Tunable Mechanical Properties Research Articles

Self-Assembled Hydrogel Membranes with Structurally Tunable Mechanical and Biological Properties.

Using supramolecular self-assembled nanocomposite materials made from protein and polysaccharide components is becoming more popular because of their unique properties, such as biodegradability, hierarchical structures, and tunable multifunctionality. However, the fabrication of these materials in a reproducible way remains a challenge. This study presents a new evaporation-induced self-assembly method producing layered hydrogel membranes (LHMs) using tropocollagen grafted by partially deacetylated chitin nanocrystals (CO-g-ChNCs). ChNCs help stabilize tropocollagen's helical conformation and fibrillar structure by forming a hierarchical microstructure through chemical and physical interactions. The LHMs show improved mechanical properties, cytocompatibility, and the ability to control drug release using octenidine dihydrochloride (OCT) as a drug model. Because of the high synergetic performance between CO and ChNCs, the modulus, strength, and toughness increased significantly compared to native CO. The biocompatibility of LHM was tested using the normal human dermal fibroblast (NHDF) and the human osteosarcoma cell line (Saos-2). Cytocompatibility and cell adhesion improved with the introduction of ChNCs. The extracted ChNCs are used as a reinforcing nanofiller to enhance the performance properties of tropocollagen hydrogel membranes and provide new insights into the design of novel LHMs that could be used for various medical applications, such as control of drug release in the skin and bone tissue regeneration.

Nested non-covalent interactions expand the functions of supramolecular polymer networks

Supramolecular polymer networks contain non-covalent cross-links that enable access to broadly tunable mechanical properties and stimuli-responsive behaviors; the incorporation of multiple unique non-covalent cross-links within such materials further expands their mechanical responses and functionality. To date, however, the design of such materials has been accomplished through discrete combinations of distinct interaction types in series, limiting materials design logic. Here we introduce the concept of leveraging “nested” supramolecular crosslinks, wherein two distinct types of non-covalent interactions exist in parallel, to control bulk material functions. To demonstrate this concept, we use polymer-linked Pd2L4 metal–organic cage (polyMOC) gels that form hollow metal–organic cage junctions through metal–ligand coordination and can exhibit well-defined host-guest binding within their cavity. In these “nested” supramolecular network junctions, the thermodynamics of host-guest interactions within the junctions affect the metal–ligand interactions that form those junctions, ultimately translating to substantial guest-dependent changes in bulk material properties that could not be achieved in traditional supramolecular networks with multiple interactions in series.

Solving the dilemma between reprocessability and mechanical properties faced by recyclable bio-based polyurethane foam through confining imine bonds in the hard domains

Introducing dynamic covalent bonds (DCBs) into polyurethane (PU) foams can solve the problem of their poor recyclability. However, a dilemma arises between reprocessability and mechanical robustness because of the low bond energies of DCBs. In this work, an aromatic diol (VAN-AM) containing imine bonds is synthesized to serve as the polyol together with castor oil. A series of bio-based polyurethane foams (BPUFs) with tunable bio-based carbon content, apparent density, cell properties and mechanical properties are prepared by adjusting the proportions of VAN-AM and castor oil. Benefiting from the molecular rigidity of VAN-AM, the dynamic imine bonds are enriched in the hard domains of PU. This allows for the kinetic control of the dynamicity of the PU networks. When the foams work at ambient temperature, which is much lower than the glass transition temperature of PU (113 ºC), the frozen segments of the hard domains inhibit the dynamic behavior of the imine bonds even if the latter may be somewhat activated (their triggering temperature ≈ 50 ºC). Consequently, the good mechanical properties of BPUFs can be maintained during service. At higher temperatures (> 113 ºC) or swollen state, the segmental mobility in the hard domains and dynamicity of imine bonds are greatly enhanced. Recycling of BPUFs is enabled as evidenced by hot-pressing the crushed foams into the compact sheets under mild conditions. The findings would facilitate the rational design of crosslinked polymeric foams with both high reprocessability and mechanical performance.

