A Spider‐Capture‐Silk‐Like Fiber with Extremely High‐Volume Directional Water Collection

A spider web collects water by its capture silk for recovering the daytime‐distorted shape during night through water‐sensitive shape memory effect. This unique smart function and geometrical structure of spider‐capture‐silk inspires the development of artificial fibers with periodic knots for directional water collection with vast potential applications in water scarce regions. Existing such fibers are mainly based on nylon filaments coated with petroleum‐originated synthetic polymer solutions. Distinct from using synthetic materials, an all silk‐protein fiber (ASPF) with periodic knots endows extremely high volume‐to‐mass water collection capability. This fiber has a main body consisting of B. mori degummed silk coated with recombinant engineered major ampullate spidroin 2 of spider dragline silk. It is 252 times lighter than synthetic polymer coated nylon fibers that once was reported to have the highest water collection performance. The ASPF collects a maximum water volume of 6.6 µL and has a 100 times higher water collection efficiency compared to existing best water collection artificial fibers in terms of volume‐to‐mass index at the shortest length (0.8 mm) of three‐phase contact line. Since silkworm silks are available abundantly, effective use of recombinant spidroins tandemly shows great potential for scalability.     

Understanding the Mechanical Properties of Antheraea Pernyi Silk—From Primary Structure to Condensed Structure of the Protein

Antheraea pernyi (A. pernyi) silk is produced and used by “wild” silkworms to construct a cocoon, but the primary structure of its protein is rather similar to that of spider major ampullate silk used to build web and dragline. Studies on this specific silk may provide valuable knowledge about the structure‐property relationship for the whole animal silk family. In this work, A. pernyi silk fibers with few macroscale defects are obtained by forcibly reeling, and are investigated in detail. It is found that such silk fibers display breaking stress and toughness of the same magnitude as spider major ampullate silks and forcibly reeled mulberry silk. The other mechanical properties, such as elasticity, supercontraction, and the effect of water on modulus are between those of spider major ampullate silks and mulberry silk. Therefore, an interpretation of the connection between the primary structures of silk proteins and the mechanical properties of silks is proposed here based on the ordered fraction, which in turn is determined by both the protein sequence and spinning process of the silk.     

Designed Multifunctional Spider Silk Enabled by Genetically Encoded Click Chemistry

Spider silk is recognized for its exceptional mechanical properties and biocompatibility, making it a versatile platform for developing functional materials. In this study, a modular functionalization strategy for recombinant spider silk is presented using SpyTag/SpyCatcher chemistry, a prototype of genetically encoded click chemistry. The approach involves AlphaFold2-aided design of SpyTagged spider silk coupled with bacterial expression and biomimetic spinning, enabling the decoration of silk with various SpyCatcher-fusion motifs, such as fluorescent proteins, enzymes, and cell-binding ligands. The silk threads can be coated with a silica layer using silicatein, an enzyme for silicification, resulting in a hybrid inorganic–organic 1D material. The threads installed with RGD or laminin cell-binding ligands lead to enhanced endothelial cell attachment and proliferation. These findings demonstrate a straightforward yet powerful approach to 1D protein materials.     

Multiple Structural Coloring of Silk‐Fibroin Photonic Crystals and Humidity‐Responsive Color Sensing

In the biological world, numerous creatures such as butterflies, insects, and birds have exploited photonic structures to produce bicolor reflections with important biofunctions in addition to unique brilliant structural coloration. Although the mimicking of bistructural color reflection is possible, the fabrication involves a process of combined layer deposition techniques, which is complicated and less flexible. Here, a bistructural color mimicking, based on silk fibroin, is reported using a simple and inexpensive self‐assembly method. Silk‐fibroin inverse opals with different spectral positions of bistructural color reflection (i.e., ultraviolet and visible peaks, ultraviolet and near infrared peaks, and visible and near infrared peaks) are obtained by simply controlling their lattice constants. Furthermore, the inline and continuous tuning of the peak positions of bistructural color reflection can be achieved by the humidity‐induced cyclic contraction of silk fibroin. The potential applications of silk‐fibroin photonic structures in eco‐dying and multifunctional silk fabrics are also demonstrated.     

