Microfluidic imaging platform for dynamic microbubble characterization under physiological flow

Variability in targeted microbubble binding experiments remains a major barrier to translating molecular ultrasound imaging agents, and existing in vitro platforms are costly, slow to fabricate, or poorly suited to surface functionalization. This work presents a low-cost microfluidic imaging platform that integrates laser-cut flow channels, high-speed brightfield microscopy, and automated video analysis to characterize microbubble dynamics under physiological flow. Microfluidic chips were fabricated by thermally bonding laser-cut Parafilm gaskets between glass slides and acrylic manifolds. Three channel sizes spanning vascular dimensions (216–1067 μm width, 120 μm depth) were produced with width variability below 3%. Microbubble flow was captured at up to 24,000 fps and processed through an automated tracking pipeline that measured per-bubble velocity, size, and position. Measured velocity profiles reproduced the parabolic distribution predicted by laminar flow theory (R^2 = 0.98), and the system resolved individual bubbles at concentrations spanning two orders of magnitude. The glass substrate supports established functionalization chemistries for future targeted-adhesion assays. This platform provides a validated, rapidly iterable benchtop tool for screening microbubble formulations prior to in vivo studies.