Microbot origami can capture, transport single cells

August 4, 2017, North Carolina State University
Magnetic microbot capturing, dragging and releasing a live cell. Credit: Koohee Han and Dr. Wyatt Shields, provided by Prof. Orlin D. Velev, NC State University.

Researchers at North Carolina State University and Duke University have developed a way to assemble and pre-program tiny structures made from microscopic cubes - "microbot origami" - to change their shape when actuated by a magnetic field and then, using the magnetic energy from their environment, perform a variety of tasks - including capturing and transporting single cells.

The findings, published today in Science Advances, pave the way for microbots and micro-origami assemblies that can serve as cell characterization tools, fluid micromixers, and components of artificial muscles and soft biomimetic devices.

"This research is about a topic of current interest - active particles which take energy from their environment and convert it into directional movement," said Orlin Velev, INVISTA Professor of Chemical and Biomolecular Engineering at NC State and co-corresponding author of the paper.

To create the microbot origami, the researchers started with microscopic polymer cubes that are metallic on one side, essentially allowing the metallic side to act as a magnet. Depending on their positioning, the cubes can be assembled in many different ways.

"Since they are magnetized and interacting, the cubes store energy," Velev said. "Tiny particles in the shape of cubes can attach together in sequences where they face in different directions to make, for example, clusters that behave like a tiny Pac-Man: You can open them by applying a magnetic field and then let them close by turning the magnetic field off. They close because they are releasing the stored . Thus, you inject internal energy every time you open the microclusters and release it when they close."

Video of magnetic field assembly and actuation of microcubes to make origami and microbot prototypes. Credit: Orlin Velev, NC State University

The researchers then gave the tiny Pac-Man a specific task: capturing a live cell, in this case a yeast cell. The microbot formed into a boxy shape and, through its opening and closing motions, "swam" to surround the yeast cell. The researchers then turned off the that controlled the folding of the microbot to capture the yeast cell, moved it and finally released it.

"We've shown here a prototype of self-folding microbot," Velev said, "that can be used as a microtool to probe the response of specific types of cells, like cancer , for instance."

"Previously reported microrobotic structures have been limited to performing simple tasks such as pushing and penetrating objects due to their rigid bodies. The ability to remotely control the dynamic reconfiguration of our microbot creates a new 'toolbox' for manipulating microscale objects and interacting with its microenvironment," said Koohee Han, a Ph.D. candidate at NC State and first author of the paper.

Video of magnetic microbot capturing, dragging and releasing a live cell. Credit: Orlin Velev, NC State University

"As the microbot folds, it can compress liquids or solids and you can use it as a tool to measure bulk mechanical properties, like stiffness," said Wyatt Shields, a postdoctoral researcher at Duke University and NC State University who co-authored the paper. "In some ways, it is a new metrological tool for gauging elasticity at the microscopic level."

The authors say that the design of microbot origami mimics nature. "The cube sequence programs the shapes of the folding microbots. Proteins work in the same way," Shields said. "The sequence of amino acids in a protein will determine how it folds, just as the sequence of cubes in our microbot will determine how it folds."

Programmed assembly of detached microcubes into one specific orientation (an ABBA sequence). Credit: Han et al., Sci. Adv. 2017;3: e1701108

Velev says that future work will concentrate on making the particles move on their own, rather than steering them with magnetic fields. Han is working on making bots that self-propel in complex fluids with non-Newtonian behavior. Shields is studying how the dynamics of the microbot reshaping could be used to study the microstructure of surrounding macromolecules.

Reversible folding of microcubes assembled in various top-bottom orientations (dubbed ABBB, ABBA, and BBAA sequences). Credit: Han et al., Sci. Adv. 2017;3: e1701108

Explore further: New system may one day steer microrobots through blood vessels for disease treatment

More information: "Sequence-encoded colloidal origami and microbot assemblies from patchy magnetic cubes" Science Advances (2017). DOI: 10.1126/sciadv.1701108 http://advances.sciencemag.org/content/3/8/e1701108

Related Stories

Researchers control soft robots using magnetic fields

March 29, 2017

A team of engineering researchers has made a fundamental advance in controlling so-called soft robots, using magnetic fields to remotely manipulate microparticle chains embedded in soft robotic devices. The researchers have ...

'Two-Faced' Particles Act Like Tiny Submarines

February 21, 2008

For the first time, researchers at North Carolina State University have demonstrated that microscopic "two-faced" spheres whose halves are physically or chemically different – so-called Janus particles – will move like ...

Sandcastles inspire new nanoparticle binding technique

August 5, 2015

If you want to form very flexible chains of nanoparticles in liquid in order to build tiny robots with flexible joints or make magnetically self-healing gels, you need to revert to childhood and think about sandcastles.

Recommended for you

Taming chaos: Calculating probability in complex systems

March 20, 2018

Daily weather patterns, brain activity on an EEG (electroencephalogram) and heartbeats on an EKG (electrocardiogram) each generate lines of complex data. To analyze this data, perhaps to predict a storm, seizure or heart ...

Shedding light on the mystery of the superconducting dome

March 20, 2018

University of Groningen physicists, and colleagues from Nijmegen and Hong Kong, have induced superconductivity in a monolayer of tungsten disulfide. By using an increasing electric field, they were able to show how the material ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.