Superparamagnetic Twist‐Type Actuators with Shape‐Independent Magnetic Properties and Surface Functionalization for Advanced Biomedical Applications

Directed nanoparticle self‐organization and two‐photon polymerization are combined to enable three‐dimensional soft‐magnetic microactuators with complex shapes and shape‐independent magnetic properties. Based on the proposed approach, single and double twist‐type swimming microrobots with programmed magnetic anisotropy are demonstrated, and their swimming properties in DI‐water are characterized. The fabricated devices are actuated using weak rotating magnetic fields and are capable of performing wobble‐free corkscrew propulsion. Single twist‐type actuators possess an increase in surface area in excess of 150% over helical actuators with similar feature size without compromising the forward velocity of over one body length per second. A generic and facile combination of glycine grafting and subsequent protein immobilization exploits the actuator's increased surface area, providing for a swimming microrobotic platform with enhanced load capacity desirable for future biomedical applications. Successful surface modification is confirmed by FITC fluorescence.     

Rolling Friction Enhanced Free‐Standing Triboelectric Nanogenerators and their Applications in Self‐Powered Electrochemical Recovery Systems

Heavy metals contained in wastewater are one of the most serious pollutions in natural resources. A self‐powered electrochemical recovery system for collecting Cu ions in wastewater by incorporating a rolling friction enhanced freestanding triboelectric nanogenerator (RF‐TENG) is developed here. The RF‐TENG utilizes integrated cylindrical surfaces using the conjunction of rolling electrification and freestanding electrostatic induction, which shows outstanding output performance and ultrarobust stability. By using the kinetic energy of flowing water, a collection efficiency of up to 80% for Cu²⁺ ions in wastewater has been achieved. Self‐powered electrochemical systems are one of the most promising applications of TENGs for independent and sustainable driving of electrochemical reactions without the need for any additional power supply. This research is a substantial advancement towards the practical applications of triboelectric nanogenerators and self‐powered electrochemical systems.     

Hybrid Smart Fiber with Spontaneous Self‐Charging Mechanism for Sustainable Wearable Electronics

Smart wearable electronics that are fabricated on light‐weight fabrics or flexible substrates are considered to be of next‐generation and portable electronic device systems. Ideal wearable and portable applications not only require the device to be integrated into various fiber form factors, but also desire self‐powered system in such a way that the devices can be continuously supplied with power as well as simultaneously save the acquired energy for their portability and sustainability. Nevertheless, most of all self‐powered wearable electronics requiring both the generation of the electricity and storing of the harvested energy, which have been developed so far, have employed externally connected individual energy generation and storage fiber devices using external circuits. In this work, for the first time, a hybrid smart fiber that exhibits a spontaneous energy generation and storage process within a single fiber device that does not need any external electric circuit/connection is introduced. This is achieved through the employment of asymmetry coaxial structure in an electrolyte system of the supercapacitor that creates potential difference upon the creation of the triboelectric charges. This development in the self‐charging technology provides great opportunities to establish a new device platform in fiber/textile‐based electronics.     

Parylene薄膜及其在MEMS中的应用

介绍了聚合物Parylene,包括其制备工艺和Parylene薄膜的图形化。着重介绍了Parylene在微流体系统的应用,包括微阀、微泵和微通道;在可植入微系统中的应用,包括人工耳蜗和视网膜假体。近来的研究表明,基于Parylene的MEMS微器件广泛应用在各种MEMS微结构、微传感器和微驱动器上,Parylene在各种完全集成微系统应用中将具有更加诱人的前景。     

Deciphering,Designing, and Realizing Self‐Folding Biomimetic Microstructures Using a Mass‐Spring Model and Inkjet‐Printed,Self‐Folding Hydrogels

Flat, organic microstructures that can self‐fold into 3D microstructures are promising for tissue regeneration, for being capable of distributing living cells in 3D while forming highly complex, biomimetic architectures to assist cells in performing regeneration. However, the design of self‐folding microstructures is difficult due to a lack of understanding of the underlying formation mechanisms. This study helps bridge this gap by deciphering the dynamics of the self‐folding using a mass‐spring model. This numerical study reveals that self‐folding procedure is multi‐modal, which can become random and unpredictable by involving the interplays between internal stresses, external stimulation, imperfection, and self‐hindrance of the folding body. To verify the numerical results, bilayered, hydrogel‐based micropatterns capable of self‐folding are fabricated using inkjet‐printing and tested. The experimental and numerical results are consistent with each other. The above knowledge is applied to designing and fabricating self‐folding microstructures for tissue‐engineering, which successfully creates 3D, cell‐scaled, and biomimetic microstructures, such as microtubes, branched microtubes, and hollow spheres. Embedded in self‐folded microtubes, human mesenchymal stem cells proliferate and form linear cell‐organization mimicking the cell morphology in muscles and tendons. The above knowledge and study platforms can greatly contribute to the research on self‐folding microstructures and applications to tissue regeneration.     

