- Scientists are working to develop machines 100 to 1,000 times smaller than a millimeter
- Potential uses range from targeted drug delivery to environmental monitoring
- Supercomputers help researchers design these machines
In this results-driven world, scientists must often focus on practical applications for their research. But sometimes the most exhilarating aspect of scientific inquiry is venturing into the unknown in order to shed new light.
Dr. Marisol Ripoll of Forschungszentrum Jülich (Germany) is currently directing her research spotlight on micromachines— objects up to 1,000 times smaller than a millimeter. Although these tiny machines have properties similar to human-scale devices, their unique attributes could open up an entirely new avenue of scientific pursuit.
How small is a micrometer?
Humans live in meter-scale, and we can imagine a millimeter-scale with ease. But it can be hard to grasp the micro-scale, which is one thousand times smaller yet. A single human hair is one of the smallest things our eyes can recognize, and it’s about 50 micrometers wide.
Working at a scale commonly used to measure bacteria, spider silk, and droplets of mist, you might think these miniature machines would have to be constructed from specially engineered high-tech materials. But that just isn’t the case.
“Micromachines are made out of everyday materials,” says Ripoll. “Silicon, a type of plastic that many things are made of, is one. Gold is another. If you put them together and heat it up, the gold heats much faster than the silica, and that may induce motion.”
The use of temperature differences to control movement is known as thermophoresis (phoresis = migration). Other potential methods for directing micromachines are electrophoresis, magnetophoresis, and diffusiophoresis.
In the machines that Ripoll studies, researchers precisely direct the temperature changes at the very small scale with lasers.
“I can use lasers to decide when I switch the machine on, when I switch it off, and very precisely at which place,” says Ripoll. “You can do that now in a very localized way and conduct the particles to move where you want them.”
But direct experimentation isn’t always the best method for exploring the possibilities of such science-fictional machines. Especially when considering how micromachines may interact or behave as a group.
“I’m a scientist—I like to understand and to build from scratch,” says Ripoll. “I want to know how each of my Lego pieces, let’s call them, works. But at some point, you want to do something big, you want to work with thousands of them at one time. That’s when you need high-performance computer simulations.”
“The machines all move in different ways and the way they interact with neighboring small particles depends on many factors,” continues Ripoll. “With simulations, you can engineer or play with the shape, for example, so that they have different properties. We can study what happens with just one or we can study many of them together.”
A lab on a chip
Ripoll envisions that the machines she studies will have eventual applications in microfluidics. These devices could transform medicine by performing analyses on a very small scale—essentially an entire lab on a chip. They could help doctors perform microsurgery or to deliver drugs just where they are needed, with fewer side effects.
“We don’t know all the potential uses,” says Ripoll. “This work is like raising a baby and you don’t know where that baby will end up. The applications will depend on the imagination of the engineer using it. It could be machines that you could propel in the bloodstream and direct: You could say ‘Go from A to B and only change your properties when you are in the place that we want you to be.’”
Ripoll says she has always wanted to be a scientist, even from a very early age, and is motivated by research that contributes to the advancement of society.
“I believe that science is crucial to slowly building a better society,” says Ripoll. “I think about my life and the life of my grandmother, and there have been so many changes. Our life has become easier in many respects, and so that enables us to reach even further. I am convinced that science, which I feel I’m a very small part of, will continue to produce more and more improvements for future generations.”