E-textiles are advanced textiles that include electronic functionality ranging from conductive yarns/tracks [1
] to sensing/actuating [5
], communications [10
] and signal processing [12
]. Emerging advanced e-textile technologies offer rich opportunities to push the boundaries of wearable healthcare applications by improving the user experience (e.g., comfort, ease of use, unobtrusiveness) thus motivating the user to adhere to the recommended usage.
Electrodes are fundamental elements used in numerous healthcare devices to measure the body’s bio-potentials, for example, electrocardiography (ECG), electroencephalography (EEG) and electromyography (EMG). They are also being used in therapeutic healthcare devices such as transcutaneous electrical nerve stimulation (TENS) for pain relief and functional electrical stimulation (FES) for muscle exercise and rehabilitation. Traditional gel electrodes are not suitable for long term wearable applications due to the reduced performance over time due to moisture evaporation and faster contamination build-up. There are increasing levels of research activity focusing on integrating dry electrodes into textiles for wearable healthcare applications. However, most applications focus on diagnostics and monitoring such as ECG [14
], EEG [16
] and EMG [18
]. Their application in therapeutics is limited mainly due to the issue of discomfort caused by the high impedance between the dry electrode and skin [20
This paper presents the development of a novel fabric electrode-based wearable training system for stroke rehabilitation through a co-design process with end users. Stroke is the leading cause of adult disability. Every year in the UK over 100,000 strokes occur, and worldwide this figure is 17 million [22
]. Half of all stroke survivors have resulting arm/hand disability and need assistance with everyday tasks, which impacts on their quality of life. Intensive, repetitive, task-oriented training is beneficial for arm rehabilitation [23
]. This can be delivered though FES, which is applied via electrodes on the skin to stimulate the underlying nerves. The stimulation contracts the muscle allowing the person to practice specific movements. Extensive motor learning and neurophysiology research, backed by substantial clinical evidence, underpins FES as an effective way of recovering movement, post-stroke [24
]. However, there are several barriers to using FES, which limits uptake of this technology among stroke survivors. For example, current commercial FES devices use large gel electrodes that are very difficult to place in the correct location and which only stimulate a limited number of muscles. To overcome the limitation of using large electrodes, a gel electrode array with multiple elements which can be individually activated has been used in many studies [27
]. This work has developed a 24-electrode array by printing an array of dry electrodes directly on a textile. The dry electrode developed in this work has a longer lifetime compared to the gel electrode because it can be washed and reused many times. The electrode array layout eliminates the need for accurate positioning as it covers a wide range of muscle groups (Figure 1
) and the control algorithm used in this study can calculate the optimized combination of electrode elements to achieve targeted movements. The e-textile-based wearable training system developed in this work can facilitate intensive, repetitive and task-oriented training. While the initial tests were targeted on stroke rehabilitation, the technology can also be used for rehabilitation activities for subjects with other neurological disorders (e.g., Parkinson’s, Multiple Sclerosis, and Spinal Cord Injury).