Surface electromyography (sEMG) is used to detect and analyze human muscle biopotential. Recently, flexible noninvasive electrodes (FNEs) have emerged to extract bioelectrical signals from individual bodies. For FNEs to be deployed as a central component of physiological signal acquisition, the quest for elevated signal-to-noise ratio and density is compelling owing to the small amplitude of sEMG. Herein, we review recent progress in FNEs for sEMG acquisition. We summarize the needed properties of FNEs, compare the differences between passive electrodes and active electrodes and exemplify applications of FNEs. We also conclude the current challenges and future opportunities in sEMG acquisition.

In this paper, boron-doped indium-zinc-oxide (InZnO) thin-film transistors (BIZO TFTs) were fabricated by solution process. The electrical performance and stability under the negative bias illumination stress (NBIS) have been greatly improved by B doping. The BIZO TFT with 5 mol.% B doping ratio shows a superior electrical performance with a field-effect mobility of 10.15 cm ² /V · s, a threshold voltage of 3.29 V, a subthreshold swing of 0.35 V/decade, and an ON/OFF ratio of 10 ⁸ . Furthermore, the 5 mol.% BIZO TFT shows only a -1.59 V shift of the threshold voltage, compared with a large negative shift of -4.24 V for pure IZO TFTs. The enhancement of electrical performance and stability under NBIS is due to the reduction of oxygen vacancies, which are suppressed by B doping. The density of states is calculated to further validate the improved electrical performance and NBIS stability of BIZO TFTs.