Self-Healable Spider Dragline Silk Materials

Developing materials with structural flexibility that permits self-repair in response to external disturbances remains challenging. Spider silk, which combines an exceptional blend of strength and pliability in nature, serves as an ideal dynamic model for adaptive performance design. In this work, a novel self-healing material is generated using spider silk. Dragline silk from spider Nephila pilipes is demonstrated with extraordinary in situ self-repair property through a constructed thin film format, surpassing that of two other silks from spider Cyrtophora moluccensis and silkworm Bombyx mori. Subsequently, R2, a key spidroin associated with self-healing, is biosynthesized, with validated cohesiveness. R2 is further programmed with tunable healability (permanent and reversible) and conductivity (graphene doping; R2G) for electronics applications. In the first demonstration, film strips from R2 and R2G are woven manually into multidimensional (1D-3D) conductive fabrics for creating repairable logic gate circuits. In the second example, a reversibly-healable R2/R2G strip is fabricated as a re-configurable wearable ring probe to fit fingertips of varying widths while retaining its detecting capabilities. Such a prototype displays a unique conformable wearable technology. Last, the remarkable finding of self-healing in spider silk can offer a new material paradigm for developing future adaptive biomaterials with tailored performance and environmental sustainability.     

Hydration-Induced β-Sheet Crosslinking of α-Helical-Rich Spider Prey-Wrapping Silk

Due to its moderate strength (≈700 MPa) and impressive extensibility before breaking (≈60–80%), orb-weaving spider aciniform (AC) prey-wrapping silks are actually the toughest of the spider silks but are remarkably understudied. The previous results indicate that native AC silk fibers are an α-helix rich coiled-coil/β-sheet hybrid nanofiber, and that conversion of disordered or helical domains to β-sheet aggregates is surprisingly minimal and overall β-sheet content is low (≈15%). In this work, it is demonstrated through scanning electron microscopy that native AC silk fibers undergo matted cross-linking upon exposure to moisture that increases silk stiffness. The unique molecular mechanism of water-induced cross-linking is revealed with solid-state NMR (SSNMR) methods; water-induced morphological changes are correlated with an increase in AC silk protein β-sheet content, and additionally a minor unfolding of coiled-coil regions is observed. Continued and increased β-sheet cross-linking is observed upon application of mechanical shear. The size of these β-sheet domains to be 4–6 nm using Wide-Line Separation SSNMR is determined. The observation that merely water treatment can be used to convert a protein-based material from a flexible/extensible α-helix-rich fiber to a rigid crossed-linked β-sheet mat is a novel observation that should provide new avenues in bioinspired materials design.     

Strong Reduced Graphene Oxide Coated Bombyx mori Silk

Bombyx mori silks possess great potential in textile industries due to the large-scale green production. However, the demand for silks with functional as well as mechanical properties are continuously rising due to the emergence of other functional textiles. It remains a great challenge to functionalize natural silk and simultaneously improve its mechanical properties. Inspired by the relationship between natural core–sheath structure and mechanical properties of cocoon silk, the application of a thin reduced graphene oxide (rGO) layer coated B. mori silk (GS) is shown via hydrogen interfacial interaction. The resultant rGO-coated silk exhibits a remarkable tensile strength of 1137.7 MPa and toughness of 304.5 MJ m⁻³, which are 1.9 and 2.6 times higher than that of pure B. mori silk, respectively. Moreover, the GS shows a high electrical conductivity of 0.37 S m⁻¹ with great thermal and deformation sensitivity. The bioinspired approach provides a universal and facile strategy for functionalizing natural fibers by applying rGO nanosheets surface coating.     

Sequence–Structure–Property Relationships of Recombinant Spider Silk Proteins: Integration of Biopolymer Design,Processing, and Modeling

The mechanical properties of spider silks drive interest as sources of new materials. However, there remains a lot to learn regarding the relationships between sequence, structure, and mechanical properties. In order to predict the types of sequence–functional relationships, synthesis–characterization–computation are integrated using recombinant spider silk‐like block copolymers. Two designs are studied, both with origins from the spider Nephila clavipes. These proteins are studied both experimentally and in silico to understand the relationships between sequence chemistry, processing, structure, and materials function. Films formed from the two proteins are thoroughly characterized. In parallel, molecular modeling is used to assess the propensity of the two sequences to form β‐sheets or crystalline structures. The results demonstrate that the modeling predicts the structural differences between the two silk‐like polymers and these features can also be related to differences in functional outcomes. With this example of relating sequence design (hydrophobic–hydrophilic domains), experiment (genetic design and synthesis), processing (film and fiber formation) and modeling (predictions of crystallinity), synergy among these methods is demonstrated for predictable material outcomes. This approach offers a robust discovery path when looking towards next generation approaches to targeted materials outcomes.     

