When you think of microtechnology or nanotechnology, you may think of small electronic devices such as phones, micro-robots, or microchips. However, coronavirus testing is also a form of miniaturization technology. Many coronavirus tests can deliver results in a matter of hours without having to send samples to a lab, and most tests use a method called microfluidics. From pregnancy tests to glucose test strips to inkjet printers to genetic testing, everything relies on microfluidic technology. This technology is ubiquitous and critical to many things that make the modern world run, yet is little known to many people.
Microfluidic systems are any devices that handle small amounts of liquid. Liquids flow through channels thinner than hair, with tiny valves that can open or close flow. These channels are made of materials such as glass, polymers, paper, or gels.
One way to move fluids is with types of microfluidic pumps. Another way is to take advantage of surface charges in certain materials; and yet another method involves what is called capillary action – often referred to as core suction. Core suction is a process by which energy stored in a liquid accelerates it through narrow spaces.
Colored liquids enter from the lower left, but due to laminar flow, even as they pass through a channel and exit from the upper right, they remain relatively unmixed. Fluids behave in non-intuitive ways on a small scale. Don't picture turbulence, chaotic water flow from a garden hose or showerhead. Instead, in the small volume of narrow micro-channels, flow is exceptionally stable. Fluids flow downstream in orderly parallel streams – known as laminar flow. Laminar flow is a wonder of microfluidics systems. Fluids and particles in laminar flow follow mathematically predictable paths, which is a necessary condition for precision engineering and medical device design. Plants use capillary action to transport nutrients from their roots up to the highest branches, inspiring naturally-driven microfluidic circuits.
Chemists have mimicked the physical properties of raindrops to design types of microfluidic devices that break down samples into millions of droplets and analyze them at dizzying speeds. Each droplet is essentially a tiny chemical laboratory, allowing chemists to study the evolution of biomolecules and perform ultra-fast genetic analysis, and more.
Finally, every nook and cranny of the human body is microfluidic. Without the complex capillaries that carry food, oxygen, and signaling molecules to every cell, we could not be born or function.