Manufacturing in low earth orbit (LEO) offers a superb opportunity to leverage the unique physical properties of a low-gravity environment to produce materials and products not accessible in terrestrial systems. For example, in microgravity, convection is suppressed, sedimentation is minimized, and fluid dynamics change in ways that allow for the formation of ultra-pure materials, defect-free crystals, and novel composite structures. As launch costs continue to decrease and orbital infrastructure grows, these advantages make LEO an ideal setting for high-value manufacturing applications. In our NASA-sponsored SBIR program, Faraday developed a 3D electrochemical printing platform for advanced electronics manufacturing (and in-space repair capabilities). The nozzle-based electrochemical deposition of copper-graphene (‘covetic’) traces demonstrated enhanced electrical conductivity (15-20% greater than copper). It is hypothesized that printing in a low-gravity environment will enhance the graphene intercalation within the copper matrix due to lower sedimentation rates; a zero-gravity flight test is currently planned for November 2025 to validate the potential for 3D electrochemical printing in LEO. Furthermore, our agile printing method enabled us to print onto silver and laser-induced graphene traces, traditionally used in 3D printing applications, to enhance material conductivity (thermal and electrical). The printed covetic material can be easily soldered and offers an advantage over other 3D electrically conductive printed materials (e.g., Ag-based, graphene, etc.) for true utility in electronics manufacturing.

INTRODUCTION:Known as the "golden hour," survival of most critically injured patients is highly dependent on providing the required treatment within the first hour of injury. Recent technological advances in additive manufacturing (also known as three-dimensional [3D] printing) allow for austere deployment and point-of-care rapid fabrication of a variety of medical supplies, including human tissues and bioactive bandages, in prolonged field care scenarios. In this pilot project, our aim was to investigate the ability to 3D print a range of potential biomedical supplies and solutions in an austere field environment. MATERIALS AND METHODS:We specifically designed and fabricated novel surgical tools, bioactive bandages, objects (screw and anatomic models), and human meniscal tissue in an austere African desert environment. A total of seven packages were sent using a commercial carrier directly to the end destination. A multi-tool ruggedized 3D printer was used as the manufacturing platform for all objects fabricated downrange. Human mesenchymal stem cells were shipped for 3D bioprinting of human menisci and bioactive bandages. Design and fabrication for all 3D-printed products utilized computer-aided design (CAD) tools. RESULTS:Initial shipment from a single U.S. site to the sub-Saharan Africa location was relatively prompt, taking an average of 4.7 days to deliver three test packages. However, the actual delivery of the seven packages from Orlando, FL, to the same sub-Saharan Africa site took an average of 16 days (range 7-23 days). The ruggedized printer successfully fabricated relevant medical supplies using biocompatible filament, bioink hydrogels, and stem cell-loaded bioinks. This prototype did not, however, have the capacity to provide a sterile environment. A multi-material complete bandage was 3D printed using polyamide polyolefin and cellulose, live cells, neomycin salve, and adhesive. The bandage, wound covering backing, and adhesive backing print took under 2 min to 3D print. Surgical instrument CAD files were based on commercially available medical-grade stainless-steel instruments. The screw CAD file was downloaded from the NIH 3D Print Exchange website. The prints of the two surgical tools and screw using thermoplastic material were successful. Menisci, relatively complex forms of the cartilage, were 3D bioprinted with a gel that held their form well after printing and were then solidified slightly using a cross-linking solution. After 2 min of solidification, it was possible to remove and handle the menisci. CONCLUSION:The current and future challenges of prolonged field care need to be addressed with new techniques, training, and technology. Ruggedized, deployable 3D printers allow for the direct fabrication of medical tools, supplies, and biological solutions for austere use. Delivery of packages can vary, and attention to routes and location is key, especially for transit of time-sensitive perishable supplies such as live cells. The significance of this study provides the real possibility to 3D print "just-in-time" medical solutions tailored to the need of an individual service member in any environment. This is a potentially exciting opportunity to bring critical products to the war front.

Design and performance of a fully-printed Ku-band aperture coupled patch antenna manufactured by making use of a direct digital manufacturing (DDM) approach that integrates fused deposition of acrylonitrile butadiene styrene (ABS) thermoplastics with in-situ micro-dispensing of conductive silver paste (CB028) is reported. Microstrip line characterizations demonstrate that the microstrip line feed loss of the antenna is minimized by printing ABS in parallel with the line directions. A wideband (20%) performance is achieved by employing a multilayer printing approach. Compared to existing work in literature, the presented antenna stands out as being fully-printed, operating within the Ku-band, and exhibiting high radiation efficiency (6.5 dB gain) with wide bandwidth performance.

