Natural Materials Research Articles

Homing into school to create the ideal classroom: young people want to combine the best of home and school learning environments

ABSTRACT We asked 28 young people (16–18 Years old) from two schools in Lancashire to reflect on their COVID-19 experience and Co-Design the ideal learning environment. In this paper, we present young people’s vision for the ideal classroom that combines the best of the home and school learning environments. Young people would like to have flexible furniture arrangements, with space for group and individual activities, a bespoke learning environment that can be appropriated and adjusted according to individual preferences (e.g. sound, light, temperature, ventilation levels). Furthermore, they aim for comfortable environments with earth colours, natural materials and a direct connection with nature. We argue the importance of taking young people's perspectives presented here to inform future policy, the design of learning spaces and school rebuilding programmes.

Switchable dual-functional optical vortex manipulation via cylindrical phase-change metagratings

Subwavelength artificial engineering microstructures, such as metasurfaces and metagratings, can realize superior optical properties that many natural materials cannot finish. However, most functionalities achieved are mostly single and fixed. The appearance of phase-change materials makes it possible to extend the functions of metagratings. Here, we propose and demonstrate a structural design of cylindrical phase-change metagratings based on VO2, which can achieve switchable dual-functional optical vortex manipulation in the terahertz range. Specifically, by excitation of the temperature-sensitive metallic and insulating states of VO2, the simple two-dimensional cylindrical gear-like structure can achieve dual-functionality for vortex waves with orbital angular momentum, namely efficient retroreflection and near-perfect absorption. In addition, we also discussed the influence of the gear-like structure dimensions on the transmissivity and absorptivity of dual-function vortex wave manipulation. This work provides a simple and effective approach for the tunable and multifunctional control of vortex waves in subwavelength artificial devices, with potential applications in automated device design and terahertz (THz) communications.

Advancing auxetic materials: Emerging development and innovative applications

Abstract The development of auxetic materials, known for their unique negative Poisson’s ratio, is transforming various industries by introducing new mechanical properties and functionalities. These materials offer groundbreaking applications and improved performance in engineering and other areas. Initially found in natural materials, auxetic behaviors have been developed in synthetic materials. Auxetic materials boast improved mechanical properties, including synclastic behavior, variable permeability, indentation resistance, enhanced fracture toughness, superior energy absorption, and fatigue properties. This article provides a thorough review of auxetic materials, including classification and applications. It emphasizes the importance of cellular structure topology in enhancing mechanical performance and explores various auxetic configurations, including re-entrant honeycombs, chiral models, and rotating polygonal units in both two-dimensional and three-dimensional forms. The unique deformation mechanisms of these materials enable innovative applications in energy absorption, medicine, protective gear, textiles, sensors, actuating devices, and more. It also addresses challenges in research, such as practical implementation and durability assessment of auxetic structures, while showcasing their considerable promise for significant advancements in different engineering disciplines.

Nanoprecipitation to produce hydrophobic cellulose nanospheres for water-in-oil Pickering emulsions

In recent years, there has been growing interest in replacing petroleum-based water-in-oil (W/O) emulsifiers with sustainable and less toxic natural materials. Pickering emulsifiers are considered well-suited candidates due to their high interfacial activity and the ability to form emulsions with long-term stability. However, only sporadic examples of natural materials have been considered as inverse Pickering emulsifiers. This study describes the synthesis of a series of hydrophobic cellulose nanospheres by bulk modification with acyl groups of different chain lengths followed by nanoprecipitation, and their application as inverse emulsifiers. Modification with acyl groups of longer chain length (C16, C18) afforded lower degrees of substitution, but resulted in greater thermal stability than groups with shorter acyl chains (C12, C14). Formation of nanospheres with low aspect ratios and narrow size distributions required low initial cellulose concentrations (< 1% w/v), high volumetric ratios of antisolvent to solvent (> 10:1), and slow addition rates (< 20 mL/h). The modified cellulose nanospheres were able to reduce the interfacial tension between water and hexane from 45.8 mN/m to 31.1 mN/m, with an effect that increased with the number of carbons in the added acyl chains. The stearate-modified nanospheres exhibited superhydrophobic behavior, showing a contact angle of 156° ± 4° with water, and demonstrated emulsification performance comparable to the commonly used molecular surfactant sorbitan stearate. Our findings suggest that hydrophobically modified cellulose nanospheres have the potential to be a bio-derived alternative to traditional molecular W/O emulsifiers.Graphical