Distributed object‐oriented switching system software platform design

Key technologies are presented and evaluated for establishing a distributed object‐oriented switching system platform. This platform is based on CORBA, which can enhance software productivity and system scalability and is thus widely used in the information technology field. Conditions and requirements specific to switching systems, such as very high‐performance and non‐stop operation, are analysed and mapped to the main elements of CORBA. How to deploy and bind objects so as to minimize the processing load is clarified. Mechanisms that guarantee system reliability (saving calls in service when a system failure occurs and avoiding the spread of faults) are also presented. Evaluation of the number of dynamic program steps for systems using fully compliant CORBA, improved CORBA, and a proprietary high‐speed object‐request broker (ORB) shows that constructing a communication switching system by using the high‐speed ORB approach is sufficient, but CORBA‐compliant approaches should be used to provide an interoperable interface for communicating with external compliant systems. Copyright © 2001 John Wiley & Sons, Ltd.     

Facile Room‐Temperature Anion Exchange Reactions of Inorganic Perovskite Quantum Dots Enabled by a Modular Microfluidic Platform

In an effort to produce the materials of next‐generation photoelectronic devices, postsynthesis halide exchange reactions of perovskite quantum dots are explored to achieve enhanced bandgap tunability. However, comprehensive understanding of the multifaceted halide exchange reactions is inhibited by their vast relevant parameter space and complex reaction network. In this work, a facile room‐temperature strategy is presented for rapid halide exchange of inorganic perovskite quantum dots. A comprehensive understanding of the halide exchange reactions is provided by isolating reaction kinetics from precursor mixing rates utilizing a modular microfluidic platform, Quantum Dot Exchanger (QDExer). The effects of ligand composition and halide salt source on the rate and extent of the halide exchange reactions are illustrated. This fluidic platform offers a unique time‐ and material‐efficient approach for studies of solution phase‐processed colloidal nanocrystals beyond those studied here and may accelerate the discovery and optimization of next‐generation materials for energy technologies.     

Self‐Assembly Mechanism of Spiky Magnetoplasmonic Supraparticles

Concave nanoparticles (NPs) with complex angled and non‐Platonic geometries have unique optical, magnetic, catalytic, and biological properties originating from the singularities of the electrical field in apexes and craters. Preparation of such particles with a uniform size/shape and core–shell morphology represents a significant challenge, largely because of the poor knowledge of their formation mechanism. Here, this challenge is addressed and a study of the mechanism of their formation is presented for a case of complex spiky morphologies that led us to the conclusion that NPs with concave geometries can be, in fact, supraparticles (SPs) produced via the self‐assembly of smaller convex integrants. This mechanism is exemplified by the vivid case of spiky SPs formed via the attachment of small and faceted Au NPs on smooth Au‐coated iron oxide (Fe₃O₄@Au) seeds. The theoretical calculations of energies of primary interactions—electrostatic repulsion and van‐der Waals repulsion, elaborated for this complex case—confirm experimental observation and the self‐limiting mechanism of SP formation. Besides demonstrating the mechanistic aspects of synthesis of NPs with complex geometries, this work also uncovers a facile approach for preparation of concave magnetoplasmonic particles. When combined with a spiky geometry, such bi‐functional magnetoplasmonic SPs can serve as a unique platform for optoelectronic devices and biomedical applications.     