Microdispensing of thick-film conductive paste has been demonstrated as a viable approach for manufacturing microwave planar transmission lines. However, the performance and upper frequency range of these lines is limited by the cross-sectional shape and electrical conductivity of the printed paste, as well as the achievable minimum feature size which is typically around 100 mu m. In this paper, a picosecond Nd: YAG laser is used to machine slots in a 20-25-mu m-thick layer of silver paste (Dupont CB028) that is microdispensed on a Rogers RT5870 substrate, producing coplanar waveguide (CPW) transmission lines with 16-20 mu m-wide slots. It is shown that the laser solidifies an about 2-mu m-wide region of the edges of the slots, thus significantly increasing the effective conductivity of the film and improving the attenuation constant of the lines. The extracted attenuation constant at 20 GHz for laser machined CB028 is 0.74 dB/cm. CPW resonators and filters show that the effective conductivity is in the range from 10 to 30 MS/m, which represents a 100x improvement when compared to the values obtained with the exclusive use of microdispensing. This paper demonstrates that a hybrid approach of additive manufacturing and laser machining enables the fabrication of higher frequency circuits (up to at least 40 GHz) with improved performance.

Direct digital manufacturing (DDM) is an emerging technology that is finding its place across a wide array of industries and applications as a cost-effective solution for low volume and mass customizable production. This technology encompasses a class of digital manufacturing techniques which can be combined to enable multimaterial fabrication and postprocessing. One of the promising applications for DDM is structural electronics, where lightweight printed plastics provide mechanical support as a fixture, package, or structural member and also host the electrical interconnects and devices, all in a contiguous fashion. Microwave structural electronics is a specific class of such systems for which the printing resolution as well as electrical and surface properties of the materials are especially important. This paper presents the current state of DDM technology, fundamental research into the electrical and mechanical properties of as-printed structures, and novel 3-D printed structures operating from C-band through Ku-band.