Interlocked wood-like composites with tunable mechanical properties

Inspired by the fact that the architecture of natural biomaterials has a great influence on their mechanical properties, the present work designed a Al2O3–poly (methyl methacrylate) composite with an interlocked wood-like architecture, which can balance the contradictions between flexural strength–fracture toughness. The results shows that the mechanical performance of the composites can be tuned through the adjustment of the tilt angle of the Al2O3 spiral fibres. The composite with a tilt angle of 30° exhibited the highest flexural strength and fracture toughness, showing the ability to overcome the trade-off between flexural strength and fracture toughness. All composites exhibited weak compressive strength anisotropy owing to the interlocked helical architecture in which the continuous fiber spiraled in 3D space. Toughening mechanisms including crack deflection, crack bridging, crack bifurcation, microcracking were observed. Numerous microcracks were nucleated in the Al2O3 ceramic skeleton, and they propagated along the main crack under the bridging effect of poly (methyl methacrylate). All of the composites featured suture-like cracks perpendicular to the direction of the main cracks, which was a unique toughening mechanism found in this architecture. Large-size composites can be prepared through the adopted technique to meet the demands of engineering applications.

Thixotropic chitosan hydrogels for biomedical applications: Unravelling the effect of chitosan concentration on the mechanical behaviour

Chitosan hydrogels are highly sought after in biomedical applications due to their biocompatibility, non-toxicity, and tunable mechanical properties. Nevertheless, achieving stable hydrogels with the required mechanical strength remains a notable obstacle. In this study, we prepared chitosan hydrogels with enhanced stability using minimal concentrations of glutaraldehyde to mitigate toxicity risks. The resulting hydrogel system is characterized by strong covalent bonds formed through imine and hydrogen bonding, facilitated by the aldehyde groups of glutaraldehyde. Rheological analyses reveal the viscoelastic properties of the hydrogels, showcasing stable gel-like structures with shear-thinning behavior, which are further enhanced with increasing chitosan concentration. Our observation demonstrates that the complex shear moduli of 0.5 - 1.5 w/v % chitosan hydrogel ranged between 3.08 kPa and 8.5 kPa, closely matching the shear moduli of the brain and connective tissues. The shear moduli obtained for the 2w/v% (10.2 kPa) and 2.5w/v% hydrogels (11.34 kPa) conform to the shear moduli of liver, fat, relaxed muscle, and breast gland tissue. Thixotropic studies reveal good structural recovery behaviour in the hydrogels. The swellability of 2w/v% and 2.5w/v% hydrogels (50-70%) suggests their suitability for bone tissue engineering, with moderate porosity required for bone growth (60-75%). Moreover, the yield stress values of 0.5 - 1.5 w/v % hydrogels satisfy the requirements for soft tissue engineering, while those of 2 and 2.5 w/v% match the requirements for bone tissue engineering. Our findings suggest that chitosan hydrogels of varying concentrations (0.5–2.5% w/v) hold promise for a range of biomedical applications, including tissue engineering for brain, nerve, soft, and bone tissues, and wound dressing. This research addresses the pressing need for stable chitosan hydrogels with tailored mechanical properties, potentially offering solutions to challenges in biomedical materials design.

Rotational 3D printing spruce-inspired helical structural material with tunable mechanical properties

Spruce branches have a continuous gradient in the microfibril angle of helically entwined cellulose fibrils in their internal cell walls, which confers the modulation of the site-specific mechanical properties. This paper draws inspiration from the microstructure within spruce branches and successfully fabricates a biomimetic structural material assembled from stiff and soft resins in a double-helix distribution using rotational co-extrusion 3D printing. The tunability of the mechanical properties of the helical structural material can be achieved by regulating the helical degree and ratio of two resins in the extrusion filament in real-time. Additionally, a strategy for controlling failure is proposed through dynamic programming of the local structure within the printed sample. Furthermore, compared with the homogeneous beam, the prepared spruce-like beam can effectively mitigate stress concentration during the loading process, achieving greater deformation capacity. This helical structural material is expected to meet customized mechanical performance requirements and enrich the bionic structural material system.

