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Improved Method of Device Area Scale-up for SWNT/Silicon Hybrid Solar Cells Using Silver Nanowires

While research on silicon solar cells has progressed the development of all organic, inorganic, and hybrid materials systems to simultaneously address the diverse set of design criteria for optimal photovoltaic (PV) performance, incorporation of hybrid materials systems has proven to be an effective method to improve some of these issues. With crystalline silicon representing the standard for high efficiency in solar cell designs, cell cost and production capacity remain concerns for the growing emphasis on broad implementation of renewable energy strategies on a global basis, with solar PV being a leading competitor. With recent studies demonstrating that the approach incorporating p-type nano-Carbon with n-type silicon in a hybrid film approach provides excellent diode junction rectification properties, improved collection and transport efficiencies due to the enhanced conductivity of the nano-C film, and superior semiconductor barrier properties at the nano-C/silicon junction. While this has proven effective for small cell design of a few square millimeters, scaling the cell area has proven challenging due to the increase in sheet resistance (Rs) of the nano-C layer as area increases resulting in a reduction in cell efficiency. Recently, Li, et.al, from the Taylor group in the Chemical and Environmental Engineering Departm ...

Jeff Morse, Ph.D. July 02, 2014 153
Solution Processing of ITO-Free Solar Cells

Organic solar cells (OSCs) are of interest for next-generation photovoltaic applications due to their lower costs and milder fabrication requirements relative to c-Si and thin-film devices. The power conversion efficiency (PCE) of these devices has risen to 11-12% in recent years, which is promising in order to gain market share in this competitive field. Requiring only simple spin- or dip-coating techniques, organic or polymer solar cells are an attractive low-cost technology; in recent years, there has been a focus on solution and roll-to-roll high throughput processing of OSCs to lower the fabrication costs even further.

Bradley Fahlman, Department of Chemistry, Central Michigan University, InterNano Editorial Staff March 27, 2014 169
Rapid and Low-Cost Graphene Film Deposition using Solution Processing

In 2004, a single layer of graphite known as graphene was synthesized for the first time via mechanical exfoliation of graphite. This discovery, for which Novoselov and Geim were awarded the Nobel Prize in Physics in 2010, has ushered in a 'graphene frontier' with worldwide interest in exploiting their intriguing potential for technological applications in fields such as nanoelectronics and energy storage. The primary method that is used to fabricate large-scale transparent graphene films is chemical vapor deposition (CVD). However, this requires high-temperature processing and relatively long deposition times. Furthermore, this precludes the deposition of graphene onto temperature-sensitive substrates. Although the deposited films may be flaked off the metallic (usually Cu) substrate for transfer to another surface, this will lead to the incorporation of impurities and structural defects.

Bradley Fahlman, Department of Chemistry, Central Michigan University, InterNano Editorial Staff March 05, 2014 259
Progress and Public Trust in Nanotechnology Require Better Material Characterization

A prevalent challenge for progress in nanotechnology is characterization [1, 2]. Characterization, the measurement of various physicochemical properties of materials, is crucial for the evolution of nanotechnology from rudimentary nanomaterials and devices to those that are precision-engineered, mass producible, and safe. Each of the main sectors of nanotechnology – research, manufacturing, and regulation – needs systematic characterization in order to maximize knowledge and control of nanomaterials. Due to a number of factors, many of the nanomaterials that have been synthesized thus far are poorly defined, which can lead to false generalizations about performance and toxicity. The advancement of nanotechnology depends upon a coordinated effort made by researchers, manufacturers, regulators, and funding agencies to improve characterization techniques and practices so that well-defined and reproducible nanomaterials are studied and manufactured. An important consequence of thoroughly characterized materials will be increased public awareness, acceptance and use of nanotechnology.

