The field of thermoelectrics has progressed enormously and is now growing steadily because of recently demonstrated advances and strong global demand for cost‐effective, pollution‐free forms of energy conversion. Rapid growth and exciting innovative breakthroughs in the field over the last 10–15 years have occurred in large part due to a new fundamental focus on nanostructured materials. As a result of the greatly increased research activity in this field, a substantial amount of new data—especially related to materials—have been generated. Although this has led to stronger insight and understanding of thermoelectric principles, it has also resulted in misconceptions and misunderstanding about some fundamental issues. This article sets out to summarize and clarify the current understanding in this field; explain the underpinnings of breakthroughs reported in the past decade; and provide a critical review of various concepts and experimental results related to nanostructured thermoelectrics. We believe recent achievements in the field augur great possibilities for thermoelectric power generation and cooling, and discuss future paths forward that build on these exciting nanostructuring concepts. 相似文献
Dip‐pen nanodisplacement lithography (DNL) is a versatile scanning probe‐based technique that can be employed for fabricating ultrafine 3D polymer brushes under ambient conditions. Many fundamental studies and applications require the large‐area fabrication of 3D structures. However, the fabrication throughput and uniformity are still far from satisfactory. In this work, the molecular displacement mechanism of DNL is elucidated by systematically investigating the synergistic effect of z extension and contact time. The in‐depth understanding of molecular displacement results in the successful achievement of ultrafine control of 3D structures and high‐speed patterning at the same time. Remarkably, one can prepare arbitrary 3D polymer brushes on a large area (1.3 mm × 1.3 mm), with <5% vertical and lateral size variations, and a patterning speed as much as 200‐fold faster than the current state‐of‐the‐art. 相似文献
Dip‐pen nanolithography (DPN) is a powerful method to pattern nanostructures on surfaces by the controlled delivery of an “ink” coating the tip of an atomic force microscope upon scanning and contacting with surfaces. The growing interest in the use of nanoparticles as structural and functional elements for the fabrication of nanodevices suggests that the DPN‐stimulated patterning of nanoparticles on surfaces might be a useful technique to assemble hierarchical architectures of nanoparticles that could pave methodologies for functional nanocircuits or nanodevices. This Review presents different methodologies for the nanolithographic patterning of metallic, semiconductor, and metal oxide nanostructures on surfaces. The mechanisms involved in the formation of the nanostructures are discussed and the effects that control the dimensions of the resulting patterns are reviewed. The possible applications of the nanostructures are also addressed.
Dip‐pen nanolithography (DPN) is a unique nanofabrication tool that can directly write a variety of molecular patterns on a surface with high resolution and excellent registration. Over the past 20 years, DPN has experienced a tremendous evolution in terms of applicable inks, a remarkable improvement in fabrication throughput, and the development of various derivative technologies. Among these developments, polymer pen lithography (PPL) is the most prominent one that provides a large‐scale, high‐throughput, low‐cost tool for nanofabrication, which significantly extends DPN and beyond. These developments not only expand the scope of the wide field of scanning probe lithography, but also enable DPN and PPL as general approaches for the fabrication or study of nanostructures and nanomaterials. In this review, a focused summary and historical perspective of the technological development of DPN and its derivatives, with a focus on PPL, in one timeline, are provided and future opportunities for technological exploration in this field are proposed. 相似文献
Knowledge of the phase behavior of polyfluorene solutions and gels has expanded tremendously in recent years. The relationship between the structure formation and photophysics is known at the quantitative level. The factors which we understand control these relationships include virtually all important materials parameters such as solvent quality, side chain branching, side chain length, molecular weight, thermal history and myriad functionalizations. This review describes advances in controlling structure and photophysical properties in polyfluorene solutions and gels. It discusses the demarcation lines between solutions, gels, and macrophase separation in conjugated polymers and reviews essential solid state properties needed for understanding of solutions. It gives an insight into polyfluorene and polyfluorene beta phase in solutions and gels and describes all the structural levels in solvent matrices, ranging from intramolecular structures to the diverse aggregate classes and network structures and agglomerates of these units. It goes on to describe the kinetics and thermodynamics of these structures. It details the manifold molecular parameters used in their control and continues with the molecular confinement and touches on permanently cross‐linked networks. Particular focus is placed on the experimental results of archetypical polyfluorenes and solvent matrices and connection between structure and photonics. A connection is also made to the mean field type theories of hairy‐rod like polymers. This altogether allows generalizations and provides a guideline for materials scientists, synthetic chemists and device engineers as well, for this important class of semiconductor, luminescent polymers. 相似文献
An extremely rapid process for self-assembling well-ordered, nano, and microparticle monolayers via a novel aerosolized method is presented. The novel technique can reach monolayer self-assembly rates as high as 268 cm2 min−1 from a single aerosolizing source and methods to reach faster monolayer self-assembly rates are outlined. A new physical mechanism describing the self-assembly process is presented and new insights enabling high-efficiency nanoparticle monolayer self-assembly are developed. In addition, well-ordered monolayer arrays from particles of various sizes, surface functionality, and materials are fabricated. This new technique enables a 93× increase in monolayer self-assembly rates compared to the current state of the art and has the potential to provide an extremely low-cost option for submicron nanomanufacturing. 相似文献
Future progress in nanoscience and nanotechnology necessitates further development of versatile, labor‐, and cost‐efficient surface patterning strategies. A new approach to nanopatterning is reported, which utilizes surface segregation of a smooth layer of an end‐grafted homopolymer in a poor solvent. The variation in polymer grafting density yields a range of surface nanostructures, including randomly organized pinned spherical micelles, worm‐like structures, networks, and porous films. The capability to use the polymer patterns for site‐specific deposition of small molecules, polymers, or nanoparticles is shown. This versatile strategy enables patterning of curved surfaces with direct access to the substrate and no need in changing polymer composition to realize different surface patterns. 相似文献
Colloidal elements have historically played a key role in “bottom‐up” self‐assembly processes for nanofabrication. However, these elementary components can also interact with light to generate complex intensity distributions and facilitate “top‐down” lithography. Here, a nanolithography technique is demonstrated based on oblique illuminations of colloidal particles to fabricate hollow‐core 3D nanostructures with complex symmetry. The light–particle interaction generates an angular light distribution as governed by Mie scattering, which can be compounded by multiple illuminations to sculpt novel 3D structures in the underlying photoresist. The fabricated geometry can be controlled by the particle parameters and illumination configurations, enabling the fabrication of a large variety of asymmetric hollow nanostructures. The proposed technique has high pattern versatility, is low cost and high throughput, and can find potential application in nanoneedles, nanonozzles, and materials with anisotropic properties. 相似文献
A reproducible wafer‐scale method to obtain 3D nanostructures is investigated. This method, called corner lithography, explores the conformal deposition and the subsequent timed isotropic etching of a thin film in a 3D shaped silicon template. The technique leaves a residue of the thin film in sharp concave corners which can be used as structural material or as an inversion mask in subsequent steps. The potential of corner lithography is studied by fabrication of functional 3D microfluidic components, in particular i) novel tips containing nano‐apertures at or near the apex for AFM‐based liquid deposition devices, and ii) a novel particle or cell trapping device using an array of nanowire frames. The use of these arrays of nanowire cages for capturing single primary bovine chondrocytes by a droplet seeding method is successfully demonstrated, and changes in phenotype are observed over time, while retaining them in a well‐defined pattern and 3D microenvironment in a flat array. 相似文献
