In this study, the effect of the core material in hairy core-shell carriers with grafted poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) polymer brushes containing immobilized laccase from Trametes versicolor (TvL) is investigated. Conductive silver, silver-Janus, carbon nanotubes, carbon black, and insulating silica particles were chosen as core materials. These carriers are easy to handle and store, enabling reproducible sensor fabrication with a well-defined and high number of immobilized enzymes. Hydroquinone (HQ) detection in an aqueous system was chosen as a model for biosensor characterization. All systems demonstrated high catalytic efficiency, significantly suppressing the oxidation of HQ at the electrode surface and thereby providing selectivity. The sensitivity of the prepared sensors did not differ significantly among the carriers. However, the limit of detection was highly dependent on the overall conductivity of the carrier and its active surface area. Our main observation is that using highly conductive, high-surface-area carriers does not necessarily enhance sensor performance and can in fact worsen the detection limit due to the dominance of capacitive currents over faradaic ones.

One major challenge in additively manufacturing soft materials such as thermoplastics, elastomers, and gels is their low mechanical stability. Nature solves this by embedding continuous fibers like collagen or cellulose into soft matrices. Integrating 3D printing with fiber spinning has remained difficult due to limited material compatibility, restricted deposition methods, insufficient control over fiber properties, and lack of interlayer reinforcement. We present a spider-inspired technology that combines 3D (bio)printing with in-situ biomimetic fiber spinning. Fibers are drawn from polymer solutions or melts and deposited via controlled oscillatory motion, enabling horizontal or tilted freestanding fibers, precise adjustment of pulling speeds, and fabrication of structures with unlimited thickness. This method surpasses existing spinning techniques and enables complex, fiber-reinforced architectures for biomedical and engineering applications.

Here, we report smart, photothermal, remotely reversibly controllable, high-aspect-ratio lamellar structures fabricated by melt electrowriting (MEW) using a polyester urethane based on poly(1,10-decylene adipate) incorporating 0.2 wt % graphene nanoplates (GNP) or multiwalled carbon nanotubes (MWCNT). The addition of these carbon-based fillers enables efficient photothermal conversion under near-infrared (NIR) laser irradiation, allowing localized heating of individual lamella. As a result, reversible buckling of the lamellar structures is achieved through the melting of the soft segments, enabling tunable interlamellar spacing and programmable topography. Moreover, the direction of bending can be guided by the capillary forces applied within the interlamellar space-by applying a water droplet. The switchable lamellar topography enables displacement of droplets and their controlled merging within a single interlamellar groove, which is demonstrated using FeCl3 and K4[Fe(CN)6] solutions, leading to the formation of Prussian blue crystals upon contact. This remotely controlled, light-responsive smart lamellar architecture provides promising applications in microfluidics, smart surfaces, and soft robotic systems.

We present an innovative strategy for fabricating strain sensors based on nonwoven, porous, and wrinkled textile architectures that mimic the mechanical behavior of biological tissues. These hybrid textiles are produced through a controlled shape transformation of composite fibrous structures fabricated by sequential electrospinning of an elastic polymer and melt electrowriting of a stiffer polymer, constituting a 4D fabrication process. The resulting wrinkled materials exhibit a biomimetic strain‐stiffening response, which can be precisely tuned by adjusting the geometry of the melt electrowritten framework. In addition, pre‐stretching provides fine control over the effective mechanical modulus, enabling accurate matching to a broad range of biological tissues—from stiff cartilage to soft skin and highly compliant adipose tissue. This versatile approach establishes a pathway toward wearable strain sensors whose mechanical properties are intrinsically harmonized with those of the human body.

