Corey Shemelya

Expanding the applicability of FDM-type technologies through materials development

Purpose – The purpose of this paper is to demonstrate the strategy for increasing the applicability of material extrusion additive manufacturing (AM) technologies, based on fused deposition modeling (FDM), through the development of materials with targeted physical properties. Here, the authors demonstrate materials specifically developed for the manufacture of electromechanical and electromagnetic applications, the use of FDM-type processes in austere environments and the application of material extrusion AM. Design/methodology/approach – Using a twin screw polymeric extrusion process, novel polymer matrix composites and blends were created where the base material was a material commonly used in FDM-type processes, namely, acrylonitrile butadiene styrene (ABS) or polycarbonate (PC). Findings – The work presented here demonstrates that, through targeted materials development, the applicability of AM platforms based on FDM technology can be increased. Here, the authors demonstrate that that the physical pr...

3-D Printed Microwave Patch Antenna via Fused Deposition Method and Ultrasonic Wire Mesh Embedding Technique

In this work, the design, fabrication and characterization of a 3-D printed microwave patch antenna is presented. The antenna is fabricated by combining fused filament fabrication method for the dielectric part and ultrasonic metal wire mesh embedding approach for the conductor part. Full wave finite-element simulations for different wire mesh structures and also the entire antenna have been done to make sure the embedded wire mesh has good performance at microwave frequency. A microstrip patch antenna working around 7.5 GHz is printed and characterized to demonstrate the efficiency and accuracy of this technique. The measured reflection coefficient shows a good resonance peak at 7.5 GHz. The measured gain of this antenna is 5.5 dB at the resonance frequency. Good agreement between simulation and measurement is obtained in both reflection coefficient and radiation pattern.

3D printed capacitive sensors

Recent advances in the field of 3D printing have utilized embedded electronic interconnects in order to construct advanced electronic devices. This work builds on these advances in order to construct and characterize arbitrarily formed capacitive sensors using fine-pitch copper mesh and embedded copper wires. Three varieties of sensors were fabricated and tested, including a small area wire sensor (320μm width), a large area mesh sensor (2cm2), and a fully embedded demonstration model. In order to test and characterize these sensors in FDM materials, three distinct tests were explored. Specifically, the sensors were able to distinguish between three metallic materials and distinguish salt water from distilled water. These capacitive sensors have many potential sensing applications, such as biomedical sensing, human interface devices, material sensing, electronics characterization, and environmental sensing. As such, this work specifically examines optimum mesh/wire capacitive parameters as well as potential applications such as 3D printed integrated material sensing.

Encapsulated Copper Wire and Copper Mesh Capacitive Sensing for 3-D Printing Applications

Advances in the field of extrusion based 3-D printing have recently allowed the incorporation of embedded electronics and interconnects, in order to increase the functionality of these structures. This paper builds on previous work in the area of fine-pitch copper mesh and embedded copper wire capacitive sensors encapsulated within a 3-D printed structure. Three varieties of sensors were fabricated and tested, including a small area wire sensor (320-μm width), a large area mesh sensor (2 cm2), and a fully embedded demonstration model. In order to test and characterize these sensors, three distinct tests were explored. Specifically, the capacitive sensors were able to distinguish between three metallic materials and distinguish salt water from distilled water. These capacitive sensors have many potential sensing applications, such as biomedical sensing, human interface devices, material sensing, electronics characterization, and environmental sensing. As such, this paper also characterizes the capacitive sensors for an active microfluidic mixer.

Stable high temperature metamaterial emitters for thermophotovoltaic applications

We report a metamaterial design for a thermophotovoltaic (TPV) emitter. TPVs are similar to photovoltaic solar cells, but they convert heat to electricity instead of sunlight. The focus of this paper is on the emitter stage of the TPV system, which converts the heat into a spectral band which is easily absorbable by the TPV photodiode. The proposed structure consists of a platinum metallic element, an alumina dielectric spacer, and platinum grounding plane on a sapphire substrate. This perfect absorber based metamaterial emitter is shown to robustly operate at 600 °C. This temperature is high enough to enable TPV use for many industrial applications.

