Massachusetts Institute of Technology
A team of researchers at the Massachusetts Institute for Technology (MIT) have modified a multi-material 3D printer so it can produce three-dimensional solenoids in one step by layering ultrathin coils of three different materials.
The system prints a U.S. quarter-sized solenoid as a spiral by layering material around the soft magnetic core, with thicker conductive layers separated by thin insulating layers.
The team spoke about how the machine can be used for certain applications, saying that although there are multiple hurdles that must be overcome to achieve fully 3D printed electronic devices such as a dialysis machine, being able to create fully 3D printed, three-dimensional solenoids is an important step in the right direction.
Solenoids are electromagnets formed by a coil of wire wrapped around a magnetic core, are a fundamental building block of many electronics, from dialysis machines and respirators to washing machines and dishwashers.
The customised 3D printer, which could utilise higher-performing materials than typical commercial printers, enabled the researchers to produce solenoids that could withstand twice as much electric current and generate a magnetic field that was three times larger than other 3D printed devices.
In addition to making electronics cheaper on Earth, this hardware could be useful in space exploration says the team. For example, instead of shipping replacement electronic parts to a base on Mars, which would take years and cost millions of dollars, someone could send a signal containing files for the 3D printer.
“There is no reason to make capable hardware in only a few centres of manufacturing when the need is global. Instead of trying to ship hardware all over the world, can we empower people in distant places to make it themselves?” said Luis Fernando Velásquez-García, a principal research scientist in MIT’s Microsystems Technology Laboratories (MTL) and senior author on the paper. “Additive manufacturing can play a tremendous role in terms of democratising these technologies.”
Velásquez-García is joined on the paper by lead author Jorge Cañada, an electrical engineering and computer science graduate student; and Hyeonseok Kim, a mechanical engineering graduate student.
Massachusetts Institute of Technology
A solenoid generates a magnetic field when an electrical current passes through it. For example, when someone rings a doorbell, electric current flows through a solenoid, which generates a magnetic field that moves an iron rod so it strikes a chime.
Integrating solenoids onto electrical circuits manufactured in a clean room poses significant challenges according to the team, as they have different form factors and are made using incompatible processes that require post assembly.
The team says that researchers have investigated making solenoids utilising many of the same processes that make semiconductor chips, but these techniques limit the size and shape of solenoids utilising many of the same processes that make semiconductor chips. But these techniques limit the size and shape of solenoids, which hampers performance.
Being able to produce devices of practically any size and shape with additive manufacturing presents its own challenges says the team, as making a solenoid involves coiling thin layers made from multiple materials that may not all be compatible with one machine.
To overcome these challenges, the researchers needed to modify a commercial extrusion 3D printer.
“Some people in the field look down on them because they are 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 multi-material, monolithic printing,” says Velásquez-García.
The team says this is key, since the solenoids are produced by precisely layering three different materials, a dielectric material that serves as an insulator, a conductive material that forms the electric coil, and a soft magnetic material that makes up the core.
The team selected four nozzles, one dedicated to each material to prevent cross-contamination. They needed four extruders because they tried two soft magnetic materials, one based on biodegradable thermoplastic and the other based on nylon.
The team retrofitted the printer so one nozzle could extrude pellets, rather than filament. The soft magnetic nylon, which is made from a pliable polymer studded with metallic microparticles, is virtually impossible to produce as a filament says the team, yet the nylon material offers better performance than filament-based alternatives.
Massachusetts Institute of Technology
Using the conductive material also posed challenges, since it would start melting and jam the nozzle. The researchers also found that adding ventilation to cool the material prevented this. The team built a new spool holder for the conductive filament that was closer to the nozzle, reducing friction that could damage the thin strands.
The modified hardware prints a U.S. quarter-sized solenoid as a spiral by layering material around the soft magnetic core, with thicker conductive layers separated by thin insulating layers.
Precisely controlling the process is important as each material prints at a different temperature. Depositing on top of one another at the wrong time might cause the materials to smear. Because the machine could print with a more effective soft magnetic material, the solenoids achieved higher performance than other 3D printed devices says the team.
The team printed a device comprising of eight layers, with 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.
The added precision of the modified printer also allowed the team to create solenoids that were around 33% smaller than other 3D printed versions. The team says that in the end, the solenoids could produce a magnetic field that was about three times larger than what other 3D printed device can achieve.
“We were not the first people to be able to make inductors that are 3D printed, but we were the first ones to make them three-dimensional, and that greatly amplifies the kinds of values you can generate. And that translates into being able to satisfy a wider range of applications,” added Velásquez-García.
The team says that while these solenoids can’t generate as much magnetic field as those made with traditional fabrication techniques, they could be used as power convertors in small sensors or actuators in soft robots.
More 3D printing news from MIT:
MIT researchers demonstrate rapid liquid metal 3D printing technique
Researchers at MIT 3D print components for a portable mass spectrometer
MIT researchers 3D print self-heating microfluidic devices to detect diseases
Space Bound: MIT researchers create completely 3D printed sensors for satellites
