Active Encapsulation in Biocompatible Nanocapsules

Co‐precipitation is generally refers to the co‐precipitation of two solids and is widely used to prepare active‐loaded nanoparticles. Here, it is demonstrated that liquid and solid can precipitate simultaneously to produce hierarchical core–shell nanocapsules that encapsulate an oil core in a polymer shell. During the co‐precipitation process, the polymer preferentially deposits at the oil/water interface, wetting both the oil and water phases; the behavior is determined by the spreading coefficients and driven by the energy minimization. The technique is applicable to directly encapsulate various oil actives and avoid the use of toxic solvent or surfactant during the preparation process. The obtained core–shell nanocapsules harness the advantage of biocompatibility, precise control over the shell thickness, high loading capacity, high encapsulation efficiency, good dispersity in water, and improved stability against oxidation. The applications of the nanocapsules as delivery vehicles are demonstrated by the excellent performances of natural colorant and anti‐cancer drug‐loaded nanocapsules. The core–shell nanocapsules with a controlled hierarchical structure are, therefore, ideal carriers for practical applications in food, cosmetics, and drug delivery.     

Colloid‐Interface‐Assisted Laser Irradiation of Nanocrystals Superlattices to be Scalable Plasmonic Superstructures with Novel Activities

High‐efficient charge and energy transfer between nanocrystals (NCs) in a bottom‐up assembly are hard to achieve, resulting in an obstacle in application. Instead of the ligands exchange strategies, the advantage of a continuous laser is taken with optimal wavelength and power to irradiate the film‐scale NCs superlattices at solid–liquid interfaces. Owing to the Au‐based NCs' surface plasmon resonance (SPR) effect, the gentle laser irradiation leads the Au NCs or Au@CdS core/shell NCs to attach each other with controlled pattern at the interfaces between solid NCs phase and liquid ethanol/ethylene glycol. A continuous wave 532 nm laser (6.68–13.37 W cm^?2), to control Au‐based superlattices, is used to form the monolayer with uniformly reduced interparticle distance followed by welded superstructures. Considering the size effect to Au NCs' melting, when decreasing the Au NCs size to ≈5 nm, stronger welding nanostructures are obtained with diverse unprecedented shapes which cannot be achieved by normal colloidal synthesis. With the help of facile scale‐up and formation at solid–liquid interfaces, and a good connection of crystalline between NCs, the obtained plasmonic superstructured films that could be facilely transferred onto different substrates exhibit broad SPR absorption in the visible and near‐infrared regime, enhanced electric conductivities, and wide applications as surface enhanced Raman scattering (SERS)‐active substrates.     

Self‐Assembly of Graphene Oxide at Interfaces

Due to its amphiphilic property, graphene oxide (GO) can achieve a variety of nanostructures with different morphologies (for example membranes, hydrogel, crumpled particles, hollow spheres, sack‐cargo particles, Pickering emulsions, and so on) by self‐assembly. The self‐assembly is mostly derived from the self‐concentration of GO sheets at various interfaces, including liquid‐air, liquid‐liquid and liquid‐solid interfaces. This paper gives a comprehensive review of these assembly phenomena of GO at the three types of interfaces, the derived interfacial self‐assembly techniques, and the as‐obtained assembled materials and their properties. The interfacial self‐assembly of GO, enabled by its fantastic features including the amphiphilicity, the negatively charged nature, abundant oxygen‐containing groups and two‐dimensional flexibility, is highlighted as an easy and well‐controlled strategy for the design and preparation of functionalized carbon materials, and the use of self‐assembly for uniform hybridization is addressed for preparing hybrid carbon materials with various functions. A number of new exciting and potential applications are also presented for the assembled GO‐based materials. This contribution concludes with some personal perspectives on future challenges before interfacial self‐assembly may become a major strategy for the application‐targeted design and preparation of functionalized carbon materials.     

Freestanding Nanostructures via Layer‐by‐Layer Assembly

Freestanding flexible nanocomposite structures fabricated by layer‐by‐layer (LbL) assembly are promising candidates for many potential applications, such as in the fields of thermomechanical sensing, controlled release, optical detection, and drug delivery. In this article, we review recent advances in the fabrication and characterization of different types of freestanding LbL structures in air and at air/liquid and liquid/liquid interfaces, including micro‐ and nanocapsules, microcantilevers, freely suspended membranes, encapsulated nanoparticle arrays, and sealed‐cavity arrays. Several recently developed fabrication techniques, such as spin‐assisted coating, dipping, and micropatterning, make the assembly process more efficient and impart novel physical properties to the freestanding films.     

