  Traditional optical tweezers techniques often rely on high-power continuous
wave (CW) lasers, which can introduce unwanted thermal effects and photodamage
to delicate samples. To overcome these limitations, we demonstrate femtosecond
laser assisted selective holding with ultra-low power (FLASH-UP). We find that
the FLASH-UP exhibits a five times greater trap stiffness than CW-OT, and can
trap at lower intensities. Furthermore, we demonstrate OT of different
pathogenic bacteria species and find that FLASH-UP does not impact cell
motility. These results pave the way for applications in sorting, bio-sensing,
in vivo cell manipulation and single cell analysis.