Spider Silk Coatings as a Bioshield to Reduce Periprosthetic Fibrous Capsule Formation

Medical grade silicones have been employed for decades in medical applications. The associated long‐term complications, such as capsule formation and contraction have, however, not been fully addressed yet. The aim of this study is to elucidate if capsule formation and/or contraction can be mitigated by veiling the surface of the silicone during the critical phase after implantation. Medical grade silicone implants are homogeneously coated with a micrometer thin layer of recombinant spider silk proteins. Biocompatibility analysis in vitro and in vivo focuses on specific physiological reactions. Applying quantitative methods for the determination of marker‐specific gene expression and protein concentration, it is detected that the silk coating inhibits fibroblast proliferation, collagen I synthesis, and differentiation of monocytes into CD68‐positive histiocytes. It significantly reduces capsule thickness, post‐operative inflammation, synthesis and re‐modeling of extracellular matrix, and expression of contracture‐mediating factors. Therefore, coatings made of recombinant spider silk proteins considerably reduce major post‐operative complications associated with implantation of silicone‐based alloprosthetics, such as capsular fibrosis and contraction, rendering spider silk coatings a bioshield for such implants.     

Recombinant Spider Silk as Mediator for One‐Step,Chemical‐Free Surface Biofunctionalization

A unique strategy for effective, versatile, and facile surface biofunctionalization employing a recombinant spider silk protein genetically functionalized with the antibody‐binding Z domain (Z‐4RepCT) is reported. It is demonstrated that Z‐silk can be applied to a variety of materials and platform designs as a truly one‐step and chemical‐free surface modification that site specifically captures antibodies while simultaneously reducing nonspecific adsorption. As a model surface, SiO₂ is used to optimize and characterize Z‐silk performance compared to the Z domain immobilized by a standard silanization method. First, Z‐silk adsorption is investigated and verified its biofunctionality in a long‐term stability experiment. To assess the binding capacity and protein–protein interaction stability of Z‐silk, the coating is used to capture human antibodies in various assay formats. An eightfold higher binding capacity and 40‐fold lower detection limit are obtained in the immunofluorescence assay, and the complex stability of captured antibodies is shown to be improved by a factor of 20. Applicability of Z‐silk to functionalize microfluidic devices is demonstrated by antibody detection in an electrokinetic microcapillary biosensor. To test Z‐silk for biomarker applications, real‐time detection and quantification of human immunoglobulin G are performed in a plasma sample and C1q capture from human serum using an anti‐C1q antibody.     

Spider Silk Capsules as Protective Reaction Containers for Enzymes

Spider silk fibres are well known for their high tensile strength in combination with high elasticity. Based on the possibility of recombinant production of spider silk proteins, technical applications of spider silk materials are nowadays feasible. The engineered recombinant spider silk protein eADF4(C16) is based on the sequence of ADF4 (Araneus diadematus fibroin), one out of at least three proteins of the dragline silk of the European garden spider A. diadematus. The protein eADF4(C16) can be processed into different morphologies. Here, capsules of eADF4(C16) are assembled at an oil/water interface. These microcapsules are mechanically stable and can be used as a transport system for higher molecular weight compounds such as enzymes or chemical catalysts. Further, they can be regarded as a small enclosed reaction chamber with a semi‐permeable membrane. Reactions can be initiated by diffusion of the reactants through the silk membrane. The eADF4(C16) capsules protect the enzyme β‐galactosidase, used as model, against proteolysis. Functional α‐complementation of β‐galactosidase visualizes the controllable activation of an enzyme within such spider silk capsule, highlighting the broad applicability thereof as reaction containers, e.g., for enzymes.     

Meso‐Functionalization of Silk Fibroin by Upconversion Fluorescence and Near Infrared In Vivo Biosensing

In biomedical applications, it is very desirable to monitor the in vivo state of implanted devices, i.e., tracking the location, the state, and the interaction between the implanted devices and cell tissues. To achieve this goal, a generic strategy of soft materials meso‐functionalization is presented. This is to acquire silk fibroin (SF) materials with added functions, i.e., in vivo bioimaging/sensing. The functionalization is by 3D materials assembly of functional components, lanthanide(Ln)‐doped upconversion nanoparticles (UCNPs) on the mesoscopic scale to acquire upconversion fluorescent emission. To implement the meso‐functionalization, the surfaces of UCNPs are modified by the hydroxyl groups (? OH) from SiO₂ or polyethylene glycol coating layers, which can interact with the carbonyl groups (C?O) in SF scaffolds. The functionalized silk scaffolds are further implanted subcutaneously into mice, which allows the silk scaffolds to have fluorescent in vivo bioimaging and other biomedical functions. This material functionalization strategy may lead to the rational design of biomaterials in a more generic way.     

