Abstract: A motion detector (10) includes a chamber (102), a resilient suspension arm (104), an air bearing slider (110), at least one piezoresistive sensor (106), and an infrared sensor module (112). The chamber has a front plate (1024) and a back plate (1026) located on the opposite side of the chamber, and each of the front plate and the back plate has a first through hole (1030) and a plurality of second through hole (1032) formed therein. The resilient suspension arm is arranged in the chamber, and has a free distal end (1042). The air bearing slider is moveable coupled to the free distal end of the resilient suspension arm. The at least one piezoresistive sensor is attached on the air bearing slider. The infrared sensor module is arranged on the front plate of the chamber, for sensing infrared light.