Facile fabrication and characteristics of enzymatically crosslinked injectable tyramine-substituted egg white hydrogels

Protein-based materials have always been preferred because they can be engineered into a wide range of biomaterials with multiple excellent properties including low immunogenicity, tunable mechanical properties and promotion of cell adhesion and proliferation. Spectacularly, chicken egg white (EW) has drawn particular attention in the biomaterial field due to its high bioactivity, low production costs and easy handling. In this study, EW was firstly modified with tyramine (TA) and then enzymatically crosslinked to form injectable EW-TA hydrogels through horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). The prepared EW-TA hydrogels demonstrated adjustable mechanical properties and degradation behavior. When co-cultured with NIH-3 T3 cells, the EW-TA hydrogels exhibited excellent biocompatibility. Based on the above results, the fabricated EW hydrogel, which has excellent performance, possesses promosing prospect for biomedical applications.

Efficient Preparation of Isotactic Polypropylene-Based Block Copolymers with Tunable Mechanical Properties: From Thermoplastics to Elastomers

Efficient Preparation of Isotactic Polypropylene-Based Block Copolymers with Tunable Mechanical Properties: From Thermoplastics to Elastomers

Production and characterization of a blood analogue based on alginate microparticles

This work addresses the need for a universal blood substitute by focusing on developing alginate-based microparticles engineered to replicate the mechanical properties of red blood cells (RBCs). Alginate, known for its biocompatibility and tunable mechanical properties, is used to create microparticles that closely resemble RBCs in size and shape. These alginate microparticles are produced through premix membrane emulsification (PME), ensuring a uniform size distribution. The viscosity ratio and the size of the filter pores influence the final size of the microparticles. Filters with pores of 20 µm were used to produce 5 wt% alginate microparticles with a diameter of 7.81 µm ± 0.77, and filters with pores of 30 µm were used to produce 0.5 wt% alginate microparticles with a diameter of 8.69 µm ± 3.30. The Deformability Index (DI) of the alginate microparticles follows the correlation that microparticles with higher elastic modulus exhibit lower DI values. The DI found for 0.5 wt% alginate microparticles solution is higher than the DI found for 5 wt% alginate microparticles. The DI of RBCs is higher than the ones found for the alginate microparticles, however the value is in the range of the experimental error. Rheological studies reveal that suspensions of 25–30 wt% alginate microparticles exhibit a shear-thinning behavior similar to human blood. The DI of the alginate microparticles shows little influence on the rheology of the suspensions. Furthermore, the Cell-Free Layer (CFL) of alginate microparticles is close to that of RBCs, reinforcing the potential of alginate as a suitable material for blood substitute development. The alginate microparticles produced in this work show a great potential to contribute to creating a blood-mimicking fluid for applications in medical treatments and research.

Emulsion template – based porous silicones with piezocapacitive response

Porous silicones were prepared by thiol-ene photoaddition or hydrolysis - condensation cross-linking in emulsion template in the presence of a pyridyl-modified siloxane oligomer as surfactant, at room temperature. Hexamethyldisiloxane (HMDS) was tested as alternative, more eco-friendly solvent in competition with toluene. Variations in the composition of silicone precursors, thus in cross-linking density and method, allowed tuning of mechanical properties. The piezocapacitive response of the porous silicones was investigated, focusing on the dielectric material as potential sensing element in capacitive pressure sensors. The capacitance variation showed linearity on wide pressure domains, roughly between 2 and 300 kPa, depending on the mechanical properties of the porous monoliths. A direct correlation between sensitivity and Young's modulus was found, which allows tuning of the sensing behavior. The softest material, prepared with a binary mixture of silicone precursors, exhibited a sensitivity of 8.7 × 10−3 kPa−1 on 9–29 kPa pressure range. A porous silicone – MWCNT composite showed spectacular increase in sensitivity, with maximum value of 0.747 kPa−1 and 0–7.5 kPa sensing range when compressed at 30%. Gauge factors of 29.2 in the compressive strain range of 13–30% and as high as 88.8 in the compressive strain range of 25–50% were found.

