In this paper flexible printed electrodes applicable to wearable electronics are presented. Using innovative materials as Laser Induced Graphene (LIG) and printed electronics, three type of electrodes based in LIG, silver chloride and carbon inks have been compared during the acquisition of bipotentials as electrocardiogram, electromyogram and electrooculogram. For this last one, a completely new framework for acquisition have been developed. This framework is based in a printed patch which integers 6 electrodes for the EOG acquisitions and an ad-hoc signal processing to detect the direction and amplitude of the eye movement. The performance of the developed electrodes have been compared with commercial ones using the characteristics parameters of each signal as comparative variables. The results obtained for the flexible electrodes have shown a similar performance than the commercial electrodes with an improvement in the comfort of the user.

Although the number of Internet of Things devices increases every year, efforts to decrease hardware energy demands and to improve efficiencies of the energy-harvesting stages have reached an ultra-low power level. However, no current standard of wireless communication protocol (WCP) can fully address those scenarios. Our focus in this paper is to introduce treNch, a novel WCP implementing the cross-layer principle to use the power input for adapting its operation in a dynamic manner that goes from pure best-effort to nearly real time. Together with the energy-management algorithm, it operates with asynchronous transmissions, synchronous and optional receptions, short frame sizes and a light architecture that gives control to the nodes. These features make treNch an optimal option for wireless sensor networks with ultra-low power demands and severe energy fluctuations. We demonstrate through a comparison with different modes of Bluetooth Low Energy (BLE) a decrease of the power consumption in 1 to 2 orders of magnitude for different scenarios at equal quality of service. Moreover, we propose some security optimizations, such as shorter over-the-air counters, to reduce the packet overhead without decreasing the security level. Finally, we discuss other features aside of the energy needs, such as latency, reliability or topology, brought again against BLE.

This paper presents a comprehensive study on the synthesis, characterization, and integration of laser-synthetized graphene-based materials in a wearable device for non-invasive physiological monitoring. Laser-induced graphene (LIG) and Laser-reduced graphene oxide (LrGO) materials are synthetized and characterized under different techniques to analyze and compare their structural and chemical properties, including scanning electron microscopy (SEM), micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These materials are used afterwards for the fabrication of temperature sensors, micro-supercapacitors (MSCs), and electrocardiogram (ECG) electrodes. In particular, the temperature dependence of the electrical conductivity of LrGO is exploited for the fabrication of temperature-dependent resistors with a sensitivity of -1.23 kΩ · °C ^-1 , which are used as body temperature sensors after being encapsulated into polydimethylsiloxane (PDMS) to increase their linearity and immunity to humidity changes. Moreover, both MSCs and ECG electrodes are developed by leveraging the highly porous structure of LIG, demonstrating a good electrochemical and ECG acquisition performance. Furthermore, a wearable device is designed and fabricated integrating these graphene-based components in a rigid-flex printed circuit board (PCB) together with a Bluetooth Low Energy (BLE) microcontroller, thus enabling the wireless transmission of the physiological data to external monitoring devices. The power consumption has been optimized for extended battery life, allowing continuous monitoring over prolonged periods. Overall, this study demonstrates the feasibility and effectiveness of integrating graphene-based materials into real wearable applications.