Ryan Bahr

Infill-Dependent 3-D-Printed Material Based on NinjaFlex Filament for Antenna Applications

This letter presents one of the first examples of the exploitation of 3-D printing in the fabrication of microwave components and antennas. Additive manufacturing represents an enabling technology for a wide range of electronic devices, thanks to its inherent features of fast prototyping, the reasonable accuracy, fully 3-D topologies, and the low fabrication cost. A novel 3-D printable flexible filament, based on NinjaFlex, has been adopted for manufacturing the substrate of a 3-D printed patch antenna. NinjaFlex is a recently introduced material with extraordinary features in terms of mechanical strain, flexibility, and printability. Initially, the electrical properties of this material are investigated at 2.4 GHz using the ring resonator technique. The capability of selectively changing the dielectric constant by modifying the printed material density by fine-tuning printing infill percentage is verified experimentally. Subsequently, a square patch antenna is prototyped through 3-D printing and measured to validate the manufacturing technology. Finally, exploiting mechanical flexibility properties of NinjaFlex, the antenna is tested under different bending conditions.

A novel strain sensor based on 3D printing technology and 3D antenna design

The additive manufacturing technique of 3D printing has become increasingly popular for time-consuming and complex designs. Due to the special mechanical properties of commercial NinjaFlex filament [1] and in-house-made electrically conductive adhesives (ECAs) [2], there is great potential for the 3D printed RF applications, such as strain sensors and flexible, wearable RF devices. This paper presents the flexible 3D printed strain sensor, as a 3D dipole antenna of ECA stretchable conductor on 3D printed Ninjaflex filament.

A Novel Solar and Electromagnetic Energy Harvesting System With a 3-D Printed Package for Energy Efficient Internet-of-Things Wireless Sensors

This paper discusses the design of a novel dual (solar + electromagnetic) energy harvesting powered communication system, which operates at 2.4 GHz ISM band, enabling the autonomous operation of a low power consumption power management circuit for a wireless sensor, while featuring a very good “cold start” capability. The proposed harvester consists of a dual port rectangular slot antenna, a 3-D printed package, a solar cell, an RF-dc converter, a power management unit (PMU), a microcontroller unit, and an RF transceiver. Each designed component was characterized through simulation and measurements. As a result, the antenna exhibited a performance satisfying the design goals in the frequency range of 2.4–2.5 GHz. Similarly, the designed miniaturized RF-dc conversion circuit generated a sufficient voltage and power to support the autonomous operation of the bq25504 PMU for RF input power levels as low as −12.6 and −15.6 dBm at the “cold start” and “hot start” condition, respectively. The experimental testing of the PMU utilizing the proposed hybrid energy harvester confirmed the reduction of the capacitor charging time by 40% and the reduction of the minimum required RF input power level by 50% compared with the one required for the individual RF and solar harvester under the room light irradiation condition of 334 lx.

Additively Manufactured RF Components and Modules: Toward Empowering the Birth of Cost-Efficient Dense and Ubiquitous IoT Implementations

In this review, the particular importance and associated opportunities of additively manufactured radiofrequency (RF) components and modules for Internet of Things (IoT) and millimeter-wave ubiquitous sensing applications is thoroughly discussed. First, the current advances and capabilities of additive manufacturing (AM) tools are presented. Then, completely printed chipless radio-frequency identification (RFID) systems, and their current capabilities and limitations are reported. The focus is then shifted toward more complex backscattering energy autonomous RF structures. For each of the essential components of these structures, that encompass energy harvesting and storage, backscattering front ends, passive components, interconnects, packaging, shape-chaging (4-D printed) topologies and sensing elements, current trends are described and representative stateof- the-art examples reported. Finally, the results of this analysis are used to argue for the unique appeal of AM RF components and systems toward empowering a technological revolution of costefficient dense and ubiquitous IoT implementations.

3D printed reconfigurable helical antenna based on microfluidics and liquid metal alloy

This paper demonstrates a new approach to build 3D reconfigurable antennas at an extremely low cost and the first 3D printed reconfigurable helical antenna based on microfluidics and liquid metal alloy (LMA). With the fused deposition modeling (FDM) 3D printing technique, 3D microfluidic channel can be fabricated in a short production cycle cost-effectively. EGaIn, a non-toxic LMA, is filled into a 3D printed helix channel and form the helical antenna. As the gain of the antenna is determined by the number of turns of the helix which is controlled by the volume of LMA, the gain of the antenna can be tuned when needed. A more than 4 dB gain increase around 5 GHz is measured with the prototype when the number of turns of helix increases from 2 to 8 (0.2 mL LMA volume change), which demonstrates the reconfigurability of the proposed helical antenna.