Schiff base crosslinked hyaluronic acid hydrogels with tunable and cell instructive time-dependent mechanical properties

The dynamic interplay between cells and their native extracellular matrix (ECM) influences cellular behavior, imposing a challenge in biomaterial design. Dynamic covalent hydrogels are viscoelastic and show self-healing ability, making them a potential scaffold for recapitulating native ECM properties. We aimed to implement kinetically and thermodynamically distinct crosslinkers to prepare self-healing dynamic hydrogels to explore the arising properties and their effects on cellular behavior. To do so, aldehyde-substituted hyaluronic acid (HA) was synthesized to generate imine, hydrazone, and oxime crosslinked dynamic covalent hydrogels. Differences in equilibrium constants of these bonds yielded distinct properties including stiffness, stress relaxation, and self-healing ability. The effects of degree of substitution (DS), polymer concentration, crosslinker to aldehyde ratio, and crosslinker functionality on hydrogel properties were evaluated. The self-healing ability of hydrogels was investigated on samples of the same and different crosslinkers and DS to obtain hydrogels with gradient properties. Subsequently, human dermal fibroblasts were cultured in 2D and 3D to assess the cellular response considering the dynamic properties of the hydrogels. Moreover, assessing cell spreading and morphology on hydrogels having similar modulus but different stress relaxation rates showed the effects of matrix viscoelasticity with higher cell spreading in slower relaxing hydrogels.

Non-swelling polyelectrolyte complex hydrogels with tissue-matchable mechanical properties for versatile wet wound closure

The stable adhesion of hydrogel-based bioadhesives with tissue-matchable mechanical properties in biological environments remains a significant challenge. In this work, we propose a polyethyleneimine-polyacrylic acid (PEI-PAA, PEA) double-network polyelectrolyte hydrogel with swelling resistant capacity and tunable mechanical properties via one-step UV-initiated polymerization. Driven by electrostatic interactions and polymer-chain entanglement, this PEA hydrogel displays a distinctive microphase separation behavior, which facilitates a wide tunability in mechanical properties. Specifically, the modulus varies from 0.4 MPa to 106 MPa, and the toughness ranges from 1479 kJ/m3 to 7641 kJ/m3, respectively. Besides, the microphase separation endows PEA hydrogel with notable anti-swelling properties in saline, TBS buffer, and blood, leading to consistent adhesion to diverse moist tissues. We further demonstrate that our PEA hydrogels provide matchable mechanical properties and long-lasting adhesion to rat skin and arteries, which promote skin injury healing and effectively halt artery rupture bleeding in vivo. This work presents a straightforward method to generate non-swelling hydrogels and offers novel insight into the development of bioadhesives to meet diverse mechanical requirements.

Development of Biphasic Injectable Hydrogels for Meniscus Scaffold from Photocrosslinked Glycidyl Methacrylate-Modified Poly(Vinyl Alcohol)/Glycidyl Methacrylate-Modified Silk Fibroin.

