Artificially engineered capacitors for discrete high-frequency electronic circuitry

The concept of the artificially engineered capacitor (AEC) is presented as a 3D printable 3D capacitive component for the use in discrete RF/microwave electronic circuitry. The intention of the AEC concept is a highly customizable 3D printable component whose capacitance value is stable over a wider frequency band when compared to commercial alternatives. AECs can be viewed as impedance structures with predominantly capacitive characteristics. Both series and shunt AEC configurations are considered with simulation and measurement data along with equivalent circuit models. The tolerance of the equivalent capacitance over frequency is focused upon in this paper. Within the 40 % tolerance band from the nominal value an improvement of 26 % and 197 % frequency band was achieved for the series and shunt variants respectively when compared to a commercial alternative. Further simulations show that with finer 3D printing resolutions, this frequency stable bandwidth can be further increased. Finally, an example design application of a halfwavelength microstrip resonator is presented in which the AECs’ Q factor is measured, and the its equivalent circuits are implemented and validated via simulations and measurements.</div

Additively Manufactured RF Components, Packaging, Modules, and Flexible Modular Phased Arrays Enabling Widespread Massively Scalable mmWave/5G Applications

The 5G era is here and with it comes many challenges, particularily facing the high frequency mmWave adoption. This is because of the cost to implement such dense networks is much greater due to the high propagation losses of signals that range from 26 GHz to 40 GHz. Therefore there needs to be a way to utilize a method of fabrication that can change with the various environments that 5G will be deployed in, be it dense urban areas or suburban sprawl. In this research, the focus is on making these RF components utilized for 5G at low cost and modular with a focus on additive manufacturing. Since additive manufacturing is a rapid prototyping technique, the technology can be quickly adjusted and altered to meet certain specifications with negligible overhead. Several areas of research will be explored. Firstly, various RF passive components such as additively manufactured antennas and couplers with a combination hybrid inkjet and 3D printing will be discussed. Passive components are critical for evaluating the process of additive manufacturing for high frequency operation. Secondly, various structures will be evaluated specifically for packaging mmWave ICs, including interconnects, smart packaging and encapsulants for use in single or multichip modules. Thirdly, various antenna fabrication techniques will be explored which enables fully integrated ICs with antennas, called System on Antenna (SoA) which utilizes both inkjet and 3D printing to combine antennas and ICs into modules. These modules, can then be built into arrays in a modular fashion, allowing for large or smaller arrays to be assembled on the fly. Finally, a method of calibrating the arrays is introduced, utilizing inkjet printed sensors. This allows the sensor to actively detect bends and deformations in the array and restore optimal antenna array performance. Built for flexible phased arrays, the sensor is designed for implementation for ubiquitous use, meaning that its can be placed on any surface, which enables widespread use of 5G technologies.Ph.D

Processing to Enable Direct-Write Additive Manufacturing of Ceramics and Ceramic Composites

This research focuses on the processing of novel feedstocks for and during direct-write additive manufacturing (AM), specifically the direct ink writing (DIW) and Ceramic On-Demand Extrusion (CODE) manufacturing processes, in order to produce ceramic and ceramic-based composite components. Strongly dispersed, concentrated (φ = 0.42), nanoparticle (d50 ~0.3 µm), zirconia (ZrO2) pastes were used to print densely filled, large continuous volume (≳ 1 cm3) ceramic components. An elastic shear modulus (G’) of 56,000 Pa and yield stresses between 6 and 10 Pa allowed for printed components of 34.5 mm in height over 115 layers without slumping due to partial drying. Printed parts exhibited lateral particle migration during post-processing. Several methods were proposed to improve future feedstocks to prevent this defect. A zirconium diboride (ZrB2) paste (φ = 0.45) was formulated to print fine-featured (\u3c335 \u3eµm), ultra-high temperature ceramic (UHTC) monoliths. The final ZrB2-based paste exhibited an elastic shear modulus of ~104 Pa, flow index of 0.34, and flow stress of ~40 Pa, as-designed for monolithic printing. In discrete multi-material printing, dielectric and conductor formulations were printed together to established considerations for co-DIW of ceramic electronic packaging technologies. Low temperature co-fired ceramic (LTCC) structures were demonstrated by co-printing but were not successfully post-processed due to mismatched co-drying. In graded printing, a Mo (φ = 0.45) paste was developed to print with ZrB2. These formulations were successfully combined to 3D print 11 layer, 10% gradings between the constituents into laminar bars. These bars were pressurelessly sintered to 2050°C without observed cracking but had an average warpage of 20 ± 9° --Abstract, p. i

