The development of innovative, miniaturized, and low-cost Radio Frequency Identification (RFID) tags for application in asset monitoring, counterfeit prevention, or personnel tracking requires advancements in materials, fabrication processes, and packaging. Typical RFID tags can be circumvented by tampering, cloning, or spoofing; however, by adding security features to the tag, nefarious actions such as these can be mitigated. Toward this objective, this paper presents the design and fabrication of an Ultra High Frequency (UHF) RFID tag through flexible hybrid electronics (FHE) materials and processes for authentication and anti-tamper /anti-counterfeit applications. The presented UHF RFID tag consists of a passive RF chip and dipole antenna with embedded hardware and software security features. The tag was fabricated using a hybrid of manufacturing techniques including, conventional photolithography and additive aerosol jet printing. The design, materials selection, processing, and tailored FHE fabrication processes, led to achieving a system-level functional RFID tag with a read distance of up to 15 in (0.381 m). The dependency of the read distance on the host surface was studied by attaching tags to different materials including surfaces with various dielectric constants and thicknesses. The performance of the tags was evaluated under realistic use conditions by performing thermal cycling, bending, and wearability tests. The RFID tag’s resistance to different tamper attack vectors (vulnerability assessment) is demonstrated. Overall, the demonstrated UHF RFID tag opens new opportunities for the development of flexible, lightweight, and low-cost RFID tags that leverage FHE fabrication techniques and materials for authentication and anti-tamper applications.

Direct writing methods created a revolution in the electronic industry due to their lower cost, fast processing and lower wasted material. Microstrip line is an important electronic component that transfers the signal and the foundation for the communication between multiple components in any circuit board. Therefore, studying its electromechanical behavior against thermal and mechanical stresses is necessary for real life applications. In this research, novel microstrip lines were printed on “Polyethylene Terephthalate” (PET) and “Polyimide” (PI) flexible substrates using an aerosol jet printer and dispensing system. An advanced post treatment technique was used to enhance the conductivity of the microstrip lines printed on low glass transition flexible PET substrate. Different microstrip line designs with various mesh ground planes were tested under mild and harsh mechanical bending and different environmental conditions and their losses were characterized. The results showed that the photonic curing enhanced the microstrip lines conductivity by 65% compared to the convectional curing. The in-situ resistance measurements during harsh bending demonstrated conclusively that the robustness of the printed microstrip lines increased as the filling percentage of the ground plane became lower. The aging at 85°C/85% RH had a significantly stronger effect on the microstrip lines conductivity compared to the aging at 85°C without humidity due to the changes in the printed ink’s microstructure and the increment in ionic conductivity. Thermal aging led to a reduction in the microstrip line’s ductility and the cracking became easier in the microstructure of the printed films. The resistance of a sample aged at 85°C increased by 81.7% after 10000 bending cycles compared to only 20.5% for a sample without thermal aging. Such findings provide important guidelines for those designing flexible hybrid electronics and for manufacturers who seek the assurance of these technologies for both maturing and reliable products.

Individuals requiring frequent urinary catheterization are especially prone to developing Catheter-Associated Urinary Tract Infections (CAUTI’s). This is especially true for individuals with Spinal Cord Injury or Disease (SCI/D) due to their need for frequent urinary catheterization and inability to experience urinary tract irritation and pain that are often the indicators of urinary tract infections. Medically relevant data for the assessment of urinary tract health may include parameters such as bladder temperature, internal bladder pressure, urine pH, catheter insertion shear forces, and the detection of leukocyte esterase. The collection of such biometric data as part of their routine and frequent catheterization process may greatly aid in the early detection of CAUTI’s, prevent the need for frequent inclinic assessment, and reduce the costs associated with preventative care for these individuals. In this study, “smart” catheter prototypes with integrated sensors were fabricated by packaging commercially available temperature and pressure sensors and an in-house fabricated flexible pH sensor onto additively-printed circuits on a flexible dielectric substrate. These assembled circuits were then further assembled on 3D-printed catheter tips. Encapsulation materials were then deposited for the purpose of electrical insulation, mechanical support of the components, and to ensure the biocompatibility of the “smart” catheter assembly. Flexible hybrid electronic circuits (FHE’s) were built due to their flexibility/conformability and low-cost/fast-speed of fabrication. To assess the electrical performance of circuits and catheter prototype devices, testing environments were established for both before and after the electronics packaging process. We have found that these smart-catheter prototypes have demonstrated the capability of providing temperature, pressure, and pH information when tested in both water and artificial urine (AU) and continue to function unchanged after exposure to repeated catheter cleaning regiments.

