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Could a New Multimaterial Fiber "Ink" Improve 3D-Printed Biomedical Devices?

MIT researchers say the new method might someday be used to print prosthetic limbs, not only matching the precise dimensions and contours of the patient’s limb but with all the electronics to monitor and control the limb embedded in place.

As a demonstration of the new 3D-printing method, the team printed a wing for a model airplane using filaments that contained both light-emitting and light-detecting electronics. These components could potentially reveal the formation of any microscopic cracks that might develop, they noted.

Felice Frankel/MIT

MIT researchers have developed a new method of 3D printing to produce devices with the electronics already embedded inside. The method, which is described in the journal Nature Communication, produces devices that are made of fibers containing multiple interconnected materials, which can light up, sense their surroundings, store energy, or perform other actions, MIT reported.

The new method could potentially be developed further to produce biomedical devices such as prosthetic limbs that would not only match the precise dimensions and contours of the patient's natural limb but would be printed with all the electronics to monitor and control the limb embedded in place, according to Yoel Fink, a professor of materials science, electrical engineering, and computer science at MIT. Fink is also CEO of the nonprofit Advanced Functional Fabrics of America, and associate director of the Research Laboratory of Electronics.

Another possible application could be biomedical implants that would provide a scaffolding for the growth of new cells to replace a damaged organ and include sensors within the implant to monitor the progress of that growth.

The researchers said the new method could also be useful for prototyping of devices — already a major application for 3D-printing, but in this case, the prototypes would have actual functionality, rather than being static models.

In addition to Fink, the research team included MIT doctoral student Gabriel Loke, Professor John Joannopoulos, and four others at MIT and elsewhere.

How It Works

The system uses conventional 3D printers outfitted with a special nozzle and a new kind of filament to replace the usual single-material polymer filament, which typically gets fully melted before it’s extruded from the printer’s nozzle. The researchers’ new filament has a complex internal structure made up of different materials arranged in a precise configuration and is surrounded by polymer cladding on the outside,

The internal components in the filament include metal wires that serve as conductors, semiconductors that can be used to control active functions, and polymer insulators to prevent wires from contacting each other. As a demonstration, the team printed a wing for a model airplane (shown above), using filaments that contained both light-emitting and light-detecting electronics. These components could potentially reveal the formation of any microscopic cracks that might develop.

In the new printer, the nozzle operates at a lower temperature and pulls the filament through faster conventional printers do, so that only its outer layer gets partially molten. The interior stays cool and solid, with its embedded electronic functions unaffected. In this way, the surface is melted just enough to make it adhere solidly to adjacent filaments during the printing process, to produce a sturdy 3D structure.

Loke said that until this work a printer capable of depositing metals, semiconductors, and polymers in a single platform did not exist because printing each of these materials requires different hardware and techniques. He also noted that the new method is up to three times faster than any other current approach to fabricating 3D devices.

The method makes use of thermally drawn fibers that contain a variety of different materials embedded within them, a process that Fink and his collaborators have been perfecting for two decades. They have created an array of fibers that have electronic components within them, making the fibers able to carry out a variety of functions. For example, for communications applications, flashing lights can transmit data that is then picked up by other fibers containing light sensors. This approach has for the first time produced fibers, and fabrics woven from them, that have these functions built-in.

To learn more about this new process, click here for the full MIT News story.

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