Additive Manufacturing: Applications and Directions in Photonics and Optoelectronics

The combination of materials with targeted optical properties and of complex, 3D architectures, which can be nowadays obtained by additive manufacturing, opens unprecedented opportunities for developing new integrated systems in photonics and optoelectronics. The recent progress in additive technologies for processing optical materials is here presented, with emphasis on accessible geometries, achievable spatial resolution, and requirements for printable optical materials. Relevant examples of photonic and optoelectronic devices fabricated by 3D printing are shown, which include light-emitting diodes, lasers, waveguides, optical sensors, photonic crystals and metamaterials, and micro-optical components. The potential of additive manufacturing applied to photonics and optoelectronics is enormous, and the field is still in its infancy. Future directions for research include the development of fully printable optical and architected materials, of effective and versatile platforms for multimaterial processing, and of high-throughput 3D printing technologies that can concomitantly reach high resolution and large working volumes

Mechanics and applications of stretchable serpentine structures

Stretchable structures have been developed for various applications, including expandable coronary stents, deployable sensor networks and stretchable bio-mimetic and bio-integrated electronics. High-performance, stretchable electronics have to utilize high-quality and long-lasting inorganic electronic materials such as silicon, oxide dielectrics and metals, which are intrinsically stiff and often brittle. It is therefore an interdisciplinary challenge to make inorganic electronics stretchable while retaining their electronic functionality. Patterning stiff materials into serpentine-shaped wavy ribbons has become a popular strategy for fabricating stretchable inorganic electronics. However due to a lack of mechanics understanding, design of serpentine structures is still largely empirical, whether for freestanding or substrate supported serpentines. This dissertation systematically investigates the mechanics of serpentine structures with emphasis on the effects of serpentine geometry and substrate stiffness, which involves theoretical analysis, numerical simulation, and experimental validation. Our theory has successfully predicted the stretchability and stiffness of various serpentine shapes and has been applied to the optimization of serpentine designs under practical constraints. We are also the first to point out that not all geometric effects are monotonic and serpentines are not always more stretchable than linear ribbons. To manufacture high quality serpentine ribbons with high throughput and low cost, we have invented a “cut-and-paste” method to fabricate both metallic and ceramic serpentines. As a demonstration of our method, a noninvasive, tattoo-like multifunctional epidermal sensor system has been built for the measurement of electrophysiological signals, skin temperature, skin hydration, and respiratory rate. Engineering of epidermal stretchable antenna for wireless communication is also detailed and rationalized.Mechanical Engineerin

Emulsion Inks: A New Class of Materials for 3D Printing Porous Tissue Engineered Grafts

