Researchers have developed a method that uses 3D printing to create products containing magnets.

When Kai von Petersdorff-Campen decided to make an artificial heart pump using 3D printing, he didn’t expect that his project would attract so much attention. The piece of plastic that he took from the printer after 15 hours was of very low quality. But as the ensuing test showed, it worked—and that was the key point.

“My goal was not to make a good heart pump, but to demonstrate the principle of how it can be produced in a single step,” says Petersdorff-Campen.

Petersdorff-Campen, a doctoral student in the mechanical and process engineering department at ETH Zurich, developed the prototypes this spring within just a few months.

The significant part of Petersdorff-Campen’s project is not the heart pump itself; this is simply an example application of the 3D printing method he developed.

Artificial heart pumps are not only geometrically complex products, but, more importantly, they contain magnets—and research on 3D printing with magnets is still in its infancy. Petersdorff-Campen’s heart pump is one of the first prototypes with magnetic components manufactured using 3D printing.

Petersdorff-Campen calls his newly developed method “embedded magnet printing.” The key is to ensure that the magnets are printed directly in the plastic. Magnetic powder and plastic are mixed before printing and processed into strands known as filaments. These then go through the 3D printer, which processes them in a similar way to conventional 3D printing—Petersdorff-Campen chose the FDM method. A nozzle automatically outputs the computer-generated form, with its various components. Finally, the printed piece is magnetized in an external field.

One of the biggest difficulties was developing the filaments: the more magnetic powder in the granulate mix, the stronger the magnet, but the more brittle the end product. However, in order for the filaments to be pressed through the 3D printer, they must be reasonably flexible. Petersdorff-Campen has now succeeded in finding a happy medium.

“We tested various plastics and mixes, until the filaments were flexible enough for printing but still had enough magnetic force,” he says.

The method is reported in Applied Sciences. The reactions varied, he explains: “Some people are already asking where they can order the material.”

Others criticized that the 3D printing is not suitable for the production of medical devices, due to the various approval processes. “That was not my focus, however,” Petersdorff-Campen says. “I simply wanted to show the principle.” He’s sure that it’s worth it for scientists and developers to develop the idea further.

Even though the method may not be suitable for heart pumps, the potential of 3D printing of magnets is huge: they are a key component in much more than just medical devices. They’re used in electric motors, such as those in numerous technical household devices, including  a computer’s hard drive, loudspeakers, and microwaves.

Today, complex injection molding produces geometrically complex components with magnets, but 3D printing could make this process significantly quicker and therefore cheaper.

However, that’s still a long way off, Petersdorff-Campen says. “There is still a lot to improve in terms of material and processing.” For example, his heart pump may have passed the initial tests and pumped 2.5 liters per minute with 1,000 rotations, but this does not yet meet the standards required in practice. “I wouldn’t want to have such a device implanted.”

The project is part of Zurich Heart under the umbrella of University Medicine Zurich.

Source: Andreas Eberhard for ETH Zurich

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Researchers have developed 3D-printed devices that can track and store their own use—without batteries or electronics.

Cheap and easily customizable, 3D-printed devices are perfect for assistive technology, like prosthetics or “smart” pill bottles that can help patients remember to take their daily medications. But these plastic parts don’t have electronics, which means they can’t monitor how patients are using them.

The new system uses a method called backscatter, through which a device can share information by reflecting signals that an antenna has transmitted to it.

“We’re interested in making accessible assistive technology with 3D printing, but we have no easy way to know how people are using it,” says coauthor Jennifer Mankoff, a professor in the Paul G. Allen School of Computer Science & Engineering at the University of Washington. “Could we come up with a circuitless solution that could be printed on consumer-grade, off-the-shelf printers and allow the device itself to collect information? That’s what we showed was possible in this paper.”

Previously the team developed the first 3D printed objects that connect to Wi-Fi without electronics. These purely plastic devices can measure if a detergent bottle is running low and then automatically order more online.

“Using plastic for these applications means you don’t have to worry about batteries running out or your device getting wet. That can transform the way we think of computing,” says senior author Shyam Gollakota, an associate professor in the Allen School. “But if we really want to transform 3D printed objects into smart objects, we need mechanisms to monitor and store data.”

The researchers tackled the monitoring problem first. In a previous study, their system tracks movement in one direction, which works well for monitoring laundry detergent levels or measuring wind or water speed. But now they needed to make objects that could monitor bidirectional motion like the opening and closing of a pill bottle.

“Last time, we had a gear that turned in one direction. As liquid flowed through the gear, it would push a switch down to contact the antenna,” says lead author Vikram Iyer, a doctoral student in the UW Department of Electrical & Computer Engineering. “This time we have two antennas, one on top and one on bottom, that can be contacted by a switch attached to a gear. So opening a pill bottle cap moves the gear in one direction, which pushes the switch to contact one of the two antennas. And then closing the pill bottle cap turns the gear in the opposite direction, and the switch hits the other antenna.”

