Entropy-Driven Self-Healing of Metal Oxides Assisted by Polymer-Inorganic Hybrid Materials

Centrifugally spun and ZnO-infiltrated PVA fibers with antibacterial activity for treatment of Acne vulgaris

The increasing spread of Acne vulgaris makes antibacterial agents increasingly important, especially for patients, who cannot use systemic antibacterial therapeutics. Recently, polymeric nano- and submicron-fibers with have attracted increasing interest in cosmetic and dermatological applications. Combined with the Vapor Phase Infiltration (VPI) process, the fibers serve as containers for the growth of metal oxides for a later use. We address the use of antibacterial agents by developing active antibacterial polymer-inorganic composites without any ZnO nanoparticles on the surface that are loose and would potentially detach. We fabricate poly(vinyl alcohol) fibers by centrifugal spinning and then infiltrate them with ZnO by applying 1 to 128 VPI cycles in the fluidized bed Atomic Layer Deposition reactor. The fibers´ morphology and structure is investigated by Scanning and Transmission Electron Microscopies and X-ray diffractometry. The presence of Zn and its uniform distribution on the surface is confirmed by scanning TEM Energy Dispersive X-ray spectroscopy. The prepared materials are subsequently tested for their antibacterial activity against Cutibacterium acnes and Staphylococcus epidermidis, main acne-causing bacteria. The results of antibacterial activity show that PVA fibers infiltrated with ZnO nanocrystals by >32 VPI cycles effectively inhibit growth of the acne-causing bacteria. Moreover, the homogeneous distribution of ZnO nanocrystals infiltrated within the fibers ensures the immediate release of Zn2+ while preserving the fibrous structure, in contrast to fibers with nanoparticles prepared directly from the spinning solution. Therefore, the study suggests that the PVA fibers infiltrated with ZnO exhibit promising potential as a material for anti-acne face masks.

Highly Stable Amorphous Metal Oxide Thin-Film Transistors for In Situ X-ray Tolerant Electronics

Thin-film transistors based on metal oxide semiconductors are essential for many unconventional electronic devices, such as flat panel displays, image sensors, medical detectors, and aerospace applications. However, the lack of a systemic understanding of the effects of X-ray irradiation on the device often limits their use in harsh space and heavy radiation environments. Here, we investigate the effects of X-ray irradiation on metal oxide thin-film transistors based on amorphous indium gallium zinc oxide (a-IGZO) and amorphous zinc tin oxide (a-ZTO) semiconductors. Under increasing doses of X-ray irradiation (1-7 kGy), a-IGZO TFTs exhibit a substantial negative shift in threshold voltage (ΔVth ≤ 16 V), indicating severe degradation of the switching behavior. The underlying mechanisms responsible for this radiation-induced damage in a-IGZO TFTs are attributed to the generation, ionization, and compensation of oxygen vacancies, which disrupted the device stability. In contrast, a-ZTO TFTs display markedly superior resilience (ΔVth ≤ 7.26 V), maintaining a stable electrical performance under similar X-ray irradiation conditions. In addition, both ex situ and in situ experimental results exhibit consistent trends in terms of the degradation and stability of the devices under X-ray irradiation, further validating the reliability of the a-ZTO TFTs in real-time radiation hardness operational environments. The proposed mechanisms elucidating the difference in radiation tolerance between a-IGZO and a-ZTO TFTs provide understanding of the stability and robustness of metal-oxide-based TFTs under extreme irradiation environments.

Data-Driven Materials Research and Development for Functional Coatings

Functional coatings, including organic and inorganic coatings, play a vital role in various industries by providing a protective layer and introducing unique functionalities. However, its design often involves time-consuming experimentation with multiple materials and processing parameters. To overcome these limitations, data-driven approaches are gaining traction in materials science. In this paper, recent advances in data-driven materials research and development (R&D) for functional coatings, highlighting the importance, data sources, working processes, and applications of this paradigm are summarized. It is begun by discussing the challenges of traditional methods, then introduce typical data-driven processes. It is demonstrated how data-driven approaches enable the identification of correlations between input parameters and coating performance, thus allowing for efficient prediction and design. Furthermore, carefully selected case studies are presented across diverse industries that exemplify the effectiveness of data-driven methods in accelerating the discovery of new functional coatings with tailored properties. Finally, the emerging research directions, involving integrating advanced techniques and data from different sources, are addressed. Overall, this review provides an overview of data-driven materials R&D for functional coatings, shedding light on its potential and future developments.

