Human motion detection utilizing strain and electromyography signals attached to a non-joint area

With the development of applications which require delicate motion detection such as soft robotics, artificial skin and electronic tattoo, a more advanced human-machine interface tracking human motion is gaining tremendous attention. Therefore, sensing method is highly desirable to reliably track human motion even when the sensor is attached to a non-joint area.
In this work, we propose a method to detect a human motion by utilizing electromyography (EMG) signals and strain sensor signals simultaneously, attaching both sensors in a non-array form to the non-joint area. Our strain sensor is facile and large-area compatible based on the spray coating method, maintaining high cycle stability and moderate resistance by taking advantage of both silver nanowire (AgNW) and carbon black (CB) blended as a sensing material. After spray-coating the mixture of AgNW and CB, polydimethylsiloxane (PDMS) is poured onto the sensor film, embedding the sensor film to the elastomer substrate. The fabricated sensor shows high cycle stability of over 6,000 cycles under repeated 10% strain with a reasonable gauge factor of 7.26. Throughout the study, the strain sensor is attached directly next to the EMG electrode to measure two types of bio-signals simultaneously. By measuring the signals of strain sensor and EMG electrodes attached to the forearm at the same time and comparing the two, we succeeded in accurately distinguishing the behavior of spreading and bending the wrist or holding a fist. Unlike previous studies that measure skin deformation, the method of measuring EMG signals simultaneously can accurately verify whether the forearm muscles are involved in certain movements, which enhance the detection performance.
Our solution has succeeded in precisely detecting the human motion without interfering with the joint flexure itself. This study provides a new pathway to utilize the strain sensor and EMG signals in precise human motion detection, which is clearly distinguished from previous studies focusing on higher resolution of sensor array attached to joint area.
This work was supported by the Technology Innovation Program (No.20008801, Development of muscular function management solution based on electronic skin with EMG IMU and Strain sensor) funded By the Ministry of Trade, Industry & Energy(MOTIE, Korea).