Fig. 6.

Handheld photoacoustic microscopy based on MEMS scanners. (A) A handheld OR-PAM based on an electrothermal MEMS scanners, with an outer size of 22 $\times$ 30 $\times$ 13 mm³ and a weight of 20 g [106]. CL, collimator. DL, doublet lens. MEMS, microelectro-mechanical system. P, prism. CG, cover glass. (B) A photograph of in vivo oral imaging using the handheld OR-PAM. (a) MAP images of microvasculature in human upper lip (b), lower lip (c), pterygomandibular fold (d), back surface of the tongue (e), and gum (f) [106]. (C) The schematic of a handheld PAI pen employing an electrostatic MEMS scanner (left). Two different mode including forward detection (middle) and lateral detection (right) are presented [113]. MEMS, microelectro-mechanical system. C, casing. DL, doublet lens. G, glass. UT, ultrasonic transducer. R, reflector. F, films. (D) PA MAPs encoded with depth of the microvasculature at the different area in oral cavity including upper lip (a), lower lip (b), sublingual (c), left wall of the oral cavity (d), right wall of the oral cavity (e), and soft palate (f) [113]. (E) A photograph of in vivo imaging of a mole on a human finger with the handheld OR-PAM probe with a diameter of 17 mm and a weight of 162 g. The inset is a photography of the electromagnetic MEMS scanners [115]. (F) MAP images (c) and cross-section slices (d) of the mole encoded with optical absorption. A MAP image encoded with depth (e) and three-dimensional rendering (f) of the mole [115]. Reprinted with permission from Ref. [106,113,115].