Biomineralization To Prevent Microbially Induced Corrosion on Concrete for Sustainable Marine Infrastructure.

Microbially induced corrosion (MIC) on concrete represents a serious issue impairing the lifespan of coastal/marine infrastructure. However, currently developed concrete corrosion protection strategies have limitations in wide applications. Here, a biomineralization method was proposed to form a biomineralized film on concrete surfaces for corrosion inhibition. Laboratory seawater corrosion experiments were conducted under different conditions [e.g., chemical corrosion (CC), MIC, and biomineralization for corrosion inhibition]. A combination of chemical and mechanical property measurements of concrete (e.g., sulfate concentrations, permeability, mass, and strength) and a genotypic-based investigation of formed concrete biofilms was conducted to evaluate the effectiveness of the biomineralization approach on corrosion inhibition. The results show that MIC resulted in much higher corrosion rates than CC. However, the biomineralization treatment effectively inhibited corrosion because the biomineralized film decreased the total and relative abundance of sulfate-reducing bacteria (SRB) and acted as a protective layer to control the diffusion of sulfate and isolate the concrete from the corrosive SRB communities, which helps extend the lifespan of concrete structures. Moreover, this technique had no negative impact on the native marine microbial communities. Our study contributes to the potential application of biomineralization for corrosion inhibition to achieve long-term sustainability for major marine concrete structures.

Effect of calcium sources on enzyme-induced carbonate precipitation to solidify desert aeolian sand.

Enzyme-induced carbonate precipitation (EICP) is a promising technique for soil reinforcement. To select a suitable calcium source and a suitable solution amount for aeolian sand stabilization using EICP, specimens treated with different solution amounts (1.5, 2, 2.5, 3, and 3.5 L/m2). Surface strength, crust thickness, calcium carbonate content (CCC) and water vapor adsorption tests were performed to evaluate the effect of two calcium sources (calcium acetate and calcium chloride) on aeolian sand solidification. The plant suitability of solidified sand was investigated by the sea buckthorn growth test. The suitable calcium source was then used for the laboratory wind tunnel test and the field test to examine the erosion resistance of solidified sand. The results demonstrated that Ca(CH3COO)2-treated specimens exhibited higher strength than CaCl2-treated specimens at the same EICP solution amount, and the water vapor equilibrium adsorption mass of Ca(CH3COO)2-treated specimens was less, indicating that Ca(CH3COO)2-solidified sand was more effective and had better long-term stability. In addition, plants grown in Ca(CH3COO)2-treated sand had greater seedling emergence percentage and higher average height, which indicated that calcium acetate is a more suitable calcium source for EICP treatment. Furthermore, the surface strength and crust thickness of solidified sand increased with increasing the solution amount. For sand treated with 3 L/m2 of solution, the excessive strength and thickness of the crust made plants growth difficult, and the performance of sand treated with more than 2 L/m2 of solution significantly improved. Thus, the solution amount of 2-3 L/m2 is suggested for engineering applications. The sand solidified using EICP in the field could effectively mitigate wind erosion and facilitate the growth of native plants. Therefore, EICP can be combined with vegetative method to achieve long-term wind erosion control in the future.

Advance of microfluidic constriction channel system of measuring single-cell cortical tension/specific capacitance of membrane and conductivity of cytoplasm.

This paper reported a microfluidic platform which realized the characterization of inherent single-cell biomechanical and bioelectrical parameters simultaneously. Individual cells traveled through a constriction channel with deformation images and impedance variations captured and processed into cortical tension Tc , specific membrane capacitance Csm , and cytoplasmic conductivity σcy based on an equivalent biophysical model. These properties of thousands of individual cells of K562, Jurkat, HL-60, HL-60 treated with paraformaldehyde (PA)/cytochalasin D (CD)/concanavalin A (ConA), granulocytes of Donor 1, Donor 2, and Donor 3 were quantified for the first time. Leveraging Tc , Csm , and σcy , (1) high accuracies of classifying wild-type and processed HL-60 cells (e.g., 93.5% of PA treated vs. CD treated HL-60 cells) were realized, revealing the effectiveness of using these three biophysical parameters in cell-type classification; (2) low accuracies of classifying normal granulocytes from three donors (e.g., 56.4% of Donor 1 vs. 2), indicating comparable parameters for normal granulocytes. In conclusion, this platform can characterize single-cell Tc , Csm , and σcy concurrently and quantify multiple parameters in single-cell analysis.

