Flexible surface electrodes targeting biopotential signals from forearm muscles for control of prosthetic hands: Part 1 - Characterisation of semg electrodes

This study is Part 1 of two studies which investigate the use of various flexible surface sensors as an alternative to the gold standard Ag/AgCl surface electromyography (sEMG) electrodes in identifying movement intention from a user during common hand gestures. Three conductive textiles, two commercial conductive elastomers and one E-skin elastomer produced on site were tested as biopotential electrodes to establish the efficacy of each in gathering movement intention from the human brain at the level of the muscle. Testing was performed in vivo on two participants across three hand gestures, with results demonstrating that sEMG electrodes made from a commercially sourced conductive fabric can outperform the traditional Ag/AgCl sEMG electrodes, obtaining substantially larger peak and RMS measurements. Given the disadvantages of Ag/AgCl electrodes over long usage periods, namely their tendency to dry out and significant skin preparation, resulting in variable impedances and skin irritation respectively, the incorporation of flexible surface EMG electrodes in hand prosthetic control systems would increase functionality of the prosthetic devices, consequently increasing the quality of life of prosthetic hand users

The status of textile-based dry EEG electrodes

Electroencephalogram (EEG) is the biopotential recording of electrical signals generated by brain activity. It is useful for monitoring sleep quality and alertness, clinical applications, diagnosis, and treatment of patients with epilepsy, disease of Parkinson and other neurological disorders, as well as continuous monitoring of tiredness/ alertness in the field. We provide a review of textile-based EEG. Most of the developed textile-based EEGs remain on shelves only as published research results due to a limitation of flexibility, stickability, and washability, although the respective authors of the works reported that signals were obtained comparable to standard EEG. In addition, nearly all published works were not quantitatively compared and contrasted with conventional wet electrodes to prove feasibility for the actual application. This scenario would probably continue to give a publication credit, but does not add to the growth of the specific field, unless otherwise new integration approaches and new conductive polymer composites are evolved to make the application of textile-based EEG happen for bio-potential monitoring

Soft Electronics and Sensors for Wearable Healthcare Applications

Wearable electronics are becoming increasingly essential to personalized medicine by collecting and analyzing massive amounts of biological signals from internal organs, muscles, and blood vessels. Conventional rigid electronics may lead to motion artifacts and errors in collected data due to the mismatches in mechanical properties between human skin. Instead, soft wearable electronics provide a better platform and interface that can form intimate contact and conformably adapt to human skin. In this respect, this thesis focuses on new materials formulation, fabrication, characterization of low-cost, high sensitivity and reliable sensors for wearable health monitoring applications. More specifically, we have studied the silver nanoparticles (AgNPs) inkjet-printed on a polydimethylsiloxane (PDMS) substrate that offers great pressure sensitivity for aterial pulse monitoring. In addition, we have investigated the conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and poly(ethylene oxide) PEO polymer blends that exhibit low sheet resistance and can resist up to 50\% of tensile strain. The highly stretchable thin film can serve as interconnects between electronic components and dry electrodes for photoplethysmography (PPG) and electrocardiography (ECG) recordings. Based on the developed PEDOT:PSS solution with high conductivity, we fabricated a porous PDMS sponge coated with conductive PEDOT:PSS to make electrodes with reduced electrode-skin contact impedance, improved signal-to-noise ratio and is suited for long-term and motion-artifact-tolerant recording of high quality biopotential signals including ECG and electromyography (EMG). Finally, we demonstrated a multimodal sensor based on the porous PEDOT:PSS/PDMS sponge for sensing and distinguishing of pressure, strain and temperature from different trends in resistance and capacitance response. Applications including object detection, gesture recognition and temperature sensing have all been demonstrated. In this thesis, the proposed materials, sensor design, low-cost inkjet printing and dip-coating fabrication process open the possibility for more complex epidermal wearable health monitoring electronic systems