Ayla Kiser, Catalan Institute of Nanoscience and Nanotechnology (ICN2) February 27, 2014 214
Nano Counterfeit Protection for Space, Aviation and Defense Electronics

Space and defense electronics are two of the most conservative markets in terms of new materials qualification – unless there is a pressing technical issue. Counterfeiting is a huge issue for space, where recall and repair are excruciatingly expensive, or impractical [1][2]. One of the root causes for a recent failure was alleged to be counterfeit SRAM memory chips. In aviation and defense, the problems may be due to the age of the systems and the reliance and rapid obsolescence of COTS (“commercial-off-the shelf”) electronics with a lifetime of a few years whereas weapons systems have lifetimes of decades. An extreme example is the B-52, first flown in 1952 with a projected retirement date of 2040! Couple this with data quoted by King that 57% of counterfeit-part reports from 2001 through 2012 involved obsolete components and we have a real problem.

Alan Rae, Ph.D., M.B.A. February 26, 2014 106
Wearable Textile Batteries

Portable electronic devices are pervasive in our society, keeping us connected to our offices and families regardless of where we are on the planet. From sensors that track daily caloric intakes and training regimes, to future uses of watching your favorite sporting event on the sleeve of your shirt, it is clear that wearable electronics will play an increasingly important role for consumers. With these advents, it will become paramount that rechargeable batteries be able to be seamlessly interfaced with fabrics to provide the requisite power over extended periods.

Bradley Fahlman, Department of Chemistry, Central Michigan University, InterNano Editorial Staff December 12, 2013 351
Carbon Nanotube-doped Liquid Crystal - Towards Faster LCDs

Liquid crystals (LCs) exhibit a phase of matter that has properties between those of a conventional liquid and those of a solid crystal. So, LCs can flow like a liquid, and at the same time the anisotropic LC-molecules maintain a long range crystalline order. Their unique combinations of liquid and solid-like properties allow liquid crystals to be used pervasively in the electro-optical display technology – known as liquid crystal display (LCD).

Rajratan Basu, US Naval Academy December 12, 2013 950
Virtual Design Methods Provide Strategy for Innovation through Nanomaterial Database Development

Recent materials informatics initiatives are fostering the establishment of open-access, federated databases that catalogue the properties of materials. While an initial emphasis, particularly in the case of nanomaterials, is to understand the toxicological properties of materials, a key goal is to establish model-based materials design methodologies wherein materials properties can be computationally predicted. Such a virtual design approach to materials represents a powerful paradigm in which tools become openly available to design new products, optimize materials performance, and understand the risk associated with human and environmental exposure before the materials has been synthesized. Such an infrastructure will benefit industry, academia, and government agencies alike in providing low cost, rapid turn-around approaches to design, and manufacture materials, incorporate into product designs, and establish the regulatory pathway for workforce and consumer protection.

Jeff Morse, PhD September 26, 2013 263
Hierarchical Integration of Multi-scale Elements for Micro-Fuel Cells

Fuel cell power sources can be an efficient technology for direct conversion of various forms of hydrocarbon fuels to electrical power, and in the case of hydrogen fuel, could provide one of the greenest energy sources available. Fuel cells have the potential to impact application areas including grid scale, automotive, and portable electronics, but the predicted impact has not yet been realized as the manufacturing, cost, and reliability of fuel cell components has not matured sufficiently to be competitive with other power sources. Fuel cell optimization challenges remain due to the need to create a hierarchical materials structure at the triple-phase boundary. This facilitates  effective mass transport of reactants and byproducts with a materials region that incorporates catalyst, electrolyte, and conductor properties within a porous diffusion scaffold. Integrating these nanoscale features with microscale flow field channels requires multiple process steps and materials layers that are typical of fuel cell architectures.

