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.