Non-Contact Microfluidic Mixing Probe for Generating Controlled Concentration Gradient

Concentration gradients influence a range of biological phenomena, such as human development, wound healing, inflammation, and cancer metastasis. Reconstructing and studying these gradients in vitro enables investigation of cellular responses and behaviors including cellular patterning, differentiation, migration, and resistance to drugs. In this work, we develop an open (non-contact) microfluidic device, named the microfluidic mixing probe (MMP). The MMP integrates the concept of microfluidic probes (MFPs) with microfluidic diffusion-based micromixers. The MMP, fully 3D printed using a stereolithography printer, is capable of generating gradients with 3 distinct concentrations: 100%, 50%, and 0%. On the substrate, these concentrations are confined within 3 individual hydrodynamic flow confinements. The generated concentration gradients are particularly useful for performing drug testing and chemotaxis studies on individual cells, including neutrophils, cancer cells, and neurons. The MMP is also capable of operating in 2D scanning mode, which allows for systematically maintaining the gradient for specific durations of time, and thus testing cell responses to spatiotemporal stimulations at single-cell levels.