High-precision flow velocity measurement in microfluidic chips using optical tweezers

Accurate monitoring of flow velocity within a microfluidic chip is of critical importance. Existing devices for flow measurement in microfluidic chips lack the ability to provide detailed local flow velocity distribution or suffer from measurement errors. We present a novel optical tweezer velocimetry technique based on quadrant position detector with enhanced measurement accuracy. The impacts of laser trapping power on measurement range and the sensitivity of the technique are investigated. The velocity distribution at various depths inside the microfluidic chip under different flow conditions is resolved using the technique.