Advanced packaging solutions for wide band-gap power devices such as SiC MOSFETs can help realize their full potential. Additively printed electronics present a promising solution to enable SiC packaging, providing an approach to reduce the parasitic inductance, miniaturize, and explore countless form factors. Although printed electronics have gained popularity in diverse electronic manufacturing fields, their application in high-power electronics remains largely unexplored. Herein, we aim to develop a planar high-power SiC module (>1.2kV) using printed electronics materials and processes. Moreover, we aim to assess the feasibility and reliability of printed electronics for power packaging. The results of device-package simulations, materials testing, and processing showed promising potential in meeting requirements for SiC power modules. Functional testing of the power modules shows performance that is in line with traditionally packaged modules. The functional test vehicles also pass high voltage isolation and partial discharge tests. However, the high contact resistance between the printed conductors and module surfaces is a limiting factor in achieving low on-resistance and high current capabilities. Tailored surfaces with pressure-assisted curing helped overcome this limit and achieve high current-carrying capacity and low on-resistance. Finally, the stress testing shows mixed results, and further improvement is needed.

The demand for high-temperature electronics in aerospace, power systems, and geothermal drilling necessitates materials that withstand $300^{\circ} \mathrm{C}+$ and thermal fluctuations from $40^{\circ} \mathrm{C}$ to $300^{\circ} \mathrm{C}$. Aluminum nitride (AIN) is promising due to its high thermal conductivity and low CTE, but surface oxidation remains a challenge, particularly when high-temperature inks require sintering at $850^{\circ} \mathrm{C}$. This study explores additive processes for Aerosol Jet printed (AJP) conductors and dielectrics on Digital Light Processing (DLP)-printed and commercial AIN substrates to develop reliable packaging for high-temperature applications. Four candidate conductors were evaluated for fine-line printability ($<100 \mu ~\mathrm{m}$), conductivity, and adhesion on different surface oxidation conditions (no oxide/partial oxidation/ full oxidation). A similar adhesion evaluation was conducted on two dielectric materials. X-ray photoelectron spectroscopy (XPS) analysis revealed that three firing cycles at $850^{\circ} \mathrm{C}$ induce full surface oxidation, and oxidation thickness reached about 670 nm after five cycles. Only one conductor showed good adhesion to the three surface oxidation conditions. This conductor, a thick film gold, was successfully diluted for AJP, achieving a line width of $100 \mu ~\mathrm{m}$. Additionally, one dielectric exhibited high adhesion ($>40 \text{MPa})$ to the three surface oxidation conditions, while the other dielectric exhibited poor adhesion on no oxide surfaces, but adhesion improved with more oxidation. Ultimately, the downselected conductor and dielectric achieved stable adhesion after aging at $300^{\circ} \mathrm{C}$ for 100 hours. Developing processes and materials for high-temperature AIN ceramics can add a valuable new tool to the toolbox of high-temperature research.

Skin is one of nature's most remarkable sensory organs, capable of detecting a wide range of inputs while remaining both stretchable and flexible. Inspired by this, we developed a fully additive stretchable pressure sensor array for soft robotics. The array is built up from a thermoplastic polyurethane (TPU) substrate with a circuit of Ag ink traces providing strain sensing and nodes of carbon for pressure sensing. The system was created fully additively with direct ink writing (DIW) with an eye towards higher throughput methods such as screen printing to be utilized in the future.