MIT Improves Microfluidics with Interlocking LEGO Blocks

An MIT team has just added an element of fun into microfluidics.

The microfluidics domain involves miniature devices that precisely control fluids at submillimeter scales. Such devices classically take the form of flat, 2D chips, etched with miniature channels and ports that are arranged to perform numerous operations, such as sorting, mixing, pumping and storing fluids as they flow.

Presently, the MIT researchers, looking past such lab-on-a-chip designs, have discovered an alternative microfluidics system in “interlocking, injection-molded blocks” - or, as most people know them, LEGO bricks.

“LEGOs are fascinating examples of precision and modularity in everyday manufactured objects,” says Anastasios John Hart, Associate Professor of mechanical engineering at MIT.

Indeed, LEGO bricks are mass-produced so consistently that regardless of where in the world they are found, any two bricks are sure to line up and snap tightly in place. Given this high degree of consistency and precision, the MIT team chose LEGO bricks as the foundation for a new modular microfluidic design.

In a paper published in the Lab on a Chip journal, the team illustrates micro-milling small channels into LEGOs and positioning the outlet of each “fluidic brick” to array precisely with the inlet of another brick. The team then sealed the walls of each altered brick with an adhesive, allowing modular devices to be easily assembled and reconfigured.

Each brick can be developed with a specific pattern of channels to perform a particular task. The researchers have thus far engineered bricks as fluid resistors and mixers, as well as droplet generators. Their fluidic bricks can be joined together or taken apart to form modular microfluidic devices that perform a variety of biological operations, such as mixing fluids, sorting cells and filtering out molecules of interest.

You could then build a microfluidic system similarly to how you would build a LEGO castle - brick by brick. We hope in the future, others might use LEGO bricks to make a kit of microfluidic tools.

Crystal Owens, Lead Author

Modular Mechanics

Hart, who is also director of MIT’s Laboratory for Manufacturing and Productivity and the Mechanosynthesis Group, largely concentrates on new manufacturing processes, with applications spanning from nanomaterials to large-scale 3D printing.

Over the years, I’ve had peripheral exposure to the field of microfluidics and the fact that prototyping microfluidic devices is often a difficult, time-consuming, resource-intensive process.

Anastasios John Hart, Associate Professor of Mechanical Engineering

Owens was part of a microfluidics lab as an undergraduate and had witnessed firsthand the meticulous efforts that went into engineering a lab on a chip. After joining Hart’s group, she was keen to find a way to streamline the design process.

Most microfluidic devices have all the essential channels and ports to perform numerous operations on one chip. Owens and Hart sort ways to, fundamentally, explode this one-chip system and make microfluidics modular; assigning one operation to a single module or unit. A researcher could then blend and match microfluidic modules to perform a range of combinations and sequences of operations.

In casting around for approaches to physically attain their modular design, Owens and Hart discovered the perfect template in LEGO bricks, which are about as long as a regular microfluidic chip.

Because LEGOs are so inexpensive, widely accessible, and consistent in their size and repeatability of mounting, disassembly, and assembly, we asked whether LEGO bricks could be a way to create a toolkit of microfluidic or fluidic bricks.

Anastasios John Hart, Associate Professor of Mechanical Engineering

Building from an Idea

To answer this query, the team bought a set of regular, off-the-shelf LEGO bricks and tried ways to add microfluidic channels to each brick. The most successful technique was micro-milling, a well-proven system usually used to drill very fine, submillimeter features into metals and other materials.

Owens used a desktop micromill to mill a simple, 500-micron-wide channel into the side wall of a basic LEGO brick. She then taped a clear film over the wall to seal it and pumped fluid through the brick’s freshly milled channel. She noticed that the fluid effectively flowed through the channel, indicating the brick functioned as a flow resistor - a device that allows extremely small quantities of fluid to flow through.

She fabricated a fluid mixer by milling a horizontal, Y-shaped channel using the same method and sent a different fluid through each arm of the Y. Where the two arms met, the fluids effectively mixed. Owens also converted a LEGO brick into a drop generator by milling a T-shaped pattern into its wall. As she pumped fluid through one end of the T, she discovered that some of the liquid dropped down through the middle, forming a droplet as it came out of the brick.

To show modularity, Owens constructed a prototype onto a regular LEGO baseplate consisting of several bricks, each designed to do a different operation as fluid is pumped through. Besides making the fluid mixer and droplet generator, she also outfitted a LEGO brick with a light sensor, precisely placing the sensor to measure light as fluid passed via a channel at the same location.

Owens says the toughest part of the project was guessing how to connect the bricks together, without fluid leakage. While LEGO bricks are engineered to snap firmly in place, there is yet a small cavity between bricks, measuring between 100 and 500 microns. To seal this cavity, Owens fabricated a small O-ring around each outlet and inlet in a brick.

The O-ring fits into a small circle milled into the brick surface. It’s designed to stick out a certain amount, so when another brick is placed beside it, it compresses and creates a reliable fluid seal between the bricks. This works simply by placing one brick next to another. My goal was to make it straightforward to use.

Crystal Owens, Lead Author

“An Easy Way to Build”

The researchers note just a few hitches to their technique. Currently, they are able to fabricate channels that are tens of microns wide. However, certain microfluidic operations require a lot smaller channels, which cannot be made using micro-milling methods. Moreover, as LEGO bricks are made from thermoplastics, they probably cannot endure exposure to some chemicals that are occasionally used in microfluidic systems.

“We’ve been experimenting with different coatings we could put on the surface to make LEGO bricks, as they are, compatible with different fluids,” Owens says. “LEGO-like bricks could also be made out of other materials, such as polymers with high-temperature stability and chemical resistance.”

Currently, a LEGO-based microfluidic device could be used to control biological fluids and perform operations such as filtering fluids, sorting cells, and encapsulating molecules in individual droplets. The team is presently designing a website that will have information on how others can design their own fluidic bricks using regular LEGO pieces.

“Our method provides an accessible platform for prototyping microfluidic devices,” Hart says. “If the kind of device you want to make, and the materials you work with, are suitable for this kind of modular design, this is an easy way to build a microfluidic device for lab research.”

This study was supported partly by a National Science Foundation Graduate Research Fellowship, the MIT Mechanical Engineering Department Ascher H. Shapiro Fellowship, the MIT Lincoln Laboratory Advanced Concepts Committee, a 3M Faculty Award, and the National Science Foundation EAGER/Cybermanufacturing Program.

Video: Melanie Gonick/MIT