Tissue grafts are often crucial in restoring function and promoting healing after traumatic injury. Many synthetic materials have been developed, but these often suffer from inadequate tissue integration, limited biodegradability, and mechanical mismatch with the target tissue. Recent advances in 3D printing technologies have enabled the fabrication of custom-fit scaffolds that resemble native tissue. Although these scaffolds can more closely mimic defect shape, new inks are needed to provide tunable control over multiple levels of scaffold structure and function. To address these limitations, we have developed an extensible system for printing complex tissue engineered scaffolds by creating emulsion templated inks. These emulsion inks exhibit tunable pore sizes, modulus, and strength. Formulation of inks with viscous, reactive macromers results in extruded material that holds its shape after extrusion and polymerizes rapidly upon exposure to UV light. New methodology was developed to permit the rational design of emulsion inks based on rheological and cure properties, and these inks were able to successfully create high fidelity scaffolds with customizable, hierarchical porosity. Emulsion inks are compatible with nearly any hydrophobic macromer allowing development of inks with limitless chemical and material properties. Next, a hybrid printing system was developed for extrusion of thermoplastic PCL and PLA along with emulsion inks to provide mechanical reinforcement. Scaffolds without reinforcement exhibited an increase in permeability with a decrease in infill density, with detriment to their modulus and strength. Mechanical reinforcement with PLA, however, resulted in a significant increase in modulus and strength in all cases. The creation of novel emulsion inks from existing biomaterial systems opens the door to the creation of scaffolds with a wide range of physical and chemical properties. Finally, this system was extended to oil-in-water emulsions, termed hydrocolloid inks, to facilitate printing of hydrogels. Due to their low viscosity, high fidelity printing of hydrogels has typically been limited to SLA methods. SFF printing of hydrogel scaffolds frequently relies on thickeners and additives, but we have refined the rheological properties without modification of the hydrogel makeup by emulsifying with innocuous mineral oil. These 3D printed hydrogel scaffolds represent some of the highest fidelity reproductions of complex anatomical geometries in the literature to date. Additionally, this system provides a methodology for creating hydrocolloid inks from nearly any hydrogel biomaterial. In summary, we have developed a library of porous materials that can be used to improve tissue regeneration. Furthermore, the emulsion structure-property relationships explored here can be used in designing future emulsion inks. A combinatorial approach of tuning the ink and fabrication system allows for creation of complex scaffolds with improved biomimicry, allowing for a new generation of hierarchically porous tissue engineered constructs

A review on materials and technologies for organic large-area electronics

New and innovative applications in the field of electronics are rapidly emerging. Such applications often require flexible or stretchable substrates, lightweight and transparent materials, and design freedom. This paper offers a complete overview concerning flexible electronics manufacturing, focusing on the materials and technologies that have been recently developed. This combination of materials and technologies aims to fuel a fast, economical, and environmentally sustainable transition from the conventional to the novel and highly customizable electronics. Organic conductors, semiconductors, and dielectrics have recently gathered lots of attention since they are compatible with printing technologies, and can be easily spread over large and flexible substrates. These printing technologies are usually simple and fast procedures, which rely on low-cost and recycle-friendly materials, intended for large-scale fabrication. Overall, even though organic large-area electronics manufacturing is still in its early stages of development, it is a field with tremendous potential that holds promise to revolutionize the way products are designed, developed, and processed from the factory premises to the consumers’ hands. Besides, this technology is highly versatile and can be applied to a large array of sectors such as automotive, medical, home design, industrial, agricultural, among others.This work was supported by NORTE-06-3559-FSE-000018, integrated in the invitation NORTE-59-2018-41, aiming the Hiring of Highly Qualified Human Resources, co-financed by the Regional Operational Programme of the North 2020, thematic area of Competitiveness and Employment, through the European Social Fund (ESF), and by the scope of projects with references UIDB/05256/2020 and UIDP/05256/2020, financed by FCT – Fundação para a Ciência e Tecnologia, Portugal. The authors also thank Prof. Luís A. Rocha for his support and guidance during the writing of this review work

Advancing aerosol jet printing via ink formulation engineering and multi-material printing