Supramolecular Crystal Engineering at the Solid–Liquid Interface from First Principles: Toward Unraveling the Thermodynamics of 2D Self‐Assembly

The formation of highly ordered 2D supramolecular architectures self‐assembled at the solid–solution interfaces is subject to complex interactions between the analytes, the solvent, and the substrate. These forces have to be mastered in order to regard self‐assembly as an effective bottom‐up approach for functional‐device engineering. At such interfaces, prediction of the thermodynamics governing the formation of spatially ordered 2D arrangements is far from being fully understood, even for the physisorption of a single molecular component on the basal plane of a flat surface. Two recent contributions on controlled polymorphism and nanopattern formation render it possible to gain semi‐quantitative insight into the thermodynamics of physisorption at interfaces, paving the way towards 2D supramolecular crystal engineering. Although in these two works different systems have been chosen to tackle such a complex task, authors showed that the chemical design of molecular building blocks is not the only requirement to fulfill when trying to preprogram self‐assembled patterns at the solid–liquid interface.     

Acoustic sensors for the control of liquid–solid interface evolution and chemical reactivity

Less classical than far-field acoustic investigations of solid materials and/or solid–liquid interfaces, near-field acoustic properties of an acoustic solid wave guide (tip), thin enough at its termination to present an external diameter smaller than the excitation acoustic wave wavelength, is shown to be able to probe interface properties. As a result of that, these near-field acoustic probes can play the role of chemical sensors, if chemical modifications or chemical reactions are concerned at their surface. In that context, a chemical sensor was realized by electrochemical deposition of an electron-conducting polymer (polypyrrole–biotin) on a metal tip, followed by enzyme attachment by molecular recognition process involving the biotin–avidin-specific interaction. Results from near-field acoustic showed that the enzyme modification of the polymer layer can be detected by this new acoustic sensor.     

Ordered Arrangement and Optical Properties of Silica‐Stabilized Gold Nanoparticle–PNIPAM Core–Satellite Clusters for Sensitive Raman Detection

Gold–polymer hybrid nanoparticles attract wide interest as building blocks for the engineering of photonic materials and plasmonic (active) metamaterials with unique optical properties. In particular, the coupling of the localized surface plasmon resonances of individual metal nanostructures in the presence of nanometric gaps can generate highly enhanced and confined electromagnetic fields, which are frequently exploited for metal‐enhanced light–matter interactions. The optical properties of plasmonic structures can be tuned over a wide range of properties by means of their geometry and the size of the inserted nanoparticles as well as by the degree of order upon assembly into 1D, 2D, or 3D structures. Here, the synthesis of silica‐stabilized gold–poly(N‐isopropylacrylamide) (SiO₂‐Au‐PNIPAM) core–satellite superclusters with a narrow size distribution and their incorporation into ordered self‐organized 3D assemblies are reported. Significant alterations of the plasmon resonance are found for different assembled structures as well as strongly enhanced Raman signatures are observed. In a series of experiments, the origin of the highly enhanced signals can be assigned to the interlock areas of adjacent SiO₂‐Au‐PNIPAM core–satellite clusters and their application for highly sensitive nanoparticle‐enhanced Raman spectroscopy is demonstrated.     

Integrated Circuits Comprising Patterned Functional Liquids

Solid‐state heterostructures are the cornerstone of modern electronics. To enhance the functionality and performance of integrated circuits, the spectrum of materials used in the heterostructures is being expanded by an increasing number of compounds and elements of the periodic table. While the integration of liquids and solid–liquid interfaces into such systems would allow unique and advanced functional properties and would enable integrated nanoionic circuits, solid‐state heterostructures that incorporate liquids have not been considered thus far. Here solid‐state heterostructures with integrated liquids are proposed, realized, and characterized, thereby opening a vast, new phase space of materials and interfaces for integrated circuits. Devices containing tens of microscopic capacitors and field‐effect transistors are fabricated by using integrated patterned NaCl aqueous solutions. This work paves the way to integrated electronic circuits that include highly integrated liquids, thus yielding a wide array of novel research and application opportunities based on microscopic solid/liquid systems.     