Surface rainfall erosion resistance and freeze-thaw durability of bio-cemented and polymer-modified loess slopes.

Microbially induced calcite precipitation (MICP) has been shown to mitigate sand erosion; however, few studies have applied MICP on loess soils. In this study, polyacrylamide (PAM) was added to the cementation solution, and combined MICP-PAM treatment was applied to improve the surface erosion resistance of loess-slopes. The freeze-thaw (FT) durability of MICP-PAM treated loess slopes was also studied. The obtained results showed that MICP-PAM treatment improved erosion resistance and addition of 1.5 g/L PAM achieved the best erosion control and highest surface strength. The high erosion resistance of MICP-PAM treated slopes could be attributed to the stable spatial structure of precipitation, and PAM addition conveyed stronger resistance to tension or shear force. With increasing number of FT cycles, the surface strength of MICP-PAM treated loess slopes decreased; however, slopes subjected to 12 FT cycles still only lost little soil. In MICP-PAM treated loess slopes, cracks and pores evolved with increasing number of FT cycles. With increasing number of FT cycles, porosity and fractal dimension increased, pore ellipticity decreased slightly, and the percentage of various pores changed slightly. The number of FT cycles had less effect on MICP-PAM treated loess slopes than on untreated slopes. MICP-PAM treatment significantly mitigated surface erosion of loess-slopes and improved FT weathering resistance, thus presenting promising potential for application in the field. In addition, based on the linear correlations between surface strength and rainfall-erosion resistance, surface strength could be measured to evaluate the rainfall-erosion resistance for MICP-PAM treated slopes in practical engineering applications.

Mineralization crust field experiment for desert sand solidification based on enzymatic calcification.

Sandstorms have been recognized as severe natural disasters worldwide and it is of great significance to propose an effective and environmentally friendly method to combat sandstorm. In this study, the enzymatic calcification (EC) treatment technology was used for mineralization crust and desert sand solidification. Both laboratory experiments and field site tests were conducted to demonstrate the feasibility of EC treatment to improve wind-erosion resistance and rainfall-erosion resistance. Results showed that with the concentration of reactants higher than 0.25 M or the ratio of urease solution to the cementation solution above 0.8, the improvement effects of wind-erosion resistance and rainfall-erosion resistance decreased. Therefore, the 0.25 M of reagent concentration and 0.8 of ratio of urease solution to the cementation solution were chosen for subsequent field site test. The two test sites had similar CaCO3 contents, thus obtaining a similar increasing range of surface strength. However, the test site one had larger surface strengths due to thicker cemented crust layers. Both the two test sites had sufficient wind-erosion resistance because of crust layer. Moreover, rainfalls decreased surface strength; the surface strength recovered to a high level after water evaporation. In addition, the effect of rainfall on thickness of crust layer and CaCO3 was small. The EC treatment had good ecological compatibility, and the combined EC and grass seed treatment was effective for mitigation of desertification. The results demonstrated that EC treatment significantly improved both wind-erosion and rainfall-erosion resistance, which presents promising potential for anti-desertification.

Microfluidic Cytometry for High-Throughput Characterization of Single Cell Cytoplasmic Viscosity Using Crossing Constriction Channels.

This article presents an approach of microfluidic flow cytometry capable of continuously characterizing cytoplasmic viscosities of single cells. The microfluidic system consists of a major constriction channel and a side constriction channel perpendicularly crossing each other. Cells are forced to rapidly travel through the major channel and are partially aspirated into the side channel when passing the channel junction. Numerical simulations were conducted to model the time dependence of the aspiration length into the side channel, which enables the measurement of cytoplasmic viscosity by fitting the model results to experimental data. As a demonstration for high-throughput measurement, the cytoplasmic viscosities of HL-60 cells that were native or treated by N-Formylmethionine-leucyl-phenylalanine (fMLP) were quantified with sample sizes as large as thousands of cells. Both the average and median cytoplasmic viscosities of native HL-60 cells were found to be about 10% smaller than those of fMLP-treated HL-60 cells, consistent with previous observations that fMLP treatment can increase the rigidity of white blood cells. Furthermore, the microfluidic system was used to process granulocytes from three donors (sample size >1,000 cells for each donor). The results revealed that the cytoplasmic viscosity of granulocytes from one donor was significantly higher than the other two, which may result from the fact that this donor just recovered from an inflammation. In summary, the developed microfluidic system can collect cytoplasmic viscosities from thousands of cells and may function as an enabling tool in the field of single-cell analysis. © 2019 International Society for Advancement of Cytometry.