The development of a hydrogel material with a modified chemical structure of poly(vinyl alcohol) (PVA) and silk fibroin (SF) using glycidyl methacrylate (GMA) (denoted as PVA-g-GMA and SF-g-GMA) is an innovative approach in the field of biomaterials and meniscus tissue engineering in this study. The PVA-g-GMA/SF-g-GMA hydrogel was fabricated using different ratios of PVA-g-GMA to SF-g-GMA: 100/0, 75/25, 50/50, 25/75, and 0/100 (w/w of dry substances), using lithium phenyl (2,4,6-trimethylbenzoyl)phosphinate (LAP) as a free radical photoinitiator, for 10 min at a low ultraviolet (UV) intensity (365 nm, 6 mW/cm2). The mechanical properties, morphology, pore size, and biodegradability of the PVA-g-GMA/SF-g-GMA hydrogel were investigated. Finally, for clinical application, human chondrocyte cell lines (HCPCs) were mixed into PVA-g-GMA/SF-g-GMA solutions and fabricated into hydrogel to study the viability of live and dead cells and gene expression. The results indicate that as the SF-g-GMA content increased, the compressive modulus of the PVA-g-GMA/SF-g-GMA hydrogel dropped from approximately 173 to 11 kPa. The degradation rates of PVA-g-GMA/SF-g-GMA 100/0, 75/25, and 50/50 reached up to 15.61%, 17.23%, and 18.93% in 4 months, respectively. In all PVA-g-GMA/SF-g-GMA conditions on day 7, chondrocyte cell vitality exceeded 80%. The PVA-g-GMA/SF-g-GMA 75:25 and 50:50 hydrogels hold promise as a biomimetic biphasic injectable hydrogel for encapsulated augmentation, offering advantages in terms of rapid photocurability, tunable mechanical properties, favorable biological responses, and controlled degradation.

Self-Healing Transparent Poly(dimethyl)siloxane with Tunable Mechanical Properties: Toward Enhanced Aging Materials for Space Applications.

When exposed to the geostationary orbit, polymeric materials tend to degrade on their surface due to the appearance of cracks. Implementing the self-healing concept in polymers going to space is a new approach to enhancing the lifespan of materials that cannot be replaced once launched. In this study, the elaboration of autonomous self-healing transparent poly(dimethylsiloxane) (PDMS) materials resistant to proton particles is presented. The PDMS materials are functionalized with various compositions of urea and imine moieties, forming dynamic covalent and/or supramolecular networks. The hydrogen bonds induced by the urea ensure the formation of a supramolecular network, while the dynamic covalent imine bonds are capable of undergoing exchange reactions. Materials with a broad range of mechanical properties were obtained depending on the composition and structure of the PDMS networks. As coating applications in a spatial environment were mainly targeted, the surface properties of the polymer are essential. Thus, percentages of scratch recovery were determined by AFM. From these data, self-healing kinetics were extracted and rationalized based on the polymer structures. The obtained data were in good agreement with the relaxation times determined by rheology in stress relaxation experiments. Moreover, the accelerated aging of materials under proton irradiation, simulating a major part of the geostationary environment, revealed a strong limitation or disappearance of cracks while keeping the transparency of the PDMS. These promising results open routes to prepare new flexible autonomous polymeric materials for space applications.

Facile formation of capillary whey protein oleogels with tunable mechanical and aesthetic properties and their applications as margarine alternatives

Edible protein-based oleogels have garnered extensive attention in food formulation, driven by the desire for enhanced nutritional profiles and improved texture perception. This is facilitated by the nutritional value of the starting ingredient proteins, coupled with high consumer acceptance. However, there exists limited knowledge regarding the connection between the microstructural properties of gels and their macroscopic rheological properties, especially concerning their potential as fat replacers in food products. The present study reveals a simple means of modulating the microstructural properties and macroscopic mechanical features of capillary whey protein oleogels, as well as their aesthetic properties. This is achieved by using whey protein variants with diverse morphologies, such as fibers, particles, and fractal clusters, or by varying the water fraction (s) and the protein concentration (φ) in the formula. Rheological scaling properties and confocal laser scanning microscopy (CLSM) were employed to investigate the structural contribution of protein particles within the gel network. Furthermore, the study explores the practical applications of the derived oleogels, particularly in terms of spreadability or shortening as a potential alternative to margarine, within real food matrices. The spreadability of capillary oleogels with a protein concentration (φ) at 0.16 and 0.18 was comparable to that of commercial margarine. Meanwhile, the capillary oleogel-cake exhibited similarity to the margarine cake in textural parameters and sensory acceptability. This suggests that these capillary whey protein oleogels hold promise for applications in bakery products as margarine alternatives with low levels of saturated/trans-fat content.