Controlled Construction of Surface Hybrid Structures of Zirconium Powder Assisted by Microdroplets and Photopolymerization Collaboration

The controlled construction of hybrid material structures can effectively regulate the physical, chemical, and functional properties of materials. This work explores the feasibility of coupling microdroplets technology and photopolymerization methods to achieve controllable construction of hybrid structures on the surface of ultrafine zirconium (Zr) powder, and investigates the effects of different hybrid structures on the surface mechanical properties, thermal oxidation performance, and electrostatic safety of Zr powder. The photopolymerization reaction process of PMMA on the surface of Zr powder was analyzed, revealing the principle of accelerated photopolymerization reactions within microdroplets, which was experimentally validated. Furthermore, by altering the polymerization reaction conditions and with the assistance of hydrofluoric acid (HF), a mechanism for controlling the hybrid structures on the surface of Zr powder was proposed. The results demonstrated that the collaborative effect of microdroplets and photopolymerization methods efficiently controlled the content and structural characteristics of the PMMA coating on the surface of Zr powder. The further introduction of HF was found to adjust the morphology of the surface hybrid structures and significantly improve the thermal oxidation performance and electrostatic safety of the Zr powder. These findings provided insights into the surface property regulation of active energetic materials and paved the way for the controlled preparation of inorganic-organic hybrid materials.

Enthalpy-Driven Self-Healing in Thin Metallic Films on Flexible Substrates

Self-healing microelectronics are needed for costly applications with limited or without access. They are needed in fields such as space exploration to increase lifetime and decrease both costs and the environmental impact. While advanced self-healing mechanisms for polymers are numerous, practical ways for self-healing in metal films have yet to be found. A concept for an autonomous intrinsic self-healing metallic film system is developed, allowing the healing of cracks in metallic films on flexible substrates. The concept relies on stabilizing metastable thin films with high mixing enthalpy via segregation barriers. This allows the films to possess autonomous intrinsic self-healing capabilities triggered by cracking at temperatures not detrimental to flexible microelectronics. The effect will be shown on metastable Mo1-xAgx thin films, stabilized via a Mo segregation barrier. Without a segregation barrier, the system is known to exhibit spontaneous Ag particle formation on the surface. This property is controlled and directed to heal cracks and partially restore the electro-mechanical properties of the multilayer system. This mechanism opens up the field of self-healing thin metallic films that could profoundly impact the design of future microelectronics.

Biohybrid microcapsules based on electrosprayed CS-immobilized nanoZrV for self-healing epoxy coating development

In this work, zirconium vanadate nanoparticles were immobilized into chitosan using a facile electrospraying technique to produce CS-ZrV hybrid microcapsules for the development of a self-healing coating. Upon assessment, hybrid microcapsules possessed desirable properties with a mean particle size of 319 μm, maintaining good thermal stability of ∼55% at 700 °C, and were subsequently incorporated into an epoxy resin to develop a biocompatible self-healing coating, CZVEx, for carbon steel corrosion protection. Scratched samples of self-healing and control coatings were analyzed in a corrosion medium of 3.5 wt% aqueous NaCl. SEM images of the scratched coating sample, after days of immersion, revealed healing of defects through the appearance of an epoxide gel-like substance due to the release of polymeric vanadate that reacted with corrosion agents, resulting in polymerization of vanadium hydrates and subsequent self-healing, validated by the proposed mechanism of self-healing. Electrochemical impedance spectroscopy analysis further confirmed CZVEx coating possessed excellent self-healing capabilities through a significant impedance rise from 4.48 × 105 to 5.52 × 105 (ohm cm2) between the 7th and 14th day of immersion. Furthermore, comparative polarization assessment of coating samples with/without defects indicated the accuracy of EIS for self-healing analysis, and showed the sample with no defect was only 2.6 times more corrosion resistant than the scratched coating, as against bare steel substrate that was 22 times less resistant, revealing superior self-healing anticorrosion properties of the coating.

Depletion Strategies for Crystallized Layers of Two-Dimensional Nanosheets to Enhance Lithium-Ion Conductivity in Polymer Nanocomposites

The assembly of long-range aligned structures of two-dimensional nanosheets (2DNSs) in polymer nanocomposites (PNCs) is in urgent need for the design of nanoelectronics and lightweight energy-storage materials of high conductivity for electricity or heat. These 2DNS are thin and exhibit thermal fluctuations, leading to an intricate interplay with polymers in which entropic effects can be exploited to facilitate a range of different assemblies. In molecular dynamics simulations of experimentally studied 2DNSs, we show that the layer-forming crystallization of 2DNSs is programmable by regulating the strengths and ranges of polymer-induced entropic depletion attractions between pairs of 2DNSs, as well as between single 2DNSs and a substrate surface, by exclusively tuning the temperature and size of the 2DNS. Enhancing the temperature supports the 2DNS-substrate depletion rather than crystallization of 2DNSs in the bulk, leading to crystallized layers of 2DNSs on the substrate surfaces. On the other hand, the interaction range of the 2DNS-2DNS depletion attraction extends further than the 2DNS-substrate attraction whenever the 2DNS size is well above the correlation length of the polymers, which results in a nonmonotonic dependence of the crystallization layer on the 2DNS size. It is demonstrated that the depletion-tuned crystallization layers of 2DNSs contribute to a conductive channel in which individual lithium ions (Li ions) migrate efficiently through the PNCs. This work provides statistical and dynamical insights into the balance between the 2DNS-2DNS and 2DNS-substrate depletion interactions in polymer-2DNS composites and highlights the possibilities to exploit depletion strategies in order to engineer crystallization processes of 2DNSs and thus to control electrical conductivity.