Hierarchical Nanoporous Copper Architectures via 3D Printing Technique for Highly Efficient Catalysts.

Nanoporous metals represent a class of functional materials with unique bicontinuous open porous structural properties, making them ideal candidates for various catalyst applications. However, the pursuit of nanoporous properties, extremely small pores, and high surface area, results in the restriction of mass transport. Herein, a free-standing hierarchical nanoporous Cu material, prepared by a selective laser melting 3D printing technique and a one-step dealloying process, is presented as a highly efficient electrocatalyst for methanol oxidation. It is demonstrated that the digitally controlled hierarchical structure with macro- and nano-scaled pores can be utilized for promoting and directing mass transport as well as for the enhancement of catalytic properties. This work highlights a facile, low-cost, and alternative strategy for hierarchical nanoporous structure design that can be applied to binary, ternary, and quaternary metal alloys for various functional applications.

Improvement of bio-cementation at low temperature based on Bacillus megaterium.

A low production rate for calcium carbonate with microbial solidification technology at low temperatures often restricts its application. For this reason, adding urea to the medium and the domestication of Bacillus megaterium at low temperature were proposed to produce more calcium carbonate based on an analysis of growth characteristics, urease activity, and the production rates for calcium carbonate under different conditions. Sand solidification tests were conducted to demonstrate improvements caused by the methods. The results showed that the higher the temperature, the faster the growth of Bacillus megaterium and the stronger the urease activity. Growth was fastest and urease activity strongest at a pH of 8. Adding urea to the medium and the domestication of B. megaterium at low temperature can both improve the production rate, effectively increasing calcium carbonate precipitation at low temperature. Combining the two methods resulted in greater improvement of the production rate for calcium carbonate. The two methods were also found to improve the effect of sand solidification. Therefore, our study provides a solid foundation for the actual engineering application of bio-cementation technology at low temperature.

Thermomechanics of a temperature sensitive covalent adaptable polymer with bond exchange reactions.

We study a covalent adaptable polymer that can rearrange its network topology through thermally activated bond exchange reactions. When the polymer is deformed, such a network rearrangement leads to macroscopic stress relaxation, which allows the polymer to be thermoformed without a mold. Based on a previously developed constitutive model, we investigate thermal-mechanical behaviors of this material under a non-uniform and evolving temperature field through numerical simulations. Our focus is on the complex coupling between mechanical deformation, heat conduction and bond exchange reactions. Several examples are presented to illustrate the effects of non-uniform heating: uniaxial tension under heat conduction, torsion of a thin strip with local heating and thermal imprinting. Our results show that during non-uniform heating the material in the high temperature region creeps. This causes a redistribution of the deformation field and thus results in a final shape that deviates from the prescribed shape. The final shapes after thermoforming can be tuned by controlling the extent of heat conduction through different combinations of heating temperature and time. For example, with high temperature and a short heating time, it is possible to approximately confine stress relaxation and thus shape fixity within the local heating region. This is not the case if low temperature and a long heating time are used. These results can be utilized to design the temporal and spatial sequences of local heating during thermoforming to achieve various complex final shapes.

Biomineralization for Reducing and Controlling Sand-Dust Storms.

The sand-dust weather and sand-dust storms have become a serious environmental disaster worldwide. It is an important challenge to develop technologies for desert sand solidification in order to prevent and control sand-dust weather. The biomineralization technology for solidifying desert sands has been a novel method for reinforced soils in recent years. The biomineralization solidification sand field tests are completed at the Wuma Highway solidification section in the Tengger Desert. The superiority of the biomineralization for solidifying sands is verified by measuring the water storage capacity of different reinforcement zones including bare sand zone, plant zone, biomineralization solidifying sand zone, and biomineralization combined plant solidifying sand zone. Simultaneously, the molecular dynamics calculation analysis is used to verify the role of biomineralization solidifying sands in preventing sand-dust storms. All results demonstrate that the biomineralization solidification sand method is effective for controlling and preventing sandstorm disasters.