Capillary Assembly of Liquid Particles

Capillary assembly is a versatile method for depositing colloidal particles within templates, resulting in nano/microarrays and colloidal superstructures for optical, plasmonic, and sensory applications. Liquid particles (LPs), comprised of oligomerized 3‐(trimethoxysilyl)propyl methacrylate, are herein shown to deposit into patterned cavities via capillary assembly. In contrast to solid colloids, LPs coalesce upon solvent evaporation and assume the geometry of the template. Incorporating small molecules such as dyes followed by LP solidification generates fluorescent polymer microarrays of any geometry. The LP size is inversely proportional to the quantity of deposited material and the convexity of the final polymer array. Cavity filling can be tuned by increasing the assembly temperature. Extraction of the polymerized regions produces solidified particles with faceted shapes including square prisms, trapezoids, and ellipsoids with sizes up to 14 µm that retain the shape of the cavity in which they are initially held. LP deposition thus presents a highly controllable fabrication scheme for geometrically diverse polymer microarrays and anisotropic colloids of any conceivable polygonal shape due to space filling of the template. The extension of capillary assembly to LPs that can be doped with small molecule dyes and analytes invaluably expands the synthetic toolbox for top‐down, scalable, hierarchically engineered materials.     

Factors determining the diameter of silicon carbide whiskers prepared by chemical vapor deposition

Since the whisker diameter is one of the important parameters for determining the characteristics of whisker-related systems, an understanding of the factors that affect its size is of great value for whisker preparation. In this study, chemical vapor deposition (CVD) of silicon carbide (SiC) whiskers using a gas mixture of methyltrichlorosilane and hydrogen has been conducted in a hot-wall reactor on graphite plates coated with Ni as a liquid-forming agent. The deposited SiC whiskers are then characterized by scanning electron microscopy (SEM) to determine their nucleation and growth behavior. Experimental results show that the diameter of SiC whiskers is determined by both the vapor—liquid—solid (VLS) mechanism and vapor—solid (VS) radial deposition, where the former is affected by the area of the solid—liquid interface from which the crystal precipitates and the latter by the thickening kinetics of vapor-deposited SiC on the lateral face. However, a comparison of the two factors indicates that an appropriate choice of the diameter of liquid droplets for VLS whisker growth is more effective than radial VS deposition for obtaining whiskers of desired diameters.     

3D,Reconfigurable, Multimodal Electronic Whiskers via Directed Air Assembly

A batch‐assembly technique for forming 3D electronics on shape memory polymer substrates is demonstrated and is used to create dense, highly sensitive, multimodal arrays of electronic whiskers. Directed air flow at temperatures above the substrate's glass transition temperature transforms planar photolithographically defined resistive sensors from 2D precursors into shape‐tunable, deterministic 3D assemblies. Reversible 3D assembly and flattening is achieved by exploiting the shape memory properties of the substrate, enabling context‐driven shape reconfiguration to isolate/enhance specific sensing modes. In particular, measurement schemes and device configurations are introduced that allow for the sensing of temperature, stiffness, contact force, proximity, and surface texture and roughness. The assemblies offer highly spatiotemporally resolved, wide‐range measurements of surface topology (50 nm to 500 µm), material stiffness (200 kPa to 7.5 GPa), and temperature (0–100 °C), with response times of <250 µs. The development of a scalable process for 3D assembly of reconfigurable electronic sensors, as well as the large breadth and sensitivity of complex sensing modes demonstrated, has applications in the growing fields of 3D assembly, electronic skin, and human–machine interfaces.     

High-yield assembly of soluble and stable gold nanorod pairs for high-temperature plasmonics

Colloidal synthetic approaches to discrete, soluble plasmonic architectures, such as nanorod pairs, offer numerous advantages relative to lithographic techniques, including compositionally asymmetric structures, atomically smooth surfaces, and continuous fabrication. Density‐driven colloidal assembly, such as by solvent evaporation, produces some intriguing structures, e.g., particle chains; however, controllability and post‐processibility of the final architecture is inadequate. Also the limited quantity of product nominally comprises a broad distribution of assembly size and type. Herein, the high‐yield formation of soluble, stable, and compositionally discrete gold nanorod (Au NR) architectures by inducing—then arresting—flocculation is demonstrated using bifunctional nanorods and reversible modulation of solvent quality to deplete and reassemble an electrostatic stabilization layer, thereby eliminating the need for an additional encapsulant. Analogous to dimer formation during step‐growth polymerization, the initial yield of Au nanorod side‐by‐side pairs can be greater than 50%. The high solubility and stability of the assembly enable purification, scale‐up of nanomolarity solutions, and subsequent chemical modification of the assembled product. As an example, in situ silica deposition via Stöber synthesis onto the assembled pair produces highly processable nanostructures with a single pair of embedded Au NRs at their center, which exhibit thermal stability at temperatures in excess of 700 °C.     

