Epitaxy-Directed Self-Assembly of Copolymers and Polymer Blends.

Directed self-assembly of materials into patterned structures is of great importance since the performance of them depends remarkably on their multiscale hierarchical structures. Therefore, purposeful structural regulation at different length scales through crystallization engineering provides an opportunity to modify the properties of polymeric materials. Here, an epitaxy-directed self-assembly strategy for regulating the pattern structures including phase structure as well as crystal modification and orientation of each component for both copolymers and polymer blends is reported. Owing to the specific crystallography registration between the depositing crystalline polymers and the underlying crystalline substrate, not only order phase structure with controlled size at nanometer scale but also the crystal structure and chain orientation of each component within the separated phases for both copolymers and polymer blend systems can be precisely regulated.

Plasticity impairment alters community structure but permits successful pattern separation in a hippocampal network model.

Patients who suffer from traumatic brain injury (TBI) often complain of learning and memory problems. Their symptoms are principally mediated by the hippocampus and the ability to adapt to stimulus, also known as neural plasticity. Therefore, one plausible injury mechanism is plasticity impairment, which currently lacks comprehensive investigation across TBI research. For these studies, we used a computational network model of the hippocampus that includes the dentate gyrus, CA3, and CA1 with neuron-scale resolution. We simulated mild injury through weakened spike-timing-dependent plasticity (STDP), which modulates synaptic weights according to causal spike timing. In preliminary work, we found functional deficits consisting of decreased firing rate and broadband power in areas CA3 and CA1 after STDP impairment. To address structural changes with these studies, we applied modularity analysis to evaluate how STDP impairment modifies community structure in the hippocampal network. We also studied the emergent function of network-based learning and found that impaired networks could acquire conditioned responses after training, but the magnitude of the response was significantly lower. Furthermore, we examined pattern separation, a prerequisite of learning, by entraining two overlapping patterns. Contrary to our initial hypothesis, impaired networks did not exhibit deficits in pattern separation with either population- or rate-based coding. Collectively, these results demonstrate how a mechanism of injury that operates at the synapse regulates circuit function.

Combining printing and nanoparticle assembly: Methodology and application of nanoparticle patterning.

Functional nanoparticles (NPs) with unique photoelectric, mechanical, magnetic, and chemical properties have attracted considerable attention. Aggregated NPs rather than individual NPs are generally required for sensing, electronics, and catalysis. However, the transformation of functional NP aggregates into scalable, controllable, and affordable functional devices remains challenging. Printing is a promising additive manufacturing technology for fabricating devices from NP building blocks because of its capabilities for rapid prototyping and versatile multifunctional manufacturing. This paper reviews recent advances in NP patterning based on the combination of self-assembly and printing technologies (including two-, three-, and four-dimensional printing), introduces the basic characteristics of these methods, and discusses various fields of NP patterning applications.

Nanofiber/hydrogel core-shell scaffolds with three-dimensional multilayer patterned structure for accelerating diabetic wound healing.

Impaired angiogenesis is one of the predominant reasons for non-healing diabetic wounds. Herein, a nanofiber/hydrogel core-shell scaffold with three-dimensional (3D) multilayer patterned structure (3D-PT-P/GM) was introduced for promoting diabetic wound healing with improved angiogenesis. The results showed that the 3D-PT-P/GM scaffolds possessed multilayered structure with interlayer spacing of about 15-80 µm, and the hexagonal micropatterned structures were uniformly distributed on the surface of each layer. The nanofibers in the scaffold exhibited distinct core-shell structures with Gelatin methacryloyl (GelMA) hydrogel as the shell and Poly (D, L-lactic acid) (PDLLA) as the core. The results showed that the porosity, water retention time and water vapor permeability of the 3D-PT-P/GM scaffolds increased to 1.6 times, 21 times, and 1.9 times than that of the two-dimensional (2D) PDLLA nanofibrous scaffolds, respectively. The in vitro studies showed that the 3D-PT-P/GM scaffolds could significantly promote cell adhesion, proliferation, infiltration and migration throughout the scaffolds, and the expression of cellular communication protein-related genes, as well as angiogenesis-related genes in the same group, was remarkably upregulated. The in vivo results further demonstrated that the 3D-PT-P/GM scaffolds could not only effectively absorb exudate and provide a moist environment for the wound sites, but also significantly promote the formation of a 3D network of capillaries. As a result, the healing of diabetic wounds was accelerated with enhanced angiogenesis, granulation tissue formation, and collagen deposition. These results indicate that nanofiber/hydrogel core-shell scaffolds with 3D multilayer patterned structures could provide a new strategy for facilitating chronic wound healing.