Radiation synthesis of covalently/non-covalently coupled all ionic liquid-based Ionogels with rapid self-healing, environmental tolerance for multifunctional ionic skin

As novel artificial ion-conducting materials with skin-like functionalities, Ionic skins (I-Skins) have attracted wide attention in the field of smart wearables. Nonetheless, the crucial hurdle of maintaining their properties in extreme conditions, such as cold, hot or long-term storage, persists. Herein, ionic liquid monomers, ionic liquid solvents, and ionic liquid cross-linkers are employed to facilitate covalently/non-covalently coupled all ionic liquid-based Ionogel for multimodal artificial I-skin through electron beam irradiation under mild conditions at the first time. Profiting from the covalently/non-covalently interactions in the Ionogel, the Ionogel has tunable mechanical properties, excellent environmental adaptability (−60 to 150 °C), long-term stability (90 days), fast response time (0.1 s), rapid self-healing ability (120 s recovery to 90 % of original), and favorable adhesion properties. Moreover, Ionogel sensors possess the remarkable capability to accurately perceive external stimuli, including strain, temperature, and humidity, similar to human skin, which can effectively monitor human movement behavior, as well as fluctuations in ambient temperature and humidity. It is expected that this all ionic liquid-based Ionogel sensor can fill the gap of I-Skin in extreme conditions and realize multifunctional flexible sensing, thus expanding more application scenarios.

Chemistry matters: A side-by-side comparison of two chemically distinct methacryloylated dECM bioresins for vat photopolymerization

Decellularized extracellular matrix (dECM) is an excellent natural source for 3D bioprinting materials due to its inherent cell compatibility. In vat photopolymerization, the use of dECM-based bioresins is just emerging, and extensive research is needed to fully exploit their potential. In this study, two distinct methacryloyl-functionalized, photocrosslinkable dECM-based bioresins were prepared from digested porcine liver dECM through functionalization with glycidyl methacrylate (GMA) or conventional methacrylic anhydride (MA) under mild conditions for systematic comparison. Although the chemical modifications did not significantly affect the structural integrity of the dECM proteins, mammalian cells encapsulated in the respective hydrogels performed differently in long-term culture. In either case, photocrosslinking during 3D (bio)printing resulted in transparent, highly swollen, and soft hydrogels with good shape fidelity, excellent biomimetic properties and tunable mechanical properties (~ 0.2–2.5 kPa). Interestingly, at a similar degree of functionalization (DOF ~ 81.5–83.5 %), the dECM-GMA resin showed faster photocrosslinking kinetics in photorheology resulting in lower final stiffness and faster enzymatic biodegradation compared to the dECM-MA gels, yet comparable network homogeneity as assessed via Brillouin imaging. While human hepatic HepaRG cells exhibited comparable cell viability directly after 3D bioprinting within both materials, cell proliferation and spreading were clearly enhanced in the softer dECM-GMA hydrogels at a comparable degree of crosslinking. These differences were attributed to the additional hydrophilicity introduced to dECM via methacryloylation through GMA compared to MA. Due to its excellent printability and cytocompatibility, the functional porcine liver dECM-GMA biomaterial enables the advanced biofabrication of soft 3D tissue analogs using vat photopolymerization-based bioprinting.