Rapid Open‐Air Digital Light 3D Printing of Thermoplastic Polymer

3D printing has witnessed a new era in which highly complexed customized products become reality. Realizing its ultimate potential requires simultaneous attainment of both printing speed and product versatility. Among various printing techniques, digital light processing (DLP) stands out in its high speed but is limited to intractable light curable thermosets. Thermoplastic polymers, despite their reprocessibility that allows more options for further manipulation, are restricted to intrinsically slow printing methods such as fused deposition modeling. Extending DLP to thermoplastics is highly desirable, but is challenging due to the need to reach rapid liquid–solid separation during the printing process. Here, a successful attempt at DLP printing of thermoplastic polymers is reported, realized by controlling two competing kinetic processes (polymerization and polymer dissolution) simultaneously occurring during printing. With a selected monomer, 4‐acryloylmorpholine (ACMO), printing of thermoplastic 3D scaffolds is demonstrated, which can be further converted into various materials/devices utilizing its unique water‐soluble characteristic. The ultralow viscosity of ACMO, along with surface oxygen inhibition, allows rapid liquid flow toward high‐speed open‐air printing. The process simplicity, enabling mechanism, and material versatility broaden the scope of 3D printing in constructing functional 3D devices including reconfigurable antenna, shape‐shifting structures, and microfluidics.     

Building Reconfigurable Devices Using Complex Liquid–Fluid Interfaces

Liquid–fluid interfaces provide a platform both for structuring liquids into complex shapes and assembling dimensionally confined, functional nanomaterials. Historically, attention in this area has focused on simple emulsions and foams, in which surface‐active materials such as surfactants or colloids stabilize structures against coalescence and alter the mechanical properties of the interface. In recent decades, however, a growing body of work has begun to demonstrate the full potential of the assembly of nanomaterials at liquid–fluid interfaces to generate functionally advanced, biomimetic systems. Here, a broad overview is given, from fundamentals to applications, of the use of liquid–fluid interfaces to generate complex, all‐liquid devices with a myriad of potential applications.     

Directional Solution Coating by the Chinese Brush: A Facile Approach to Improving Molecular Alignment for High‐Performance Polymer TFTs

Directional solution coating by the Chinese brush provides a facile approach to fabricate highly oriented polymer thin films by finely controlling the wetting and dewetting processes under directional stress. The biggest advantage of the Chinese brush over the normal western brush is the freshly emergent hairs used, whose unique tapered structure renders a dynamic balance of the liquid within the brush by multiple forces when interacting with the liquid. Consequently, the liquid is steadily held within the brush without any unexpected leakage, making the liquid transfer proceed in a well‐controllable manner. It is demonstrated that the Chinese brush coating enables the crystallization of the polymer and the self‐assembly of conjugated backbones to proceed in a quasi‐steady state via a certain direction, which is attributed to the controllable receding of the three‐phase contact line during the dewetting process by the multiple parallel freshly emergent hairs. The as‐prepared polymer thin films exhibit over six times higher charge‐carrier mobility compared to the spin‐coated films, which therefore provides a general approach for high‐performance organic thin‐film transistors.     

Dynamically Tuning Particle Interactions and Assemblies at Soft Interfaces: Reversible Order–Disorder Transitions in 2D Particle Monolayers

Particles trapped at fluid interfaces experience long‐range interactions that determine their assembly behavior. Because particle interactions at fluid interfaces tend to be unusually strong, once particles organize themselves into a 2D assembly, it is challenging to induce changes in their microstructure. In this report, a new approach is presented to induce reversible order–disorder transitions (ODTs) in the 2D monolayer of colloidal particles trapped at a soft gel–fluid interface. Particles at the soft interface, consisting of a nonpolar superphase and a weakly gelled subphase, initially form a monolayer with a highly ordered structure. The structure of this monolayer can be dynamically varied by the addition or removal of the oil phase. Upon removing the oil via evaporation, the initially ordered particle monolayer undergoes ODT, driven by capillary attractions. The ordered monolayer can be recovered through disorder‐to‐order transition by simply adding oil atop the particle‐laden soft interface. The possibility to dynamically tune the interparticle interactions using soft interfaces can potentially enable control of the transport and mechanical properties of particle‐laden interfaces and provide model systems to study particle‐laden soft interfaces that are relevant to biological tissues or organs.     