Jeff Morse, PhD July 31, 2013 362
Nanotextured Surfaces Impregnated with Lubricant for Enhanced Condensation

Incorporation of specific nanostructures and textured patterns on surfaces is a growing area of research for controlling surface wetting properties. By tailoring the hydrophobicity for a given surface, enhanced features may be achieved by design such as anti-icing or anti-fog, self-cleaning and repellency to a range of liquids. Another significant area of application for such surfaces is condensation for industrial processes such as power generation, thermal management, air conditioning, desalination, and transportation. Enhancing the heat transfer during condensation will significantly impact the energy efficiency for these applications, further reducing cost and physical impact on the system. Depending on the wettability of the surface, the condensate either forms as a film or as discrete drops on the surface. The latter is more desirable for effective heat transfer, as a film can behave as a thermal barrier, while the dropwise condensate can be continuously shed allowing for renewed nucleation and growth of drops. As a result of these possible advantages, there has been significant interest in developing superhydrophobic surfaces to promote dropwise condensation. Such surfaces to date have typically incorporated complex surface patterns to obtain extreme non-wetting properties in which droplets are formed and sit atop the sur ...

Jeff Morse, PhD October 31, 2012 465
Nanotechnology-enabled Smart Packaging for Longer Produce Shelf-life

In order to optimize produce shelf-life from time of harvest through storage and transportation, smart packaging and sensor technologies are readily being explored and evaluated for various scenarios encountered in the horticultural industry. Recently, Esser et. al. reported on the selective detection of ethylene gas using carbon nanotube-based sensors as a means of determining fruit ripeness.

Jeff Morse, PhD September 28, 2012 1006
Solution Processing of Transparent Polymer Solar Cells

Polymer solar cells (PSCs) are being actively developed for applications in which large area, high-rate solution based processes provide a low-cost alternative to more traditional photovoltaic device technologies. Progress in PSC performance has demonstrated power conversion efficiency exceeding 10% for tandem device architectures, thereby opening the door for competitive cost-performance trade-off for applications such as building integrated photovoltaics, or chargers for portable electronic devices. A related opportunity is transparent PSCs that could be used to generate power from windows on homes and buildings while still allowing people to see outside. While such a smart window technology for generating electricity could find widespread use, the cost and performance targets are even more critical in order to gain market entry. From a technology standpoint, the PSC would have to convert mainly infrared light to electricity, not the visible part of the spectrum, leaving the cells at least 70% transparent to the human eye, while demonstrating power conversion efficiency approaching that of normal PSCs. For manufacturing, the cells would have to be made through solution processing in order to achieve the necessary economy of scale for market acceptance, while further enhancing the value proposition through an extended lifecycle ...

Jeff Morse, PhD July 26, 2012 505
Rapid Assembly of Functional Thin Films Using Spin-Spray Layer-by Layer Processing

Functional nanocomposite thin films are traditionally synthesized by techniques such as casting or dip-coating wherein the quality and properties of the film are determined by the concentrations of the initial dispersion and casting time, with limited parameters to control or tune the properties of the film. Layer-by-layer (LbL) assembly has emerged as a method to circumvent this issue by offering exquisite control over the composition and properties of a multilayer, polymer-nanostructure materials hybrid, and has become an effective method for synthesis of carbon nanotube (CNT)-polymer composite films. LbL assembly utilizes the sequential deposition of polyelectrolyte pairs through a dip-coating procedure. The deposition of materials during each cycle is self-limiting, dictated by the charge concentration of the polyelectrolyte solution and the surface being coated. Yet LbL assembly is still a relatively slow process, requiring time-scales on the order of days to produce films with targeted conductivity and thickness. Utilizing spraying techniques to apply the polyelectrolyte solutions to the substrate, significant reduction in process time has been demonstrated. While spraying the polyelectrolyte-CNT solution is both materially and temporally efficient, the time requirements to deposit thin films remain excessive for batch and ...

