Flexible Confinement Research Articles

"Rigid-Flexible" Dual-Ferrocene Chimeric Nanonetwork for Simultaneous Tumor-Targeted Tracing and Photothermal/Photodynamic Therapy.

There is an urgent need to develop phototherapeutic agents with imaging capabilities to assess the treatment process and efficacy in real-time during cancer phototherapy for precision cancer therapy. The safe near-infrared (NIR) fluorescent dyes have garnered significant attention and are desirable for theranostics agents. However, until now, achieving excellent photostability and fluorescence (FL) imaging capability in aggregation-caused quenching (ACQ) dyes remains a big challenge. Here, for the only FDA-approved NIR dye, indocyanine green (ICG), we developed a dual-ferrocene (Fc) chimeric nanonetwork ICG@HFFC based on the rigid-flexible strategy through one-step self-assembly, which uses rigid Fc-modified hyaluronic acid (HA) copolymer (HA-Fc) and flexible octadecylamine (ODA) bonded Fc (Fc-C18) as the delivery system. HA-Fc reserved the ability of HA to target the CD44 receptor of the tumor cell surface, and the dual-Fc region provided a rigid space for securely binding ICG through metal-ligand interaction and π-π conjugation, ensuring excellent photostability. Additionally, the alkyl chain provided flexible confinement for the remaining ICG through hydrophobic forces, preserving its FL. Thereby, a balance is achieved between outstanding photostability and FL imaging capability. In vitro studies showed improved photobleaching resistance, enhanced FL stability, and increased singlet oxygen (1O2) production efficiency in ICG@HFFC. Further in vivo results display that ICG@HFFC had good tumor tracing ability and significant tumor inhibition which also exhibited good biocompatibility.. Therefore, ICG@HFFC provides an encouraging strategy to realize simultaneous enhanced tumor tracing and photothermal/photodynamic therapy (PTT/PDT) and offers a novel approach to address the limitations of ACQ dyes.

Semiconductor Membranes for Electrostatic Exciton Trapping in Optically Addressable Quantum Transport Devices

Combining the capabilities of gate-defined quantum transport devices in $\mathrm{Ga}\mathrm{As}$-based heterostructures and of optically addressed self-assembled quantum dots could open up broad perspectives in quantum technologies. For example, interfacing stationary solid-state qubits with photonic quantum states would open up a pathway towards the realization of a quantum network with extended quantum processing capacity in each node. While gated devices allow very flexible confinement of electrons or holes, the confinement of excitons without some element of self-assembly is much harder. To address this limitation, we introduce a technique to realize exciton traps in quantum wells via local electric fields by thinning a heterostructure down to a 220-nm-thick membrane. We show that mobilities over $1\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.2em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.2em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ can be retained and that quantum point contacts and Coulomb oscillations can be observed on this structure, which implies that the thinning does not compromise the heterostructure quality. Furthermore, the local lowering of the exciton energy via the quantum-confined Stark effect is confirmed, thus forming exciton traps. These results lay the technological foundations for devices like single-photon sources, spin-photon interfaces and eventually quantum network nodes in $\mathrm{Ga}\mathrm{As}$ quantum wells, realized entirely with a top-down fabrication process.

Interlaced CoOx Nanosheets Composited with Reduced Graphene Oxide and Carbonized Bacterial Cellulose as Anode Materials for Lithium‐ion Batteries

AbstractConstructing peculiar carbon‐based networks built from hybrid structures has been considered as an effective approach to establish a superior scaffold for immobilization of nanoparticles. Herein, we demonstrate a facile and green approach to prepare cobalt oxides (CoOx)‐based anode, which is realized by rationally exploiting unique properties of carbonized bacterial cellulose (CBC) and graphene (GN). The unique configuration of GN/CoOx/CBC composite fully enables utilization of the synergistic effects from both three‐dimensional nanofibrous network and two‐dimensional “flexible confinement” function. Benefiting from their intriguing structural features, the synthesized composite is directly used as electrode for lithium‐ion batteries (LIBs), and achieves superior flexibility and reliability, enhanced energy/power density and outstanding cycling stability.

