MIT Engineers 3D Print Electromagnets in Heart of Multiple Electronics | MIT News

Imagine being able to build an entire dialysis machine using nothing but a 3D printer.

Not only does this reduce costs and eliminate manufacturing waste, but because this machine can be manufactured outside of a factory, people with limited resources or living in remote areas can easily access this medical device.

Although many hurdles must be overcome to create fully 3D printed electronic devices, a team at MIT has demonstrated an important step in this direction with fully 3D-printed, three-dimensional solenoids.

Solenoids, electromagnets formed by a coil of wire wrapped around a magnetic core, are the basic building block of many electronics, from dialysis machines and ventilators to washing machines and dishwashers.

The researchers modified a multimaterial 3D printer so that it could print tiny, magnetically-cored solenoids in one step. This eliminates defects introduced during post-assembly processes.

This customized printer, which can use higher-performance materials than conventional commercial printers, enabled the researchers to produce solenoids that can withstand twice as much electricity and generate a magnetic field three times larger than other 3D-printed devices.

In addition to making electronics cheaper on Earth, this printing hardware could be very useful for space exploration. For example, instead of sending replacement electronic components to a Mars base, which could take years and cost millions of dollars, a signal containing files for a 3D printer could be sent, says Luis Fernando Velázquez-Garcia, principal research scientist at MIT. Microsystems Technology Laboratories (MTL).

„In times of global demand there is no reason to create efficient hardware only in a few manufacturing centers. Instead of trying to ship hardware around the world, can we empower people in remote locations to make it themselves? Additive manufacturing can play a huge role in democratizing these technologies,” said Velasquez, senior author of the new paper. -Garcia says. A paper on 3D printed solenoids that appears in the magazine Virtual and physical prototype.

He is joined on the paper by lead author George Canada, an electrical engineering and computer science graduate student; and Hyeonseok Kim, a mechanical engineering graduate student.

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A solenoid creates a magnetic field when current is passed through it. For example, when someone rings a doorbell, electricity flows through a solenoid, which creates a magnetic field that moves a steel wire so that it strikes a bell.

Integrating solenoids into circuits manufactured in a clean room poses significant challenges because they have very different form factors and are manufactured using unsuitable processes. As a result, researchers have studied making solenoids using the same processes that make semiconductor chips. But these techniques limit the size and shape of the solenoids, which hampers performance.

Through additive manufacturing, one can make devices of practically any size and shape. However, this presents its own challenges, as making a solenoid involves rolling thin layers made from many materials that are incompatible with a machine.

To overcome these challenges, the researchers needed to adapt a commercial extrusion 3D printer.

Extrusion printing creates materials one layer at a time by extruding the material through a nozzle. Typically, a printer uses one type of material feedstock, often spools of filament.

„Some people out there look down on them because they're simple and don't have a lot of bells and whistles, but extrusion is one of the very few methods that allows you to do multimaterial, monolithic printing,” says Velázquez-Garcia.

This is important because solenoids are precisely manufactured by stacking three different materials – an insulating material, a conductive material that forms the coil, and a soft magnetic material that forms the core.

The team opted for a four-sided printer – dedicated to each object to prevent cross-contamination. They needed four extruders as they tried two soft magnetic materials, one based on biodegradable thermoplastic and the other based on nylon.

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Printing with particles

They redesigned the printer so that one nozzle ejects particles instead of filament. Soft magnetic nylon is made from a flexible polymer embedded with metal microparticles that are nearly impossible to manufacture as a fiber. Yet this nylon material offers better performance than fiber-based alternatives.

Using the conductive material also posed challenges because it would start to melt and clog the tip. The researchers found that adding air to cool the material prevented this. They also developed a new spool holder for the conductive fiber closer to the tip, reducing friction that damages thin fibers.

Even with the team's modifications, custom hardware costs about $4,000, so the technique could be used by others at a lower cost than other approaches, Velásquez-García adds.

The modified hardware prints a US quarter-sized solenoid in the shape of a spiral by stacking material around a soft magnetic core, with thick conductive layers separated by thin insulating layers.

Since each material prints at a different temperature, precise control of the process is critical. Depositing one on top of the other at the wrong time can smear the materials.

Because their machine can print with a highly effective soft magnetic material, the solenoids achieve higher performance than other 3D-printed devices.

The printing method enabled them to create a three-dimensional device consisting of eight layers, coils of conductive and insulating material stacked around the core like a spiral staircase. Multiple layers increase the number of coils in the solenoid, which improves the amplification of the magnetic field.

Because of the extra precision of the modified printer, solenoids can be made that are about 33 percent smaller than other 3D-printed versions. More coils in a smaller area will increase amplification.

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Ultimately, their solenoids can generate a magnetic field three times larger than what other 3D-printed devices can achieve.

„We weren't the first to be able to make 3D-printed actuators, but we were the first to make them three-dimensional, and that greatly increases the types of values ​​you can create. And that translates into satisfying a wide range of applications,” he says.

For example, although these solenoids cannot generate a magnetic field generated by traditional fabrication techniques, they can be used as energy transducers in small sensors or as actuators in soft robots.

Moving forward, researchers look to continue to improve their performance.

For one thing, they can try to use substitutes with better properties. They are also investigating additional modifications that can more precisely control the temperature at which each material is deposited and reduce defects.

This work is funded by Empirico Corporation.

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