Sustainable extraction and conservation of soil resources: New insights through Natural Gamma-ray Spectrometry based Proximal Sensing Method

Soil is one the most extracted natural raw materials. The vast expanses of fertile alluvial soils of the Indo Gangetic Plains have long remained as abundant soil resource pool for brick manufacturing and construction sectors. Unmonitored continuous removal of soil is reported to cause depletion of soil reserves, loss of soil fertility and affect crop yield. Excavation and removal of soil from isolated patches of land creates low lying and elevated degraded areas which disrupts normal crop cultivation pattern. Natural gamma-ray spectrometry (NGS) can be used as a non-destructive and rapid geophysical sensing method, for identification and delineation of areas with suitable soils. During this work brick kiln areas were visited to understand soil's availability and extraction pattern. NGS measurements of samples from soil profiles were carried out to find if gamma-ray intensities varied with soil clay content. Soil texture and plasticity of the same samples were obtained following standard testing procedures. Winkler and Plasticity charts were used to assess suitability of the soils. A strong linear relationship between gamma-ray potassium (K) intensity and clay contents of soil profile samples (R2 = 0.88) was observed. NGS based devices can be used to scan soil samples rapidly and log shallow depth boreholes in grid sampling design. The gathered spectral gamma-ray data can be then used to predict and generate high resolution 3D models of soil properties, based on which resource areas of suitable soils can be delineated for long term soil extraction without affecting cultivated areas. This will help in delineating areas restricted for soil extraction, which will not only make soil mining sustainable but also address soil conservation by setting aside large cultivated fertile soil areas untouched. Adopting NGS methods will prevent unsystematic removal of fertile soil and creation of degraded lands. This will ultimately result in efficient soil resource management.

A computational design integrated digital fabrication framework for mass customization in industry 5.0 manufacturing with non-standard natural materials

Industry 5.0 manufacturing requires a highlighted emphasis on resilience, sustainability, and human-centricity. Circular bioeconomy could play an important role in practicing Industry 5.0 through using natural materials and minimizing the waste. Mass production with natural materials focuses on utilizing materials of standard geometry, resulting in under-utilized non-standard materials. To facilitate the transition to Industry 5.0 and practicing circular bioeconomy, this study proposes a framework to utilize non-standard natural materials for mass customization using an integrated computational design – digital fabrication methodology. The proposed framework offers opportunities for waste reduction, sustainability in production, and human-centric design for customized manufacturing. Two case study projects were discussed to further explain the framework, followed by the challenges of the proposed integrated approach and the direction for future studies.

Synthesis of cellulose nano fiber from palmyrah fruit fiber and its applicability as a reinforcement agent on starch based biodegradable film