In situ magnesium-doped calcium phosphate microtube-reinforced magnesium-doped hydroxyapatite composites with tunable mechanical properties and biodegradability

Hydroxyapatite, commonly employed in bone defect repair, demonstrates limitations in load-bearing applications due to its poor mechanical property and biodegradability. This research introduces an innovative bone substitute material, namely, in situ magnesium-doped calcium phosphate microtube (Mg-CaPMT)-reinforced magnesium-doped hydroxyapatite composites (Mg-CaPMT/Mg-HA) inspired by microtube material with outstanding mechanical property and capillary tube in a plant. The in situ Mg-CaPMT, with a ~7 μm diameter and 400-500nm wall thickness, was formed by pore-forming carbon fiber (CF) and the coating on it. These microtubes are uniformly distributed within Mg-HA matrix. The composites can meet load-bearing bone requirements, demonstrating compressive strength of 167.0±20.7MPa and fracture toughness of 2.04±0.13MPa·m1/2. Notably, it exhibits exceptional permeability and biodegradability, attributed to capillary action by the Mg-CaPMT structure. The adjustable mechanical and biological properties of Mg-CaPMT/Mg-HA, based on microtube dimensions, content, and composition, offer a versatile solution for repairing various bone defects in load-bearing areas.

Tongue-inspired gelatin/poly(acrylate-co-acrylamide)-Fe3+ organic hydrogel with tunable mechanical, electrical, and sensory properties

Conductive hydrogels have emerged as one of the most promising candidates for the next generation of wearable soft electronics. However, they face limitations during practical implementation owing to their unbalanced overall properties. In this study, we present a dynamic cross-linked gelatin/poly(acrylic acid-co-acrylamide) (GxPyFez) hydrogel with tunable mechanical strength, self-healing, freezing resistance, electrical conductivity, and high sensitivity, which was prepared by incorporating Fe3+ ions. The hydrogel was prepared based on the tongue, in which gelatin/poly(acrylic acid-co-acrylamide) and Fe3+ ions mimic the connective tissue and receptor cells of the human tongue. The synergistic effect of reversible crosslinking, along with the modulation of rigid and flexible components enabled tunable flexible structures that exhibit excellent mechanical properties such as elongation at break (569 %) and toughness (8.82 MJ m−3). Notably, the G2P3Fe0.1 hydrogel exhibited remarkable self-healing ability, even at room temperature, while maintaining a good freezing resistance. Furthermore, the G2P3Fe0.1 demonstrated fast response characteristics along with a high sensitivity (GF = 2.75). Consequently, it could be assembled into sensors capable of effectively detecting various movements of the human body; it serves as an electronic skin that responds to diverse external stimuli and monitors underwater motion signals. This study provides new insights into the design of conductive hydrogels with tunable overall properties that can be modified to suit specific application scenarios.

Physicochemical Effects of PEG Content in Alginate-based Double Network Hydrogels as Hybrid Scaffolds

This study aims to prepare a double-network hydrogel as hybrid networks bearing both natural and synthetic polymers to obtain scaffolds with increased swelling capacity and tunable mechanical and morphological properties. Physically cross-linked alginate hydrogel was reinforced with various ratios of Poly(ethylene glycol) (PEG) polymers which were chemically gellated via UV light exposure with a water soluble initiator. Physicochemical properties of the resulting hydrogels were systematically investigated via Fourier-transform infrared (FT-IR) spectroscopy for chemical composition and Scanning Electron Microscopy (SEM) for their morphological features like porosity. Furthermore, the effect of PEG amount in the final hydrogel (10, 20 and 40%) on swelling capacity was evaluated as well as the rheological properties. Prepared double-network hydrogels were demonstrated to be composed of both natural alginate polymer and synthetic PEG chains in FT-IR spectrum. Although 10%PEG containing hydrogel was not significantly different in terms of swelling capacity from the alginate hydrogel alone, increasing PEG amount seems to have improved the swelling ability. Comparative reological studies presented that introducing covalently cross-linked PEG network into alginate one increased crosspoint of storage and loss moduli almost 12 times more providing a stiffer scaffold. Increasing PEG content decreased the pore size on SEM images, indicating more crosslinking points in hydrogel structure.