Carbohydrate‐Based Block Copolymer Thin Films: Ultrafast Nano‐Organization with 7 nm Resolution Using Microwave Energy

Block copolymers (BCP) can self‐assemble into nanoscale patterns with a wide variety of applications in the semiconductor industry. The self‐assembly of BCPs is commonly accomplished by solvent vapor or thermal annealing, but generally these methods require long time (few hours) to obtain nanostructured thin films. In this contribution, a new and ultrafast method (using microwaves) is proposed—high temperature solvent vapor annealing (HTSVA), combining solvent vapor annealing with thermal annealing, to achieve fast and controllable self‐assembly of amphiphilic BCP thin films. A promising carbohydrate‐based BCP capable of forming cylindrical patterns with some of the smallest feature sizes is used for demonstrating how to obtain a highly ordered vertical cylindrical pattern with sub‐10 nm feature sizes in few seconds by HTSVA. HTSVA provides not only a simple way to achieve BCP fast self‐assembly in practical applications but also a tool to study the self‐assembly behavior of BCPs under extreme conditions.     

Self‐Organized Multiconstituent Catalytic Nanomotors

Self‐organized catalytic nanomotors consisting of more than one individual component are presented. Tadpole‐like catalytic nanomotors fabricated by dynamic shadowing growth (DSG) self‐organize randomly to form two‐nanomotor clusters (≈1–3% yield) that spin as opposed to circular motion exhibited by the individual structures. By introducing magnetic materials to another system, self‐assembled “helicopter” nanomotors consisting of a V‐shaped nanomotor and a microbead are formed with ≈25% yield, showing a significantly higher yield than the control (0%). A flexible swimmer system that performs complex swimming, such as maneuvering around stationary objects, is also presented. These nanomotor systems are inherently more complex than those previously studied and may be the next step towards building sophisticated multifunctional nanomachinery systems.     

Dynamic Self‐Assembly of Homogenous Microcyclic Structures Controlled by a Silver‐Coated Nanopore

The self‐assembly of nanoparticles is a challenging process for organizing precise structures with complicated and ingenious structures. In the past decades, a simple, high‐efficiency, and reproducible self‐assembly method from nanoscale to microscale has been pursued because of the promising and extensive application prospects in bioanalysis, catalysis, photonics, and energy storage. However, microscale self‐assembly still faces big challenges including improving the stability and homogeneity as well as pursuing new assembly methods and templates for the uniform self‐assembly. To address these obstacles, here, a novel silver‐coated nanopore is developed which serves as a template for electrochemically generating microcyclic structures of gold nanoparticles at micrometers with highly homogenous size and remarkable reproducibility. Nanopore‐induced microcyclic structures are further applied to visualize the diffusion profile of ionic flux. Based on this novel strategy, a nanopore could potentially facilitate the delivery of assembled structures for many practical applications including drug delivery, cellular detection, catalysis, and plasmonic sensing.     

Multibuilding Block Janus Synthesized by Seed‐Mediated Self‐Assembly for Enhanced Photothermal Effects and Colored Brownian Motion in an Optical Trap

The asymmetrical features and unique properties of multibuilding block Janus nanostructures (JNSs) provide superior functions for biomedical applications. However, their production process is very challenging. This problem has hampered the progress of JNS research and the exploration of their applications. In this study, an asymmetrical multibuilding block gold/iron oxide JNS has been generated to enhance photothermal effects and display colored Brownian motion in an optical trap. JNS is formed by seed‐mediated self‐assembly of nanoparticle‐loaded thermocleavable micelles, where the hydrophobic backbones of the polymer are disrupted at high temperatures, resulting in secondary self‐assembly and structural rearrangement. The JNS significantly enhances photothermal effects compared to their homogeneous counterpart after near‐infrared (NIR) light irradiation. The asymmetrical distribution of gold and iron oxide within JNS also generates uneven thermophoretic force to display active colored Brownian rotational motion in a single‐beam gradient optical trap. These properties indicate that the asymmetrical JNS could be employed as a strong photothermal therapy mediator and a fuel‐free nanoscale Janus motor under NIR light.     

