Carbon Nanotube Inkjet Printing for Flexible Electronics and Chemical Sensor Applications

Carbon nanotubes (CNTs) are becoming a promising new material for use in many fields including the field of electronics. Their mechanical and electrical properties lend themselves to be used in a new generation of electronic devices, namely flexible electronics. Although many deposition methods for carbon nanotubes exist, inkjet printing offers many advantages including superior patterning ability and low-cost fabrication. Presented in this work is the use of inkjet printing in order to deposit carbon nanotubes onto a flexible transparency film. The methods for developing and printing an aqueous single-walled carbon nanotube (SWCNT) ink and an aqueous multi-walled carbon nanotube (MWCNT) ink are discussed in detail. The carbon nanotubes are dispersed using sodium n-dodecyl sulfate (SDS), an anionic surfactant. It is discovered that the SDS:CNT ratio plays a crucial role in determining the conductivity of the printed carbon nanotube network. Thus, methods for optimizing this ratio are presented. To the author’s knowledge, this is the first report of carbon nanotube ink optimization regarding the ratio of dispersant concentration to carbon nanotube concentration. Additionally, the sheet resistance and transparency of the inkjet-printed carbon nanotube films are discussed. Incredibly conductive carbon nanotube networks were printed, reaching as low as 132 Ω/☐ for SWCNTs and 286 Ω/☐ for MWCNTs for 35 prints. These values are among the lowest reported sheet resistance values for carbon nanotube inkjet printing. Finally, the fabrication of a fully printed electrochemical sensor using inkjet-printed carbon nanotube electrodes is presented. The sensor was characterized using cyclic voltammetry, and the results confirm that inkjet-printed carbon nanotubes are indeed a candidate for use as flexible electrodes

A Comprehensive Study on Printed Circuit Board Backdoor Coupling in High Intensity Radiated Fields Environments

Due to the prevalence of unintentional electromagnetic interference (EMI) and the growth of intentional electromagnetic interference (IEMI) or high power microwave (HPM) sources, it is now more important than ever to understand how electronic systems are affected by high intensity radiated fields (HIRF) environments. Both historic events and experimental testing have demonstrated that HIRF environments are capable of disrupting and potentially damaging critical systems including but not limited to civil and military aircraft, industrial control systems (ICS), and internet of things (IoT) devices. However, there is limited understanding on the complex electromagnetic interactions that lead to such effects. This study provides unique insight into the backdoor coupling mechanisms associated with printed circuit boards (PCBs) as well as design techniques for reducing electromagnetic coupling in HIRF environments. Among existing literature, there is very little quantification of PCB coupling leading to multiple gaps in understanding. In this study, both PCB plane coupling and PCB trace coupling are explored under various conditions using 3D full-wave electromagnetic modeling and experimental testing. Data is provided for each individual technique as well as combinations of techniques which show greater immunity. Through this comprehensive study on PCB backdoor coupling, this work demonstrates that simple and explainable techniques can be incorporated into multi-layer PCB designs to mitigate coupling in HIRF environments. Additionally, variations in PCB layout as well as plane wave angle of incidence and polarization are explored to ensure that the conclusions are broadly applicable. It is expected that the information in this study as well as future work in this area will enable hardening design guidelines in order to reduce coupling and therefore better protect systems in such harsh electromagnetic environments

Carbon-Nanotube-PDMS Composite Coatings on Optical Fibers for All-Optical Ultrasound Imaging

Polymer-carbon nanotube composite coatings have properties that are desirable for a wide range of applications. However, fabrication of these coatings onto submillimeter structures with the efficient use of nanotubes has been challenging. Polydimethylsiloxane (PDMS)-carbon nanotube composite coatings are of particular interest for optical ultrasound transmission, which shows promise for biomedical imaging and therapeutic applications. In this study, methods for fabricating composite coatings comprising PDMS and multiwalled carbon nanotubes (MWCNTs) with submicrometer thickness are developed and used to coat the distal ends of optical fibers. These methods include creating a MWCNT organogel using two solvents, dip coating of this organogel, and subsequent overcoating with PDMS. These coated fibers are used as all-optical ultrasound transmitters that achieve high ultrasound pressures (up to 21.5 MPa peak-to-peak) and broad frequency bandwidths (up to 39.8 MHz). Their clinical potential is demonstrated with all-optical pulse-echo ultrasound imaging of an aorta. The fabrication methods in this paper allow for the creation of thin, uniform carbon nanotube composites on miniature or temperature-sensitive surfaces, to enable a wide range of advanced sensing capabilities

Sustainable Electronics Based on Crop Plant Extracts and Graphene: A “Bioadvantaged” Approach

In today’s fast-paced and well-connected world, consumer electronics are evolving rapidly. As a result, the amount of discarded electronic devices is becoming a major health and environmental concern. The rapid expansion of flexible electronics has the potential to transform consumer electronic devices from rigid phones and tablets to robust wearable devices. This means increased use of plastics in consumer electronics and the potential to generate more persistent plastic waste for the environment. Hence, today, the need for flexible biodegradable electronics is at the forefront of minimizing the mounting pile of global electronic waste. A “bioadvantaged” approach to develop a biodegradable, flexible, and application-adaptable electronic components based on crop components and graphene is reported. More specifically, by combining zein, a corn-derived protein, and aleuritic acid, a major monomer of tomato cuticles and sheellac, along with graphene, biocomposite conductors having low electrical resistance (≈10 Ω sq−1) with exceptional mechanical and fatigue resilience are fabricated. Further, a number of high-performance electronic applications, such as THz electromagnetic shielding, flexible GHz antenna construction, and flexible solar cell electrode, are demonstrated. Excellent performance results are measured from each application comparable to conventional nondegrading counterparts, thus paving the way for the concept of “plant-e-tronics” towards sustainability