Design and manufacturing of a dry electrode for EMG signals recording with microneedles

Electromyography (EMG) is usually done with wet electrodes. They are commonly made with Ag/AgCl (silver chloride). In this case, an interface with the skin is created with a gel. The problem with such electrodes is that the signal is affected by the way the electrodes are fixed over the skin and the use of gel. Besides, they irritate the skin and they are sensible to artifacts of movement and other interferences. In order to avoid these problems, dry electrodes with microneedles, which records the EMG signals, were manufactured. The microneedles pierced the stratum corneum of the skin. They improved the contact with the skin and avoided the interference caused by the dead cells. Besides, the application of a conductor gel and the preparation of the skin was not required. The mecroneedles were manufactured on a copper substratum with a laser beam. They were coated with gold, which is a biocompatible material. Although the size of the microneedles was very small, a good shape was obtained. The manufacturing process was carried out with a high precision and its repeatability was guaranteed. This manufacturing process is quick and cheap. The determination of the operation parameters of the dry electrodes was based on the contact impedance between the skin and the electrode. The performance of the proposed electrodes was compared with the performance of the commercial wet electrodes. The average impedance obtained were 6.5 and 9 kΩ for the wet and dry electrodes, respectively.