Single-crystal MAPbI3 microwire arrays by a bilayer flexible interface confinement method for photodetectors

High-quality MAPbI3 single-crystal microwires were synthesized by a facile bilayer flexible interface confinement method for high-performance photodetectors.

Suspended water droplet confined laser shock processing at elevated temperatures

The temperature-assisted laser shock process has application prospects in various manufacturing fields such as forming and surface strengthening. However, the large-scale application of this process is limited by the instability and failure of confinement medium at high temperatures (>300 °C). To address this problem, this paper proposes a novel laser shock strategy based on the Leidenfrost effect, wherein suspended droplets are used as the confinement medium. The dynamic behaviors of the droplets during laser shock process were studied. The focusing enhancement effect of the droplets was comprehensively explored. By combining the dynamic behaviors and focusing enhancement effect of the droplets, a theoretical model of the laser shock pressure under droplet confinement was established. Finally, a typical application of the droplet-confined laser shock process in the fields of forming and strengthening was demonstrated to verify its effectiveness and feasibility at high temperatures. The proposed process provides a flexible, convenient, and green plasma confinement strategy that allows stable operation of laser shock at high temperatures. Moreover, the droplet confinement strategy broadens the application prospects of laser shock, and provides a technical support for enabling enhanced ductility and dynamic strain aging of alloys at high temperatures.

Flexible Confinement and Manipulation of Mie Resonances via Nano Rectangular Hollow Metasurfaces

AbstractMie resonances excited in high‐index all‐dielectric metasurfaces provide a powerful platform for the constraint and manipulation of light at the subwavelength scale, which enable tremendous advanced developments in optical field manipulation, imaging, and sensing. Recently, how to manipulate and confine Mie resonances in the frequency domain has attracted tremendous interest since it is invaluable for the implementation of frequency‐selective and ‐multiplexed optical devices. Here, the authors theoretically analyze and experimentally demonstrate that the nano rectangular hollow (NRH) metasurfaces are promising candidates for the flexible confinement and effective manipulation of Mie resonances in the frequency domain. They reveal that the diameter of the hollow in the NRH can provide an efficient degree of freedom for the constraint of displace currents in the space domain, which results in the confinement of Mie resonances in the frequency domain. The excitation wavelength of the Mie resonance can also be manipulated by adjusting the side length of the NRH. The potential uses of NRH metasurfaces in the implementation of frequency‐selective intensity encoding and optical encryption are theoretically and experimentally demonstrated. The results provide a fertile ground for confining Mie resonances in the frequency domain and can be further applied in frequency‐multiplexed optical devices.

Quantifying the hierarchy of structural and mechanical length scales in granular systems

Continuum modeling of granular media is made possible by the existence of a length scale at and above which grain-resolved properties can be meaningfully homogenized. Progress has been made in identifying such length scales relevant to local structural properties such as porosity. However, a systematic analysis of scales above which different mechanical properties can be homogenized has yet to emerge. Here, X-ray tomography and 3D X-ray diffraction data are examined to identify such length scales. The data was obtained in-situ in compressed granular materials with rigid and flexible confinement. The experimental data are supplemented with validated discrete element simulations which examine different system sizes and different boundary conditions. Our study reveals a hierarchy in the length scales of granular solids, with lengths governing structural variables being the shortest, lengths of stress variables being intermediate, and lengths of energy dissipation being the longest. All structural and mechanical length scales obey a power law based on the theory of Geostatistics, implying that the length scales can be found by analyzing samples significantly smaller than the length scales themselves. The length scales are also found to be sensitive to boundary conditions, implying that they are extrinsic features of granular media.

