Binu B. Narakathu

Bio: Binu B. Narakathu is an academic researcher from Western Michigan University. The author has contributed to research in topics: Screen printing & Substrate (printing). The author has an hindex of 24, co-authored 124 publications receiving 2105 citations.

Development of printed and flexible dry ECG electrodes

Abstract: Printed, flexible and wearable dry electrodes for monitoring electrocardiogram (ECG) signals, without any skin preparation and use of wet gel, has been developed. Silver (Ag) flake ink was screen printed on a flexible polyethylene terephthalate (PET) substrate to fabricate the dry ECG electrode. Multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composite, as a conductive polymer, was then deposited on the printed Ag electrode by using a bar coating technique. The performance of the printed electrodes was investigated by testing the MWCNT/PDMS composite conductivity and measuring the electrode-skin impedance for electrode radii varying from 8 mm to 16 mm. It was observed that the dry ECG electrode, with the largest area, demonstrated better performance, in terms of MWCNT/PDMS composite conductivity, ECG signal intensity and correlation when compared to a commercial wet silver/silver chloride (Ag/AgCl) electrode. In addition, the capability of the dry ECG electrodes for monitoring ECG signals in both the relaxed sitting position and while the subject is in motion, was also investigated and the results were compared with a wet Ag/AgCl ECG electrode (T716). While the subject is in motion, the printed dry electrodes were less noisy and were able to better identify the typical ECG characteristics in the signals due to its better conformal contact at the electrode-skin interface. The results obtained demonstrated the feasibility of employing conventional screen printing process for the development of flexible dry ECG electrodes for applications in the biomedical industry.

Printed strain sensor based on silver nanowire/silver flake composite on flexible and stretchable TPU substrate

Abstract: A novel printed strain sensor, based on metal-metal composite, was developed for applications in the biomedical and civil infrastructural industries. The sensor was fabricated by screen printing a silver nanowire (Ag NW)/silver (Ag) flake composite on a flexible and stretchable thermoplastic polyurethane (TPU) substrate in two design configurations: straight line and wavy line. The capability of the fabricated strain sensors was investigated by studying its electro-mechanical response towards varying elongations. Average resistance changes of 104.8%, 177.3% and 238.9%, over 100 cycles, and 46.8%, 141.4% and 243.6%, over 200 cycles, were obtained for the sensors with the straight and wavy line configurations at elongations of 1 mm, 2 mm and 3 mm, respectively. A sensitivity of 21% and 33%, in resistance change for every 1% strain, was calculated for the printed strain sensors with the straight and wavy line configurations, respectively. The results obtained thus demonstrate the feasibility of employing conventional addictive screen printing process for the development of strain sensors for applications that require a flexible and stretchable form factor.

Screen Printing of Multilayered Hybrid Printed Circuit Boards on Different Substrates

Abstract: This paper reports on the successful fabrication of a multilayered hybrid printed circuit board (PCB) for applications in the consumer electronics products, medical technologies, and military equipment. The PCB was fabricated by screen-printing silver (Ag) flake ink, as metallization layer, and UV acrylic-based ink, as dielectric layer, on different substrates such as paper, polyethylene terephthalate, and glass. Traditional electronic components were attached onto the printed pads to create the multilayered hybrid PCB. The feasibility of the hybrid PCB was demonstrated by integrating an embedded microcontroller to drive an liquid-crystal display ( $160\times 100$ pixels). In addition, the amount of the ink spreading after printing, the effect of bending on the printed lines, and the effect of the roughness of the substrates on the resistance of the printed lines was investigated. It was observed that the resistance of the lines increased by $\approx 1.8$ %, after 10 000 cycles of bending, and the lowest resistance of 1.06 $\Omega $ was measured for the 600 $\mu $ m printed lines on paper, which had a roughness of 0.175 $\mu $ m. The advantage of fabricating PCBs on flexible substrates is the ability to fold and place the boards on nearly any platform or to conform to any irregular surface, whereas the additive properties of printing processes allow for a faster fabrication process, while simultaneously producing less material waste in comparison with the traditional subtractive processes. The results obtained show the promising potential of employing screen printing process for the fabrication of flexible and light-weight hybrid PCBs.

