To omit the use of ultrasound transducercoupling gel in photoacoustic microscopy (PAM), we propose a photo-acoustic-optical tomography (PAOT) for non-contact photoacoustic sensing. Its process consists of two parts: the first portion is the same as typical photoacoustic microscopy, which employs pulsed laser to induce acoustic waves what the difference is the second part, which applies a DC 

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