Active Materials for Functional Origami.

In recent decades, origami has been explored to aid in the design of engineering structures. These structures span multiple scales and have been demonstrated to be used toward various areas such as aerospace, metamaterial, biomedical, robotics, and architectural applications. Conventionally, origami or deployable structures have been actuated by hands, motors, or pneumatic actuators, which can result in heavy or bulky structures. On the other hand, active materials, which reconfigure in response to external stimulus, eliminate the need for external mechanical loads and bulky actuation systems. Thus, in recent years, active materials incorporated with deployable structures have shown promise for remote actuation of light weight, programmable origami. In this review, active materials such as shape memory polymers (SMPs) and alloys (SMAs), hydrogels, liquid crystal elastomers (LCEs), magnetic soft materials (MSMs), and covalent adaptable network (CAN) polymers, their actuation mechanisms, as well as how they have been utilized for active origami and where these structures are applicable is discussed. Additionally, the state-of-the-art fabrication methods to construct active origami are highlighted. The existing structural modeling strategies for origami, the constitutive models used to describe active materials, and the largest challenges and future directions for active origami research are summarized.

State-of-the-art review of soil erosion control by MICP and EICP techniques: Problems, applications, and prospects.

In recent years, the application of microbially induced calcite precipitation (MICP) and enzyme-induced carbonate precipitation (EICP) techniques have been extensively studied to mitigate soil erosion, yielding substantial achievements in this regard. This paper presents a comprehensive review of the recent progress in erosion control by MICP and EICP techniques. To further discuss the effectiveness of erosion mitigation in-depth, the estimation methods and characterization of erosion resistance were initially compiled. Moreover, factors affecting the erosion resistance of MICP/EICP-treated soil were expounded, spanning from soil properties to treatment protocols and environmental conditions. The development of optimization and upscaling in erosion mitigation via MICP/EICP was also included in this review. In addition, this review discussed the limitations and correspondingly proposed prospective applications of erosion control via the MICP/EICP approach. The current review presents up-to-date information on the research activities for improving erosion resistance by MICP/EICP, aiming at providing insights for interdisciplinary researchers and guidance for promoting this method to further applications in erosion mitigation.

Transforaminal posterior lumbar interbody fusion microscopic safe operating area: a three-dimensional model study based on computed tomography imaging.

BACKGROUND: Endoscopic spine lumbar interbody fusion (Endo-LIF) is well-regarded within the academic community. However, it presents challenges such as intraoperative disorientation, high rates of nerve damage, a steep learning curve, and prolonged surgical times, often occurring during the creation of the operative channel. Furthermore, the undefined safe operational zones under endoscopy continue to pose risks to surgical safety. We aimed to analyse the anatomical data of Kambin's triangle via CT imaging to define the parameters of the safe operating area for transforaminal posterior lumbar interbody fusion (TPLIF), providing crucial insights for clinical practice. METHODS: We selected the L4-L5 intervertebral space. Using three-dimensional (3D), we identified Kambin's triangle and the endocircle within it, and recorded the position of point 'J' on the adjacent facet joint as the centre 'O' of the circle shifts by angle 'ß.' The diameter of the inscribed circle 'd,' the abduction angle 'ß,' and the distances 'L1' and 'L2' were measured from the trephine's edge to the exiting and traversing nerve roots, respectively. RESULTS: Using a trephine with a diameter of 8 mm in TPLIF has a significant safety distance. The safe operating area under the TPLIF microscope was also clarified. CONCLUSIONS: Through CT imaging research, combined with 3D simulation, we identified the anatomical data of the L4-L5 segment Kambin's triangle, to clarify the safe operation area under TPLIF. We propose a simple and easy positioning method and provide a novel surgical technique to establish working channels faster and reduce nerve damage rates. At the same time, according to this method, the Kambin's triangle anatomical data of the patient's lumbar spine diseased segments can be measured through CT 3D reconstruction of the lumbar spine, and individualised preoperative design can be conducted to select the appropriate specifications of visible trephine and supporting tools. This may effectively reduce the learning curve, shorten the time operation time, and improve surgical safety.

