Systematic framework for a real-time algorithm and machine interfaces for microfluidic cross-slot particle trapping at high strain rates

The stagnation point flow formed within a microfluidic cross-slot device is a potential tool for single-cell experiments to understand a cell's mechanoresponse. The orthogonal orientation of the channel inlets and outlets generates a pure straining flow, in such a way that the centre of the cross-slot junction is the stagnation point where a cell can be trapped and then exposed to different flow strain rates. While numerous studies have been conducted to trap different biological specimens, based on a real-time image-based feedback control technique, a detailed understanding of how the real-time algorithm and machine interfaces affect the trapping at high strain rates is still not clear. Here, we present a systematic framework for the hydrodynamic trapping of a particle in cross-slot channels with different algorithm models in different machines and operating systems. Our results demonstrate that the stability of a trapped particle at high strain rates is significantly impacted by the chosen machine interfaces which contribute to different time delays of the real-time algorithm. The different time delays correlate with the stability of the trapped particle at varying strain rates. Additionally, it was found that achieving a higher strain rate for a trapped particle does not only depend on the reduced time delay concerning the algorithm model and machine interface but also the particle resolution (px/μm). Finally, for the proof-of-concept studies, we extended our experiments in trapping a red blood cell at higher strain rates to reveal the deformation dynamics of an individual cell. Therefore, we anticipate our measurements would provide a reference framework for trapping different blood cells at high strain rates for detailed characterization between healthy and diseased cells.