From Molecular Machines to Stimuli-Responsive Materials

Artificial molecular machines are able to produce and exploit precise nanoscale actuations in response to chemical or physical triggers. Recent scientific efforts have been devoted to the integration, orientation, and interfacing of large assemblies of molecular machines in order to harness their collective actuations at larger length scale and up to the generation of macroscopic motions. Making use of such “hierarchical mechanics” represents a fundamentally new approach for the conception of stimuli-responsive materials. Furthermore, because some molecular machines can function as molecular motors—which are capable of cycling a unidirectional motion out of thermodynamic equilibrium and progressively increasing the work delivered to their environment—one can expect unique opportunities to design new kinds of mechanically active materials and devices capable of autonomous behavior when supplied by an external source of energy. Recently reported achievements are summarized, including the integration of molecular machines at surfaces and interfaces, in 3D self-assembled materials, as well as in liquid crystals and polymer materials. Their detailed functioning principles as well as their functional properties are discussed along with their potential applications in various domains such as sensing, drug delivery, electronics, optics, plasmonics, and mechanics.     

A three‐dimensional hybrid meshfree‐Cartesian scheme for fluid–body interaction

A numerical method based on a hybrid meshfree‐Cartesian grid is developed for solving three‐dimensional fluid–solid interaction (FSI) problems involving solid bodies undergoing large motion. The body is discretized and enveloped by a cloud of meshfree nodes. The motion of the body is tracked by convecting the meshfree nodes against a background of Cartesian grid points. Spatial discretization of second‐order accuracy is accomplished by the combination of a generalized finite difference (GFD) method and conventional finite difference (FD) method, which are applied to the meshfree and Cartesian nodes, respectively. Error minimization in GFD is carried out by singular value decomposition. The discretized equations are integrated in time via a second‐order fractional step projection method. A time‐implicit iterative procedure is employed to compute the new/evolving position of the immersed bodies together with the dynamically coupled solution of the flow field. The present method is applied on problems of free falling spheres and tori in quiescent flow and freely rotating spheres in simple shear flow. Good agreement with published results shows the ability of the present hybrid meshfree‐Cartesian grid scheme to achieve good accuracy. An application of the method to the self‐induced propulsion of a deforming fish‐like swimmer further demonstrates the capability and potential of the present approach for solving complex FSI problems in 3D. Copyright © 2011 John Wiley & Sons, Ltd.     

Self‐Formed Channel Devices Based on Vertically Grown 2D Materials with Large‐Surface‐Area and Their Potential for Chemical Sensor Applications

2D layered materials with sensitive surfaces are promising materials for use in chemical sensing devices, owing to their extremely large surface‐to‐volume ratios. However, most chemical sensors based on 2D materials are used in the form of laterally defined active channels, in which the active area is limited to the actual device dimensions. Therefore, a novel approach for fabricating self‐formed active‐channel devices is proposed based on 2D semiconductor materials with very large surface areas, and their potential gas sensing ability is examined. First, the vertical growth phenomenon of SnS₂ nanocrystals is investigated with large surface area via metal‐assisted growth using prepatterned metal electrodes, and then self‐formed active‐channel devices are suggested without additional pattering through the selective synthesis of SnS₂ nanosheets on prepatterned metal electrodes. The self‐formed active‐channel device exhibits extremely high response values (>2000% at 10 ppm) for NO₂ along with excellent NO₂ selectivity. Moreover, the NO₂ gas response of the gas sensing device with vertically self‐formed SnS₂ nanosheets is more than two orders of magnitude higher than that of a similar exfoliated SnS₂‐based device. These results indicate that the facile device fabrication method would be applicable to various systems in which surface area plays an important role.     