Shape‐Memory Microfluidics

Materials with embedded vascular networks afford rapid and enhanced control over bulk material properties including thermoregulation and distribution of active compounds such as healing agents or stimuli. Vascularized materials have a wide range of potential applications in self‐healing systems and tissue engineering constructs. Here, the application of vascularized materials for accelerated phase transitions in stimuli‐responsive microfluidic networks is reported. Poly(ester amide) elastomers are hygroscopic and exhibit thermo‐mechanical properties (T_g ≈ 37 °C) that enable heating or hydration to be used as stimuli to induce glassy‐rubbery transitions. Hydration‐dependent elasticity serves as the basis for stimuli‐responsive shape‐memory microfluidic networks. Recovery kinetics in shape‐memory microfluidics are measured under several operating modes. Perfusion‐assisted delivery of stimulus to the bulk volume of shape‐memory microfluidics dramatically accelerates shape recovery kinetics compared to devices that are not perfused. The recovery times are 4.2 ± 0.1 h and 8.0 ± 0.3 h in the perfused and non‐perfused cases, respectively. The recovery kinetics of the shape‐memory microfluidic devices operating in various modes of stimuli delivery can be accurately predicted through finite element simulations. This work demonstrates the utility of vascularized materials as a strategy to reduce the characteristic length scale for diffusion, thereby accelerating the actuation of stimuli‐responsive bulk materials.     

Hydrodynamically Guided Hierarchical Self‐Assembly of Peptide–Protein Bioinks

Effective integration of molecular self‐assembly and additive manufacturing would provide a technological leap in bioprinting. This article reports on a biofabrication system based on the hydrodynamically guided co‐assembly of peptide amphiphiles (PAs) with naturally occurring biomolecules and proteins to generate hierarchical constructs with tuneable molecular composition and structural control. The system takes advantage of droplet‐on‐demand inkjet printing to exploit interfacial fluid forces and guide molecular self‐assembly into aligned or disordered nanofibers, hydrogel structures of different geometries and sizes, surface topographies, and higher‐ordered constructs bound by molecular diffusion. PAs are designed to co‐assemble during printing in cell diluent conditions with a range of extracellular matrix (ECM) proteins and biomolecules including fibronectin, collagen, keratin, elastin‐like proteins, and hyaluronic acid. Using combinations of these molecules, NIH‐3T3 and adipose derived stem cells are bioprinted within complex structures while exhibiting high cell viability (>88%). By integrating self‐assembly with 3D‐bioprinting, the study introduces a novel biofabrication platform capable of encapsulating and spatially distributing multiple cell types within tuneable pericellular environments. In this way, the work demonstrates the potential of the approach to generate complex bioactive scaffolds for applications such as tissue engineering, in vitro models, and drug screening.     

Bio‐Inspired Anisotropic Wettability Surfaces from Dynamic Ferrofluid Assembled Templates

The biomimetic principle of harnessing topographical structures to determine liquid motion behavior represents a cutting‐edge direction in constructing green transportation systems without external energy input. Here, inspired by natural Nepenthes peristome, a novel anisotropic wettability surface with characteristic structural features of periodically aligned and overlapped arch‐shaped microcavities, formed by employing ferrofluid assemblies as dynamic templates, is presented. The magnetic strength and orientation are precisely adjustable during the generation process, and thus the size and inclination angle of the ferrofluid droplet templates could be tailored to make the surface morphology of the resultant polymer replica achieve a high degree of similarity to the natural peristome. The resultant anisotropic wettability surface enables autonomous unidirectional water transportation in a fast and continuous way. In addition, it could be tailored into arbitrary shapes to induce water flow along a specific curved path. More importantly, based on the anisotropic wettability surface, novel pump‐free microfluidic devices are constructed to implement multiphase flow reactions, which offer a promising solution to building low‐cost, portable platform for lab‐on‐a‐chip applications.     

Acrylate‐Based Photopolymer for Two‐Photon Microfabrication and Photonic Applications

This paper provides a photopolymerizing material suitable for stereolithography of complex submicrometer‐sized three‐dimensional (3D) structural elements to a broad scientific public. Here, we present the formulation of a polymer (LN1 resin) that allows further research in the field of nanofabrication and ‐technology as it surpasses current material limitations. The polymer consists of multifunctional acrylate oligomers as binder, polyfunctional monomers, and a photoinitiator (PI). The chemistry to form 3D structures is based on photopolymerization of the acrylate system initiated by free‐radical species that are triggered by two‐photon absorption of a PI. Important parameters of photocuring, such as the effects of PI concentration, temperature, and light intensity, were studied using photocalorimetry. The thermal stability of the material was tested using thermal gravimetric analysis, providing key information for electronic and photonic applications. Photonic‐crystal structures generated from this resin exhibiting photonic stop gaps in near‐infrared‐ and telecommunication‐wavelength regions are presented.     

