The (mu)PIVOT: an integrated particle image velocimeter and optical tweezers instrument for microenvironment investigations

摘要

A novel instrument to manipulate and characterize the mechanical environment in and around microscale objects in a fluidic environment has been developed by integrating two laser-based techniques: micron-resolution particle image velocimetry ((mu)PIV) and optical tweezers (OT). This instrument, the (mu)PIVOT, enables a new realm of microscale studies, yet still maintains the individual capabilities of each optical technique. This was demonstrated with individual measurements of optical trap stiffness (approx70 pN (mu)m~(-1) for a 20 (mu)m polystyrene sphere and a linear relationship between trap stiffness and laser power) and fluid velocities within 436 nm of a microchannel wall. The integrated device was validated by comparing computational flow predictions to the measured velocity profile around a trapped particle in either a uniform flow or an imposed, gravity-driven microchannel flow (R~(2) velence 0.988, RMS error velence 13.04 (mu)m s~(-1)). Interaction between both techniques is shown to be negligible for 15 (mu)m to 35 (mu)m diameter trapped particles subjected to fluid velocities from 50 (mu)m s~(-1) to 500 (mu)m s~(-1) even at the highest laser power (1.45 W). The integrated techniques will provide a unique perspective toward understanding microscale phenomena including single-cell biomechanics, non-Newtonian fluid mechanics and single particle or particle-particle hydrodynamics.