Picoliter Droplet Generation for Fast Monitoring the Brain Chemistry with Scaled Silicon Nanodyalisis Probe

To monitor neurochemicals while minimizing brain damage, a microdialysis system is developed with fluidic channels scaled to 5 μm-radius to fit into 15x50 μm² silicon neural probe. Droplet generation is utilized to halt Taylor dispersion to achieve high temporal resolution. To extend the stability region for monodisperse droplet generation in such a space-limited probe at ultra-low nL/min flow rates, we varied the T-junction angle, parameter that is typically omitted from consideration for larger channels. In a series of experiments, we found that increase of the T-junction angle increases the critical capillary number separating squeezing and jetting segmentation regimes. With optimized geometry, we demonstrated generation of monodisperse pL-volume droplets in silicon nanofluidic channels. Finite element analysis indicated that these effects are due to interplay between differential pressure and viscous shear forces.