Printed electronics is a familiar term that is taking on more meaning as the technology matures. Flexible electronics is sometimes referred to as a subset of this and the printing approach is one of the enabling factors for roll to roll processes. Printed electronics is improving in performance and has many applications that compete directly with printed circuit boards. The advantage of roll to roll is the speed of manufacturing, the large areas possible, and a reduction in costs. As this technology continues to mature, it is also merging with the high profile 3D printing. 3D printing is becoming more than just a rapid prototyping tool and more than just printing small plastic toys. Companies are embracing 3D printing as a manufacturing approach to fabricate complex parts that cannot be done using traditional manufacturing techniques. The combination of 3D printing and printed electronics has the potential to make novel products and more specifically making objects electrically functional. Electrically functional objects have the advantage of competing with printed circuit boards. Printed circuit structures will be a new approach to electronic packaging. It is the desire of many companies to reduce assembly processes, decrease the size of the electronics, and do this at a reduced cost. This is challenging, but the potential of printing the structure and the electronics as a single monolithic unit has many advantages. This will reduce the human touch in assembly, as the electronics and the object are printed. This will increase the ruggedness of the product, as it is a monolithic device. This will eliminate wires, solder, and connectors, making the device smaller. This has the potential to be the future of printed circuit boards and microelectronic packaging. This paper will show working demonstrations of printed circuit structures, the obstacles, and the potential future of 3D printed electronics. Introduction While 3D printing, as stereolithography (SLA), has been around since the early 1980s, it is has evolved considerably into many forms. For the purposes of this paper, fused filament deposition (FFD) also known as fused deposition modeling (FDM) will be considered. Only recently has FDM printing been joined by electronic printing to create 3D printed electronics. With this evolution in 3D printing, Printed Circuit Structures (PCS) can possess distinct advantages over Printed Circuit Boards (PCB). Many components that are present on a PCB can be integrated into a PCS. It has been shown that PCSs can contain fully embedded circuity such as antennas [1][2], lumped components [3], and even connectors [4]. Instead of creating a PCB to attach to an object, it would be possible to print the object with the circuitry as an integrated part of it. This printing method is made possible using a Direct Digital Manufacturing (DDM) machine which combines the use of multiple tool heads including a micro-dispensing pump, a heated extrusion head, a pick-and-place head, and a micro-milling, drilling, and polishing head. While PCBs require the use of many machines and require masking, PCSs can be completely automated as total fabrication is done in-situ on a single machine [5][6]. Although PCSs do have advantages, there are still several obstacles to overcome, namely speed of fabrication and strength of final parts. Fabrication Speeds FDM style 3D printing is notorious for being slow. This is mainly due to the low volumetric extrusion rates of conventional desktop 3D printers. There are many factors that determine extrusion rate. Some of these include nozzle diameter, nozzle temperature, bed temperature, X-Y movement speed, material, and even the extrusion motor. While all of these have an effect on the total amount of filament being extruded, the nozzle diameter is the main determiner of extrusion rate. Layer height, extrusion widths, and print speeds are all based on the nozzle diameter, therefore this is the facet of the printing process that stands to generate the most benefits from improving. The standard printing nozzle has a 0.4mm inside diameter. This allows for print speeds of up to 80-100 mm/s, depending on machine and desired print quality. Nozzle size can be increased, however, while this can shorten the overall print time, a decrease in quality will be seen. These decreases in quality can be things such as a rougher surface finish, rounded corners, and incorrect dimensions. Larger diameter nozzles are also limited when printing small objects as the small features can be problematic. While the quality-related downsides of selecting a large diameter nozzle are not attractive, they can be dealt with. A method of printing called “Spaghetti” printing was developed to greatly increase extrusion rates and decrease print times. This process involves printing filament out of a specially designed 1.75mm nozzle and then utilizing a milling head to give a high-quality surface finish where required as well as bringing the print into dimension. A speed experiment was set up comparing the printing speed of an ASTM D638 Type V tensile specimen printed using a 0.4mm nozzle and the “Spaghetti” printing approach. Two types of tensile specimens were printed; one with a 0° infill and one with a 90° infill from the horizontal. These samples were printed with no perimeters as this would throw off tensile testing. Both of these sample types are 1.0 mm thick and were printed with a nozzle temperature of 235° C and a bed temperature of 50° C. The perimeters seen in Figure 1 and Figure 2 are used to show dimensions. Figure 1: ASTM D638 Type V Tensile Specimen 0° Infill Figure 2: ASTM D638 Type V Tensile Specimen 90° Infill When printed with the 0.4 mm nozzle, each tensile specimen completed printing in 4 minutes and 24 seconds. When done with the Spaghetti method, each tensile specimen averaged 1 minute and 58 seconds total time with the actual 3D printing portion only taking 32 seconds. This experiment was repeated 25 times. Not only did the “Spaghetti” method complete the object more than twice as fast, the final surface finish from milling was far superior to that of the conventionally printed specimen. Figure 3: Spaghetti Printed Tensile Specimen Before and After Milling Figure 4: 0° Printed Tensile Specimen Using 0.4mm Nozzle Figure 5: Micro-Dispensed Conductive Paste on 3D Printed Substrate This benefits PCS greatly as printing the electronics portions requires a smooth surface for conductive material to be dispensed. Normally, for a conductive print to be successful, the FDM substrate layer needs to be printed with a nozzle as small as 100 microns to provide a smooth surface for the conductive material to be printed accurately and true to design. Although surface mapping is available, which enables contour printing, a smooth surface is preferred. This also provides an ideal surface when printing multiple thermoplastics onto one another. Figure 6: Steps of a Printed USB Device The smooth surface enabled the level placement of a USB chip using pick-and-place. Then conductive paste was dispensed to extend the pads of the USB from the chip. Next, a polycarbonate shell was printed around the perimeter of the circular portion to form a cup for an epoxy to be dispensed. Once cured, the epoxy was milled smooth. This is a small demonstration of multi-material, multi-process in-situ PCS fabrication. Strength of Printed Parts Printable fused filaments range from somewhat durable materials such as acrylonitrile butadiene styrene (ABS) to flexible thermoplastic elastomers (TPE) and even FST-rated ULTEM. These materials have their own strengths and weaknesses. Whether it is the high impact strength of ABS or the chemical and temperature stability of ULTEM, choosing the right material for a particular application can determine whether or not it is successful. However, FDM printed parts fall well short of the strengths of other fabrication methods such as injection molding [7]. This is due to the fact that the strength of 3D printed parts rely on layer-to-layer surface adhesion, adhesion of side-by-side printed lines, and print direction as well as the mechanical properties of the material itself. Another aspect of 3D printing that decreases overall strength of printed parts compared to bulk material properties is the presence of voids that are introduced into the part during the printing process. Figure 7: Cross Section View of Printed Layers with a 0.4mm Nozzle Figure 8: Cross Section View of "Spaghetti" Printed Layers In both of these examples (Figure 7 and Figure 8), voids can be observed wherever there is an overlap of side-by-side lines. This is due to the fact that the edges of printed lines are rounded. To combat voids, an overlap factor can be input into the generation of the print path of the object. This will squeeze the lines closer together, minimizing voids, to an extent. When a high overlap factor is specified, the material being squeezed together must go somewhere and thus it is displaced upwards. This will create a rough surface finish if on the top layer and could throw off overall height dimensions if allowed to compound throughout the print. When printed with the 0.4mm nozzle, many, albeit smaller, voids are introduced into the object. While the few voids that are present with the Spaghetti printed layer are larger, the total void area of the parts printed with the 0.4mm nozzle is greater. These voids contribute to the ~10% difference in ultimate tensile strength for the printed specimens (Figure 9). Figure 9: UTS Comparison of "Spaghetti" and 0.4mm Nozzle Tensile Specimens The print direction plays a major role in the strength of printed parts [7][8]. It is common practice when printing structural parts to have layers printed in the direction of force that the final part will experience. To exemplify why printing in the direction of force is important, tensile specimens were printed in the direction of force (0° specimens) and

