Albert McKeon

Sep 30th 2022

Artificial Cilia: More Flexible Than the Real Thing


Programmable microstructures hold the promise of giving tiny devices greater flexibility and functionality — capabilities that could reshape the delivery of healthcare and even improve the exploration of planets.

However, there’s long been one large hurdle to these miniature devices accomplishing big tasks: They not only have to be microscopic, but they also need to bend and twist in a way that suits the job in front of them. Cilia in cellular organisms have those capabilities, but not for wide-scale applications. Recent scientific advances might finally have a solution: artificial cilia that can be more flexible than the real thing.

Harvard researchers say they have developed a single-material, single-stimuli microstructure that can outmaneuver even living cilia. In other words, unlike other developments in the field, their invention needs only one trigger — in this case, light — to move, and requires only one material for its design. Their creation could change “the ways we design materials and devices for a variety of applications, including robotics, medicine and information technologies,” as one of the researchers notes.

Recreating Helpful Cilium

As you might remember from high school biology class, cilia can be found in almost every type of cell in animals. According to Sciencing, these hair-like organelles are typically no more than 10 micrometers long and, among many biological roles, move beneficial cells as well as harmful materials such as pathogens.

Scientists and engineers admire the productivity of these tiny workers and have tried to replicate their nimbleness, but creating artificial cilia has been challenging. It usually requires fabrication processes that involve several steps as well as different stimuli that will trigger the microstructure’s movement — basically, too much activity behind development and too many impetuses to function.

An invention by North Carolina State University and Elon University brilliantly exemplifies this complexity: synthetic cilia that bend into new shapes in response to a magnetic field and return to their original shape when exposed to light. As Advanced Science News explains, this creation comes about through several steps. It begins with dipping a mold into a polymer that’s dissolved through an organic solvent, and then, once the solvent is drawn off, the cilia take shape.

Simple to Build, Simple to Move

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) say they have designed an artificial cilium with a single material. Instead of relying on “complex multi-component materials,” they instead use only a photoresponsive liquid crystal elastomer.

They say it also functions simply: When exposed to light, its building blocks realign and the structure changes shape. And as those changes occur, a cycle of perpetuation takes hold. A new spot on the microstructure will also be exposed to light, changing that area as well. This feedback loop creates a self-propelled and endlessly programmable microstructure. “Once you turn the light on, it does all its own work,” says one of the Harvard researchers.

The shape changing of the artificial cilia drives the “endlessly reconfigurable” twisting and turning that will hopefully make microstructures “potentially transformative” for a wide range of applications that require repetitive and defined movement, the researchers say.

Ideal for “Soft” Applications

Microstructures are all about flexibility. In a paper submitted last year to the Proceedings of the National Academy of Sciences, another Harvard SEAS team explained how their work in designing shape-shifting materials could similarly create new, dynamic uses for application. “These structures allow for independent control of the geometry and mechanics, laying the foundation for engineering functional shapes using a new type of morphable unit cell,” a researcher explained.

By all accounts, artificial cilia accomplish a new way of configuring structural elements — which spurs robotics potential. Instead of facing limitations with “hard” components, soft robotics driven by artificial cilia could achieve tasks that have been out of reach.

For instance, a recent Georgia Tech College of Engineering story detailed how soft, flexible robots could revolutionize healthcare. Their wide range of motion means they could navigate catheters or endoscopes to the right places in the body, all while minimizing stress and damage to tissue. Amputees could have prosthetics that mimic the softness and suppleness of skin. Stroke patients who lost mobility could have their full range of motion restored from joint supports powered by soft robotics.

The possibilities don’t end on Earth. NASA is studying how soft robots could explore the tight spots of a moon or planet, as explains. That’s a long way from what you learned about cilia in high school.

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