The global trend in packaging is shifting towards environmentally friendly, natural materials that decompose easily. Among the bio-based packaging materials, starch is a renewable, biodegradable, bio-compatible, and easily accessible source. However, starch-based biodegradable films depict weak mechanical properties compared with synthetic polymers. This problem can be solved by incorporating reinforcement fillers into the starch matrix. Palmyrah fruit (Borassus flabellifer L.) waste can be a good source to obtain fillers due to its high cellulose content. The aim of the study was to investigate the reinforcement of starch-based biodegradable films with the incorporation of pure cellulose nanofiber (CNF) obtained from palmyrah fruit fiber (PFF). Chemical treatments such as alkaline treatment (4% NaOH), bleaching [1% Ca(OCl)2], and acid hydrolysis (10 moldm-3 H2SO4) were done successively to obtain pure CNF from PFF. CNF was characterized using FTIR and particle size distribution (PSD) was analyzed by granulometry. The yield of CNF from PFF was 37.890±0.008 %. The results of FTIR depicted CNF was synthesized successfully. Five different biodegradable films were prepared by varying the amount of palmyrah tuber starch (4.5-2.5 w/w %) and CNF (0.0-2.0 w/w %) while the amount of glycerin (1.5 w/w %) and gelatin (1 w/w %) were kept constant. PSD results revealed that nano-sized CNF (10-100 nm) was synthesized successfully. The optimized film was selected based on the tensile strength and low water vapor transmission rate. Optimized film formulation, with palmyra tuber starch (3 w/w %) and CNF (1.5 w/w %) showed desirable physical, mechanical and optical properties, including the thickness, moisture content, water vapor transmission rate, water uptake, transparency at 600 nm, water activity, water solubility and tensile strength of 0.192±0.004 mm, 11.07±0.04 %, 3.870±0.005 g/m2.day, 22.34±0.05 %, 3.97±0.01 %, 0.440±0.001, 51.68±0.140 % and 9.55 MPa respectively. All films showed excellent soil biodegradability within two weeks. In conclusion, palmyra fruit CNF can be effectively used to reinforce starch-based biodegradable packaging films.

Hygrothermal performance of timber-framed walls in Turkey – Long-term monitoring

The increasing energy consumption emphasizes the urgency of sustainable building practices. Worldwide, there is a tendency towards local, natural, durable, and recyclable materials like timber. Furthermore, timber's excellent thermal insulation and natural hygroscopic properties enable it to efficiently regulate indoor humidity levels, ensuring stability and comfort. In Turkey, timber construction declined significantly in the 20th century due to the shift towards vertical reinforced concrete, however, recent years have witnessed a renewed interest driven by earthquake concerns and global inclination. Despite this resurgence, timber construction practices are still limited, and the hygrothermal performance of exterior walls in both restoring traditional timber buildings and constructing new ones is often disregarded. Furthermore, there is a lack of scientific research in this area. Understanding the hygrothermal behaviour of these structures is essential for meeting modern energy efficiency standards. This study evaluates the hygrothermal performance of prevalent practices in timber-framed constructions in Turkey. Long-term monitoring in a full-scale test cabin exposed to real climatic effects provides insights. Findings indicate the exterior plywood sheathing on the North-west facing walls being more susceptible to moisture, particularly when the indoor relative humidity is elevated. South-east facing walls are better at drying, but air barrier membrane slows down drying. Timber cladding with ventilated cavity offers improved protection but its high exposure to rainfall in North-west, and solar radiation in South-east, implies potential performance degradation over time. Installing suitable vapour retarders and additional exterior thermal insulation particularly to the North-west facing walls could possibly reduce risks associated with moisture, as well as preventing thermal bridges.

Unified approach for describing rheological behavior of soil and mineral substrates modified with polymers

Studies in the rheology of natural aqueous dispersions (soils and their mineral substrates) as well as the approaches to control rheological parameters of these systems are of the prime importance to progress in the modern agricultural technologies, geoengineering, construction, etc. To advance in these fundamental and applied directions both original processing of the experimental results and search for the promising modifying agents are required. In this paper, rheological behavior of a representative range of virgin and modified aqueous soils, quartz sand and clays was studied. Modification of the above aqueous dispersed systems with polyelectrolytes and their complexes provided variation of the basic viscoelastic parameters corresponding to the linear viscoelastic region (initial storage modulus G0′, initial loss modulus G0", and strain γ0) and to the transition to steady-state flow (storage modulus Gin′ and strain γin) within 1 – 2 orders of magnitude. For samples studied, correlations for these mechanical characteristics were found – with the growth in the values of G0′ and G0′′, the increase in the values of Gin′ and decrease in the values of γ0 and γin were observed. Based on these correlations the master curves for the strain dependences of storage and loss modulus as well as for loss tangent were constructed. The appearance of the master curves reflected the unified regularities of the rheological response of dispersed systems which were attributed to the general features of structural evolution caused by the mechanical loading. Procedure for prediction of the rheological behavior of aqueous soil samples based on the experimental measurement of only two experimental characteristics (initial values of storage and loss modulus G0′ and G0′′ respectively) was proposed. The validity of this approach was tested using independent experimental data. The original approach obtained can be used for express analysis of the rheology of natural aqueous dispersed materials.