Movement is captured when the switch contacts one of the two antennas. Both of the antennas are identical, so the team had to devise a way to decode which direction the cap was moving.

“The gear’s teeth have a specific sequencing that encodes a message. It’s like Morse code,” says coauthor Justin Chan, a doctoral student in the Allen School. “So when you turn the cap in one direction, you see the message going forward. But when you turn the cap in the other direction, you get a reverse message.”

In addition to tracking, for example, pill bottle cap movement, this same method can monitor how people use prosthetics, such as 3D-printed e-NABLE arms. These mechanical hands, which attach at the wrist, help children with hand abnormalities grasp objects. When children flex their wrists, cables on the hand tighten to make the fingers close. So the team 3D printed an e-NABLE arm with a prototype of their bidirectional sensor that monitors the hand opening and closing by determining the angle of the wrist.

The researchers also wanted to create a 3D-printed object that could store its usage information while out of Wi-Fi range. For this application, they chose an insulin pen that could monitor its use and then signal when it was getting low.

“You can still take insulin even if you don’t have a Wi-Fi connection,” Gollakota says. “So we needed a mechanism that stores how many times you used it. Once you’re back in the range, you can upload that stored data into the cloud.”

This method requires a mechanical motion, like the pressing of a button, and stores that information by rolling up a spring inside a ratchet that can only move in one direction. Each time someone pushes the button, the spring gets tighter. It can’t unwind until the user releases the ratchet, hopefully when in range of the backscatter sensor. Then, as the spring unwinds, it moves a gear that triggers a switch to contact an antenna repeatedly as the gear turns. Each contact is counted to determine how many times the user pressed the button.

Each time someone pushes the button, a spring inside the ratchet gets tighter.

These devices are only prototypes to show that it is possible for 3D printed materials to sense bidirectional movement and store data. The next challenge will be to take these concepts and shrink them so that they can work in real pill bottles, prosthetics, or insulin pens, Mankoff says.

“This system will give us a higher-fidelity picture of what is going on,” she says. “For example, right now we don’t have a way of tracking if and how people are using e-NABLE hands. Ultimately what I’d like to do with these data is predict whether or not people are going to abandon a device based on how they’re using it.”

The team will present its findings at the ACM Symposium on User Interface Software and Technology in Berlin.

The National Science Foundation and Google Faculty Awards funded the research.

Source: Sarah McQuate for University of Washington

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Octopus-like ‘smart gel’ walks and moves objects underwater

Engineers have created a 3D-printed smart gel that can walk underwater, grab objects, and move them.

The watery creation could lead to soft robots that mimic sea animals like the octopus, which can walk underwater and bump into things without damaging them. It may also lead to artificial heart, stomach, and other muscles, along with devices for diagnosing diseases, detecting and delivering drugs, and performing underwater inspections.

Soft materials like the smart gel are flexible, often cheaper to manufacture than hard materials, and can be miniaturized. Devices made of soft materials typically are simple to design and control compared with mechanically more complex hard devices.

“Our 3D-printed smart gel has great potential in biomedical engineering because it resembles tissues in the human body that also contain lots of water and are very soft,” says Howon Lee, senior author of a new study and an assistant professor in the department of mechanical and aerospace engineering at Rutgers University. “It can be used for many different types of underwater devices that mimic aquatic life like the octopus.”

The study, which appears in ACS Applied Materials & Interfaces, focuses on a 3D-printed hydrogel that moves and changes shape when activated by electricity. Hydrogels, which stay solid despite their 70-plus percent water content, are found in the human body, diapers, contact lenses, Jell-O, and many other things.

During the 3D-printing process, researchers project light on a light-sensitive solution that becomes a gel. Researchers place the hydrogel in a salty water solution (or electrolyte) and two thin wires apply electricity to trigger motion: walking forward, reversing course, and grabbing and moving objects, says Lee. The human-like walker that the team created is about one inch tall.

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The speed of the smart gel’s movement is controlled by changing its dimensions (thin is faster than thick), and the gel bends or changes shape depending on the strength of the salty water solution and electric field. The gel resembles muscles that contract because it’s made of soft material, has more than 70 percent water and responds to electrical stimulation, Lee says.

“This study demonstrates how our 3D-printing technique can expand the design, size, and versatility of this smart gel,” he says. “Our microscale 3D-printing technique allowed us to create unprecedented motions.”

Additional authors of the study are from Rutgers and Korea University in Seoul, Republic of Korea.

Source: Rutgers University

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