  The ability of detecting and separating CTCs can play a key role in early
cancer detection and treatment. In recent years, there has been growing
interest in using deformability-based CTC separation microfilters due to their
simplicity and low cost. Most of previous studies in this area are mainly based
on experimental work. Although experimental research provides useful insights
in designing CTC separation devices, there is still a lack of design guidelines
based on fundamental understandings of the cell separation process in the
filers. While experimental efforts face challenges especially microfabrication
difficulties, we adopt numerical simulation here to study conical-shaped
microfilters using deformability difference between CTCs and blood cells for
separation process. We use liquid drop model for modeling a CTC passing through
such microfilters. The accuracy of the model in predicting the pressure
signature of the system is validated by comparing with previous experiments.
Pressure-deformability analysis of the cell going through the channel is then
carried out in detail in order to better understand how a CTC behaves
throughout the filtration process. Different system design criteria such as
system throughput and unclogging of the system are discussed. Specifically,
pressure behavior under different system throughput is analyzed. Regarding the
unclogging issue, we define pressure ratio as a key parameter representing the
ability to overcome clogging in such CTC separation devices and investigate the
effect of conical angle on the optimum pressure ratio. Finally, the effect of
unclogging applied pressure on the system performance is examined. Our study
provides detailed understandings of the cell separation process and its
characteristics, which can be used for developing more efficient CTC separation
devices.