Monodisperse Thermoresponsive Microgels with Tunable Volume‐Phase Transition Kinetics

A facile method to control the volume‐phase transition kinetics of thermo‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) microgels is presented. Monodisperse PNIPAM microgels with spherical voids are prepared using a microfluidic device. The swelling and shrinking responses of these microgels with spherical voids to changes in temperature are compared with those of voidless microgels of the same size and chemical composition prepared using the same microfluidic device. It is shown that the PNIPAM microgels with voids respond faster to changes in temperature as compared with their voidless counterparts. Also, the induced void structure does not have a detrimental effect on the equilibrium volume change of the microgels. Thus, the volume phase transition kinetics of the microgels can be finely tuned by controlling the number and size of the voids. The flexibility, control, and simplicity in fabrication rendered by this approach make these microgels appealing for applications that range from drug delivery systems and chemical separations to chemical/biosensing and actuators.     

An All Hydrophilic Fluid Diode for Unidirectional Flow in Porous Systems

A fluid diode that allows fluid flow in one direction but blocks fluid flow in the opposite direction has wide applications including oil recovery, drug delivery, and lab‐on‐a‐chip microfluidics. Many studies are conducted to facilitate directional liquid motion on the solid surface or across thin porous layers. However, the self‐driven one‐way flow inside porous systems still remains a significant challenge. Here, a novel all‐hydrophilic fluid diode (AHFD) made of porous materials with asymmetric pores is reported, which allows capillary flow in a chosen direction. The direction‐dependent flow process and the breakthrough pressure are experimentally and theoretically examined. The proposed AHFD can have many potential applications such as functional protective clothing, microfluidic valve, and oil–water separator, and the idea can be extended to develop other all lyophilic fluid diodes such as oleophilic diode.     

Interfacial Self‐Assembly of Amphiphilic Dual Temperature Responsive Actuating Janus Particles

Amphiphilic Janus particles feature the combination of two different functional materials in one single colloid, as well as the possibility of self‐assembly at interfaces into complex superstructures. In this article, the self‐assembly of dual temperature responsive amphiphilic Janus particles at liquid–liquid interfaces and their subsequent conversion into an actuating layer‐shaped surface are presented. These microparticles are produced in a capillaries based continuous flow microfluidic device by photoinitiated radical polymerization. The hydrophobic part of the Janus particles contains a liquid crystalline elastomer (LCE), which performs a strong actuation up to 95% during the nematic–isotropic phase transition. The other side consists of a p(NIPAAm) hydrogel, which features volumetric expansions up to 280% below the lower critical solution temperature. A multistep molding process is developed to uniformly align the Janus particles at a toluene/water boundary surface and to embed the particles into a hydrogel matrix. A particle covered hydrogel layer is obtained, which features a collective actuation of the rod‐like LCE parts on the surface and a bundling of the resulting forces during the phase transition.     

Artificial Light‐Harvesting Material Based on Self‐Assembly of Coordination Polymer Nanoparticles

Artificial light‐harvesting antenna materials as potential mimics for photosynthetic systems have attracted intense attention recently. Herein, a new modular approach to construct light‐harvesting material, which involves the self‐assembly of coordination polymer nanoparticles (CPNs) at room temperature, is presented. Fluorescence resonance energy transfer (FRET) occurs between donor and acceptor molecules encapsulated in the CPNs, and the emission signal of acceptor is amplified significantly. To the best of our knowledge, this is the first example of artificial light‐harvesting material generated from biomolecule‐based coordination polymer nanoparticles. The modularity of the material makes it convenient to manipulate the system by changing the composite of CPNs and the type and amount of dyes confined, implying it is a general strategy. The material functions not only in fluid medium, but also in the form of solid state, which extends its application areas greatly. Furthermore, photocurrent generation can be realized by the dye‐encapsulated CPNs system upon irradiation with visible light, implying the potential usefulness in light‐energy conversion and photoelectronic applications. Besides, the creation of FRET system provides a platform to mimic dual‐channel logic gate at nanoscale level, which is beneficial to the construction of integrated logic devices with multiple functions.     

