Inkjet-printed fully customizable and low-cost electrodes matrix for gesture recognition.

The use of surface electromyography (sEMG) is rapidly spreading, from robotic prostheses and muscle computer interfaces to rehabilitation devices controlled by residual muscular activities. In this context, sEMG-based gesture recognition plays an enabling role in controlling prosthetics and devices in real-life settings. Our work aimed at developing a low-cost, print-and-play platform to acquire and analyse sEMG signals that can be arranged in a fully customized way, depending on the application and the users' needs. We produced 8-channel sEMG matrices to measure the muscular activity of the forearm using innovative nanoparticle-based inks to print the sensors embedded into each matrix using a commercial inkjet printer. Then, we acquired the multi-channel sEMG data from 12 participants while repeatedly performing twelve standard finger movements (six extensions and six flexions). Our results showed that inkjet printing-based sEMG signals ensured significant similarity values across repetitions in every participant, a large enough difference between movements (dissimilarity index above 0.2), and an overall classification accuracy of 93-95% for flexion and extension, respectively.

Effects of cognitive workload on heart and locomotor rhythms coupling.

Different physiological signals could be coupled under specific conditions, in some cases related to pathologies or reductions in system complexity. Cardiac-locomotor synchronization (CLS) has been one of the most investigating coupling. The influence of a cognitive task on walking was investigated in dual-task experiments, but how different cognitive tasks may influence CLS has poorly been investigated. Twenty healthy subjects performed a dual-task walking (coupled with verbal fluency vs calculation) on a treadmill at three different speeds (comfortable speed CS; fast-speed: CS + 2 km/h; slow-speed: CS-2 km/h) while cardiac and walking rhythms were recorded using surface electrodes and a triaxial accelerometer, respectively. According to previous studies, we found a cognitive-motor interference for which cognitive performance was affected by motor exercise, but not vice-versa. We found a CLS at the baseline condition, at fast speed in both cognitive tasks, while at comfortable speed only for the verbal fluency task. In conclusion, the cardiac and locomotor rhythms were not coupled at slow speed and at comfortable speed during subtraction task. Cognitive performances generally increased at faster speed, when cardiac locomotor coupling was stronger.