only, while OSTR‐B has additional near‐infrared (NIR)‐absorbing conjugated polymer layers for further sensing of NIR light upon gate voltage stimulations. The PAMPSA:EDA films are found to contain permanent charge bridges (ion pairs of –SO3− +NH3‐) that play a charge‐trapping role in OSTRs. Both devices with the PAMPSA:EDA layers exhibit clear postsynaptic current (PSC) signals upon gate voltage pulses, leading to long‐term potentiation/depression characteristics. The flexible OSTR‐B devices can sense the NIR light (905 nm) upon gate pulse stimulation and their PSC signals are well maintained even after bending (>5000 times). Artificial neural network simulations disclose that the flexible OSTR‐B devices can stably perform synaptic operations under the NIR light with high accuracy (>90%) even after repeated bending (5000 times), indicative of potential use in artificial neuromorphic skin applications.

Glucose-responsive soluble microneedle prepared with “Gelatin - hydroxyethylcellulose ethoxylate complex coacervate” for the transdermal drug delivery

A glucose-responsive “complex coacervate” based drug delivery system has tremendous potential to improve the quality of life and health. Polyquaternium-10, a cationic cellulose derivative offers a potential solution for creating a soluble, painless microneedle patch capable of responding to glucose levels and loaded with the enzyme glucose oxidase (GOx). The gelatin at pH 7.4 forms complex coacervate with polyquaternium at the ratio of 7:3 respectively. As the pH decreases to the isoelectric point of gelatin, the coacervate disassembles and enhances the release of the payload. Microneedles MNs were fabricated in a pyramid shape, containing complex coacervate improved the mechanical strength of MNs, enhancing penetration capability. The incorporation of GOx into the microneedles enabled glucose-responsive behavior. In vitro experiments with artificial skin demonstrated decreased pH within the buffer medium due to the generation of gluconic acid in the presence of GOx. This pH shift triggered enhanced drug release, especially under hyperglycemic conditions, making the system a valuable tool for regulating transdermal drug delivery. In summary, this innovative glucose-responsive drug delivery system based on complex coacervate of gelatin and polyquaternium combines pH-sensitive drug release, mechanical reinforcement, and real-time glucose monitoring, making it a promising solution for improving transdermal drug delivery.

Bionic artificial skin with a fully implantable wireless tactile sensory system for wound healing and restoring skin tactile function

Tactile function is essential for human life as it enables us to recognize texture and respond to external stimuli, including potential threats with sharp objects that may result in punctures or lacerations. Severe skin damage caused by severe burns, skin cancer, chemical accidents, and industrial accidents damage the structure of the skin tissue as well as the nerve system, resulting in permanent tactile sensory dysfunction, which significantly impacts an individual’s daily life. Here, we introduce a fully-implantable wireless powered tactile sensory system embedded artificial skin (WTSA), with stable operation, to restore permanently damaged tactile function and promote wound healing for regenerating severely damaged skin. The fabricated WTSA facilitates (i) replacement of severely damaged tactile sensory with broad biocompatibility, (ii) promoting of skin wound healing and regeneration through collagen and fibrin-based artificial skin (CFAS), and (iii) minimization of foreign body reaction via hydrogel coating on neural interface electrodes. Furthermore, the WTSA shows a stable operation as a sensory system as evidenced by the quantitative analysis of leg movement angle and electromyogram (EMG) signals in response to varying intensities of applied pressures.

Artificial keloid skin models: understanding the pathophysiological mechanisms and application in therapeutic studies.

Keloid is a type of scar formed by the overexpression of extracellular matrix substances from fibroblasts following inflammation after trauma. The existing keloid treatment methods include drug injection, surgical intervention, light exposure, cryotherapy, etc. However, these methods have limitations such as recurrence, low treatment efficacy, and side effects. Consequently, studies are being conducted on the treatment of keloids from the perspective of inflammatory mechanisms. In this study, keloid models are created to understand inflammatory mechanisms and explore treatment methods to address them. While previous studies have used animal models with gene mutations, chemical treatments, and keloid tissue transplantation, there are limitations in fully reproducing the characteristics of keloids unique to humans, and ethical issues related to animal welfare pose additional challenges. Consequently, studies are underway to create in vitro artificial skin models to simulate keloid disease and apply them to the development of treatments for skin diseases. In particular, herein, scaffold technologies that implement three-dimensional (3D) full-thickness keloid models are introduced to enhance mechanical properties as well as biological properties of tissues, such as cell proliferation, differentiation, and cellular interactions. It is anticipated that applying these technologies to the production of artificial skin for keloid simulation could contribute to the development of inflammatory keloid treatment techniques in the future.

