For life to emerge, the confinement of catalytic reactions within protocellular environments has been proposed to be a decisive aspect to regulate chemical activity in space
. Today, cells and ...organisms adapt to signals
by processing them through reaction networks that ultimately provide downstream functional responses and structural morphogenesis
. Re-enacting such signal processing in de novo-designed protocells is a profound challenge, but of high importance for understanding the design of adaptive systems with life-like traits. We report on engineered all-DNA protocells
harbouring an artificial metalloenzyme
whose olefin metathesis activity leads to downstream morphogenetic protocellular responses with varying levels of complexity. The artificial metalloenzyme catalyses the uncaging of a pro-fluorescent signal molecule that generates a self-reporting fluorescent metabolite designed to weaken DNA duplex interactions. This leads to pronounced growth, intraparticular functional adaptation in the presence of a fluorescent DNA mechanosensor
or interparticle protocell fusion. Such processes mimic chemically transduced processes found in cell adaptation and cell-to-cell adhesion. Our concept showcases new opportunities to study life-like behaviour via abiotic bioorthogonal chemical and mechanical transformations in synthetic protocells. Furthermore, it reveals a strategy for inducing complex behaviour in adaptive and communicating soft-matter microsystems, and it illustrates how dynamic properties can be upregulated and sustained in micro-compartmentalized media.
Wetting behaviors of structured metal surfaces have received considerable attention due to the wide range of applications for commercial, industrial, and military uses as well as fundamental research ...interests. Due to its adaptability, precision, and ease of automation, laser-based texturing techniques are desirable platforms to create micro- and nano-structures, including laser-induced periodic surface structures, or hierarchical structures on a metal substrate. However, micro- and nanostructures alone often do not achieve the desired wettability. A subsequent surface chemistry modification method must be performed to attain target extreme wettability for laser textured metal substrates. This review aims to provide a systematic understanding of the interdependence of surface chemistry modification and physical surface structures formed during the laser-based surface engineering methods. The role of surface chemistry on top of the surface structures is presented to decide the final wetting scenario. Specifically, by controlling the surface chemistry of a laser textured surface, wetting can be modulated from extreme hydrophobicity to hydrophilicity, allowing freedom to achieve complex multi-wettability situations. In each section, we highlight the most fruitful approaches and underlying mechanisms to achieve a fitting combination of surface structures and surface chemistry. Durability and stability of the treated surface are also discussed in corrosive and abrasive environments. Finally, challenges in current studies and prospects in future research directions of this rapidly developing field are also discussed. This review will provide a comprehensive guideline for the design of laser texturing methods and the fabrication of extreme wetting surfaces for metal alloys.
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•Laser-induced surface structures and following surface chemistry modification are equally critical for extreme wettability.•Underlaying mechanisms of surface chemistry modification are explained.•Recent progress in durability laser textured extreme wetting surface is addressed.•It provides a comprehensive guidance for fabricating extreme wetting surfaces for metal alloys by laser texturing methods.
DNA has traditionally been used for the programmable design of nanostructures by exploiting its sequence-defined supramolecular recognition. However, control on larger length scales or even ...hierarchical materials that translate to the macroscale remain difficult to construct. Here, we show that the polymer character of single-stranded DNA (ssDNA) can be activated via a nucleobase-specific lower critical solution temperature, which provides a unique access to mesoscale structuring mechanisms on larger length scales. We integrate both effects into ssDNA multiblock copolymers that code sequences for phase separation, hybridization and functionalization. Kinetic pathway guidance using temperature ramps balances the counteracting mesoscale phase separation during heating with nanoscale duplex recognition during cooling to yield a diversity of complex all-DNA colloids with control over the internal dynamics and of their superstructures. Our approach provides a facile and versatile platform to add mesostructural layers into hierarchical all-DNA materials. The high density of addressable ssDNA blocks opens routes for applications such as gene delivery, artificial evolution or spatially encoded (bio)materials.