Hydrogels are widely used materials for biomedical applications. In particular, supramolecular hydrogels bioinspired on guanosine-quadruplexes (GQ) have been utilized in the last decade for drug delivery, biocatalysis and biosensing. However, when applied as scaffolds for cell and bioengineering applications, existing GQ hydrogels suffer from important limitations: i) scarcity of fabrication strategies under mild aqueous conditions, ii) quick disintegration within few hours under physiological conditions, iii) narrow tunability of their properties in relation to native tissues. These shortcomings hamper the broad use of GQ hydrogels in bioengineering. Herein, stable and versatile GQ hydrogels are developed as dynamic biomatrices for cell culture and tissue engineering applications. The GQ matrices are easily fabricated under mild aqueous conditions, present improved physical integrity and tunable mechanical properties within physiological ranges, besides fibrillar, porous microstructure, ion conductivity and cytocompatibility. Detailed characterization of GQ self-assembly process driving hydrogelation is presented through various spectroscopic, structural, rheological and microscopic techniques. For the first time, mechanistic insight on the ion conductivity of GQ hydrogels is revealed by electro-rheology. These matrices support the culture of diverse cell types in 2D and 3D, and showcase injectability and printability, making these scaffolds suitable for manufacturing soft medical devices. The results of this study expand the applicability potential of GQ hydrogel for advancing in vitro tissue models.

For the first time, a highly sensitive electrochemical biosensor based on SiO 2 hairy particles grafted with polymerize poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) polymer brushes containing immobilized Laccase from Trametes versicolor (TvL) is reported. This system offers major advantages in enzyme loading, catalytic efficiency, and detection sensitivity. The biosensor achieves a high enzyme immobilization density of up to 0.57 g g −1 of polymer, while the enzymatic activity of the immobilized Laccase is enhanced 75‐fold compared to the free enzyme in the buffer. These carriers are easy to handle and store, enabling reproducible sensor fabrication with well‐defined enzyme content. The biosensor is tested for hydroquinone (HQ) detection, where Laccase rapidly catalyzes HQ oxidation near the electrode, generating a locally high quinone concentration. This suppresses direct HQ oxidation at the electrode surface, enhancing selectivity. The sensor demonstrates excellent analytical performance, with a sensitivity of 0.14 A· m −1 , a detection limit of 0.1 µ m , and a wide linear range of 0.3–750 µ m —surpassing most comparable systems even without optimization. This work serves as a proof of concept and a promising platform for developing advanced biosensors. Furthermore, the approach can be adapted to other core–shell particle systems and enzyme‐based electrochemical detection platforms.

Elastocapillarity, the interplay between elasticity and capillarity, is of great importance for various fields, including surface control, microfluidics, biotechnology, robotics, medicine, microtechnology, and more. This study investigates the elastocapillarity of surfaces with partially cantilever-like vertical lamellae with switchable mechanical properties, where one side is fixed to a substrate, and the other side can move freely. In this work, we want to understand the interaction between lamellae and water droplets during their sliding. Specifically, we want to understand how the flexibility of the lamellae affects the sliding of water droplets and how the deformation of the lamellae during sliding depends on their flexibility and interaction with the water droplet. We control flexibility by the mechanical properties of the lamellae, which depend on the mechanical properties of the polymer forming them, and how lamellae are attached/adhered to the substrate. Depending on fabrication, lamellae can have three kinds of contacts with the substrate: strong adhesion (fusion of the bottom of the lamellae to the substrate), intermediate adhesion (high-friction lamellae-substrate contact), and weak adhesion (low-friction lamellae-substrate contact─lamellae with an air gap underneath). Moreover, it was found that lamellae neglect the effect of the material of the substrate on water droplet sliding, and freely moving lamellae promote the fastest sliding of droplets due to capillary forces. The water droplets are also able to cause the deformation of lamellae during sliding. We found that rigid lamellae rigidly and strongly/intermediately attached to a substrate are not deformed by droplets; the upper parts of soft lamellae strongly and intermediately attached to a substrate were deformed by the water droplet, while their lower parts remained immobile, and the sliding droplet can deform both rigid and soft lamellae weakly connected to a substrate.