A Self‐Powered and Flexible Organometallic Halide Perovskite Photodetector with Very High Detectivity

Flexible and self‐powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self‐powered and flexible PD based on the methylammonium lead iodide (CH₃NH₃PBI₃) perovskite is demonstrated. Such a self‐powered PD can operate even with irregular motion such as human finger tapping, which enables it to work without a bulky external power source. In addition, with high‐quality CH₃NH₃PBI₃ perovskite thin film fabricated with solvent engineering, the PD exhibits an impressive detectivity of 1.22 × 10¹³ Jones. In the self‐powered voltage detection mode, it achieves a large responsivity of up to 79.4 V mW^?1 cm^?2 and a voltage response of up to ≈90%. Moreover, as the PD is made of flexible and transparent polymer films, it can operate under bending and functions at 360 ° of illumination. As a result, the self‐powered, flexible, 360 ° omnidirectional perovskite PD, featuring high detectivity and responsivity along with real‐world sensing capability, suggests a new direction for next‐generation optical communications, sensing, and imaging applications.     

Hierarchical Electrohydrodynamic Structures for Surface‐Enhanced Raman Scattering

Surface enhanced Raman scattering (SERS) is a well‐established spectroscopic technique that requires nanoscale metal structures to achieve high signal sensitivity. While most SERS substrates are manufactured by conventional lithographic methods, the development of a cost‐effective approach to create nanostructured surfaces is a much sought‐after goal in the SERS community. Here, a method is established to create controlled, self‐organized, hierarchical nanostructures using electrohydrodynamic (HEHD) instabilities. The created structures are readily fine‐tuned, which is an important requirement for optimizing SERS to obtain the highest enhancements. HEHD pattern formation enables the fabrication of multiscale 3D structured arrays as SERS‐active platforms. Importantly, each of the HEHD‐patterned individual structural units yield a considerable SERS enhancement. This enables each single unit to function as an isolated sensor. Each of the formed structures can be effectively tuned and tailored to provide high SERS enhancement, while arising from different HEHD morphologies. The HEHD fabrication of sub‐micrometer architectures is straightforward and robust, providing an elegant route for high‐throughput biological and chemical sensing.     

Motion Manipulation of Micro‐ and Nanomotors

Inspired by the self‐migration of microorganisms in nature, artificial micro‐ and nanomotors can mimic this fantastic behavior by converting chemical fuel or external energy into mechanical motion. These self‐propelled micro‐ and nanomotors, designed either by top‐down or bottom‐up approaches, are able to achieve different applications, such as environmental remediation, sensing, cargo/sperm transportation, drug delivery, and even precision micro‐/nanosurgery. For these various applications, especially biomedical applications, regulating on‐demand the motion of micro‐ and nanomotors is quite essential. However, it remains a continuing challenge to increase the controllability over motors themselves. Here, we will discuss the recent advancements regarding the motion manipulation of micro‐ and nanomotors by different approaches.     

Biocomputing with Nanostructures on Lipid Bilayers

Biocomputation is the algorithmic manipulation of biomolecules. Nanostructures, most notably DNA nanostructures and nanoparticles, become active substrates for biocomputation when modified with stimuli‐responsive, programmable biomolecular ligands. This approach—biocomputing with nanostructures (“nano‐bio computing”)—allows autonomous control of matter and information at the nanoscale; their dynamic assemblies and beneficial properties can be directed without human intervention. Recently, lipid bilayers interfaced with nanostructures have emerged as a new biocomputing platform. This new nano‐bio interface, which exploits lipid bilayers as a chemical circuit board for information processing, offers a unique reaction space for realizing nanostructure‐based computation at a previously unexplored dimension. In this Concept, recent advances in nano‐bio computing are briefly reviewed and the newly emerging concept of biocomputing with nanostructures on lipid bilayers is introduced.     

Dark‐Field Sensors based on Organometallic Halide Perovskite Microlasers

The detection of nanoscale objects is essential for homeland security, environmental monitoring, and early‐stage diagnostics. In the past few years, optical sensors have mostly been developed with passive devices such as microcavity and plasmonic nanostructures, which require external laser sources to operate and significantly increase the costs and bulks of sensing systems. To date, the potential of their active counterparts in optical sensors has not been well explored. Herein, a novel and robust mechanism to detect nanoscale objects with lead halide perovskite microlasers is demonstrated. Nanoparticles can be simply detected and sized by measuring the intensity of scattered laser light. In principle, the proposed concept is also applicable to electrically driven microlasers and it could find applications in portable point‐of‐care devices.     