Mechanical, Electromagnetic, and X-ray Shielding Characterization of a 3D Printable Tungsten–Polycarbonate Polymer Matrix Composite for Space-Based Applications

Material-extrusion three-dimensional (3D) printing has recently attracted much interest because of its process flexibility, rapid response to design alterations, and ability to create structures “on-the-go”. For this reason, 3D printing has possible applications in rapid creation of space-based devices, for example cube satellites (CubeSat). This work focused on fabrication and characterization of tungsten-doped polycarbonate polymer matrix composites specifically designed for x-ray radiation-shielding applications. The polycarbonate–tungsten polymer composite obtained intentionally utilizes low loading levels to provide x-ray shielding while limiting effects on other properties of the material, for example weight, electromagnetic functionality, and mechanical strength. The fabrication process, from tungsten functionalization to filament extrusion and material characterization, is described, including printability, determination of x-ray attenuation, tensile strength, impact resistance, and gigahertz permittivity, and failure analysis. The proposed materials are uniquely advantageous when implemented in 3D printed structures, because even a small volume fraction of tungsten has been shown to substantially alter the properties of the resulting composite.

GaSb Thermophotovoltaic Cells Grown on GaAs Substrate Using the Interfacial Misfit Array Method

We present gallium antimonide (GaSb) p–i–n photodiodes for use as thermophotovoltaic (TPV) cells grown on gallium arsenide (100) substrates using the interfacial misfit array method. Devices were grown using molecular beam epitaxy and fabricated using standard microfabrication processes. X-ray diffraction was used to measure the strain, and current–voltage (I–V) tests were performed to determine the photovoltaic properties of the TPV cells. Energy generation at low efficiencies was achieved, and device performance was critically analyzed.

Two dimensional metallic photonic crystals for light trapping and anti-reflective coatings in thermophotovoltaic applications

We report the development of a front-side contact design for thermophotovoltaics that utilizes metallic photonic crystals (PhCs). While this front-side grid replacement covers more surface area of the semiconductor, a higher percentage of photons is shown to be converted to usable power in the photodiode. This leads to a 30% increase in the short-circuit current of the gallium antimonide thermophotovoltaic cell.

3D printed multilayer microstrip line structure with vertical transition toward integrated systems

In this paper, a 3D printed multilayer microstrip line structure with vertical transition is designed, fabricated and characterized. The dielectric part of the structure is printed using the FDM method and the conductor part is printed using the ultrasonic wire embedding approach. The measured total insertion loss of the 3D printed multilayer microstrip (90 mm long) including the vertical transition is smaller than 2 dB below 6 GHz. The measured results agree well with the simulation. The performance of this structure demonstrates that 3D printing techniques may be able to realize functional multilayer RF components / systems. As an example, a 3D printed multilayer phased array is designed based on similiar microstrip and vertical transition structure in this work. The simulated results show good impedance matching around 3.5GHz and a high directive beam at expected direction.

Multi-functional 3D printed and embedded sensors for satellite qualification structures

Three dimensional (3D) printing has recently gained attention in a variety of industries ranging from aerospace to biomedical. However, in order to create truly functional 3D printed structures, electronic functionality must be integrated into building sequence. This work explores the integration of both printed sensors (copper capacitive touch sensors) and embedded COTS sensors (surface mount accelerometers) in order to fabricate a space-flight qualification test coupon in the shape of a 1U CubeSat (10 × 10 × 10 cm) as required for stress testing. The 3D printed electronics were fabricated by an enhanced Multi3D 3D Printing system, allowing the direct integration of 3D printed dielectric structures with electronics components fabricated together using a single non-assembly build sequence. Both sensors and structures successfully demonstrated electronic functionality after full encapsulation, and show promise for integration in space based cube satellites.