Abstract Electronic skins (e-skins) seek to go beyond the natural human perception, e.g., by creating magnetoperception to sense and interact with omnipresent magnetic fields. However, realizing magnetoreceptive e-skin with spatially continuous sensing over large areas is challenging due to increase in power consumption with increasing sensing resolution. Here, by incorporating the giant magnetoresistance effect and electrical resistance tomography, we achieve continuous sensing of magnetic fields across an area of 120 × 120 mm2 with a sensing resolution of better than 1 mm. Our approach enables magnetoreceptors with three orders of magnitude less energy consumption compared to state-of-the-art transistor-based magnetosensitive matrices. A simplified circuit configuration results in optical transparency, mechanical compliance, and vapor/liquid permeability, consequently permitting its imperceptible integration onto skins. Ultimately, these achievements pave the way for exceptional applications, including magnetoreceptive e-skin capable of undisturbed recognition of fine-grained gesture and a magnetoreceptive contact lens permitting touchless interaction.

Polymer brush-modified core-shell particles are already known as good carriers for enzymes, which can improve enzyme activity and stability compared to free enzymes[1]. However, for application in electrochemical biosensors, electron transfer between the electrode and immobilized enzyme is important. To achieve this, the materials used should combine the high enzyme loading of the polymer brush-modified particles with reasonable conductivity. In this work, two different approaches to introduce conductivity and high enzyme loading into polymer brush functionalized hybrid particles are pursued. In the first approach, conductive nanoparticles (Ag and Au) and enzymes were incorporated into poly(2(dimethylamino)ethyl methacrylate) brush shells on silica particle cores. In the second approach, conductive Ag particles were synthesized (as a core material), then grafted with PDMAEMA brush shell and afterwards loaded with enzymes. Polymer grafting density, polymer chain length, as well as the position of the conductive component either in the core or in the shell of hybrid particles showed an influence on the final particles' conductivity and loading enzyme (Laccase from Trametes versicolor) capacities. This fundamental study clarifies an interplay between the conductivity of polymer-brush functionalized core-shell particles and their enzyme loading efficiency and catalytic activity.

Biofabrication is an emerging interdisciplinary field of engineering that aims to develop technologies for applications in tissue engineering and regenerative medicine. A progressing biofabrication technology is 3D (bio) printing (3DBP), which allows for controlled spatial deposition of cell‐laden bioinks in a layer‐by‐layer approach to fabricate biologically active constructs. Although 3DBP can create some biologically relevant structures, it uses hydrogels, which are isotropic in nature and do not provide sufficient mechanical properties to reconstruct many tissues, such as cartilage, bone, and skin. Additionally, hydrogels alone do not replicate the complex hierarchical buildup of native tissue extracellular matrix (ECM), which contains both gel‐like and fibrous components. Replicating native tissue's structure both mechanically and biologically by incorporating fibers would result in enhanced biological performance. This is possible by integrating biofabrication technologies such as 3DBP and fiber fabrication techniques. Thus, harnessing the strengths of each technique and eliminating their limitations. This will enable the fabrication of hybrid 3D constructs with multiscale hierarchy and enhanced mechanical and biological performance comparable to native tissue. This review aims to highlight attempts to combine fiber fabrication methods with 3DBP for tissue engineering applications. Additionally, different fiber fabrication techniques are discussed, showcasing their limitations and possible integration with 3DBP.

Four-dimensional (4D) printing, combining three-dimensional (3D) printing with time-dependent stimuli-responsive shape transformation, eliminates the limitations of the conventional 3D printing technique for the fabrication of complex hollow constructs. However, existing 4D printing techniques have limitations in terms of the shapes that can be created using a single shape-changing object. In this paper, we report an advanced 4D fabrication approach for vascular junctions, particularly T-junctions, using the 4D printing technique based on coordinated sequential folding of two or more specially designed shape-changing elements. In our approach, the T-junction is split into two components, and each component is 4D printed using different synthesized shape memory polyurethanes and their nanohybrids, which have been synthesized with varying hard segment contents and by incorporating different weight percentages of photo-responsive copper sulfide-polyvinyl pyrrolidone nanoparticles. The formation of a T-junction is demonstrated by assigning different shape memory behaviors to each component of the T-junction. A cell culture study with human umbilical vein endothelial cells reveals that the cells proliferate over time, and almost 90% of cells remain viable on day 7. Finally, the formation of the T-junction in the presence of near-infrared light has been demonstrated after seeding the endothelial cells on the programmed flat surface of the two components and fluorescence microscopy at day 3 and 7 reveals that the cells adhered well and continue to proliferate over time. Hence, the proposed alternative approach has huge potential and can be used to fabricate vascular junctions in the future.

