Nanoscale fluidics or microfluidics studies the behavior of fluids at the microscale. The properties of fluids become fundamentally different. For example, at very low Reynolds, number water in tiny channels becomes as viscous as honey (without a change of viscosity, only by reducing the dimensions). The fluid-liquid interface is charged, where molecules accumulate. It is challenging to pump fluids through microchannels using mechanical pressure. It turned out that applying small currents requires much less energy or electroosmosis. It also affects tiny swimmers like bacteria or microrobots, which cannot utilize the motion strategy of big creatures. Biological cells are very different from the mechanical design of other man-made machines. Cells are microfluidic containers with rapidly mixing and reacting molecules that meet several times per second due to ultra-short traffic and diffusion time. During past decades new microfluidic devices have been discovered that utilize properties of fluids at a small scale. For example, glass capillary and PDMS microfluidics are used to manipulate fluids at a low Reynolds number to fabricate droplets and double emulsions. These products have multiple applications in the design of new ultra-light materials with new properties, agriculture, cosmetics, medicine, and environmental science. For example, using picoliter drops, high-throughput screening on the target of interest helps conduct thousands of experiments per second using minimal reagents. It enables the screening of millions of reactions, such as during the discovery of new drugs, in a short time. The course contains back-of-the-envelope calculations and multiple examples for students and scientists interested in experimental droplet microfluidics.