Flexible and Stretchable Electronics

Flexible and stretchable electronics are receiving tremendous attention as future electronics due to their flexibility and light weight, especially as applications in wearable electronics. Flexible electronics are usually fabricated on heat sensitive flexible substrates such as plastic, fabric or even paper, while stretchable electronics are usually fabricated from an elastomeric substrate to survive large deformation in their practical application. Therefore, successful fabrication of flexible electronics needs low temperature processable novel materials and a particular processing development because traditional materials and processes are not compatible with flexible/stretchable electronics. Huge technical challenges and opportunities surround these dramatic changes from the perspective of new material design and processing, new fabrication techniques, large deformation mechanics, new application development and so on. Here, we invited talented researchers to join us in this new vital field that holds the potential to reshape our future life, by contributing their words of wisdom from their particular perspective

A Hybrid-Powered Wireless System for Multiple Biopotential Monitoring

Chronic diseases are the top cause of human death in the United States and worldwide. A huge amount of healthcare costs is spent on chronic diseases every year. The high medical cost on these chronic diseases facilitates the transformation from in-hospital to out-of-hospital healthcare. The out-of-hospital scenarios require comfortability and mobility along with quality healthcare. Wearable electronics for well-being management provide good solutions for out-of-hospital healthcare. Long-term health monitoring is a practical and effective way in healthcare to prevent and diagnose chronic diseases. Wearable devices for long-term biopotential monitoring are impressive trends for out-of-hospital health monitoring. The biopotential signals in long-term monitoring provide essential information for various human physiological conditions and are usually used for chronic diseases diagnosis. This study aims to develop a hybrid-powered wireless wearable system for long-term monitoring of multiple biopotentials. For the biopotential monitoring, the non-contact electrodes are deployed in the wireless wearable system to provide high-level comfortability and flexibility for daily use. For providing the hybrid power, an alternative mechanism to harvest human motion energy, triboelectric energy harvesting, has been applied along with the battery to supply energy for long-term monitoring. For power management, an SSHI rectifying strategy associated with triboelectric energy harvester design has been proposed to provide a new perspective on designing TEHs by considering their capacitance concurrently. Multiple biopotentials, including ECG, EMG, and EEG, have been monitored to validate the performance of the wireless wearable system. With the investigations and studies in this project, the wearable system for biopotential monitoring will be more practical and can be applied in the real-life scenarios to increase the economic benefits for the health-related wearable devices

A Preliminary Study on Flexible Temperature Sensors for Eskin Medical Devices

In the latest years, the need of a renewed paradigm for healthcare arose promoting the research towards the idea of remote diagnosis, care and monitoring of physiological parameters. Thus, the wearable and eskin devices arose to be embedded in the standard medical equipment. In this work, a preliminary study on flexible AJP-printed temperature sensors is reported in order to propose a novel approach to evaluate infection sites, monitor the body temperature and compensate the effects of temperature on other on-body sensors. Two different geometries are proposed, designed, produced, evaluated and compared. The results shown a similar dependance on temperature (average TCR = 2.5 ∙ 10 -3 °C-1) and the dependance on substrate deformation was enquired as well as the geometrical features of the sensors

Smart Textiles Production

The research field of smart textiles is currently witnessing a rapidly growing number of applications integrating intelligent functions in textile substrates. With an increasing amount of new developed product prototypes, the number of materials used and that of specially designed production technologies are also growing. This book is intended to provide an overview of materials, production technologies, and product concepts to different groups concerned with smart textiles. It will help designers to understand the possibilities of smart textile production, so that they are enabled to design this type of products. It will also help textile and electronics manufacturers to understand which production technologies are suitable to meet certain product requirements

Electrical impedance performance of metal dry bioelectrode with different surface coatings

To improve the electrical impedance performance of bioelectrodes, a novel metal dry bioelectrodes with different coating layers are developed with laser micromilling and electroplating technology. Based on the analysis of the coating layer on the bioelectrode surface, the effect of different coating layers on the electrical impedance performance of bioelectrodes is investigated. The results show that the silver content increases with electroplating time when the silver layer is coated on the bioelectrode surface. However, the decrease of silver layer weight is observed with much longer electroplating time, and the optimal electroplating time is 20 min. Compared with the uncoated bioelectrode, the bioelectrode coated with silver layer exhibits much lower impedance value and better impedance stability. Especially, when the silver-coated bioelectrode is subsequently coated with silver-silver chloride layer, the lowest impedance value and best impedance stability are obtained