Fabrication of Artificial Skin for Robotic Head Based on Silicone Rubber

In this study, artificial skin based on silicone rubber is introduced for a robot head of the same size and shape as an actual person. The artificial skin is described from designing to molding the skin for a robot head, which mimics a young woman’s head. Fabricated skin is different from regular masks because it has to cover the core mechanical systems and move together. Skin movements create emotions on the face and give the appearance of a robot head. The robot has the same expressive and oral capabilities as humans and is integrated with artificial intelligence platforms. The knowledge of head anatomy and the parameters of the operation of the head will be applied in the design and fabrication of core mechanical mechanisms and their covering skin. This study analyses the basic knowledge of skin anatomy as well as the fabricating steps to make artificial skin made of silicone rubber material. The knowledge of skin anatomy is the foundation to study and analyze the general characteristics of human skin such as elasticity, color, elasticity, etc. Manufacturing methods for artificial skin are researched and selected accordingly. Finally, the artificial skin is created to make the robot head’s expression more realistic. Experimental results showed that the robot meets design requirements, has an 89.83% accuracy rate of human identification of robot expressions, and is highly appreciated by users in interactive experiments.

Three-Dimensional Cultured Human Dermal Papilla Cells in HGC-Coated Environments Enhance Hair Regeneration and Artificial Skin Integration

The rapid development of biomimetic materials in the field of regenerative medicine has made it possible to mimic natural cellular environments and allow in vitro systems to replace in vivo systems. In particular, the emergence of hexanoyl glycol chitosan (HGC) is playing an important role the development of 3-dimensional (3D) cell culture and tissue engineering. We employed HGC-coated dishes to cultivate human hair follicle dermal papilla (HDP) cells in 3D spheroids, assessing their ability to form hair-like structures. The study also tested the effect of minoxidil on these spheroids and explored their integration into artificial skin models. HDP cell spheroids successfully formed hair-like structures within the 3D culture. Minoxidil treatment showed enhanced hair growth in spheroids cocultured with keratinocytes. In addition, transplantation of these spheroids into artificial skin led to the formation of functional papilla structures, suggesting a closer mimicry of human skin. Hair-like structure formation and successful integration into artificial skin models pave the way for innovative approaches in hair loss treatment research, cosmetic, and pharmaceutical evaluations and skin restoration therapies.

EchoGest: Soft Ultrasonic Waveguides based Sensing Skin for Subject-Independent Hand Gesture Recognition.

Gesture recognition is crucial for enhancing human-computer interaction and is particularly pivotal in rehabilitation contexts, aiding individuals recovering from physical impairments and significantly improving their mobility and interactive capabilities. However, current wearable hand gesture recognition approaches are often limited in detection performance, wearability, and generalization. We thus introduce EchoGest, a novel hand gesture recognition system based on soft, stretchable, transparent artificial skin with integrated ultrasonic waveguides. Our presented system is the first to use soft ultrasonic waveguides for hand gesture recognition. Ecoflex™ 00-31 and Ecoflex™ 00-45 Near Clear™ silicone elastomers were employed to fabricate the artificial skin and ultrasonic waveguides, while 0.1 mm diameter silver-plated copper wires connected the transducers in the waveguides to the electrical system. The wires are enclosed within an additional elastomer layer, achieving a sensing skin with a total thickness of around 500 μm. Ten participants wore the EchoGest system and performed static hand gestures from two gesture sets: 8 daily life gestures and 10 American Sign Language (ASL) digits 0-9. Leave-One-Subject-Out Cross-Validation analysis demonstrated accuracies of 91.13% for daily life gestures and 88.5% for ASL gestures. The EchoGest system has significant potential in rehabilitation, particularly for tracking and evaluating hand mobility, which could substantially reduce the workload of therapists in both clinical and home-based settings. Integrating this technology could revolutionize hand gesture recognition applications, from real-time sign language translation to innovative rehabilitation techniques.