Machine learning-enabled forward prediction and inverse design of 4D-printed active plates.

Shape transformations of active composites (ACs) depend on the spatial distribution of constituent materials. Voxel-level complex material distributions can be encoded by 3D printing, offering enormous freedom for possible shape-change 4D-printed ACs. However, efficiently designing the material distribution to achieve desired 3D shape changes is significantly challenging yet greatly needed. Here, we present an approach that combines machine learning (ML) with both gradient-descent (GD) and evolutionary algorithm (EA) to design AC plates with 3D shape changes. A residual network ML model is developed for the forward shape prediction. A global-subdomain design strategy with ML-GD and ML-EA is then used for the inverse material-distribution design. For a variety of numerically generated target shapes, both ML-GD and ML-EA demonstrate high efficiency. By further combining ML-EA with a normal distance-based loss function, optimized designs are achieved for multiple irregular target shapes. Our approach thus provides a highly efficient tool for the design of 4D-printed active composites.

Chemical Circularity in 3D Printing with Biobased Δ-Valerolactone.

Digital Light Processing (DLP) is a vat photopolymerization-based 3D printing technology that fabricates parts typically made of chemically crosslinked polymers. The rapidly growing DLP market has an increasing demand for polymer raw materials, along with growing environmental concerns. Therefore, circular DLP printing with a closed-loop recyclable ink is of great importance for sustainability. The low-ceiling temperature alkyl-substituted δ-valerolactone (VL) is an industrially accessible biorenewable feedstock for developing recyclable polymers. In this work, acrylate-functionalized poly(δ-valerolactone) (PVLA), synthesized through the ring-opening transesterification polymerization of VL, is used as a platform photoprecursor to improve the chemical circularity in DLP printing. A small portion of photocurable reactive diluent (RD) turns the unprintable PVLA into DLP printable ink. Various photocurable monomers can serve as RDs to modulate the properties of printed structures for applications like sacrificial molds, soft actuators, sensors, etc. The intrinsic depolymerizability of PVLA is well preserved, regardless of whether the printed polymer is a thermoplastic or thermoset. The recovery yield of virgin quality VL monomer is 93% through direct bulk thermolysis of the printed structures. This work proposes the utilization of depolymerizable photoprecursors and highlights the feasibility of biorenewable VL as a versatile material platform toward circular DLP printing.

Effect of the Combination of Torsional and Tensile Stress on Corrosion Behaviors of Biodegradable WE43 Alloy in Simulated Body Fluid.

The real physiological environment of the human body is complicated, with different degrees and forms of loads applied to biomedical implants caused by the daily life of the patients, which will definitely influence the degradation behaviors of Mg-based biodegradable implants. In the present study, the degradation behaviors of modified WE43 alloys under the combination of torsional and tensile stress were systematically investigated. Slow strain rate tensile tests revealed that the simulated body fluid (SBF) solution could deteriorate the ultimate tensile stress of WE43 alloy from 210.1 MPa to 169.2 MPa. In the meantime, the fracture surface of the specimens tested in the SBF showed an intergranular corrosion morphology in the marginal region, while the central area appeared not to have been affected by the corrosive media. The bio-degradation performances under the combination of torsional and tensile stressed conditions were much more severe than those under unstressed conditions or single tensile stressed situations. The combination of 40 MPa tensile and 40 MPa torsional stress resulted in a degradation rate over 20 mm/y, which was much higher than those under 80 MPa single tensile stress (4.5 mm/y) or 80 MPa single torsional stress (13.1 mm/y). The dynamic formation and destruction mechanism of the protective corrosion products film on the modified WE43 alloy could attribute to the exacerbated degradation performance and the unique corrosion morphology. The dynamic environment and multi-directional loading could severely accelerate the degradation process of modified WE43 alloy. Therefore, the SCC susceptibility derived from a single directional test may be not suitable for practical purposes. Complex external stress was necessary to simulate the in vivo environment for the development of biodegradable Mg-based implants for clinical applications.

A novel method combining VAT photopolymerization and casting for the fabrication of biodegradable Zn-1Mg scaffolds with triply periodic minimal surface.