The Proximate Composition, Mineral and Pectin Content and Fatty Acid Profile of the Pomace Fraction of 16 Rowanberry Cultivars

The berry pomace could be a potential source for food applications due to its high content of polyphenols, but also dietary fiber, PUFAs and pectin. This is the first study that aims to compare the total dietary fiber (TDF), protein, fat, mineral, pectin and fatty acid content of the following 16 different pomace samples of Sorbus aucuparia L. cultivars (cvs): ‘Likernaja’, ‘Burka’, ‘Alaja Krupnaja’, ‘Granatnaja’, ‘Rubinovaja’, ‘Bussinka’, ‘Vefed’, ‘Angri’, ‘Krasnaja’, ‘Solnechnaja’, ‘Sahharnaja’, ‘Oranzevaja’, ‘Kubovaja’, ‘Moravica’, ‘Rosina’ and ‘Rossica’, in order to find new natural materials for valorization. The contents of pectin and dietary fibers were analyzed using the respective Megazyme enzymatic kits. The TDF content was the highest in the pomace samples of hybrid cvs ‘Granatnaja’ (63.04% dry mass DM), ‘Burka’ (64.52% DM), ‘Rubinovaja’ (65.66% DM) and ‘Likernaja’ (67.17% DM). The pomace of hybrid cv ‘Rubinovaja’ was distinguished from other samples by its high protein content, cv ‘Alaja Krupnaja’ by its high pectin content and cv ‘Oranzevaja’ by its high fat content, which were 7.58% DM, 8.39% DM and 7.47% DM, respectively. The pomace of cv ‘Sahharnaja’ possessed the highest average macro-element content (1.56 g/kg DM). The average fatty acids profile was characterized by a high content of linoleic acid (51.94%), oleic acid (20.55%) and palmitic acid (12.96%). The lowest n6/n3 ratio was found in the hybrid cv ‘Alaja Krupnaja’ (6.70%). The data obtained demonstrate that the pomaces of certain cultivars of rowanberry contain significant amounts of valuable components, which can be used in functional food and cosmetic applications.

Dual-functional natural rubber latex foam composites for solar-driven clean water production and heavy metal decontamination

Solar steam generation (SSG) offers a sustainable approach to fresh water production. Herein, a novel dual-functional natural rubber/carbon black composite foam evaporator is presented for a cost-efficient SSG system that both produces fresh water and eliminates heavy metals present in the water. The composite foam is produced using the Dunlop process, and in its optimized form, it absorbed >96 % of sunlight. The foam evaporator exhibited a thermal conductivity of 0.052 W/m⋅K, a water evaporation rate of 1.40 kg/m2/h, converted 83.38 % of light to heat under 1 sun irradiation, and showed outstanding stability. The technology required to produce this composite foam is already available to make large-scale production feasible, while the natural raw materials are abundant. On the basis of its performance qualities, the rubber foam composite appears to be an excellent candidate for application as a viable solar absorber for SSG to produce fresh, clean water for commercial purposes.

Application of natural earth-based materials as adsorbents for the treatment of chromium (VI)-contaminated tannery wastewater: Box-Behnken and fixed-bed column optimization