Abstract Four-dimensional (4D) printing is an advanced manufacturing technology that has rapidly emerged as a transformative tool with the capacity to reshape various research domains and industries. Distinguished by its integration of time as a dimension, 4D printing allows objects to dynamically respond to external stimuli, setting it apart from conventional 3D printing. This roadmap has been devised, by contributions of 44 active researchers in this field from 32 affiliations world-wide, to navigate the swiftly evolving landscape of 4D printing, consolidating recent advancements and making them accessible to experts across diverse fields, ranging from biomedicine to aerospace, textiles to electronics. The roadmap’s goal is to empower both experts and enthusiasts, facilitating the exploitation of 4D printing’s transformative potential to create intelligent, adaptive objects that are not only feasible but readily attainable. By addressing current and future challenges and proposing advancements in science and technology, it sets the stage for revolutionary progress in numerous industries, positioning 4D printing as a transformative tool for the future.

We report the fabrication of topographically structured surfaces with reversibly switchable topography by using melt electrowriting (MEW). In particular, MEW was used to produce continuous high aspect ratio lamellae of semicrystalline polyester urethane with a poly(1,10-decylene adipate) soft segment. The switching of topography is achieved by the expansion and contraction of the polymer caused by the melting and crystallization of the soft segment that results in the buckling of lamellae. In the molten stage, lamellae can be buckled in a certain direction by capillary forces caused by water droplets between two lamellae. In addition, the interlamellar distance between neighbors' lamellae can be managed by water droplets. Finally, we have demonstrated the possibility of creating electrically conductive surfaces with switchable conductivity achieved by the reversible buckling of the lamellae.

Skeletal muscle tissue can be severely damaged by disease or trauma beyond its ability to self-repair, necessitating the further development of biofabrication and tissue-engineering tools for reconstructive processes. Hence, in this study, a composite bioink of oxidized alginate (ADA) and gelatin (GEL) including cell-laden ribbon-shaped fillers is used for enhancing cell alignment and the formation of an anisotropic structure. Different plasma treatments combined with protein coatings were evaluated for the improvement of cell adhesion to poly(lactic-co-glycolic acid) (PLGA) ribbon surfaces. Oxygen plasma activation of 30 W for 5 min showed high immobilization of fibronectin as a protein coating on the PLGA ribbon surface, which resulted in enhanced cell adhesion and differentiation of muscle cells. Furthermore, the effect of various concentrations of CaCl2 solution, used for ionic cross-linking of ADA, on ADA-GEL physical and mechanical properties as well as encapsulated C2C12 cell viability and proliferation behavior was investigated. The pore area was measured via two approaches, cryofixation and lyophilization, which, in accordance with degradation tests and mechanical analysis, showed that 60 mM CaCl2 concentration is the optimum range for cross-linking of the formulation of ADA 2.5%w/v-GEL 3.75%w/v. These cross-linked hydrogels showed a compression modulus of 11.5 kPa (similar to the native skeletal muscle tissue), a high viability of C2C12 muscle cells (>80%), and a high proliferation rate during 7 days of culture. Rheological characterization of the ADA-GEL composite hydrogel containing short fillers (100 μm long) showed its suitability as a bioink with shear-thinning and flow behavior compared to ADA-GEL.

4D printing recently emerges as an exciting evolution of conventional 3D printing, where a printed construct can quickly transform in response to a specific stimulus to switch between a temporary variable state and an original state. In this work, a photocrosslinkable polyethylene-glycol polyurethane ink is synthesized for light-assisted 4D printing of smart materials. The molecular weight distribution of the ink monomers is tunable by adjusting the copolymerization reaction time. Digital light processing (DLP) technique is used to program a differential swelling response in the printed constructs after humidity variation. Bioactive microparticles are embedded into the ink and the improvement of biocompatibility of the printed constructs is demonstrated for tissue engineering applications. Cell studies reveal above 90% viability in 1 week and ≈50% biodegradability after 4 weeks. Self-folding capillary scaffolds, dynamic grippers, and film actuators are made and activated in a humid environment. The approach offers a versatile platform for the fabrication of complex constructs. The ink can be used in tissue engineering and actuator applications, making the ink a promising avenue for future research.