Zinc alloy porous scaffolds are expected to be the next generation of degradable orthopedic implants attributed to their suitable degradation rate. However, a few studies have thoroughly investigated its applicable preparation method and functionality as an orthopedic implant. This study fabricated Zn-1Mg porous scaffolds with triply periodic minimal surface (TPMS) structure by a novel method combining VAT photopolymerization and casting. As-built porous scaffolds displayed fully connected pore structures with controllable topology. The manufacturability, mechanical properties, corrosion behaviors, biocompatibility, and antimicrobial performance of the bioscaffolds with pore sizes of 650 µm, 800 µm, and 1040 µm were investigated, and then compared and discussed with each other. In simulations, the mechanical behaviors of porous scaffolds exhibited the same tendency as the experiments. In addition, the mechanical properties of porous scaffolds as a function of degradation time were studied through a 90-day immersion experiment, which can provide a new option for analyzing the mechanical properties of porous scaffolds implanted in vivo. The G06 scaffold with lower pore size presented better mechanical properties before and after degradation compared with G10. The G06 scaffold with the pore size of 650 µm revealed good biocompatibility and antibacterial properties, which makes it possible to be one of the candidates for orthopedic implants.

Single-vat single-cure grayscale digital light processing 3D printing of materials with large property difference and high stretchability.

Multimaterial additive manufacturing has important applications in various emerging fields. However, it is very challenging due to material and printing technology limitations. Here, we present a resin design strategy that can be used for single-vat single-cure grayscale digital light processing (g-DLP) 3D printing where light intensity can locally control the conversion of monomers to form from a highly stretchable soft organogel to a stiff thermoset within in a single layer of printing. The high modulus contrast and high stretchability can be realized simultaneously in a monolithic structure at a high printing speed (z-direction height 1 mm/min). We further demonstrate that the capability can enable previously unachievable or hard-to-achieve 3D printed structures for biomimetic designs, inflatable soft robots and actuators, and soft stretchable electronics. This resin design strategy thus provides a material solution in multimaterial additive manufacture for a variety of emerging applications.

Cold-programmed shape-morphing structures based on grayscale digital light processing 4D printing.

Shape-morphing structures that can reconfigure their shape to adapt to diverse tasks are highly desirable for intelligent machines in many interdisciplinary fields. Shape memory polymers are one of the most widely used stimuli-responsive materials, especially in 3D/4D printing, for fabricating shape-morphing systems. They typically go through a hot-programming step to obtain the shape-morphing capability, which possesses limited freedom of reconfigurability. Cold-programming, which directly deforms the structure into a temporary shape without increasing the temperature, is simple and more versatile but has stringent requirements on material properties. Here, we introduce grayscale digital light processing (g-DLP) based 3D printing as a simple and effective platform for fabricating shape-morphing structures with cold-programming capabilities. With the multimaterial-like printing capability of g-DLP, we develop heterogeneous hinge modules that can be cold-programmed by simply stretching at room temperature. Different configurations can be encoded during 3D printing with the variable distribution and direction of the modular-designed hinges. The hinge module allows controllable independent morphing enabled by cold programming. By leveraging the multimaterial-like printing capability, multi-shape morphing structures are presented. The g-DLP printing with cold-programming morphing strategy demonstrates enormous potential in the design and fabrication of shape-morphing structures.

One-Pot Synthesis of Depolymerizable δ-Lactone Based Vitrimers.

A depolymerizable vitrimer that allows both reprocessability and monomer recovery by a simple and scalable one-pot two-step synthesis of vitrimers from cyclic lactones is reported. Biobased δ-valerolactone with alkyl substituents (δ-lactone) has low ceiling temperature; thus, their ring-opening-polymerized aliphatic polyesters are capable of depolymerizing back to monomers. In this work, the amorphous poly(δ-lactone) is solidified into an elastomer (i.e., δ-lactone vitrimer) by a vinyl ether cross-linker with dynamic acetal linkages, giving the merits of reprocessing and healing. Thermolysis of the bulk δ-lactone vitrimer at 200 °C can recover 85-90 wt% of the material, allowing reuse without losing value and achieving a successful closed-loop life cycle. It further demonstrates that the new vitrimer has excellent properties, with the potential to serve as a biobased and sustainable replacement of conventional soft elastomers for various applications such as lenses, mold materials, soft robots, and microfluidic devices.