Highly Stretchable,Adaptable, and Durable Strain Sensing Based on a Bioinspired Dynamically Cross‐Linked Graphene/Polymer Composite

Flexible strain sensors can detect physical signals (e.g., temperature, humidity, and flow) by sensing electrical deviation under dynamic deformation, and they have been used in diverse fields such as human motion detection, medical care, speech recognition, and robotics. Existing sensing materials have relatively low adaptability and durability and are not stretchable and flexible enough for complex tasks in motion detection. In this work, a highly flexible self‐healing conductive polymer composite consisting of graphene, poly(acrylic acid) and amorphous calcium carbonate is prepared via a biomineralization‐inspired process. The polymer composite shows good editability and processability and can be fabricated into stretchable strain sensors of various structures (sandwich structures, fibrous structures, self‐supporting structures, etc.). The developed sensors can be attached on different types of surfaces (e.g., flat, cambered) and work well both in air and under water in detecting various biosignals, including crawling, undulatory locomotion, and human body motion.     

Wetting‐Controlled Localized Placement of Surface Functionalities within Nanopores

In the context of sensing and transport control, nanopores play an essential role. Designing multifunctional nanopores and placing multiple surface functionalities with nanoscale precision remains challenging. Interface effects together with a combination of different materials are used to obtain local multifunctionalization of nanoscale pores within a model pore system prepared by colloidal templating. Silica inverse colloidal monolayers are first functionalized with a gold layer to create a hybrid porous architecture with two distinct gold nanostructures on the top surface as well as at the pore bottom. Using orthogonal silane‐ and thiol‐based chemistry together with a control of the wetting state allows individual addressing of the different locations within each pore resulting in nanoscale localized functional placement of three different functional units. Ring‐opening metathesis polymerization is used for inner silica‐pore wall functionalization. The hydrophobized pores create a Cassie–Baxter wetting state with aqueous solutions of thiols, which enables an exclusive functionalization of the outer gold structures. In a third step, an ethanolic solution able to wet the pores is used to self‐assemble a thiol‐containing initiator at the pore bottom. Subsequent controlled radical polymerization provides functionalization of the pore bottom. It is demonstrated that the combination of orthogonal surface chemistry and controlled wetting states can be used for the localized functionalization of porous materials.     

Quantum Sensing in a Physiological‐Like Cell Niche Using Fluorescent Nanodiamonds Embedded in Electrospun Polymer Nanofibers

Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits.     

Engineering Contactless Particle–Particle Interactions in Active Microswimmers

Artificial self‐propelled colloidal particles have recently served as effective building blocks for investigating many dynamic behaviors exhibited by nonequilibrium systems. However, most studies have relied upon excluded volume interactions between the active particles. Experimental systems in which the mobile entities interact over long distances in a well‐defined and controllable manner are valuable so that new modes of multiparticle dynamics can be studied systematically in the laboratory. Here, a system of self‐propelled microscale Janus particles is engineered to have contactless particle–particle interactions that lead to long‐range attraction, short‐range repulsion, and mutual alignment between adjacent swimmers. The unique modes of motion that arise can be tuned by modulating the system's parameters.     

Photonic Devices Out of Equilibrium: Transient Memory,Signal Propagation,and Sensing

Soft photonic materials are important for sensors, displays, or energy management and have become switchable under static equilibrium conditions by integration of responsive polymer features. The next step is to equip such materials with the ability for autonomously dynamic and self‐regulating behavior, which would advance their functionality and application possibilities to new levels. Here, this study shows the system integration of a nonlinear, biocatalytic pH‐feedback system with a pH‐responsive block copolymer photonic gel, and demonstrates autonomous transient memories, remotely controlled signal propagation, and sensing. This study utilizes an enzymatic switch to program the lifetime of the reflective state of a photonic gel, and induces propagation of pH‐waves extinguishable by illumination with UV‐light. The described combination of nonlinear chemistry and responsive photonic gels opens pathways toward out‐of‐equilibrium photonic devices with active and autonomous behavior useful for sensing, computation, and communication.     