Ambient energy harvesting from two-way talk radio for on-body autonomous wireless sensing network using inkjet and 3D printing

A novel wearable and flexible energy harvesting circuit from a hand-held two-way radio for an energy autonomous on-body sensing network is proposed. The proposed circuit is more efficient than conventional ambient RF energy harvesting architectures because both the dc and the harmonics generated by the rectifier is simultaneously utilized to serve two different functions. The dc power is used to drive dc loads and the harmonic is used to build a carrier emitter for backscatter RFID tags for on-body sensing. The 3D printed substrate is used to alleviate the limitations imposed by the substrate. Both the energy harvester and the custom backscatter RFID tags are fabricated and characterized. The measured dc and the second harmonic, 928 MHz, output power from the proposed rectifier are 17.5 dBm and 1.43 dBm while a two-way talk radio is 9 cm away. The reading range of the custom tag is extended to 17 m with the help of the proposed energy harvester.

Novel 3D-printed “Chinese fan” bow-tie antennas for origami/shape-changing configurations

This paper presents a novel approach to realize 3D-printed flexible reconfigurable antennas, along with a proof-of-concept tunable bow-tie antenna inspired from Chinese origami fan. Stereolithography (SLA) printing, a low-cost high-performance additive manufacturing technique, is utilize to enable the easy fabrication of origami structure prototypes and the structure is metallized using a liquid metal alloy (LMA) to facilitate folding without breakages. The proposed bow-tie antenna features a frequency tuning range from 896 MHz to 992 MHz and bandwidth reconfigurability. This reconfigurable antenna can be applied to various dynamically changing scenarios such as wireless communications, collapsible/portable radars, wearable applications.

Novel uniquely 3D printed intricate Voronoi and fractal 3D antennas

While 3D printing has enabled the rapid prototyping of numerous 3D structures, only very few designs have exploited this technology to create structures that are difficult or impossible to manufacture in any other way. In this paper, a novel surface modification technique is combined with high-resolution Stereo-lithography 3D printing to enable arbitrary 3D antenna designs that have never been demonstrated before including a Voronoi tessellation for light weight, low volume, and aerodynamic properties and 3D fractal geometries featuring similar physical advantages. Both antenna topologies utilize a novel metallization technique, electroless copper plating, to overcome the highly lossy properties of common 3D printed dielectric materials.

Inkjet-/3D-/4D-printed autonomous wearable RF modules for biomonitoring, positioning and sensing applications

In this paper, numerous inkjet-/3D-/4D-printed wearable flexible antennas, RF electronics, modules and sensors fabricated on paper and other polymer (e.g. LCP) substrates are introduced as a system-level solution for ultra-low-cost mass production of autonomous Biomonitoring, Positioning and Sensing applications. This paper briefly discusses the state-of-the-art area of fully-integrated wearable wireless sensor modules on paper or flexible LCP and show the first ever 4D sensor module integration on paper, as well as numerous 3D and 4D multilayer paper-based and LCP-based RF/microwave, flexible and wearable structures, that could potentially set the foundation for the truly convergent wireless sensor ad-hoc “on-body networks of the future with enhanced cognitive intelligence and “rugged” packaging. Also, some challenges concerning the power sources of “nearperpetual” wearable RF modules, including flexible miniaturized batteries as well as power-scavenging approaches involving electromagnetic and solar energy forms are discuessed. The final step of the paper will involve examples from mmW wearable (e.g. biomonitoring) antennas and RF modules, as well as the first examples of the integration of inkjet-printed nanotechnology-based (e.g.CNT) sensors on paper and organic substrates for Internet of Things (IoT) applications. It has to be noted that the paper will review and present challenges for inkjetprinted organic active and nonlinear devices as well as future directions in the area of environmentally-friendly “green”) wearable RF electronics and “smart-skin conformal sensors.

Additive manufacturing techniques for origami inspired 4D printed RF components and modules

Additive manufacturing (AM) is a growing method due to the ability to produce with little to no waste, construction of previously impossible designs, and less tooling needed for fabrication. While every manufacturing method has advantages and drawbacks, this paper covers AM techniques for 2D, 3D, and 4D printing, demonstrating RF devices which utilize each dimension and discussing the challenges related to using each technology towards microwave designs. Complex, previously impossible, modules can be fabricated rapidly setting the foundation for the way new designs are prototyped and manufactured.