a) Subtle physiological signals monitoring at different parts of human body. b) Monitoring the strain change of the inhalation and exhalation with time by using the as-fabricated optical sensor. The inhalation and exhalation of a volunteer was detected by using the microfiber coupler sensor fixed on the mask. c) Monitoring the pulse signals of a volunteer at different body’s sites: finger, neck, wrist, and ankle. d) Monitoring the weak movement of wrist, where the motion was driven by the far end fingers bending. e) Monitoring the tiny epidermis and muscle movement during speech for phonation recognition.