In this research work, fundamental concepts behind the process engineering of Aerosol Jet Printing (AJP) are explored. AJP is a direct write technique in which functional inks are aerosolized and deposited onto a substrate with resolutions on the order of 10 µm and, so far, has been used in the fabrication of devices relevant to the microelectronics industry. Some peculiarities of the AJP process make it particularly compelling for advanced applications. First, this printing method is compatible with a wide variety of inks that can be formulated with a viscosity between 1-1000 mPa s and particle size below 0.5 µm, is digital in nature, and has a high operational standoff (1-5 mm); the combination of these properties makes AJP well suitable for the rapid device prototyping, especially on substrates that are either sensitive to harsh deposition conditions and/or post-processing procedures (i.e. polymeric materials with low glass transition temperature, such as PET) or have conformal geometries, in which the non-contact nature of AJP gives considerable advantages over more traditional techniques such as lithography. Although available since the early 2000s, AJP has yet to become as widely used as other additive manufacturing processes like inkjet printing, as significant process drift, difficulty in theoretical modeling, and lack of commercially available inks hinder daily use and, more importantly, process reliability. In particular, the lack of chemical formulation efforts specifically tailored for the deposition method exacerbate AJP reliability issues, leaving a considerable literature gap to be filled. As stated by Wilkinson in his comprehensive AJP review, “Many applications of AJP are facilitated through the formulation of materials with the required processing and functional characteristics. Although AJP has expanded the range of printable viscosities and enabled the deposition of two-part and composites, ink formulation requires a large body of empirical work for consistent deposition. Defining the criteria for a suitable ink through process modelling and experimental observation will accelerate the adoption of the process in commercial settings by decreasing development time scales and cost”,1 a sentiment that fundamentally captures the motivation of the present work. To address some of the more fundamental challenges associated with ink formulation and process engineering concerning daily AJP operation, the current research presents in its first half a systematic approach to define a general solvent system which enables consistent deposition of graphene, addresses typical deposition rate/resolution tradeoffs associated with the technique, and enables manufacturing of stable 2.5D structures without the need of restrictive and strictly controlled process parameters. In the latter half, this research will focus on high-level characterization and applications of multi-material printing, with novel manufacturing outcomes. Briefly, the ability of mixing different functional materials in the aerosol phase allows AJP to deposit composite traces with versatile control over the stoichiometry of the final product. This peculiarity of multi-material AJP is first explored with energetic materials, in which microstructural investigations of printed thermites allowed to investigate aerosol phase mixing and deposit high-resolution energetic devices with great potential for further miniaturization and integration, and then expanded to functionally graded carbon systems with locally defined charge transfer properties. Lastly, as shown throughout the entirety of this manuscript, the chemistry of multi-component solvent system originally derived for graphene was seamlessly applied to four different materials with fundamentally different chemistries (two carbon allotropes, a metal, and a ceramic), generalizing the chemical formulation approach with great potential for widespread application with other materials

Marshall Space Flight Center Research and Technology Report 2017

This report features over 60 technology development and scientific research efforts that collectively aim to enable new capabilities in spaceflight, expand the reach of human exploration, and reveal new knowledge about the universe in which we live. These efforts include a wide array of strategic developments: launch propulsion technologies that facilitate more reliable, routine, and cost effective access to space; in-space propulsion developments that provide new solutions to space transportation requirements; autonomous systems designed to increase our utilization of robotics to accomplish critical missions; life support technologies that target our ability to implement closed-loop environmental resource utilization; science instruments that enable terrestrial, solar, planetary and deep space observations and discovery; and manufacturing technologies that will change the way we fabricate everything from rocket engines to in situ generated fuel and consumables

The role of ceramic and glass science research in meeting societal challenges: Report from an NSF-sponsored workshop

Under the sponsorship of the U.S. National Science Foundation, a workshop on emerging research opportunities in ceramic and glass science was held in September 2016. Reported here are proceedings of the workshop. The report details eight challenges identified through workshop discussions: Ceramic processing: Programmable design and assembly; The defect genome: Understanding, characterizing, and predicting defects across time and length scales; Functionalizing defects for unprecedented properties; Ceramic flatlands: Defining structure-property relations in free-standing, supported, and confined two-dimensional ceramics; Ceramics in the extreme: Discovery and design strategies; Ceramics in the extreme: Behavior of multimaterial systems; Understanding and exploiting glasses and melts under extreme conditions; and Rational design of functional glasses guided by predictive modeling. It is anticipated that these challenges, once met, will promote basic understanding and ultimately enable advancements within multiple sectors, including energy, environment, manufacturing, security, and health care