Fabrication of Highly Thermally Resistant and Self-Healing Polysiloxane Elastomers by Constructing Covalent and Reversible Networks

The fabrication of self-healing elastomers with high thermal stability for use in extreme thermal conditions such as aerospace remains a major challenge. A strategy for preparing self-healing elastomers with stable covalent bonds and dynamic metal-ligand coordination interactions as crosslinking sites in polydimethylsiloxane (PDMS) is proposed. The added Fe (III) not only serves as the dynamic crosslinking point at room temperature which is crucial for self-healing performance, but also plays a role as free radical scavenging agent at high temperatures. The results show that the PDMS elastomers possessed an initial thermal degradation temperature over 380 °C and a room temperature self-healing efficiency as high as 65.7%. Moreover, the char residue at 800 °C of PDMS elastomer reaches 7.19% in nitrogen atmosphere, and up to 14.02% in air atmosphere by doping a small amount (i.e., 0.3 wt%) of Fe (III), which is remarkable for the self-healing elastomers that contain weak and dynamic bonds with relatively poor thermal stability. This study provides an insight into designing self-healing PDMS-based materials that can be targeted for use as high-temperature thermal protection coatings.

Modular Engineering of a DNA Tetrahedron-Based Nanomachine for Ultrasensitive Detection of Intracellular Bioactive Small Molecules

Bioactive small molecules serve as invaluable biomarkers for recognizing modulated organismal metabolism in correlation with numerous diseases. Therefore, sensitive and specific molecular biosensing and imaging in vitro and in vivo are particularly critical for the diagnosis and treatment of a large group of diseases. Herein, a modular DNA tetrahedron-based nanomachine was engineered for the ultrasensitive detection of intracellular small molecules. The nanomachine was composed of three self-assembled modules: an aptamer for target recognition, an entropy-driven unit for signal reporting, and a tetrahedral oligonucleotide for the transportation of the cargo (e.g., the nanomachine and fluorescent markers). Adenosine triphosphate (ATP) was used as the molecular model. Once the target ATP bonded with the aptamer module, an initiator was released from the aptamer module to activate the entropy-driven module, ultimately activating the ATP-responsive signal output and subsequent signal amplification. The performance of the nanomachine was validated by delivering it to living cells with the aid of the tetrahedral module to demonstrate the possibility of executing intracellular ATP imaging. This innovative nanomachine displays a linear response to ATP in the 1 pM to 10 nM concentration range and demonstrates high sensitivity with a low detection limit of 0.40 pM. Remarkably, our nanomachine successfully executes endogenous ATP imaging and is able to distinguish tumor cells from normal ones based on the ATP level. Overall, the proposed strategy opens up a promising avenue for bioactive small molecule-based detection/diagnostic assays.

High-Entropy Enhanced Microwave Attenuation in Titanate Perovskites

High-entropy oxides (HEOs), which incorporate multiple-principal cations into single-phase crystals and interact with diverse metal ions, extend the border for available compositions and unprecedented properties. Herein, a high-entropy-stabilized (Ca_0.2 Sr_0.2 Ba_0.2 La_0.2 Pb_0.2 )TiO₃  perovskite is reported, and the effective absorption bandwidth (90% absorption) improves almost two times than that of BaTiO₃ . The results demonstrate that the regulation of entropy configuration can yield significant grain boundaries, oxygen defects, and an ultradense distorted lattice. These characteristics give rise to strong interfacial and defect-induced polarizations, thus synergistically contributing to the dielectric attenuation performance. Moreover, the large strains derived from the strong lattice distortions in the high-entropy perovskite offer varied transport for electron carriers. The high-entropy-enhanced positive/negative charges accumulation around grain boundaries and strain-concentrated location, quantitatively validated by electron holography, results in unusual dielectric polarization loss. This study opens up an effective avenue for designing strong microwave absorption materials to satisfy the increasingly demanding requirements of advanced and integrated electronics. This work also offers a paradigm for improving other interesting properties for HEOs through entropy engineering.