Under the excitation of acoustic radiation, the amount of energy absorbed and rebounded by cells have the relationship with mechanical properties, e.g. stiffness, shape, weight and so on. In this paper, a femtosecond laser-activated micro-detector is designed to convert this relationship into an electrical signal. First, the acoustic radiation is generated by a femtosecond laser pulse in a microchannel and acts on neighbor cells / beads. Then, an ultra-thin glass sheet (UTGS)-based pressure sensor (cantilever) is fabricated at the bottom of the microfluidic chip to monitor changes in acoustic pressure during detection process. In this detection system, the pressure sensor is fabricated with a 10 μm UTGS in a shape of rectangular cantilever and functions like a detector to convert acoustic waves into shift response. Based on the amplitude of detected pulses, we can directly analyze the acoustic energy, coming from either femtosecond laser pulse or that remains after penetrating target cells. We have taken experiments on 10 μm beads and verified the applicability of this micro-detector, and the proposed method has great potential to be applied in label-free cell manipulation (i.e., sorting) as a detection mechanism.