Investigation of Carbon-Based Composites for Elastic Heaters and Effects of Hot Pressing in Thermal Transfer Process on Thermal and Electrical Properties

Carbon-Based Composites with Biodegradable Matrix for Flexible Paper Electronics

The authors explore the development of paper-based electronics using carbon-based composites with a biodegradable matrix based on ethyl cellulose and dibasic ester solvent. The main focus is on screen-printing techniques for creating flexible, eco-friendly electronic devices. This research evaluates the printability with the rheological measurements, electrical properties, flexibility, and adhesion of these composites, considering various compositions, including graphene, graphite, and carbon black. The study finds that certain compositions offer sheet resistance below 1 kΩ/sq and good adhesion to paper substrates with just one layer of screen printing, demonstrating the potential for commercial applications, such as single-use electronics, flexible heaters, etc. The study also shows the impact of cyclic bending on the electrical parameters of the prepared layers. This research emphasizes the importance of the biodegradability of the matrix, contributing to the field of sustainable electronics. Overall, this study provides insights into developing environmentally friendly, flexible electronic components, highlighting the role of biodegradable materials in this evolving industry.

Synchronous recording of magnetocardiographic and electrocardiographic signals

We present a system for simultaneous recording of the electrocardiogram and the magnetocardiogram. The measurement system contained of printed carbon electrodes and SERF magnetometer. The use of this system confirms that the position of the end of the magnetic T wave extends further than the electric T wave, which is an important indicator for the diagnosis of cardiological patients and for drug arrhythmogenicity. We analyze this phenomenon in depth, and demonstrate, that it originates from the fundamental difference between electric and magnetic measurements. The measured value is always bipolar since the electric measurements require two electrodes. We demonstrate how the dual electric and magnetic measuring system adds a new information to the commonly used electrocardiographic diagnosis. The ECG should be interpreted as the spatial asymmetry of the electric cardiac potential, and not as the potential itself. The results seem to prove, that the relation between the magnetic and the electric imaging of neural activities may be broadly applied for the benefit of medical diagnosis in cardiology and many other fields, where the neural activity is measured. This is a pilot study which requires further confirmation at the clinical level.

Influence of the Heat Transfer Process on the Electrical and Mechanical Properties of Flexible Silver Conductors on Textiles

With the increase in the popularity of wearable and integrated electronics, a proper way to manufacture electronics on textiles is needed. This study aims to analyze the effect of different parameters of the heat transfer process on the electrical and mechanical properties of flexible electronics made on textiles, presenting it as a viable method of producing such electronics. Wires made from different composites based on silver microparticles and an insulating layer were screen-printed on a release film. Then, they were transferred onto a polyester cloth using heat transfer with different parameters. Research showed that different heat transfer parameters could influence the electrical properties of screen-printed wires, changing their resistance between -15% and +150%, making it imperative to adjust those properties depending on the materials used. Changes in the settings of heat transfer also influence mechanical properties, increasing adhesion between layers at higher temperatures. This study shows the importance of tailoring heat transfer properties and the differences that these properties make.

Durability Study of Thermal Transfer Printed Textile Electrodes for Wearable Electronic Applications

Textile-based electronics hold great promise because they can endow wearable devices with soft and comfortable characteristics. However, the inherent porosity and fluffiness of fabrics result in high surface roughness, which presents great challenges in the manufacture of high-performance fabric electrodes. In this work, we propose a thermal transfer printing method to address the above challenges, in which electrodes or circuits of silver flake/thermoplastic polyurethane (TPU) composites are prefabricated on a release film by coating and laser engraving and then laminated by hot-pressing to a variety of fabrics and textiles. This universal and scalable production technique enables fabric electrodes to be made without compromising the original wearability, washability, and stretchability of textiles. The prepared fabric electrodes exhibit high conductivity (5.48 × 10⁴ S/cm), high adhesion (≥1750 N/m), good abrasion/washing resistance, high patterning resolution (∼40 μm), and good electromechanical performance up to 50% strain. To demonstrate the potential applications, we developed textile-based radio frequency identification (RFID) tags for remote identification and a large-sized heater for wearable thermotherapy. More importantly, the solvent-free thermal transfer printing technology developed in this paper enables people to DIY interesting flexible electronics on clothes with daily tools, which can promote the commercial application of smart textile-based electronics.