This study focuses on the application of earth materials (gravel, clay, zeolite, lime rock, sea shell (Diplodonta)) as adsorbents for the removal of chromium (VI) from tannery wastewater. The removal efficiencies and adsorption capacities of chromium (VI) followed this order: pristine lime rock (63.59 %, qe: 65.5 mg/g)> pristine gravel (48.88 % and 50.4 mg/g)> pristine sea shell (39.03 %, qe: 40.2 mg/g)> pristine zeolite (38.5 %, qe: 39.7 mg/g) > pristine clay (33.55 %, qe: 34.5 mg/g). Lime rock and gravel gave the highest chromium (VI) adsorption capacities and hence, were used in subsequent experiments. Employing Box-Behnken design through response surface methodology, gravel exhibited the highest adsorption capacity (40.7 mg/g) at pH 4, and lime rock (56.1 mg/g) at pH 2, with initial chromium (VI) concentration of 150 mg/L and 11-hour contact time. Scanning electron microscopy and Brunauer–Emmett–Teller analysis showed a lack of pores on both adsorbents suggesting electrostatic attraction as the primary removal mechanism. Best-fitted models were Dubinin-Radushkevich and Temkin isotherms for lime rock and gravel, respectively, while pseudo-first-order kinetics suited both. Thermodynamics calculations showed adsorption is exothermic for lime rock and endothermic for gravel. Application of lime rock in fixed-bed column study showed the highest removal percentage and adsorption capacity (16.64 %, qe: 2.3 mg/g). Applying optimum conditions from column study to synthetic tannery wastewater achieved 63.61 % removal and adsorption capacity (qe: 12.7 mg/g) at 150 mg/L initial chromium (VI) concentration. Regeneration of the adsorbents after 3 cycles maintained strong adsorption capacity. The cost-effective, easily-prepared adsorbent underscores its potential for large-scale wastewater treatment.

Measurement of Naturally-Occurring Radioactive Materials (NORM) using a scintillator-based alpha detector

It is important to differentiate between natural and artificial radioactive materials such as plutonium in nuclear facilities. In this study, a scintillator-based alpha-particle detector was developed using YAP:Ce scintillator and Multi-Anode PhotoMultiplier Tube. The detector was used to measure various naturally occurring radioactive materials (NORM) samples including radon progeny, lead plate, lantern mantle, and radium ceramic ball. The measurement results were compared with Monte Carlo simulation calculations and were found to be in agreement. The energy resolution of the detector is 8.6%FWHM. In the measurement results of radon progeny, peaks of 212Bi (6.1 MeV), 214Po (7.7 MeV), and 212Po (8.8 MeV) can be observed. The lead plate contains 210Po and emits 5.3 MeV alpha particle. The simulation with the same energy was able to reproduce the actual measurement. The results showed the energy and distribution of the alpha particles emitted by the NORM samples. The study successfully demonstrated the capability of the developed alpha-particle detector in identifying NORM.

Geotextile filters: from idealization to real behaviour (Giroud Lecture 2023)

Geotextiles have been used as filters in geotechnical and geoenvironmental works for decades. Despite their broad utilization, these filters still find obstacles to the expansion of their application in larger projects and under complex soil and flow conditions. However, environmental issues are increasingly pressing for a greater use of geotextile filters in substitution to natural granular materials. Even though many important studies in the literature have improved the understanding of soil-fluid-geotextile filter interaction, some issues still require thorough investigation aiming at a better understanding of the behaviour of geotextile filters and the development of better design methodologies. This paper discusses how geotextiles filters are expected to behave in the field and some contradictions between idealized and real behaviour. Concerns regarding the use of geotextile filters under severe and critical conditions and how filter malfunction can be avoided or minimised are also addressed as well as approaches available to predict filter behaviour. A broad investigation on geotextile filter behaviour under severe and critical conditions was carried out and shows that these filters have been very successful, particularly bearing in mind the small number of failures in comparison with the huge number of applications of geotextile filters.