Jeff Morse, PhD June 07, 2012 558
Inkjet-Printed Graphene Flexible Electronics

Electronic devices on flexible substrates has been a growing area for research and development due to rapidly expanding applications and markets for touch screens, electronic paper and displays, photovoltaics, lighting, and sensor tags. To achieve the economy of scale for large area substrates requiring active transistor functionality, the primary focus has been to fabricate the electronics directly on the flexible substrate. A typical drawback of this approach is that the fabrication processes must be compatible with the nominally low-temperature plastic materials that are being considered for the substrates. As a result, the semiconductor materials have relatively poor electronic transport properties, which can translate to large switching voltages, as well other performance limitations such as switching current ON/OFF ratio. The most promising materials and processes to date include thin-film metal oxide materials deposited by moderate temperature processes such as chemical vapor deposition (CVD) or atomic layer deposition (ALD), yet there are still concerns associated with substrate compatibility, throughput, and subsequent process integration for final device and circuit designs. In contrast, a range of semiconducting nanomaterials ink formulations have been studied suitable for coating by techniques such as spin-casting, r ...

Jeff Morse, PhD March 30, 2012 1127
Additive-Driven Assembly of Block Copolymer-Nanoparticle Hybrid Materials for Solution Processable Floating Gate Memory

Floating gate memory devices were fabricated using well-ordered gold nanoparticle/block copolymer hybrid films as the charge-trapping layers, SiO2 as the dielectric layer and poly(3-hexylthiophene) as the semiconductor layer.  The charge-trapping layer was prepared via self-assembly. The addition of Au nanoparticles that selectively hydrogen-bond with pyridine in a poly(styrene-b-2-vinyl pyridine) block copolymer yields well-ordered hybrid materials at Au nanoparticle loadings up to 40 wt%. The characteristics of the memory window were tuned by simple control of the Au nanoparticle concentration. This approach enables the fabrication of well-ordered charge storage layers by solution processing, which is extendable for the fabrications of large-area and high-density devices via roll-to-roll processing. 

Qingshuo Wei, Ying Lin, Eric R. Anderson, Alejandro L. Briseno, Samuel P. Gido and James J. Watkins February 07, 2012 600
Voltage Controlled Drug Release from Nanoparticles for Hybrid Smart Drug Delivery Systems

Stimulus-responsive biomaterials are of significant interest as in vivo drug delivery systems. Such materials provide a means for controlled and long-term drug release as new treatments for a range of chronic diseases that require daily injections or precise doses of specific medications. Various materials systems investigated to date have exhibited response to heat, light, pH, enzymes, ultrasonic waves, and magnetic fields. While some interesting performance has been reported utilizing these stimulus methods, activation of these materials typically requires large or specialized equipment. In comparison, electric-field stimulus is much simpler to generate and control. Electrical signals have been shown to release molecules via conducting polymeric bulk materials or implantable electronic delivery devices, yet often require invasive surgery to implant and activate the devices. In order to implement electrically activated drug delivery, a technique is required that encapsulates the drug compound in a platform suitable for injection to a specific locale where the release can be triggered.

Jeff Morse, PhD January 25, 2012 547
Spatial Atomic Layer Deposition for Industrial Scale Nanomanufacturing of Thin Films

Atomic layer deposition (ALD) has emerged over the past decade as a viable alternative to physical and chemical vapor deposition (PVD, CVD) techniques for a range of strategic thin film coatings. This is due to the improved control of thin film properties including the incorporation of extrinsic dopants, reduction of contaminants, and the formation of intrinsic defects during film growth through a low temperature, non-vacuum process. These benefits result from the time-sequenced introduction of precursors in the deposition zone where selective and self-limiting half reactions occur on the surface. In this manner, thin-film growth is determined by surface kinetics, and is able to avoid parasitic gas-phase reactions. As such, film properties can be controlled by variation of temperature and reactant partial pressure. However, conventional time-sequenced ALD is not compatible with many scaled industrial applications as film growth rates (~0.01 nm/s) are rather slow due to the need to purge reactants during each growth half-cycle.