Direct Growth of High Mobility and Low‐Noise Lateral MoS2–Graphene Heterostructure Electronics

Reliable fabrication of lateral interfaces between conducting and semiconducting 2D materials is considered a major technological advancement for the next generation of highly packed all‐2D electronic circuitry. This study employs seed‐free consecutive chemical vapor deposition processes to synthesize high‐quality lateral MoS₂–graphene heterostructures and comprehensively investigated their electronic properties through a combination of various experimental techniques and theoretical modeling. These results show that the MoS₂–graphene devices exhibit an order of magnitude higher mobility and lower noise metrics compared to conventional MoS₂–metal devices as a result of energy band rearrangement and smaller Schottky barrier height at the contacts. These findings suggest that MoS₂–graphene in‐plane heterostructures are promising materials for the scale‐up of all‐2D circuitry with superlative electrical performance.     

Ink‐on‐Probe Hydrodynamics in Atomic Force Microscope Deposition of Liquid Inks

The controlled deposition of attolitre volumes of liquids may engender novel applications such as soft, nano‐tailored cell‐material interfaces, multi‐plexed nano‐arrays for high throughput screening of biomolecular interactions, and localized delivery of reagents to reactions confined at the nano‐scale. Although the deposition of small organic molecules from an AFM tip, known as dip‐pen nanolithography (DPN), is being continually refined, AFM deposition of liquid inks is not well understood, and is often fraught with inconsistent deposition rates. In this work, the variation in feature‐size over long term printing experiments for four model inks of varying viscosity is examined. A hierarchy of recurring phenomena is uncovered and there are attributed to ink movement and reorganisation along the cantilever itself. Simple analytical approaches to model these effects, as well as a method to gauge the degree of ink loading using the cantilever resonance frequency, are described. In light of the conclusions, the various parameters which need to be controlled in order to achieve uniform printing are dicussed. This work has implications for the nanopatterning of viscous liquids and hydrogels, encompassing ink development, the design of probes and printing protocols.     

Metal Ion‐Induced Self‐Assembly of a Multi‐Responsive Block Copolypeptide into Well‐Defined Nanocapsules

Protein cages are an interesting class of biomaterials with potential applications in bionanotechnology. Therefore, substantial effort is spent on the development of capsule‐forming designer polypeptides with a tailor‐made assembly profile. The expanded assembly profile of a triblock copolypeptide consisting of a metal ion chelating hexahistidine‐tag, a stimulus‐responsive elastin‐like polypeptide block, and a pH‐responsive morphology‐controlling viral capsid protein is presented. The self‐assembly of this multi‐responsive protein‐based block copolymer is triggered by the addition of divalent metal ions. This assembly process yields monodisperse nanocapsules with a 20 nm diameter composed of 60 polypeptides. The well‐defined nanoparticles are the result of the emergent properties of all the blocks of the polypeptide. These results demonstrate the feasibility of hexahistidine‐tags to function as supramolecular cross‐linkers. Furthermore, their potential for the metal ion‐mediated encapsulation of hexahistidine‐tagged proteins is shown.     

Carbon Nanolights in Piezopolymers are Self‐Organizing Toward Color Tunable Luminous Hybrids for Kinetic Energy Harvesting

Herein, an all‐solid‐state sequential self‐organization and self‐assembly process is reported for the in situ construction of a color tunable luminous inorganic/polymer hybrid with high direct piezoresponse. The primary inorganic self‐organization in solid polymer and the subsequent polymer self‐assembly are achieved at high pressure with the first utilization of piezo‐copolymer (PVDF‐TrFE) as the host matrix of guest carbon quantum dots (CQDs). This process induces the spontaneous formation of a highly ordered, microscale, polygonal, and hierarchically structured CQDs/PVDF‐TrFE hybrid with multicolor photoluminescence, consisting of very thermodynamic stable polar crystalline nanowire arrays. The electrical polarization‐free CQDs/PVDF‐TrFE hybrids can efficiently harvest the environmental available kinetic mechanical energy with a new large‐scale group‐cooperation mechanism. The open‐circuit voltage and short‐circuit current outputs reach up to 29.6 V cm^?2 and 550 nA cm^?2, respectively. The CQDs/PVDF‐TrFE–based hybrid nanogenerator demonstrates drastically improved durable and reliable features during the real‐time demonstration of powering commercial light emitting diodes. No attenuation/fluctuation of the electrical signals is observed for ≈10 000 continuous working cycles. This study may offer a new design concept for progressively but spontaneously constructing novel multiple self‐adaptive complex inorganic/polymer hybrids that promise applications in the next generation of self‐powered autonomous optoelectronic devices.