Fully integrated automatic reusable microfluidic setup for immobilization, analysis and non-selective release of particles

Abstract: We present a microfluidic device that enables trapping, analysis, and on-demand release of individual microparticles through membrane deformation driven by pneumatic actuation. Inspired by Pachinko-style architectures, the system features an array of traps supported by a deformable PDMS membrane, actuated via pressure control in a pneumatic chamber bonded above. Unlike conventional rigid designs, our configuration enhances membrane flexibility using a wide elliptical cavity and suspended rectilinear flow guides. Device characterization was performed using confocal microscopy to measure membrane deformation under controlled negative pressure. The displacement profiles obtained were compared to several theoretical models, showing strong agreement with a thick-membrane approximation. Vertical membrane displacement exceeded 120 $\mu$m under -100 mbar, allowing release of 80 $\mu$m particles. We demonstrated rapid and repeatable particle trapping and release by applying coordinated fluidic and pneumatic pressures. The system was further integrated with a Python-based control interface using $\mu$Manager libraries, enabling automated sequences of particle trapping, imaging, and release. The protocol includes automated priming to eliminate air bubbles in the microchannels. This work introduces a robust and fully automated microfluidic platform capable of reversible microparticle immobilization. It is well suited for applications such as high-throughput screening, mechanobiology, or real-time imaging workflows that require precise control over individual object handling.