Novel scattering and color converting substrates for simple-structured white organic light-emitting diodes

Organic light-emitting diodes (OLEDs) have shown great success in the display applications recently. However, the applications of OLEDs in lighting are still limited due to their complex device structures. Here, we developed a novel phosphor doped glass substrate with both high scattering and excellent color conversion capability to greatly simplify the device structures of white organic light-emitting diodes (WOLEDs). A simple-structured WOLED comprising a blue OLED and the scattering fluorescent substrate was demonstrated to realize high quality white light for lighting applications. The WOLED exhibits a turn-on voltage of 2.7 V, a maximum power efficiency of 29.8 lm/W, an external quantum efficiency (EQE) of 14.2%, a color rendering index (CRI) of 86, and a correlated color-temperature (CCT) of 3900 K. The low turn-on voltage can be attributed to the single emissive layer structure used in the WOLED. The high power efficiency as well as the high EQE are due to both the high color conversion efficiency and the high scattering capability of the fluorescent substrate. In addition, the WOLED is favorable for high-quality solid-state lighting in our daily life due to its high color rendering ability along with an adequate CCT CC.     

Rugged Textile Electrodes for Wearable Devices Obtained by Vapor Coating Off‐the‐Shelf,Plain‐Woven Fabrics

Fabrics are pliable, breathable, lightweight, ambient stable, and have unmatched haptic perception. Here, a vapor deposition method is used to transform off‐the‐shelf plain‐woven fabrics, such as linen, silk, and bast fiber fabrics, into metal‐free conducting electrodes. These fabric electrodes are resistant to wear, stable after laundering and ironing, and can be body‐mounted with little detriment to their performance. A unique by‐product of conformally vapor coating plain‐woven fabrics is that textile parameters, such as thread material and fabric porosity, significantly affect the conductivity of the resulting fabric electrodes. The resistivities of the electrodes reported herein are linearly, not exponentially, dependent on length, meaning that they can be feasibly incorporated into garments and other large‐area body‐mounted devices. Further, these fabric electrodes possess the feel, weight, breathability, and pliability of standard fabrics, which are important to enable adoption of wearable devices.     

High‐Performance Thermoresponsive Dual‐Output Dye System for Smart Textile Application

Smart textiles exhibiting optical response to external temperature stimuli are promising functional materials for a wide range of applications. It is critical yet challenging to endow these materials with high‐contrast, vivid, and real‐time optical signals, such as changes in color or fluorescent emission, for the indication of heating and/or cooling. A thermoresponsive dye system featuring simultaneous thermochromism and thermofluorescence is developed and applied to dyeing of polyester fabrics. The dye system is constructed by encapsulating a solution of indenoquinacridone (IQA) in aliphatic alcohol into SiO₂ nanoparticles. The dual‐output response relies on the mechanism of solvent‐modulated dissociation/aggregation of the IQA molecules. Upon heating, the dye system and the dyed fabric exhibit clear color change and high‐contrast, turned‐on fluorescence, in a real time and highly reversible manner. The thermoresponsive temperature can be tailored by varying the aliphatic alcohol solvent with different melting point. The integration of high‐contrast dual optical outputs into this programmable, robust, and reversible dye system lays the foundation for its employment in a wide range of challenging applications in smart textiles.     

Structural Origin of the Strain‐Hardening of Spider Silk

Spider dragline silk, as a type of high‐performance natural fiber, displays a unique combination of tensile strength and extensibility that gives rise to a greater toughness than any other natural or synthetic fiber. In contrast to silkworm silk, spider dragline silk displays a remarkable strain‐hardening character for which the origin remains unknown. In this paper, the performance of silkworm silk and spider dragline fibers under stretching is compared based on a combined structural and mechanical analysis. The molecular origin of the strain‐hardening of spider silk filaments is addressed in comparison to rubber and Kevlar. Unlike rubber, the occurrence of strain‐hardening can be attributed to the unfolding of the intramolecular β‐sheets in spider silk fibrils, which serve as “molecular spindles” to store lengthy molecular chains in space compactly. With the progressive unfolding and alignment of protein during fiber extension, protein backbones and nodes of the molecular network are stretched to support the load. Consequently the dragline filaments become gradually hardened, enabling efficient energy buffering when an abseiling spider escapes from a predator. As distinct from synthetic materials such as rubber (elastomers), this particular structural feature of spider draglines not only enables quick energy absorption, but also efficiently suppresses the drastic oscillation which occurs upon an impact. The mimicking of this strain‐hardening character of spider silk will give rise to the design and fabrication of new advanced functional materials with applications in kinetic energy buffering and absorption.     

