Today's consumer electronics are made from nonrenewable and toxic components. They are also rigid, bulky, and manufactured in an energy-inefficient manner via CO 2 -generating routes. Though petroleum-based polymers such as polyethylene terephthalate and polyethylene naphthalate can address the rigidity issue, they have a large carbon footprint and generate harmful waste. Scalable routes for manufacturing electronics that are both flexible and ecofriendly (Fleco) could address the challenges in the field. Ideally, such substrates must incorporate into electronics without compromising device performance. In this work, we demonstrate that a new type of wood-based [nanocellulose (NC)] material made via nanosilicate (NS) reinforcement can yield flexible electronics that can bend and roll without loss of electrical function. Specifically, the NSs interact electrostatically with NC to reinforce thermal and mechanical properties. For instance, films containing 34 wt % of NS displayed an increased young's modulus (1.5 times), thermal stability (290 → 310 °C), and a low coefficient of thermal expansion (40 ppm/K). These films can also easily be separated and renewed into new devices through simple and low-energy processes. Moreover, we used very cheap and environmentally friendly NC from American Value Added Pulping (AVAP) technology, American Process, and therefore, the manufacturing cost of our NS-reinforced NC paper is much cheaper ($0.016 per dm −2 ) than that of conventional NC-based substrates. Looking forward, the methodology highlighted herein is highly attractive as it can unlock the secrets of Fleco electronics and transform otherwise bulky, rigid, and "difficult-to-process" rigid circuits into more aesthetic and flexible ones while simultaneously bringing relief to an already-overburdened ecosystem.
Periodontitis is a ubiquitous chronic inflammatory, bacteria-triggered oral disease affecting the adult population. If left untreated, periodontitis can lead to severe tissue destruction, eventually resulting in tooth loss. Despite previous efforts in clinically managing the disease, therapeutic strategies are still lacking. Herein, melt electrowriting (MEW) is utilized to develop a compositionally and structurally tailored graded scaffold for regeneration of the periodontal ligament-to-bone interface. The composite scaffolds, consisting of fibers of polycaprolactone (PCL) and fibers of PCL-containing magnesium phosphate (MgP) were fabricated using MEW. To maximize the bond between bone (MgP) and ligament (PCL) regions, we evaluated two different fiber architectures in the interface area. These were a crosshatch pattern at a 0/90°angle and a random pattern. MgP fibrous scaffolds were able to promote in vitro bone formation even in culture media devoid of osteogenic supplements. Mechanical properties after MgP incorporation resulted in an increase of the elastic modulus and yield stress of the scaffolds, and fiber orientation in the interfacial zone affected the interfacial toughness. Composite graded MEW scaffolds enhanced bone fill when they were implanted in an in vivo periodontal fenestration defect model in rats. The presence of an interfacial zone allows coordinated regeneration of multitissues, as indicated by higher expression of bone, ligament, and cementoblastic markers compared to empty defects. Collectively, MEW-fabricated scaffolds having compositionally and structurally tailored zones exhibit a good mimicry of the periodontal complex, with excellent regenerative capacity and great potential as a defect-specific treatment strategy.
The combination of bioactive components such as calcium phosphates and fibrous structures are encouraging niche-mimetic keys for restoring bone defects. However, the importance of hemocompatibility of the membranes is widely ignored. Heparin-loaded nanocomposite poly(ε-caprolactone) (PCL)-α-tricalcium phosphate (α-TCP) fibrous membranes are developed to provide bioactive and hemocompatible constructs for bone tissue engineering. Nanocomposite membranes are optimized based on bioactivity, mechanical properties, and cell interaction. Consequently, various concentrations of heparin molecules are loaded within nanocomposite fibrous membranes. In vitro heparin release profiles reveal a sustained release of heparin over the period of 14 days without an initial burst. Moreover, heparin encapsulation enhances mesenchymal stem cell (MSC) attachment and proliferation, depending on the heparin content. It is concluded that the incorporation of heparin within TCP-PCL fibrous membranes provides the most effective cellular interactions through synergistic physical and chemical cues.
A significant clinical challenge in the surgery of peripheral nervous system injured via accidents and natural disease is development of biomimetic grafts which could potentially promote nerve repair and regeneration. Although various engineered neural tissue scaffolds have been proposed to support the neural cell functions, they have not been able to instantaneously mimic the whole characteristics of endogenous microenvironment. In this study, we proposed a three-layered tubular scaffold which could provide appropriate electrical, mechanical and biological properties for peripheral nerve engineering. While the inter layer was graphene (Gr) embedded alginate-polyvinyl alcohol (AP-Gr) fibrous scaffold with well-defined anisotropy, the outer layer was double network scaffold of polycaprolactone fumarate (PCLF) and eggshell membrane (ESM). These two layers were attached together using a polycaprolactone (PCL) fibrous membrane, a middle layer, via a simple melting process. Results showed that while the electrical conductivity of the three-layered scaffold was similar to that of AP-Gr fibrous layer, the strength of the three-layered scaffold was significantly improved compared to AP-Gr and ESM-PCLF (1.5 and 1.1 times, respectively) attributed to well attachment of the two layers. As a proof-of-concept, PC12 cell attachment, proliferation, and alignment were studied on the developed three-layered scaffold. The majority of the cells (55%) aligned (<20°) along the major axis of fibers features. Furthermore, electrical stimulation revealed positive effect on the alignment of PC12 cells and change in the cell morphology. With the ease of fabrication and mechanical robustness, the three-layered scaffold of AP-Gr and ESM-PCLF might be utilized as a versatile system for the engineering of peripheral nerve tissue.
Since humanity is rapidly moving toward the era of the Internet of Things (IoT) and artificial intelligence (AI) to achieve a higher level of comfort and connection, biocompatible, elastic, and self-healable soft electronic devices such as wearable sensors are needed to overcome the traditional silicon-based electronics rigidity. Inspired by catecholic amino acid (l-3,4-dihydroxyphenylalanine, DOPA) from the mussel foot plaque of marine organisms and Mytilus galloprovincialis mussels, which contribute significantly to the robust underwater adhesion of mussels to the surfaces, here, we report the synthesis and fabrication of a library of materials. These materials comprise adhesive, self-healable, and stretchable gum-like materials, hydrogels, and aerogels based on cross-linking of three components of the silk fibroin (SF) biopolymer, MXene (Ti3C2) two-dimensional nanosheets, and tannic acid (TA). The synthesis relies on the coordination of oxidized SF (SF-DOPA), TA, and polydopamine (PDA)-modified MXene nanosheets with ferric ions to fabricate materials with a mussel-inspired adhesiveness, mechanical flexibility (stretchability), electrical conductivity, and self-healing features. To control the type of the obtained materials as well as their resulting properties, namely, elasticity and electrical conductivity, the molar ratio of TA, MXene, and Fe(III) cross-linker as well as pH values was carefully varied to control the gelation kinetics and phase separation. The resulting optimized materials consist of highly flexible gum to 3D porous homogeneous hydrogels and subsequently aerogels after freeze-drying. The stretchability, electrical conductivity (6.5 × 10–4 S cm–1), human motion sensing performance, and significant strain sensitivity of the final gums confirmed their remarkable performance as intriguing next-generation materials for soft-electronic devices, such as electronic skins and piezoresistive wearable pressure sensors.
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