Integrated Sensing and Warning Multifunctional Devices Based on the Combined Mechanical and Thermal Effect of Porous Graphene.

Wearable devices with integrated alarm functions play a vital role in daily life and can help people prevent potential hazards. Although many wearable sensors have been extensively studied and proposed to monitor various physiological signals, most of them are needed to integrate with the external alarm elements to realize warning, such as light-emitting diodes and buzzers, resulting in the system complexity and poor flexibility. In this paper, an integrated sensing and warning multifunctional device based on the mechanical and thermal effect of porous graphene is proposed on a bilayer asymmetrical pattern of laser-induced graphene (LIG). Compared with the strain sensor with nonpatterned LIG, the mechanical performance is greatly improved with the highest gauge factor value of up to 950 for the strain sensor with mesh-patterned LIG. On the contrary, the heating performance of the heater with nonpatterned LIG is better than that with mesh-patterned LIG. Combining the performance differences of different LIG patterns, the integrated wearable device with a bilayer asymmetrical LIG pattern is demonstrated. It can generate enough heating energy to warn the person when the detected signal meets the threshold condition measured in real time by the ultrasensitive strain sensor. This work will provide a new way to construct an integrated wearable device for realizing multifunctional applications. This integrated multifunctional device shows great potential toward the applications in healthcare monitoring and timely warning.

A pre-wetting induced superhydrophilic/superlipophilic micro-patterned electrospun membrane with self-cleaning property for on-demand emulsified oily wastewater separation.

In this work, a pre-wetting induced superhydrophilic/superlipophilic micro-patterned membrane with surface-loaded BiVO4 nanoparticles (Bi/PDA@PT) was successfully prepared by electrospinning and polydopamine (PDA) surface modification technology for highly efficient emulsified oily wastewater separation. The results showed that the as-prepared membranes exhibited micro hole-patterned structures and the BiVO4 nanoparticles were uniformly deposited on the surfaces of fibers to construct hierarchical porous structures by using PDA as an adhesive polymeric bridge. During the separation process of emulsified oily wastewater, the hierarchical porous structures in membranes significantly improved the separation flux, which was nearly 2-3 times than that of the non-patterned membranes. Based on the existence of PDA, the membranes exhibited prewetting-induced superoleophobicity under water and superhydrophobicity under oil, which made it possible for them to separate both water-in-oil and oil-in-water emulsified oily wastewater selectively and efficiently. Moreover, the BiVO4 nanoparticles loaded on the membranes could degrade the oily contaminants adsorbed on the membranes (nearly 100%) under visible light. All these attractive features demonstrate that the Bi/PDA@PT membranes show a great potential for sustainable and efficient emulsified oily wastewater separation.

Ion- and Electron-Conductive Buffering Layer-Modified Si Film for Use as a High-Rate Long-Term Lithium-Ion Battery Anode.

The rational design of electrochemically and mechanically stable Si anodes is of great importance for the development of high energy density lithium-ion batteries. In this study, patterned Si-based (Si/ZnO/C) trilayer composite films were synthesized by magnetron sputtering with the assistance of a patterned mask. The electron-conductive C layer at the top of the composite film is deposited to enhance the interfacial stability between active film and electrolyte. The ion- and electron-conductive Li2 O-Zn middle layer can be ingeniously introduced by means of the poor reversed conversion reaction between ZnO and Li+ ions after the first cycle. The resultant Si/Li2 O-Zn/C trilayer composite film delivers a high reversible capacity of 1536 mAh g-1 after 800 cycles at a current density of 1.0 A g-1 and a long high-rate cycling stability (1400 mAh g-1 after 6000 cycles even at a high current density of 10.0 A g-1 ). Excellent rate capability and improved Coulombic efficiency are also achieved. The influences of the patterned structure and each modified layer on the electrochemical properties are analyzed systematically. This work offers a new and promising direction to enhance the lithium-storage properties of Si-based thin-film anodes.

Thermodynamics versus Kinetics Dichotomy in the Linear Self-Assembly of Mixed Nanoblocks.

We report classical and replica exchange molecular dynamics simulations that establish the mechanisms underpinning the growth kinetics of a binary mix of nanorings that form striped nanotubes via self-assembly. A step-growth coalescence model captures the growth process of the nanotubes, which suggests that high aspect ratio nanostructures can grow by obeying the universal laws of self-similar coarsening, contrary to systems that grow through nucleation and elongation. Notably, striped patterns do not depend on specific growth mechanisms, but are governed by tempering conditions that control the likelihood of depropagation and fragmentation.