A FlexTrateTM Based High Spatial Resolution Surface Electromyography (sEMG) System
Developing devices to monitor muscular activity on a continuous basis is an important area of research and patient care. Standard surface electromyography (sEMG) systems record the muscle physiology through electrodes placed on the surface of the skin. In conventional sEMG systems, signals are transmitted through wired connections to amplifiers and subsequently stored for further processing. Wired connections are cumbersome to handle, non-portable and cause signal artifacts due to movement of cables. Thus, sEMG monitoring remains a specialized endeavor, requiring specialist knowledge. We propose to democratize sEMG monitoring by creating a wireless multi-channel sEMG monitoring hardware. We package electrodes, signal processing, wireless communication using Bluetooth, battery, and wireless charging capability on the FlexTrateTM platform and we call this fully integrated system as “FlexsEMG”. The “FlexsEMG” can be folded to decrease its area by ~50%. FlexTrateTM is a physically flexible platform that allows heterogeneous integration using state-of-the-art Fan-Out Wafer Level Packaging (FOWLP) technique. It allows heterogeneous integration of dies at fine interconnect pitches of ≤ 40 µm. Moreover, FlexTrateTM does not require bonding of dies at high temperatures and instead embeds dies in the molding compound at room temperature. Overall, the FlexTrateTM platform is bendable to a 1 mm bending radius for over 3000 bending cycles. The flexibility of the platform enables intimate contact of the electrodes with the skin to acquire reliable muscle activation signals. Here we demonstrate (1) two metallization layers at interconnect pitches of 20-40 µm on FlexTrateTM, that are flexible to 1 mm bending radius for over 3000 bending cycles, (2) compare the performance of the de-novo Au capped Cu-based FlexTrateTM sEMG electrodes of 4 mm, 5 mm, and 6 mm diameter with standard Ag/AgCl electrodes, and (3) demonstrate experimentally that the fabricated system is robust to detect complex physiological features in the musculoskeletal system.