Measurement of channel depth by using a general microscope based on depth of focus

Abstract

This paper presents a simple and rapid method to measure the depth of the channel of
microfluidic chip. With the depth of focus (DOF) low to few micro-meters, general
microscopes show the strong axial (or longitudinal) resolving power. With the assistant of
fine-adjustment, the objective was controlled accurately to focus on the channel side and
channel bed respectively. Then the depth was calculated from the scales that fine adjustments
turned. Experiments results demonstrated the possibilities of depth measurement with normal
microscope. Compared with other methods, this method showed high degree of precision
with a deviation less than 0.6µm while the magnification was 100X. This method is rapid,
simple and reliable, and it is very suitable for monitoring the etching process to optimize the
function of microfluidic chip