In this letter, a three-dimensional packaged half-wave dipole antenna is presented. The design includes a grounded coplanar waveguide (GCPW) balun that is printed on an inclined surface and used to connect the 50-Ω feedline on the lower layer to the dipole on the top layer. For matching purposes, a GCPW quarter-wave transformer is incorporated between the 50-Ω feedline and the balun. The 6-GHz half-wave dipole is approximately λ/4 above the ground plane. Fabrication is done using the direct digital manufacturing technique with an acrylonitrile butadiene styrene substrate (relative permittivity of 2.7 and a loss tangent of 0.008) and Dupont CB028 silver paste. The simulated and measured gains are 4.88 and 4.7 dBi, respectively. Antenna substrate surface roughness is analyzed to explain discrepancies between simulation and measurement results.

NASA is pursuing a demonstration of coherent uplink arraying at 7.145-7.190 GHz (X-band) and 30-31 GHz (Kaband) using three 12m diameter COTS antennas separated by 60m at the Kennedy Space Center in Florida. In addition, we have used up to three 34m antennas separated by ~250m at the Goldstone Deep Space Communication Complex in California at X-band 7.1 GHz incorporating real-time correction for tropospheric phase fluctuations. Such a demonstration can enable NASA to design and establish a high power, high resolution, 24/7 availability radar system for (a) tracking and characterizing observations of Near Earth Objects (NEOs), (b) tracking, characterizing and determining the statistics of small-scale (≤10cm) orbital debris, (c) incorporating the capability into its space communication and navigation tracking stations for emergency spacecraft commanding in the Ka band era which NASA is entering, and (d) fielding capabilities of interest to other US government agencies. We present herein the results of our phased array uplink combining at near 7.17 and 8.3 GHz using widely separated antennas demonstrations at both locales, the results of a study to upgrade from a communication to a radar system, and our vision for going forward in implementing a high performance, low lifecycle cost multi-element radar array. .

I. Abstract This paper will discuss the development of additive manufacturing as a process integration methodology for printed electronics and 3D printed structures. This integration enables the ability to move from printed circuit boards (PCBs) to printed circuit structures (PCS). Historically packaging has been identified as a hierarchical (or levels) approach to interconnect electronic products or systems. Level one packaging addresses the interconnection between bare die and the module while level four moves up in the packaging chain to connections between subassemblies. With the advent of digital manufacturing and emergence of more robust materials, the enabling technology provides a manufacturing tool for building electronic packages with integrated passives (some printed) and actives. This further enables the capability to adjust the form factor to the mission or product requirements - also known as personalization. This ability to become form factor agnostic has produced the ability for printing or digitally manufacturing application specific electronic packages, ASEPs. With this emerging capability it begs the question of reliability and in particular to qualification for harsh environment applications. This paper will discuss the application of current standards, Mil-Std-883 or JESD93 for example and how these might be applied to ASEPs and to also explore the development of new or hybridization of current standards.