Nanoscale Bubble Domains and Topological Transitions in Ultrathin Ferroelectric Films

Observation of a new type of nanoscale ferroelectric domains, termed as “bubble domains”—laterally confined spheroids of sub‐10 nm size with local dipoles self‐aligned in a direction opposite to the macroscopic polarization of a surrounding ferroelectric matrix—is reported. The bubble domains appear in ultrathin epitaxial PbZr_0.2Ti_0.8O₃/SrTiO₃/PbZr_0.2Ti_0.8O₃ ferroelectric sandwich structures due to the interplay between charge and lattice degrees of freedom. The existence of the bubble domains is revealed by high‐resolution piezoresponse force microscopy (PFM), and is corroborated by aberration‐corrected atomic‐resolution scanning transmission electron microscopy mapping of the polarization displacements. An incommensurate phase and symmetry breaking is found within these domains resulting in local polarization rotation and hence impart a mixed Néel–Bloch‐like character to the bubble domain walls. PFM hysteresis loops for the bubble domains reveal that they undergo an irreversible phase transition to cylindrical domains under the electric field, accompanied by a transient rise in the electromechanical response. The observations are in agreement with ab‐initio‐based calculations, which reveal a very narrow window of electrical and elastic parameters that allow the existence of bubble domains. The findings highlight the richness of polar topologies possible in ultrathin ferroelectric structures and bring forward the prospect of emergent functionalities due to topological transitions.     

3D Orthogonal Woven Triboelectric Nanogenerator for Effective Biomechanical Energy Harvesting and as Self‐Powered Active Motion Sensors

The development of wearable and large‐area energy‐harvesting textiles has received intensive attention due to their promising applications in next‐generation wearable functional electronics. However, the limited power outputs of conventional textiles have largely hindered their development. Here, in combination with the stainless steel/polyester fiber blended yarn, the polydimethylsiloxane‐coated energy‐harvesting yarn, and nonconductive binding yarn, a high‐power‐output textile triboelectric nanogenerator (TENG) with 3D orthogonal woven structure is developed for effective biomechanical energy harvesting and active motion signal tracking. Based on the advanced 3D structural design, the maximum peak power density of 3D textile can reach 263.36 mW m^?2 under the tapping frequency of 3 Hz, which is several times more than that of conventional 2D textile TENGs. Besides, its collected power is capable of lighting up a warning indicator, sustainably charging a commercial capacitor, and powering a smart watch. The 3D textile TENG can also be used as a self‐powered active motion sensor to constantly monitor the movement signals of human body. Furthermore, a smart dancing blanket is designed to simultaneously convert biomechanical energy and perceive body movement. This work provides a new direction for multifunctional self‐powered textiles with potential applications in wearable electronics, home security, and personalized healthcare.     

Preferential Tumor Accumulation of Polyglycerol Functionalized Nanodiamond Conjugated with Cyanine Dye Leading to Near‐Infrared Fluorescence In Vivo Tumor Imaging

Preferential accumulation of nanoparticles in a tumor is realized commonly by combined effects of active and passive targeting. However, passive targeting based on an enhanced permeation and retention (EPR) effect is not sufficient to observe clear tumor fluorescence images in most of the in vivo experiments using tumor‐bearing mice. Herein, polyglycerol‐functionalized nanodiamonds (ND‐PG) conjugated with cyanine dye (Cy7) are synthesized and it is found that the resulting ND‐PG‐Cy7 is preferentially accumulated in the tumor, giving clear fluorescence in in vivo and ex vivo fluorescence images. One of the plausible reasons is the longer in vivo blood circulation time of ND‐PG‐Cy7 (half‐life: 58 h determined by the pharmacokinetic analysis) than that of other nanoparticles (half‐life: <20 h in most of the previous reports). In a typical example, the fluorescence intensity of tumors increases due to continuous tumor accumulation of ND‐PG‐Cy7, even more than one week postinjection. This may be owing to the stealth effect of PG that was reported previously, avoiding recognition and excretion by reticuloendothelial cells, which are abundant in liver and spleen. In fact, the fluorescence intensities from the liver and spleen is similar to those from other organs, while the tumor exhibits much stronger fluorescence in the ex vivo image.