MIT Researchers Develop X-Ray-Like 3D Prints from Medical Scans

MIT researchers have developed a technique which turns 3D scans into highly detailed, multi-material 3D prints. Utilizing voxel-based printing championed by the likes of Stratasys, the process could be beneficial for presurgical planning. 

We’ve seen many instances in which 3D printing has been very useful for medical professionals. However, when taking a MRI or CAT scan and printing it, the results are often no more than mono-colored external “boxes�. Often, interiors need to be printed separately as an external 3D model for medical professionals to get an inside look at their scans.

This can reduce the potential for 3D printing in many industries, especially medicine as medical situations will become less clear when an internal part is taken out of context. But, researchers from Massachusetts Institute of Technology (MIT) are working on changing this.

Rather than just taking and printing an outer surface scan in just one color, the researchers are working on an alternative that utilizes the three-dimensional detail control offered by voxel printing.

“By using voxel-printing methods, superfluous preparation overhead and loss in detail can be prevented. This approach enables one to directly translate volumetric property gradients to 3D printable material gradients. Hence, if preservation of the given data representation is of importance, including volumetric color, transparency, or continuous material property transitions, our method presents a valuable alternative to current practices,� they explain in a research article for Science Advances.

Voxel printing

Voxel printing

Voxel Printing for Presurgical Planning & Education

With voxel printing, the idea is that the structure has distinct interiors and can show different tissue types. Such a print would likely be more instructive than a 3D model without observable interiors.

To test out the “voxel-based analysis technique�, the researchers turned medical data into highly detailed 3D multi-material 3D models which they then 3D printed on certain machines.

The process began with the researchers turning “discontinuous data types such as point cloud data� from a medical scanner into a complex geometry of high resolution multi-material voxels layer by layer. To print, the researchers use Stratasys’ PolyJet technology including the full-color J750 device.

Voxel printing works by mapping internal structures in a bright color, such as red or blue. Around this, the researchers print a transparent material. This means a doctor can easily hold and look at a 3D print of a medical scan in high resolution.

The researchers mentioned several uses for such technology. These include, presurgical planning, learning and education or preserving artifacts. Read more about the researcher’s work in Science Advances.

Source: SolidSmack

Voxel printing

Voxel printing

License: The text of “MIT Researchers Develop X-Ray-Like 3D Prints from Medical Scans” by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

Subscribe to updates from All3DP

You are subscribed to updates from All3DP

Subscribe

You can’t subscribe to updates from All3DP. Learn more…

Researchers 3D Print Acoustic Metamaterials That Can Block Sound Waves and Vibrations

Pin It
Email

Metamaterials, which can morph according to their environment, make up a new class of 3D printable, engineered surfaces which can perform nature-defying tasks, like making holograms and shaping sound. Recently, a collaborative team led by researchers from the USC Viterbi School of Engineering created new 3D printed acoustic metamaterials that are able to be remotely switched on and off, using a magnetic field, between active control and passive states.

This makes it possible to control vibration and sound, which other researchers have been trying unsuccessfully to do with abnormal property-exhibiting structures. The difference is that those metamaterials are built in fixed geometries, so their abilities will also remain fixed.

“When you fabricate a structure, the geometry cannot be changed, which means the property is fixed,� explained Qiming Wang, USC Viterbi Assistant Professor of Civil and Environmental Engineering. “The idea here is, we can design something very flexible so that you can change it using external controls.�

Close up of the team’s metamaterial. [Image: Qiming Wang]

Wang, together with USC Viterbi PhD student Kun-Hao Yu, University of Missouri Professor Guoliang Huang, and MIT Professor Nicholas X. Fang, whose work with 3D metamaterials we’re familiar with, have developed 3D printed metamaterials that can block both mechanical vibrations and sound waves. This opens up applications in vibration control, noise cancellation, and sonic cloaking (used to hide objects from acoustic waves), because, unlike current metamaterials, these can be controlled remotely with a magnetic field.

Yu said, “Traditional engineering materials may only shield from acoustics and vibrations, but few of them can switch between on and off.�

Yu, Fang, Huang, and Wang, whose research was funded by the National Science Foundation and the Air Force Office of Scientific Research Young Investigator Program, recently published a paper, titled “Magnetoactive Acoustic Metamaterials,� in the Advanced Materials journal.

The abstract reads, “In conventional acoustic metamaterials, the negative constitutive parameters are engineered via tailored structures with fixed geometries; therefore, the relationships between constitutive parameters and acoustic frequencies are typically fixed to form a 2D phase space once the structures are fabricated. Here, by means of a model system of magnetoactive lattice structures, stimuli�responsive acoustic metamaterials are demonstrated to be able to extend the 2D phase space to 3D through rapidly and repeatedly switching signs of constitutive parameters with remote magnetic fields. It is shown for the first time that effective modulus can be reversibly switched between positive and negative within controlled frequency regimes through lattice buckling modulated by theoretically predicted magnetic fields.�

Metamaterials can manipulate wave phenomena, like light, radar, and sound, which helps create technology like cloaking devices. Environmental sounds and structural vibrations, which have similar waveforms, can now be controlled by the team’s unique metamaterials. These can be compressed, but not constrained, with a magnetic field by 3D printing a deformable material, which contains iron particles, in a lattice structure. So, when a mechanical or acoustic wave makes contact with the 3D printed metamaterial, it disturbs it, which then produces the properties that can block certain frequencies of mechanical vibrations and sound waves.