Abstract
The fundamental life-defining processes in living cells, such as replication, division, adaptation, and tissue formation, occur via intertwined metabolic reaction networks that process ...signals for downstream effects with high precision in a confined, crowded environment. Hence, it is crucial to understand and reenact some of these functions in wholly synthetic cell-like entities (protocells) to envision designing soft materials with life-like traits. Herein, we report on all-DNA protocells composed of a liquid DNA interior and a hydrogel-like shell, harboring a catalytically active DNAzyme, that converts DNA signals into functional metabolites that lead to downstream adaptation processes via site-selective strand displacement reactions. The downstream processes include intra-protocellular phenotype-like changes, prototissue formation via multivalent interactions, and chemical messenger communication between active sender and dormant receiver cell populations for sorted heteroprototissue formation. The approach integrates several tools of DNA-nanoscience in a synchronized way to mimic life-like behavior in artificial systems for future interactive materials.
Chemical, photochemical and electrical stimuli are versatile possibilities to exert external control on self‐assembled materials. Here, a trifunctional molecule that switches between an “adhesive” ...and a “non‐adhesive” state in response to metal ions, or light, or oxidation is presented. To this end, an azobenzene–ferrocene conjugate with a flexible N,N′‐bis(3‐aminopropyl)ethylenediamine spacer was designed as a multistimuli‐responsive guest molecule that can form inclusion complexes with β‐cyclodextrin. In the absence of any stimulus the guest molecule induces reversible aggregation of host vesicles composed of amphiphilic β‐cyclodextrin due to the formation of intervesicular inclusion complexes. In this case, the guest molecule operates as a noncovalent cross‐linker for the host vesicles. In response to any of three external stimuli (metal ions, UV irradiation, or oxidation), the conformation of the guest molecule changes and its affinity for the host vesicles is strongly reduced, which results in the dissociation of intervesicular complexes. Upon elimination or reversal of the stimuli (sequestration of metal ion, visible irradiation, or reduction) the affinity of the guest molecules for the host vesicles is restored. The reversible cross‐linking and aggregation of the cyclodextrin vesicles in dilute aqueous solution was confirmed by isothermal titration calorimetry (ITC), optical density measurements at 600 nm (OD600), dynamic light scattering (DLS), ζ‐potential measurements and cyclic voltammetry (CV). To the best of our knowledge, a dynamic supramolecular system based on a molecular switch that responds orthogonally to three different stimuli is unprecedented.
Press release: A bifunctional molecule with a flexible spacer was used as a noncovalent cross‐linker that induces aggregation of host vesicles composed of amphiphilic β‐cyclodextrins by the formation of host–guest inclusion complexes at the surface of the vesicles. In response to different stimuli (see figure) the guest molecule changes conformation and polarity and loses its affinity for the host vesicles, which causes dispersion of vesicle clusters.
Friction stir processing (FSP) is a friction stir-based material processing method for enhancement of material microstructural and surface properties. As FSP is a multi-physics problem coupled with ...severe plastic deformation, material flow, heat flow, and microstructure evolution, modeling of the FSP process can be very complicated and challenging. Few research work has been reported on modeling and simulations of FSP for material modification. In this study, a computation-efficient process model is developed using ABAQUS/Explicit based on coupled Eulerian-Lagrangian (CEL) formulation to simulate FSP of aluminum alloy 5083. The three-dimensional (3D) finite element model simulates the entire process of FSP including tool plunging, dwelling, and stirring phases. Simulations are performed to evaluate the effects of tool-rotational speed and tool pin profile during the FSP process. The computational efficiency of the developed model is also evaluated in comparison with other existing models for friction stir–welding processes. FSP experiment is performed with measurements of process force and temperature for model validation. This study shows that the CEL model can be a powerful numerical tool to simulate the complex process mechanics and optimize the FSP process parameters for industrial applications.
In this study, an attempt is made to examine the effects of loading pattern on critical temperature of the cold-formed steel (CFS) members under fire. Most of the past studies on CFS flexural members ...at elevated temperature included either point loading or uniform moment cases, however, critical temperature established for one loading pattern may prove to be unsafe or over-conservative in other loading scenario. Finite element model is developed using commercially available program
ABAQUS
and is validated against experimental and numerical results available in literature. Four types of loading patterns are considered namely, 4-point loading, 3-point loading, uniformly distributed load and uniform moment. Three load ratios: 0.3, 0.5 and 0.7 are considered in this study. Results from parametric study clearly indicate there is a significant effect on the critical temperature of the CFS steel flexural members due to change in loading patterns. Other parameters affecting the critical temperature such as non-dimensional slenderness, initial applied load levels, grade and geometric properties are also discussed in detail. Based on findings of this research two proposals are suggested in order to define critical temperature of the CFS flexural members under various loading conditions. Both the proposals are found to predict the safe critical temperature of CFS flexural members with accuracy.