“Nano‐Fishnet” Structure Making Silk Fibers Tougher

Based on the combined technologies of atomic force microscopy, X‐ray diffraction/scattering, Fourier transform infrared spectra analysis, etc., it is demonstrated that the nano‐fishnet‐like networks, one of the most flexible but toughest structures, turn out to be the basic structure of silk filaments. The force patterns of pulling individual fibrils allow the identification of the pathways of unfolding protein segments in stacking β‐crystallites, which reveal the fishnet‐like topology. The calculation shows that the β‐crystallites in silk nanofibrils are the cross‐linking points of the nano‐fishnets, which may enhance the toughness of silk filaments up to 1000 times, compared with amyloid‐like and unlinked string structures. It follows that the strong β‐sheet–β‐sheet interaction, a high degree of ordering, and a high density of β‐crystallites in silk fibers toughen the fishnet structure, then strengthen silk filaments, in consistency with the experiments for both spider and silkworm silks. The knowledge on the fishnet structure of silk fibers sheds light on the design and synthesis of either protein or synthetic fibers of ultraperformance in a more generic way.     

Functionalized‐Silk‐Based Active Optofluidic Devices

Silk protein from the silkworm Bombyx mori has excellent chemical and mechanical stability, biocompatibility, and optical properties. Additionally, when the protein is purified and reformed into materials, the biochemical functions of dopants entrained in the protein matrix are stabilized and retained. This unique combination of properties make silk a useful multifunctional material platform for the development of sensor devices. An approach to increase the functions of silk‐based devices through chemical modifications to demonstrate an active optofluidic device to sense pH is presented. Silk protein is chemically modified with 4‐aminobenzoic acid to add spectral‐color‐responsive pH sensitivity. The functionalized silk is combined with the elastomer poly(dimethyl siloxane) in a single microfluidic device. The microfluidic device allows spatial and temporal control of the delivery of analytic solutions to the system to provide the optical response of the optofluidic device. The modified silk is stable and spectrally responsive over a wide pH range from alkaline to acidic.     

Heterogeneous Fluorescent Organohydrogel Enables Dynamic Anti-Counterfeiting

Fluorescent patterns showing the unique color change in response to external stimuli are of considerable interest for their applications in anti-counterfeiting. However, there is still a lack of intelligent fluorescent patterns with high-security levels, presenting a dynamic display of encrypted information. In this study, a fluorescent organohydrogel is fabricated through a two-step interpenetrating technique, leading to the co-existence of naphthalimide moieties (DEAN, green-yellow fluorescent monomer) contained Poly(N,N-dimethylacrylamide) (PDMA) hydrogel network and Polyoctadecyl methacrylate (PSMA) organogel network bearing spiropyran moieties (SPMA, photochromic monomer). Due to the unique heterogeneous networks, the fluorescence color goes through a continuous change from green to yellow to red via the fluorescence resonance energy transfer (FRET) process with the extension of irradiation time. In addition, when H⁺ is introduced into the system, SP units exhibit transformation into the protonated merocyanine (MCH⁺) rather than merocyanine (MC) under UV light, which inhibits the FRET process. By selectively being treated with H⁺, the fluorescent organohydrogel can act as an effective platform for encrypting secret information, making them more difficult to forge.     

Dispersion State and Fiber Toughness: Antibacterial Lysozyme‐Single Walled Carbon Nanotubes

Novel multicomponent fibers that include single‐walled carbon nanotubes (SWNT) and lysozyme (LSZ) are reported. These fibers exhibit antibacterial and mechanical properties suitable for fabrics, clothing and technical textiles in medical environments. The challenging combination of several components in a single fiber material is achieved via fundamental studies on the phase behavior of aqueous LSZ–SWNT dispersions. The addition of molecular cationic surfactants proved to be critical to achieving stable liquid mixtures that can be spun into fibers. In the absence of the cationic surfactant tetradecyl trimethylammonium bromide (TTAB), depletion effects result in large aggregates at relatively low SWNT concentration. However, the addition of TTAB increases the concentration at which demixing occurrs by approximately one order of magnitude. Dry‐spun fibers with significant antibacterial activity and toughness are obtained from LSZ–TTAB–SWNT dispersions combined with a polyvinyl alcohol (PVA) solution. Toughness is strongly affected by the initial dispersion state. The most remarkable fibers are produced from concentrated LSZ–TTAB–SWNT supernatants; they both have four times the toughness of spider silk and 70% of the native LSZ activity.