Novel Confinement Possibility for Laser Shock: Use of Flexible Polymer Confinement at 1064 nm Wavelength

Through the years, laser shock peening became a treatment of choice in the aerospace industry to prolong the life of certain critical pieces. Water flow is commonly used as a confinement to improve the process capability but some applications cannot allow for water presence in the area of interest. In a previous article, an alternative to the water confinement was presented, a flexible polymer confinement was used and demonstrated the production of pressures equivalent to the water configuration treatment. However, laser parameters have been restricted to a wavelength in the visible range at 532 nm. In this paper, the study is extended to 1064 nm which is commonly used in LSP applications and with two different pulse durations. A 1064 nm near infra-red laser is used to do pressure characterization of shots with polymer confinement through Velocity Interferometer System for Any Reflector (VISAR) measurements coupled with Finite Element Modelling on Abaqus software. The results show that the pressures produced by the confinement is slightly lower with the 1064 nm wavelength, similar to what is observed with the classic water confined regime when switching from 532 nm to a near infra-red wavelength. Nevertheless, the high level of pressure produced by laser shock under the polymer confinement configuration allows for the treatment of common types of metal alloys used in the aerospace industry. Although the use of such a confinement has yet to be applicable to peening setups, it has already uses in some single shot configurations such as LasAT where it allows the avoidance of the water flow optimization.

Bismuth oxide self-standing anodes with concomitant carbon dots welded graphene layer for enhanced performance supercapacitor-battery hybrid devices

To meet the energy storage demand of developing electronic information technology, the supercapacitor-battery hybrid devices based on Bi2O3 have attracted much attention due to their superior energy storage characteristics. However, the poor cycling stability limits its application. Herein, through the nano-welding technique induced by the microwave thermal effect of graphene, the carbon nanotube film-supported Bi2O3 electrode with a graphene/carbon dots encapsulation structure is fabricated. The as-prepared composite electrode delivers a remarkable capacity of 1.90 mAh cm−2 at 1 mA cm−2 as well as high rate performance (1.57 mAh cm−2 at 100 mA cm−2). Assembled device with above composite electrode as anode and the carbon nanotube loaded nickel cobalt as cathode exhibits a maximum energy density of 589.3 μWh cm−2 (98.2 Wh kg−1) at power density of 0.8 mW cm−2 and maintain 288.3 μWh cm−2 (48.1 Wh kg−1) at 57.1 mW cm−2. Most notably, by virtue of the flexible confinement of graphene, the device exhibits impressive cycle stability (80.1% capacity retention after 8000 cycles, ∼4.5 times than that of a device assembled with a raw anode). This work opens a new pathway to the design and fabrication for high energy density and durable cyclic stability energy storage devices.

Microstructure Formation of Functional Polymers by Evaporative Self-Assembly under Flexible Geometric Confinement.

Polymer microstructures are widely used in optics, flexible electronics, and so forth. We demonstrate a cost-effective bottom-up manner for patterning polymer microstructures by evaporative self-assembly under a flexible geometric confinement at a high temperature. Two-parallel-plates confinement would become curve-to-flat shape geometric confinement as the polydimethylsiloxane (PDMS) cover plate deformed during solvent swelling. We found that a flexible cover plate would be favorable for the formation of gradient microstructures, with various periodicities and widths obtained at varied heights of clearance. After thermal annealing, the edge of the PMMA (Poly-methylmethacrylate) microstructures would become smooth, while the RR-P3HT (regioregular-poly(3-hexylthiophene)) might generate nanocrystals. The morphologies of RR-P3HT structures included thick films, straight lines, hierarchical stripes, incomplete stripes, and regular dots. Finally, a simple field-effect transistor (FET) device was demonstrated with the RR-P3HT micropattern as an active layer.

Coexistence of Multilayered Phases of Confined Water: The Importance of Flexible Confining Surfaces.

Flexible nanoscale confinement is critical to understanding the role that bending fluctuations play on biological processes where soft interfaces are ubiquitous or to exploit confinement effects in engineered systems where inherently flexible 2D materials are pervasively employed. Here, using molecular dynamics simulations, we compare the phase behavior of water confined between flexible and rigid graphene sheets as a function of the in-plane density, ρ2D. We find that both cases show commensurate mono-, bi-, and trilayered states; however, the water phase in those states and the transitions between them are qualitatively different for the rigid and flexible cases. The rigid systems exhibit discontinuous transitions between an (n)-layer and an (n+1)-layer state at particular values of ρ2D, whereas under flexible confinement, the graphene sheets bend to accommodate an (n)-layer and an (n+1)-layer state coexisting in equilibrium at the same density. We show that the flexible walls introduce a very different sequence of ice phases and their phase coexistence with vapor and liquid phases than that observed with rigid walls. We discuss the applicability of these results to real experimental systems to shed light on the role of flexible confinement and its interplay with commensurability effects.