HASIL PEMERIKSAAN TELUR SOIL TRANSMITTED HELMINTH MENGGUNAKAN CAMPURAN PEWARNA ALAMI DARI DAUN MIANA DAN KULIT BUAH NAGA

The simplest method for checking worm eggs is by a native technique using a 2% eosin reagent. Eosin itself has properties that are not easily decomposed, causing hazardous and easily flammable waste. Hence, an alternative staining method is needed, environmentally friendly, using natural materials, such as natural dye substances. This research aims to understand the depiction of results in examining Soil Transmitted Helminth (STH) eggs using mint leaves and dragon fruit skin as alternative reagents. The research method involves examining feces using a direct method (wet preparation) to detect worm eggs in feces directly using a 2% Eosin solution. The comparison results between dragon fruit peel extract concentration using aquadest, tested with SPSS analysis version 20 using the Kruskal-Wallis method with a significance value of 0.09 ≥ 0.05, indicating significantly different research outcomes. Thus, it can be concluded that there is no difference in staining quality compared to the control. The conclusion drawn from this study is that there's no difference in staining worm egg suspensions using mint leaf extract. This is evident as when observing the worm egg suspension using mint leaf extract, the worm eggs were not clearer, unlike with dragon fruit skin and miana.

Three-dimensional reconstruction of subsurface stratigraphy using machine learning with neighborhood aggregation

In engineering geology and geotechnical engineering, it is well recognized that subsurface soils/rocks are natural materials and exhibit variability in stratigraphy due to the complex geological formation processes they have undergone. Knowledge of subsurface soil stratigraphy is of great importance to geotechnical engineers. However, accurate and reliable interpretation of subsurface soil stratigraphy is challenging due to the limited number of site investigation boreholes available at the site and the highly heterogeneous properties of soil stratigraphy (e.g., interbedded or non-ordered layers). This paper proposes an improved data-driven machine learning framework boosted with the neighborhood aggregation technique for modelling three-dimensional (3D) subsurface soil stratigraphy in a more general and robust manner. Neighborhood aggregation, a technique often adopted in graph network learning, is integrated into this framework to regulate and improve the prediction results of classical machine learning models. The proposed framework is then cross-validated using 165 real site investigation boreholes for four selected machine learning models respectively. Cross-validation results suggest that the eXtreme Gradient Boosting (XGBoost) and Random Forest (RF) models are more suitable for the task of soil stratigraphy prediction than Artificial Neural Network (ANN) and Support Vector Machine (SVM). Particularly, the XGBoost and RF are also amenable to neighborhood aggregation and can yield around 5% improvement in terms of average borehole prediction accuracy after introducing neighborhood aggregation. The improved machine learning framework allows for explicit 1D to 3D geological modelling, uncertainty quantification, and convenient visualization. The proposed framework facilitates digital transformation of geological and geotechnical site investigation.

Pemanfaatan Campuran Pati Singkong Dan Pati Ubi Jalar Sebagai Bahan Baku Pembuatan Plastik Biodegradasi

Plastic waste is already polluting the environment both land and oceans, as plastic consumption continues to increase. Biodegradable plastics are an effort to reduce environmental pollution, biodegradation plastics are plastics made from natural materials usually biodegradable plastics made from natural starch. Cassava starch is the most widely used type of starch and is developed for the manufacture of biodegradable plastics, and sweet potatoes are tubers whose starch content is quite numerous even though it has not been widely developed into plastic material. This research aims to produce natural plastics that can replace conventional plastics and reduce environmental pollution due to plastic waste. The study was conducted with variations in the composition of starch mixtures (50:0 gr, 35:15 gr, 25:25 gr, 15:35 gr, 0:50 gr) and variations in drying temperatures (40°C, 50°C, 60°C).In this study carried out organoleptic test, thickness value test, water absorption value test and degradation test. The results of this study showed biodegradable plastics that have the best characteristics are in the variation of the composition of the mixture 50:0 gr at a drying temperature of 60°C, with a thickness value of 0.11 mm and a water absorption value of 36.5%, but the rate of degradation in this variation is very slow

Characterizing Cryptostegia grandiflora stem fiber for reinforcing lightweight polymer composites: A comprehensive study of its physical, chemical, and thermal properties

This study aimed to characterize Cryptostegia grandiflora stem fiber (CGSF) as a potential reinforcement material for lightweight polymer composites. Natural fiber-reinforced materials have gained attention as a promising alternative to synthetic fibers due to their comparable strength and modulus, and lack of harmful chemicals. The physical, chemical, and thermal properties of CGSF were investigated through fiber roughness, chemical measurement, physical measurement, Fourier transform infrared spectroscopy, XRD, water absorption, thermogravimetric analysis, and SEM conformation analysis. The results showed that CGSF has a high cellulose content (80.3 wt.%) and specific strength, making it suitable for use in polymer composites. Its flaky layered outer surface provides a high modulus, and its low microfibril angle observed through electron microscopy results in strong bonding qualities. The fiber also demonstrated improved heat stability up to 254–387 °C through thermogravimetric analysis, meeting the requirements for polymerization. These findings demonstrate the potential of CGSF as a natural reinforcement material for lightweight polymer composites.