Ultrasonic welding (UW) process offers the ability to create highly efficient solid-state joints for lightweight metal alloys with low power consumption. During the process, a distinct diffusion ...layer is observed at the joint interface that undergoes severe plastic deformation at elevated temperature. A hierarchical multiscale method is proposed in this study to predict the diffusion behavior of the UW process of dissimilar materials. The method combines molecular dynamics and classical diffusion theory to calculate the thickness of the diffusion layer at the welded interface. A molecular dynamics model is developed for the first time that considers the effect of transverse ultrasonic vibration to simulate the evolution of the diffusion layer. The effect of ultrasonic vibration at the atomic level is assumed to provide thermal energy at the joint interface and the mechanical movement of atoms. The influence of sinusoidal velocity change during ultrasonic vibration is incorporated by numerically time integrating the diffusivity at different ultrasonic velocity. The simulation result shows that the solid-state diffusivity depends on temperature, pressure, and transverse ultrasonic velocity. Higher temperature, pressure, and ultrasonic velocity result in higher diffusivity leading to larger diffusion layer thickness. This article provides a comprehensive review of the diffusion bonding behavior and its dependence on process variables. It also presents a numerical approach combining molecular dynamics and hierarchical multiscale calculation to predict the diffusion layer thickness for the UW process of dissimilar materials.
Co-crystallization of K+ and Li+ ions with γ-cyclodextrin (γ-CD) has been shown to substitute the K+ ion sites partially by Li+ ions, while retaining the structural integrity and accessible porosity ...of CD-MOF-1 (MOF, metal–organic framework). A series of experiments, in which the K+/Li+ ratio was varied with respect to that of γ-CD, have been conducted in order to achieve the highest possible proportion of Li+ ions in the framework. Attempts to obtain a CD-MOF containing only Li+ ions resulted in nonporous materials. The structural occupancy on the part of the Li+ ions in the new CD-MOF has been confirmed by single-crystal X-ray analysis by determining the vacancies of K+-ion sites and accounting for the cation/γ-CD ratio in CD-MOF-1. The proportion of Li+ ions has also been confirmed by elemental analysis, whereas powder X-ray diffraction has established the stability of the extended framework. This noninvasive synthetic approach to generating mixed-metal CD-MOFs is a promising method for obtaining porous framework unattainable de novo. Furthermore, the CO2 and H2 capture capacities of the Li+-ion-substituted CD-MOF have been shown to exceed the highest sorption capacities reported so far for CD-MOFs.
There exists a critical need in biomedical molecular imaging and diagnostics for molecular sensors that report on slight changes to their local microenvironment with high spatial fidelity. Herein, a ...modular fluorescent probe, termed StyPy, is rationally designed which features i) an enormous and tunable Stokes shift based on twisted intramolecular charge transfer (TICT) processes with no overlap, a broad emission in the far‐red/near‐infrared (NIR) region of light and extraordinary quantum yields of fluorescence, ii) a modular applicability via facile para‐fluoro‐thiol reaction (PFTR), and iii) a polarity‐ and viscosity‐dependent emission. This renders StyPy as a particularly promising molecular sensor. Based on the thorough characterization on the molecular level, StyPy reports on the viscosity change in all‐DNA microspheres and indicates the hydrophilic and hydrophobic compartments of hybrid DNA‐based mesostructures consisting of latex beads embedded in DNA microspheres. Moreover, the enormous Stokes shift of StyPy enables one to detect multiple fluorophores, while using only a single laser line for excitation in DNA protocells. The authors anticipate that the presented results for multiplexing information are of direct importance for advanced imaging in complex soft matter and biological systems.
The rational design of StyPy enables a push–pull system that undergoes a twisted intramolecular charge transfer (TICT) in its excited state and is applied to sense local viscosities and polarities in DNA hybrid mesostructures. The enormous Stokes shift of 250 nm enables to concurrently detect StyPy and conventional dyes with a single laser excitation.
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