Abstract Printed electronics and 3D printing have proved their viability for manufacturing functional devices. The state of the art is now at a crossroads where yield, reliability, survivability, and longevity improvements will govern its continued success in manufacturing. Currently, 3D printed electronics demonstration parts are either grossly oversized or are meticulously fabricated and involve significant human interaction and repair and ultimately have low manufacturing yield. Presented here are techniques for improving manufacturing yield. Coefficient of thermal expansion (CTE) mismatch problems frequently occur in devices with heterogeneous materials such as bulk metals, thermoplastics, thermosets, conductive pastes and inks, and pourable dielectrics. Controlling the interfaces between these materials in new and creative ways is key to solving these problems during manufacturing and lifecycle. Selecting materials with good properties such as adhesion, surface energy, flexibility, conductivity, and dielectric properties is the path forward to excellence in this field. Certain improvements in the design of 3D printed electronic devices (demonstrated here) show improved ruggedness. A long-lasting 3D printed electronic device that has been operating 24/7 for 21,000 hours is shown, and the techniques of its design and fabrication are described in detail. Several testing procedures evaluate the performance of the devices. Microscope photos show key problem areas, solutions are implemented, and material selections are presented. Overall device function is monitored wirelessly before, during, and after temperature changes.

3D printing structures is natural for the layer by layer approach. Using a single type of material and building complex structures is not optimized but it is mature. This digital approach to manufacturing has the advantages of lighter structures that maintain strength and can also address the emerging custom market. While these are important contributions, adding electrically functional characteristics to the structures will open new opportunities for next generation products. In the case of the presented materials, the target application is small satellite or Satlets. Adding electronics to 3D structures is not optimized or mature and therefore studying this will be important to understand the potential and the obstacles that must be addressed. Utilizing the combination of 3D printing and printed electronics, we printed a number of device demonstrations the show it is feasible to make diverse shapes with functional electronics. Demonstrations included 3D printed multilayer ceramic Ethernet harness, 3D printed plastic RF controlled impedance interconnect and USB harness and finally 3D printed connectors. Data will be presented on mechanical integrity of printed structures and electrical performance.

This paper reports on the design, fabrication and characterization of a 3-D printed RF front end for a 2.45 GHz phased array unit cell. The printed unit cell, which includes a circularly-polarized dipole antenna, a miniaturized capacitive-loaded open-loop resonator filter and a 4-bit phase shifter, is fabricated using a direct digital manufacturing (DDM) approach that integrates fused deposition of thermoplastic substrates with micro-dispensing for deposition of conductive traces. The individual components are combined in a passive phased array antenna unit cell comprised of seven stacked substrate layers with seven conductor layers. The measured return loss of the unit cell is > 12 dB across the 2.45 GHz ISM band and the measured gain is -11 dBi including all components. Experimental and simulation-based characterization is performed to investigate electrical properties of as-printed materials, in particular the inhomogeneity of printed thick-film conductors and substrate surface roughness. The results demonstrate the strong potential for fully-printed RF front ends for light weight, low cost, conformal and readily customized applications.

3D multi-material additive manufacturing has promising potential to improve the performance and form factor of microwave and electromagnetic components. The ability to design and produce truly 3D form factors can lead to smaller volume and better performing antennas, allow the combining of different materials to optimize and reduce the weight of distributed circuit designs, and cost effectively produce structural electronic systems. Along with these new capabilities come increased needs for material choices, innovative methods for materials characterization, and changes in the CAD tools that are used for design. These challenges, along with examples of 3D RF design with additive manufacturing are given in this paper.

3-D printing is enabling next generation manufacturing of RF and microwave circuits but little work has been done to demonstrate the true potential of this approach. This study shows that transmission lines fabricated using 3-D printing equipment are comparable in performance to traditionally-made versions. Basic transmission line parameters such as characteristic impedance, effective dielectric constant, dielectric loss, and conductor loss are modeled and measured for a variety of materials and types of transmission lines at frequencies up to 10 GHz. Data are given for use in future 3-D printed RF designs.

3D printing and printed electronics are combined to demonstrate the feasibility of printing electrically functional RF devices. A combined process is used to demonstrate the feasibility of fabricating a 2.4 GHz antenna in a fully-3D printed object. Both dielectric, which also serves as the structure, and conductors are printed. Full-wave models are generated using Ansoft HFSS. Real-world tests using a Class 1 “100 m” Bluetooth module are conducted and compared against the performance of an industry-standard quarter wavelength monopole antenna.

3-D printing allows increased design flexibility in the fabrication of microwave circuits and devices and is reaching a level of maturity that allows for functional parts. Little is known about the RF and microwave properties of the standard materials that have been developed for 3-D printing. This paper measures a wide variety of materials over a broad spectrum of frequencies from 1 MHz to 10 GHz using a variety of well-established measurement methods.