Research status and development of laser shock peening

Laser shock peening (LSP) is a noncontact surface strengthening technology. It has been widely used because of its advantages in applied scope and strengthening effects. LSP has made considerable progress during the past four decades, but some technical issues affecting their applications remain to be resolved, for instance, the utilization rate of laser shock energy is only about 50%, the processing adaptability of rigid confinement layer is poor, and the thickness of the flexible confinement layer represented by a water layer is difficult to control. In this paper, the current research status of LSP technology was reviewed, and an outlook was given toward further development of this technology. On this basis, a method to form composite shock waves by designing a cavity to confine the water layer is presented in this paper, which is expected to address the issues mentioned above. A preliminary simulation for analyzing the relationship between the strengthening effect and the characteristic parameters of the composite shock wave was carried out, and the simulated results were discussed. The results show that the time interval between the adjacent waves and the wave attenuation factor have significant influence on the strengthening effects, which is helpful to the cavity design.

High efficiency immobilization of sulfur on Ce-doped carbon aerogel for high performance lithium-sulfur batteries

A sulfur-carbon composite from sulfur and carbon aerogel decorated with ultrafine CeO2 nanoparticles has been prepared by a conventional sol-gel strategy as a host material of the sulfur cathodes for lithium-sulfur batteries. The physical and electrochemical properties of the prepared composite materials have been evaluated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 sorption isotherms, X-ray photoelectron spectroscopy and electrochemical measurements. Apart from offering flexible confinement function, carbon aerogels decorated with CeO2 are also found to suppress the loss of polysulfide ions. The Ce2-CA/S cathode with Ce/C molar ratio of 0.0233 delivers high initial discharge capacity of 1381mAhg−1 at 0.2 C and remains 1127.6mAhg−1 after 100 cycles. The sulfur electrodes have excellent rate performance with initial discharge capacity of 768.5 mAh g−1 at 5 C.

Packing of elastic wires in flexible shells

The packing problem of long thin filaments that are injected into confined spaces is of fundamental interest for physicists and biologists alike. How linear threads pack and coil is well known only for the ideal case of rigid containers, though. Here, we force long elastic rods into flexible spatial confinement borne by an elastic shell to examine under which conditions recently acquired knowledge on wire packing in rigid spheres breaks down. We find that unlike in rigid cavities, friction plays a key role by giving rise to the emergence of two distinct packing patterns. At low friction, the wire densely coils into an ordered toroidal bundle with semi-ellipsoidal cross-section, while at high friction, it packs into a highly disordered, hierarchic structure. These two morphologies are shown to be separated by a continuous phase transition. Our findings demonstrate the dramatic impact of friction and confinement elasticity on filamentous packing and might drive future research on such systems in physics, biology and even medical technology toward including these mutually interacting effects.

Graphene-Coated Silicon Alloy with High Capacity and Good Cycling Stability for Lithium-Ion Batteries

The growing demand for high-performance energy storage devices for applications in portable electronic devices, electric vehicles and energy storage systems requires dramatic improvement in the energy density and cycle life. Silicon-based anode materials hold promise for these applications due to their high theoretical capacity and abundant availability for large-scale applications. However, silicon anodes are known to have problems such as electrode pulverization due to its high volume expansion during repeated cycling and poor cycle life due to unstable solid-electrolyte interphase (SEI) layer. To solve these problems, many studies have been carried out in terms of thin film, nanostructure, alloy and composites. In this work, we synthesized Si-based alloy materials with high specific capacity. To improve their cycling stability, the silicon alloy materials were surface modified with reduced graphene oxide (rGO). The rGO layer formed on the Si alloy played as a flexible confinement for accommodating volume changes during cycling. And also, its high mechanical strength prevented the pulverization of the electrode. In addition, its 2-dimensional structure enabled to electronically connect the individual Si alloy particles to the current collector. Their interfacial studies and cycling performances are investigated by electrochemical impedance spectroscopy, XPS, FE-SEM, HR-TEM and cycling test. Detailed characterization of the rGO-coated silicon alloy materials along with their electrochemical performance will be presented.