Jeff Morse, PhD January 18, 2012 926
Flexible, Large Area Active Matrix Backplane Technology By Solution Cast Carbon Nanotube Thin Film Transistors

Flexible electronics are receiving significant attention for enabling a broad range of new applications and markets otherwise not possible with conventional silicon integrated circuit technology. Specifically in the areas of integrated electronics and sensors, thin-film transistors (TFTs) formed utilizing a range of nanomaterials now appear to be a viable competitor to more conventional TFT technologies such as amorphous silicon. The benefit of utilizing nanomaterials for active devices is the semiconducting properties of the specific nanomaterials. They can be optimized either during or after synthesis, then integrated into the thin-film device process sequence as a solution-based coating step. This enables the carrier transport properties of the nanomaterials to be optimized independently of device design and integration, and also provides a versatile means for adapting TFT circuit designs for flexible electronics applications. These include highly semiconductor enriched single wall carbon nanotubes (SWNTs) which are now being commercialized with >99% purity, and a range of semiconducting nanowire materials that have demonstrated charge mobility comparable to that of crystalline semiconductors. A key nanomanufacturing challenge is to maintain the performance of the individual nanoelements for the integrated system. As such ...

Jeff Morse, PhD January 12, 2012 806
Lead-Free Nanowire Piezoelectric Nanogenerator: Potential for Ubiquitous Power

Scavenging energy from the environment at meaningful power densities remains an elusive and costly target for a range of small-scale applications, such as wireless sensors and autonomous information networks. In addition, prospects for scaling such technologies to provide real energy production from renewable sources could be a driver, but require much more stringent cost and scaled manufacturing targets. Environmentally renewable sources of energy that scale from miniaturized power sources to large scale energy production include solar, thermal, and vibrational, all of which have been enhanced by the incorporation of nano-enabled materials and nanomanufacturing processes. In many scenarios, an ideal system might include each type of energy conversion device implemented in a thin stack with energy storage elements. As this vision gains momentum, optimization of each type of conversion element is still required, both from a materials and scaled fabrication standpoint. In the case of vibration energy scavenging, research on nanowire (NW) piezoelectric power generation has focused on the use of zinc oxide (ZnO) or ferroelectric materials (lead zirconate (PbZrO3), lead titanate (PbTiO3), barium titanate (BaTiO3)). Piezoelectric nanogenerators fabricated from these materials have demonstrated modest power densities, yet still have ch ...

Jeff Morse, PhD December 15, 2011 1012
Integrated Nanowire Logic Circuitry on Deformable Nonplanar Substrates

While a significant amount of recent research and development has focused on flexible electronics and improvements in thin film transistor performance on flexible substrates, less attention has been given to electronics application requiring deformable layouts or extreme, complex surface shapes and curvatures. As flexible electronics technology matures, a growing number of applications require stretchable or extreme nonplanar systems approaches. Examples of these applications include electronic eye cameras, hemispherical or curvilinear electronics, prosthetic or medical sensors, and stretchable LEDs, displays, photovoltaics, sensors, or logic devices utilizing thin silicon. In all of these applications it is critical to maintain the performance of the active electronic devices as the substrate is deformed due to changes in shape or external applied forces. A key issue related to this is the adjustment in resistive properties of nanomaterial-elastomer composites as the elastomeric substrates is stretched, thereby necessitating different approaches for the design and manufacture of deformable electronic systems.

Jeff Morse, PhD December 14, 2011 1497
 
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  • Testbeds  ( 4 items )

    System level test-beds are public-private partnerships designed to transfer promising fundamental discoveries and developments from the research laboratory to viable manufacturing platforms that can be adopted by industry. The NNN is taking a close look at some of these collaborations from our affiliate research centers.

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    Topics in Nanomanufacturing are short, encyclopedia-like entries designed to provide provide an overview of a specific topic of relevance to nanomanufacturing in enough detail to serve as a reference in itself, but also provide additional information for those who wish for more in-depth analysis.