A biodegradable, highly sensitive and multifunctional mechanical sensor based on rGO-silk fibroin hydrogel for human motion detection and gesture recognition

Hydrogel based flexible sensors have attracted tremendous attention in the fields of artificial skin, motion detection and health management due to their excellent characteristics such as portability and wearability.

Design and fabrication of alginate hydrogel nanohybrid as a promising cancer treatment.

Basal cell carcinoma (BCC) is the most common form of skin cancer and the most frequently occurring form of all cancers, affecting sun-exposed areas like the face. Surgery is the main treatment, focusing on safe and minimally invasive methods for better outcomes. Technology has enabled the development of artificial skin substitutes for tissue repair. Tissue engineering uses scaffolds to create functional replacements. This project aims to create an alginate-based hydrogel with PEG-coated gold nanoparticles. The project extensively explored the modification of alginate hydrogels with PEG-coated gold nanoparticles, involving the synthesis of gold nanoparticles, their integration with the polymer, and the subsequent preparation of the concentrated hybrid hydrogel. Utilizing various physicochemical techniques, such as UV-visible spectroscopy, transmission electron microscopy, dynamic light scattering, zeta potential analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy, the fabrication process was optimized and characterized. The successful synthesis of the hybrid biomaterial was achieved through robust and highly reproducible methods. The MTT assay results offered valuable insights into the biocompatibility and safety of the PEG-coated gold nanoparticle-loaded alginate-based films. The incorporation of PEG-coated gold nanoparticles allowed for potential drug loading on the nanoparticle surface and, consequently, within the hydrogel. Cellular assays were conducted to assess the potential applications of this novel biomaterial. The addition of polyethylene glycol made it possible to load different drugs onto the gold nanoparticles and also within the hydrogel. This makes it a promising choice for potential uses in tissue engineering.

Toward a high-voltage practical lithium ion batteries with ultraconformal interphases and enhanced battery safety

Nickel-rich layered lithium transition metal oxides, LiNixCoyMn1-x-yO2, are key cathode materials for high-energy lithium–ion batteries owing to their high specific capacity. However, the commercial deployment of nickel-rich oxides is hampered by their parasitic reactions and the associated safety issues at high voltages. Developing a stable cathode–electrolyte interphase (CEI) is a promising strategy to overcome this problem. Herein, we report a novel approach, based on the in situ polymerization reaction, to build a protective polymer skin on LiNi0.6Co0.2Mn0.6O2 (NCM622) cathode materials. The artificial CEI skin was found to drastically improve the intrinsic thermal stability, mitigate the evolution of phase transition, and effectively inhibit the associated parasitic reactions between cathodes and the electrolyte in the high-charge states. This coating approach leads to enhanced capacity retention and battery safety under high-voltage operations. The CEI design concept offers a promising strategy for develop advanced nickel-rich cathodes for batteries.

Bio-inspired hierarchical wrinkles for tunable infrared reflectance

Wrinkles with large infrared emissivity regulation are attractive for thermal management. Here we present the design and preparation of hierarchical wrinkles (H-wrinkles) of POE-POE/Al, which exhibit a high reflectance modulation range from 0.60 to 0.16 upon mechanical actuation. The POE-POE/Al primary wrinkles (P-wrinkles) with optimum structure factors are prepared by hot-pressing. According to the FDTD calculation, the infrared absorption by plasma resonance in periodic structure mainly occurs at the troughs. Hierarchical troughs would further promote the infrared absorption by dual plasma resonance. Then sub-troughs via mechanical instability are introduced in the primary troughs according to prediction of theoretical analysis. When placed on a hot stage of 40°C, a temperature difference of ∼5.3°C is obtained for the H-wrinkles before and after a uniaxial stretching of 150%. Meanwhile, when being covered on the artificial skin, the H-wrinkles could achieve a dynamic temperature modulation of ∼1.4°C upon mechanical actuation. The study offers a strategy for preparation of the biomimetic wrinkles with high infrared modulation ability for applications in infrared camouflage and thermal management.