A carbon nanotube based NTC thermistor using additive print manufacturing processes

Abstract: A fully printed carbon nanotube (CNT) based negative temperature coefficient (NTC) thermistor was developed for temperature sensing applications. The multi-layer NTC thermistor was fabricated using additive print manufacturing processes on a flexible polyethylene terephthalate (PET) substrate. Two silver (Ag) electrodes were printed using screen printing process. CNT based active layer was deposited by means of gravure printing. Organic and silver encapsulation layers were deposited using screen printing. The capability of the fabricated thermistor was investigated by measuring its response towards temperatures varying from −40 °C to 100 °C, in steps of 10 °C. As the temperature was increased from −40 °C to 100 °C, the resistive response of the thermistor decreased exponentially with an overall percentage change of 53% with the temperature coefficient of resistance (TCR) of −0.4%/°C. The stability of the printed thermistor towards relative humidity (RH) varying from 20% RH to 70% RH, in steps of 10% RH at two constant temperatures of 30 °C and 50 °C, was also studied. A maximum change of 0.34% and 0.1% was observed at 30 °C and 50 °C, respectively when compared to its base resistance at 20% RH. In addition, a response time of ≈300 ms and a recovery time of 4 s were measured for the printed thermistor with an accuracy of ± 0.5 °C.

Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications.

Abstract: With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interes...

Technologies for Printing Sensors and Electronics Over Large Flexible Substrates: A Review

Abstract: Printing sensors and electronics over flexible substrates are an area of significant interest due to low-cost fabrication and possibility of obtaining multifunctional electronics over large areas. Over the years, a number of printing technologies have been developed to pattern a wide range of electronic materials on diverse substrates. As further expansion of printed technologies is expected in future for sensors and electronics, it is opportune to review the common features, the complementarities, and the challenges associated with various printing technologies. This paper presents a comprehensive review of various printing technologies, commonly used substrates and electronic materials. Various solution/dry printing and contact/noncontact printing technologies have been assessed on the basis of technological, materials, and process-related developments in the field. Critical challenges in various printing techniques and potential research directions have been highlighted. Possibilities of merging various printing methodologies have been explored to extend the lab developed standalone systems to high-speed roll-to-roll production lines for system level integration.

Humidity Sensors Principle, Mechanism, and Fabrication Technologies: A Comprehensive Review

Abstract: Humidity measurement is one of the most significant issues in various areas of applications such as instrumentation, automated systems, agriculture, climatology and GIS. Numerous sorts of humidity sensors fabricated and developed for industrial and laboratory applications are reviewed and presented in this article. The survey frequently concentrates on the RH sensors based upon their organic and inorganic functional materials, e.g., porous ceramics (semiconductors), polymers, ceramic/polymer and electrolytes, as well as conduction mechanism and fabrication technologies. A significant aim of this review is to provide a distinct categorization pursuant to state of the art humidity sensor types, principles of work, sensing substances, transduction mechanisms, and production technologies. Furthermore, performance characteristics of the different humidity sensors such as electrical and statistical data will be detailed and gives an added value to the report. By comparison of overall prospects of the sensors it was revealed that there are still drawbacks as to efficiency of sensing elements and conduction values. The flexibility offered by thick film and thin film processes either in the preparation of materials or in the choice of shape and size of the sensor structure provides advantages over other technologies. These ceramic sensors show faster response than other types.

Internet of Things for Smart Healthcare: Technologies, Challenges, and Opportunities

Abstract: Internet of Things (IoT) technology has attracted much attention in recent years for its potential to alleviate the strain on healthcare systems caused by an aging population and a rise in chronic illness. Standardization is a key issue limiting progress in this area, and thus this paper proposes a standard model for application in future IoT healthcare systems. This survey paper then presents the state-of-the-art research relating to each area of the model, evaluating their strengths, weaknesses, and overall suitability for a wearable IoT healthcare system. Challenges that healthcare IoT faces including security, privacy, wearability, and low-power operation are presented, and recommendations are made for future research directions.