The magnetoactive acoustic metamaterial affixed to petri dish. [Image: Ashleen Knutsen]

“You can apply an external magnetic force to deform the structure and change the architecture and the geometry inside it,� said Wang. “Once you change the architecture, you change the property. We wanted to achieve this kind of freedom to switch between states. Using magnetic fields, the switch is reversible and very rapid.�

In order to work, the mechanism needs the negative modulus and density of the metamaterials; these are both positive in regular materials. An object will typically push back against you if you push it, but objects with a negative modulus pull you forward as you push; objects with negative density move toward you when you push them.

Yu explained, “Material with a negative modulus or negative density can trap sounds or vibrations within the structure through local resonances so that they cannot transfer through it.�

Schematic for the acoustic experiment. Cotton pads were attached to the inner surface of the plastic tube to reduce the acoustic reflection.

Just one negative property, be it density or modulus, is able to independently block vibrations and noise within certain frequencies, but these can pass through if the two negative properties work together. By switching the magnetic field, the researchers have versatile control and can switch the metamaterial between double-positive (sound passing), single-negative (sound blocking), and double-negative (sound passing again).

Wang said, “This is the first time researchers have demonstrated reversible switching among these three phases using remote stimuli.�

The team’s current system can only 3D print metamaterials with beam diameters between one micron and one millimeter, so it either needs to grow or shrink. Larger beams would affect lower frequency waves, while smaller ones would control waves of higher frequencies.

“There are indeed a number of possible applications for smartly controlling acoustics and vibrations. Traditional engineering materials may only shield from acoustics and vibrations, but few of them can switch between on and off,� Yu said.

Now, Wang thinks the team could get their metamaterial to demonstrate another unique property – negative refraction, or “anti-physics,� where a wave goes through the material and comes back in at an unnatural angle. Once the researchers manage to 3D print larger structures, they’ll focus more on studying this phenomenon.

“We want to scale down or scale up our fabrication system. This would give us more opportunity to work on a larger range of wavelengths,� Wang said.

Discuss this research and other 3D printing topics at 3DPrintBoard.com or share your thoughts below. 

[Source/Images: USC Viterbi]

Japanese Researchers Take 3D Bioprinting Another Step Forward

Pin It
Email

As 3D bioprinting advances, it also diversifies, with researchers from all around the world developing new ways of 3D printing living cells. Each new bioprinting technique is developed to address certain challenges in the technology, and one frequent challenge is formulating an ink that can pass through a 3D printer’s nozzle, stick together well enough to form and hold a solid structure, and keep the cells intact and alive at the same time. This is a particular challenge in inkjet printing, but a group of researchers from Japan’s Osaka University have come up with a new method of inkjet bioprinting that does all of those things.

The researchers used an enzyme-driven approach to getting the inks to stick together and solidify, allowing for a variety of cells to be 3D printed. The research was published in a paper entitled “Drop-On-Drop Multimaterial 3D Bioprinting Realized by Peroxidase-Mediated Cross-Linking,� which you can access here.

“Printing any kind of tissue structure is a complex process,� said lead author Shinji Sakai. “The bio-ink must have low enough viscosity to flow through the inkjet printer, but also needs to rapidly form a highly viscose gel-like structure when printed. Our new approach meets these requirements while avoiding sodium alginate. In fact, the polymer we used offers excellent potential for tailoring the scaffold material for specific purposes.�

Schematic drawing of multi-ink inkjet modeling and photograph of three-dimensional structure modeled

Currently, sodium alginate is the most commonly used gelling agent for inkjet bioprinting, but it’s not compatible with all types of cells. The Osaka University researchers used a method based on hydrogelation mediated by horseradish peroxidase, an enzyme that can create cross-links between phenyl groups of an added polymer in the presence of the oxidant hydrogen peroxide.

Hydrogen peroxide can also damage cells, but the researchers very carefully tuned the delivery of cells and hydrogen peroxide to limit the contact between the two and to make sure the cells remained alive. In biological test gels prepared in this way, more than 90% of the cells were viable. Several complex test structures could also be grown from different types of cells.

“Advances in induced pluripotent stem cell technologies have made it possible for us to induce stem cells to differentiate in many different ways,� co-author Makoto Nakamura said. “Now we need new scaffolds so we can print and support these cells to move closer to achieving full 3D printing of functional tissues. Our new approach is highly versatile and should help all groups working to this goal.�

The 3D printing of complex, functional tissues is the goal of everyone working in the bioprinting sphere, and the work of the researchers at Osaka University brings everyone a step closer, making the dream of functional, transplantable 3D printed human organs a little bit closer to reality. Authors of the paper include S. Sakai, K. Ueda, E. Gantumur, M. Taya and M. Nakamura. The research was funded by the Japan Society for the Promotion of Science. If you’d like to learn more about this particular bioprinting research, you can do so here.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below. 

[Images: Osaka University]