Dentin Collagen versus Er:YAG Laser as Surface Biomodifiers for Intact Root Slices Simulating Delayed Replanted Roots.

Objective: To evaluate effects of dentin collagen versus Er:YAG laser application through enhancing human periodontal ligament fibroblast (PDLF) cells to attach to intact root surfaces imitating delayed replanted roots. Background Data: Accidental traumatic injuries with teeth avulsion are managed by replantation. Root resorption, poor conditioning, and non-viable fibroblasts are factors responsible for failure. Methods: Thirty six human healthy single-rooted premolars were collected. Six teeth were used for PDLF, six teeth used for dentin collagen, whereas the remaining 24 teeth (48 root slices) were used for PDLF cell density and morphology. Each root was soaked in 5.25% NaOCl. Three groups (n = 16 slices/each) were planned as follows: I: Control (untreated); II: dentin collagen application; III: Er:YAG laser irradiation (4 mm distance, 40 mJ/pulse, under coolant). Following incubation, cell density and morphology of PDLF were investigated under SEM. Statistical analysis was performed using analysis of variance with Scheffé's test, and p < 0.05 was considered significant. Results: All groups showed increased cultured PDLF following incubation. Regarding cell density, attached PDLFs were significantly lower in untreated controls (36.5 ± 6.36) (p < 0.00001 i.e., <0.05) in negative empty and/or light cellular areas, compared with dentin collagen (65 ± 6) and laser-irradiated (66.75 ± 5.77) groups that did not show significant differences (p = 0.940 i.e., >0.05) and showed intermediate and/or heavy cellular areas. Regarding cell morphology, controls showed round and/or oval appearance with less lamellipodia, whereas dentin collagen and laser groups showed flat morphology with cytoplasmic processes. Conclusions: Both dentin collagen and Er:YAG laser showed comparable effectiveness as biomodification tools with good biocompatibility for human PDLF cell attachment on intact root slices imitating delayed replantation. Dentin collagen as a natural bioactive material is considered an alternative to Er:YAG laser to enhance the regenerative effects.

Micro/Nano‐Structured Superhydrophobic Gas Diffusion Electrode for Boosting the Stability of Industrial‐Compatible Electrochemical CO Production in Flow Cells

AbstractElectrochemical flow cells based on gas diffusion electrodes (GDEs) provide a potential means to achieve industrial‐compatible massive CO production. However, the application of flow cells is hindered by the stability issue caused by GDE hydrophilizing and electrolyte flooding. The current strategies have certain limitations in maintaining the long‐term hydrophobicity of GDE. Inspired by the superhydrophobic materials in nature, here a constructionally engineered superhydrophobic GDE is presented for boosting the stability of CO2 reduction to CO in flow cells under industrial‐compatible current densities. This superhydrophobic GDE is comprised of micro/nano‐structured CNTs/graphene composites with abundant and robust single‐atomic Ni‐Nx active sites (NiSA‐CNT@G). The unique integrated hierarchical structure with highly exposed surface area and enhanced mass/charge transfer contributes to an industrial‐scale CO partial current density of 406.5 mA cm−2 with a FECO of 96.3% in a flow cell. Notably, the robust superhydrophobic micro/nanostructure efficiently resists electrolyte flooding over the GDE during the CO2RR, thus maintaining a stable three‐phase interface. Over 70 h stability is demonstrated at an industrial‐compatible current density of 300 mA cm−2. These results open up new opportunities for industrial‐level CO production via electrochemical CO2RR.