The small and beautiful technology hidden all around you

When you think of micro or nanotechnology, you probably think of small electronic devices like your phone, a small robot, or a microchip. But COVID-19 testing – which has proven essential in controlling the pandemic – is also a form of miniaturized technology. Many COVID-19 tests can give results within hours without having to send a sample to a lab, and most of these tests use an approach called microfluidics.

I am a professor of bioengineering and work with microfluidics for my research. Everything from pregnancy tests and glucose strips to inkjet printers and genetic testing rely on microfluidics. This technology, unbeknownst to many people, is everywhere and is essential to many things that make the modern world go round.

What is microfluidics?

Microfluidic systems are any device that processes tiny amounts of liquids. Fluids travel through channels thinner than a hair, and tiny valves can turn the flow on and off. These channels are made of materials such as glass, polymers, paper or gels. One way to move fluids is to use a mechanical pump; another way is to use the surface loads of some materials; and yet another is to use the so-called capillarity – more commonly called wick. The wick is the process by which the energy stored in the liquid propels liquid through narrow spaces.

Colored liquids enter from the bottom left, but due to laminar flow, remain relatively unmixed even though they pass through a single channel and exit at the top right.
Greg Cooksey and Albert Folch

On a small scale, fluids behave in an unintuitive way. Don’t imagine the turbulent, chaotic flow that comes out of a garden hose or your shower head. Instead, in the tight volumes of a microchannel, the flows are strangely stable. Fluids move through the channel in organized parallel flows – called laminar flows. Laminar flow is one of the great wonders of microfluidic systems. Laminar flow fluids and particles follow paths that are mathematically predictable – a necessity for precision engineering and the design of medical devices.

These processes – inspiring to researchers – have existed in nature for eons. Plants transport nutrients from their roots to the tallest branches using capillary action, which is the inspiration for autonomously powered microfluidic circuits. Mimicking the physical properties of raindrops, chemists have designed devices that split a sample into millions of droplets and analyze them at breakneck speeds. Each droplet is essentially a tiny chemistry lab that allows chemists to study the evolution of biomolecules and perform ultra-fast genetic analyzes, among other things.

And finally, every corner of the human body is microfluidic. We could not be born or function without complex blood capillaries that deliver food, oxygen, and signaling molecules to every cell.

A person's finger with a small drop of blood and a strip of blue paper.
Glucose strips are microfluidic devices that only require a tiny amount of blood to measure blood sugar.
Albert Folch, CC BY-ND

The advantages of tiny technology

Like microelectronics, size is the key to microfluidics.

As components get smaller, devices can rely on the strange properties of liquids at small scales, run faster and more efficiently and are cheaper to manufacture. The microfluidics revolution has been silently superimposed on its electronic counterpart.

Another major advantage of microfluidic devices is that they only require very small amounts of liquid and therefore can be small. NASA considered microfluidic analyzers for its long-standing Martian rovers. Analysis of valuable fluids – such as human blood – also benefits from the ability to use small samples. For example, glucometers are microfluidic instruments that only require a drop of blood to measure a diabetic’s blood sugar.

Three microvalves in a microchannel. The first and third valves, leading to the channel filled with orange, are closed. The valve in the middle is open.
Greg Cooksey and Albert Folch

Microfluidics in technology, biology and medicine

There is a good chance that you will use microfluidics quite often in your life. Inkjet printers emit tiny droplets of ink. 3D printers extract the molten polymer through a microfluidic nozzle. The ink of fountain pens and ballpoint pens flows according to microfluidic principles. Nebulizers for asthma patients spray a mist of microscopic drug droplets. A pregnancy test relies on the flow of urine in a strip of microfluidic paper.

In scientific research, microfluidics can direct drugs, nutrients, or any other fluid to very specific parts of organisms to more accurately simulate biological processes.

For example, researchers have trapped the worms in the canals and stimulated them with odors to learn more about neural circuits. Another team directed nutrients to specific areas of a plant root to observe different reactions to growth chemicals. Other groups have designed microfluidic traps that physically capture rare tumor cells from the blood. A multitude of microfluidic gene chips provide the power rapidly sequence the human genome and do personalized DNA tests such as 23andMe a reality. None of this would have been possible without microfluidics.

A device covered with wells of multicolored liquids.
This device is a “tumor-on-chip” and each well contains a different drug that is pumped to the center, where the tumor samples are placed.
Adan Rodriguez and Albert Folch, CC BY-ND

The future of microfluidics

Microfluidics will be key to bringing medicine into a new, fast-paced and affordable era. Handheld devices that measure substances in sweat for exercise monitoring and implantable devices that locally deliver anticancer drugs to a patient’s tumor are some of the next frontiers in biomedical microfluidics.

Researchers are developing complex and fascinating microfluidic systems called organ on chip which aim to simulate various aspects of human physiology. In my own lab and in other labs around the world, teams are developing tumor-on-a-chip platforms to more effectively test anticancer drugs. These patient avatars will allow scientists to test new treatments in a way that doesn’t bring the cost, suffering, and ethical issues associated with testing on animals or humans. In my lab, we first dissect a tumor biopsy from a cancer patient into thousands of regular microscopic pieces that we keep alive. Due to their small size, we can use microfluidics for trapping tiny pieces of tumor in multiple wells, one well per drug. These samples maintain the appropriate cellular environment for the tumor, which will allow us to more accurately predict how a drug will work for a specific person.

Imagine going to the doctor, getting a biopsy taken, and in less than a week, using our microfluidic machine, the doctor can determine which drug cocktail works best to clear your tumor. It’s still in the future, but what we do know is that the future will be microfluidic.

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About Hector Hedgepeth

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