Flexible confinement leads to multiple relaxation regimes in glassy colloidal liquids.

Understanding relaxation of supercooled fluids is a major challenge and confining such systems can lead to bewildering behaviour. Here, we exploit an optically confined colloidal model system in which we use reduced pressure as a control parameter. The dynamics of the system are "Arrhenius" at low and moderate pressure, but at higher pressures relaxation is faster than expected. We associate this faster relaxation with a decrease in density adjacent to the confining boundary due to local ordering in the system enabled by the flexible wall.

Integrated SnO2 nanorod array with polypyrrole coverage for high-rate and long-life lithium batteries.

Conversion/alloying reactions, in which more lithium ions are involved, are severely handicapped by the dramatic volume changes. A facile and versatile strategy has been developed for integrating the SnO2 nanorod array in the PPy nanofilm for providing a flexible confinement for anchoring each nanorod and maintaining the entire structural integrity and providing sustainable contact; therefore, exhibiting much more stable cycling stability (701 mA h g(-1) after 300 cycles) and better high-rate capability (512 mA h g(-1) at 3 A g(-1)) when compared with the core-shell SnO2-PPy NA.

Simulation of electric potentials and ion motion in planar electrode structures for lossless ion manipulations (SLIM).

We report a conceptual study and computational evaluation of novel planar electrode structures for lossless ion manipulations (SLIM). Planar electrode SLIM components were designed that allow for flexible ion confinement, transport, and storage using a combination of radio frequency (rf) and DC fields. Effective potentials can be generated that provide near ideal regions for confining and manipulating ions in the presence of a gas. Ion trajectory simulations using SIMION 8.1 demonstrated the capability for lossless ion motion in these devices over a wide m/z range and a range of electric fields at low pressures (e.g., a few Torr). More complex ion manipulations (e.g., turning ions by 90(o) and dynamically switching selected ion species into orthogonal channels) are also shown feasible. The performance of SLIM devices at ~4 Torr pressure for performing ion mobility-based separations (IMS) is computationally evaluated and compared with initial experimental results, and both are also shown to agree closely with experimental and theoretical IMS performance for a conventional drift tube design.

Surface Phase Transition in Anomalous Fluid in Nanoconfinement

We explore by molecular dynamic simulations the thermodynamical behavior of an anomalous fluid confined inside rigid and flexible nanopores. The fluid is modeled by a two length scale potential. In the bulk, this system exhibits the density and diffusion anomalous behavior observed in liquid water. We show that the anomalous fluid confined inside rigid and flexible nanopores forms layers. As the volume of the nanopore is decreased the rigid surface exhibits three consecutive first-order phase transitions associated with the change in the number of layers. These phase transitions are not present for flexible confinement. Our results indicate that the nature of confinement is relevant for the properties of the confined liquid, which suggests that confinement in carbon nanotubes should be quite different from confinement in biological channels.

A Scalable Graphene Sulfur Composite Synthesis for Rechargeable Lithium Batteries with Good Capacity and Excellent Columbic Efficiency

Sulfur nanoparticles wrapped with a conductive graphene framework was synthesized with a high sulfur loading through a scalable one-step process. The graphene-coated sulfur nanostructured composite, when used as cathode for lithium sulfur battery, shows a reversible capacity of 808 mAh g(-1) at a rate of 210 mA g(-1) and an average columbic efficiency of ∼98.3% over 100 cycles. It is found that graphene oxide (GO) with a porous structure offers flexible confinement function that helps prevent the loss of active materials, thus extending the cycling life of the electrode. Moreover, reduced graphene oxide provides a conductive network surrounding the sulfur particles, which facilitates both electron transport and ion transportation. This novel one-step, all-solution-based process is scalable and provides a promising approach for potential industrial applications.