This work presents a new method for 4D fabrication of two-way shape memory materials that are capable of reversible shapeshifting right after manufacturing, upon application of proper heating and cooling cycles. The innovative solution presented here consists in the combination of highly stretched electrospun shape memory polymer (SMP) nanofibers with a melt electrowritten elastomer. More specifically, the stretched nanofibers are made of a biocompatible thermoplastic polyurethane (TPU) with crystallizable soft segments, undergoing melt-induced contraction and crystallization-induced elongation upon heating and cooling, respectively. Reversible actuation during crystallization becomes possible due to the elastic recovery of the elastomer component, obtained by melt electrowriting of a commercial TPU filament. Thanks to the design freedom offered by additive manufacturing, the elastomer structure also has the role of guiding the shape transformation. Electrospinning and melt electrowriting process parameters are set up so to obtain smart 4D objects capable of two-way shape memory effect (SME), and the possibility of reversible and repeatable actuation is demonstrated. The two components are then combined in different proportions with the aim of tailoring the two-way SME, taking into account the effect of design parameters such as the SMP content, the elastomer pattern, and the composite thickness.

We report the design of materials with a unique combination of self-healing ability, electrical conductivity (8-150 Ohm & sdot;m), softness (G = 1 MPa), extremely low loss coefficient (tan delta approximate to 0.04) even at large deformations and linearity of resistivity dependence on strain in a broad range. The conductive material can bounce with very low energy dissipation at fast deformation, and it flows and self-heals at a large time scale and when sufficient stress is applied. The key to such properties is a combination of very stable interpenetrated networks formed by multiwalled carbon-nanotubes (MWCNT) filler and by viscoelastic polyborosiloxane (PBS) polymer matrix rendering relaxation processes and self-healing ability. We demonstrated the promise of the developed materials for the design of strain sensors with a very large linear regime and rubber-substitute as a protective coating or a sealing agent material.

In this work, we address the inherent limitations of porous, flexible, fibrous, and self-healing strain sensors. Specifically, we tackle issues such as the fatigue failure of carbon-fibrous materials and the long-term flow and low mechanical stability of self-healing materials. We achieve this by combining self-healing carbon/PBS blends with fibrous materials, creating a fiber-reinforced self-healing composite. The self-healing carbon/PBS blends provide strain sensitivity and the ability to recover after fatigue and impact failure, while the fibers prevent the long-term flow of material and the scattering of pieces during impact and fatigue failure within the elastic deformation regime, enabling shape recovery. We fabricated composite wearable strain sensors with a viscoelastic functional layer composed of two continuous phases: (i) a self-healing polymer-carbon blend and (ii) long electrospun fibers of commercial polyurethane. This setup also eliminates the other drawbacks of bulk materials, such as nonlinearity of volt-ampere characteristics, irreversibility of deformation, and a low working factor, and allows improvement of the working factor after failure and healing. Most importantly, we discovered that hindered self-healing, like in the case of the MWCNT/PBS system, enables improvement of sensor sensitivity after large strains and failure, which is due to partial failure of the network formed by conductive particles.

Digital light processing (DLP) 3D printing has become a powerful manufacturing tool for the fast fabrication of complex functional structures. The rapid progress in DLP 3D printing has been linked to research on optical design factors and ink selection. This critical review highlights the main challenges in the DLP 3D printing of photopolymerizable inks. The kinetics equations of photopolymerization reaction in a DLP printer are solved, and the dependence of curing depth on the process optical parameters and ink chemical properties are explained. Developments in DLP platform design and ink selection are summarized, and the roles of monomer structure and molecular weight on printing resolution are shown by experimental data. A detailed guideline is presented to help engineers and scientists to select inks and optical parameters for fabricating functional structures for multi-material and 4D printing.