An Inclined Push-Pull Probe for In Situ Cell Staining and Calcium Channel Activation

Microfluidics is now extensively used for cellular analysis due to its merits of sensitivity, accuracy, and miniaturization. The push-pull probe is built on microfluidic principles but innovatively uses hydrodynamic forces instead of closed microchannels for liquid confinement. Although various microfluidic probes have been developed for cell manipulation and analysis, few have addressed the integration and optical challenges posed by vertically oriented probes, which are difficult to accommodate in compact experimental setups and often interfere with optical imaging pathways. In this work, we present an inclined push-pull (IPP) microfluidic probe designed with a 45° angle for precise cell staining and calcium channel activation in situ. Compared with conventional vertical push-pull probes, the inclined design not only enabled in situ cell manipulation with high-resolution bright-field imaging but also freed up vertical space for operations and device integration. The results indicated that the proposed IPP probe could provide an alternative tool for in situ cell manipulation and analysis, and it is expected to enable broader applications in research including cellular regulation, drug discovery, and efficacy assessment.