Droplets Crawling on Peristome‐Mimetic Surfaces

Controlling the mobility of liquids along surfaces is widely exploited in various technologies to achieve self‐lubrication, phase‐change heat transfer, and microfluidics. Despite commendable progress in directional liquid transport on peristome‐mimetic surfaces, liquid merely spreads directionally with a wetted trail remaining. It is a challenge to achieve directional contracting of spreading liquid at the rear side and ultimately unidirectional motion in bulk from one site to another. Here it is shown that liquids resting on the peristome‐mimetic surfaces can crawl directionally and rapidly in an inchworms‐like way under the action of sudden spontaneous bubbles levitation. Vacuuming or chemical reaction induces sudden nucleation, growth, coalescence (Ostwald ripening process), and rupture of bubbles in the asymmetric microcavities of the peristome‐mimetic surface with directional overpressure beneath the liquid, resulting in the guided contracting and spreading of the liquid. Bubbles regulate this new mode of liquid directional motion. The strategy offers opportunities for liquids directional motion for various applications, such as in microfluidic devices, oil–water separation, and water collection systems.     

An On‐Chip Break Junction System for Combined Single‐Molecule Conductance and Raman Spectroscopies

Systems that are capable of robustly reproducing single‐molecule junctions are an essential prerequisite for enabling the wide‐spread testing of molecular electronic properties, the eventual application of molecular electronic devices, and the development of single‐molecule based electrical and optical diagnostics. Here, a new approach is proposed for achieving a reliable single‐molecule break junction system by using a microelectromechanical system device on a chip. It is demonstrated that the platform can (i) provide subnanometer mechanical resolution over a wide temperature range (≈77–300 K), (ii) provide mechanical stability on par with scanning tunneling microscopy and mechanically controllable break junction systems, and (iii) operate in a variety of environmental conditions. Given these fundamental device performance properties, the electrical characteristics of two standard molecules (hexane‐dithiol and biphenyl‐dithiol) at the single‐molecule level, and their stability in the junction at both room and cryogenic temperatures (≈77 K) are studied. One of the possible distinctive applications of the system is demonstrated, i.e., observing real‐time Raman scattering in a single‐molecule junction. This approach may pave a way to achieving high‐throughput electrical characterization of single‐molecule devices and provide a reliable platform for the convenient characterization and practical application of single‐molecule electronic systems in the future.     

Self‐Assembly of Nanostructured,Complex, Multication Films via Spontaneous Phase Separation and Strain‐Driven Ordering

Spontaneous self‐assembly of a multication nanophase in another multication matrix phase is a promising bottom‐up approach to fabricate novel, nanocomposite structures for a range of applications. In an effort to understand the mechanisms for such self‐assembly, complimentary experimental and theoretical studies are reported to first understand and then control or guide the self‐assembly of insulating BaZrO₃ (BZO) nanodots within REBa₂Cu₃O_7–δ (RE = rare earth elements including Y, REBCO) superconducting films. The strain field developed around BZO nanodots embedded in the REBCO matrix is a key driving force dictating the self‐assembly of BZO nanodots along REBCO c‐axis. The size selection and spatial ordering of BZO self‐assembly are simulated using thermodynamic and kinetic models. The BZO self‐assembly is controllable by tuning the interphase strain field. REBCO superconducting films with BZO defect arrays self‐assembled to align in both vertical (REBCO c‐axis) and horizontal (REBCO ab‐planes) directions result in the maximized pinning and J_c performance for all field angles with smaller angular J_c anisotropy. The work has broad implications for the fabrication of controlled self‐assembled nanostructures for a range of applications via strain‐tuning.     

Protein‐Based Hydrogels that Actuate Self‐Folding Systems

An approach to build a chemomechatronic system inspired by self‐folding robots is described. This system, which comprises a protein‐based hydrogel bound to a low‐profile laminate, responds to different aqueous environments by undergoing geometric transformations. This response is dependent on the thickness and stiffness of the templating hydrogel, which directly regulates the diffusion of water into and out of the platform to initiate its reversible shape changes. When modified to include more complex geometries, these controllable shape changes can also be used to selectively trigger multiple folding events, illustrating a new platform for chemically initiated mechatronic devices. Together, these data show how compositionally discrete components are physically, chemically, and mechanically coupled together to generate a new actuator for biohybrid self‐folding systems.