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Printing inside the body through air? This 3D printing technology has been featured in Science magazine!

2024-04-03 07:55:19  News


On December 7, a Duke University research team released an ultrasonic-based 3D printing technology, which is scientifically known as "deep penetration acoustic volume printing (DAVP)."

This DAVP technology uses viscoelastic ink and high-intensity focused ultrasound, breaking through traditional 3D's reliance on printing platforms or photosensitivity. It can reach a few centimeters deep from opaque media (such as deep tissues, bones, and organs in living organisms). "Hitting cattle across mountains" style printing.

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(The technology has now been published in Science magazine)

1. Limitations of traditional 3D printing technology

3D printing technology is a rapid prototyping technology that uses a programmable laser beam or an inkjet printer to deposit materials layer by layer to build a three-dimensional object. 3D technology can be used to manufacture models, parts, tools, etc., and can be applied to different materials, such as plastics, metals, ceramics, etc.

However, traditional 3D technology also has some problems, such as a printing speed that is too slow and an accuracy that is not high enough. Most of them rely on light to trigger the photopolymerization reaction of translucent ink. These shortcomings are particularly evident when used in the medical field.

Over the past few years, to address the above issues, researchers have developed a photosensitive ink that responds directly to a target beam and quickly hardens into the desired structure. Although this photosensitive printing technology greatly improves the speed and quality of printing, it is limited to the fact that it can only use specific transparent inks for printing. Photosensitive 3D printing is also limited in its biomedical uses because light cannot penetrate deep enough through the surface layer of the skin to penetrate deeper than a few millimeters into deep tissue within the body.

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2. Ultrasonic 3D printing, getting rid of "light dependence"

To solve the application problems of 3D printing in medicine, Y. Shrike Zhang, associate bioengineer at Brigham Hospital in the United States and associate professor at Harvard Medical School, and Junjie Yao, associate professor of biomedical engineering at Duke University, jointly developed this new ultrasonic-based "deep penetration" "Acoustic volume printing" technology.

The innovation of this new technology focuses on a special sonic ink, which is a combination of hydrogels, particles and molecules that specifically respond to ultrasound waves.

The ultrasonic 3D printing process is as follows: first, the sonic ink is delivered to the target area using injection, etc., and then a dedicated ultrasonic printing probe is used to send focused ultrasonic waves into the ink.

The sonic ink then absorbs the energy in the sound waves, and the materials in the ink heat up, join together and harden, eventually forming a solid object in the designated location.

The solid structures formed after the sonic ink hardens can take many forms, such as scaffolds that can mimic the hardness of bone or hydrogel bubbles that are soft enough to be placed inside organs. The ink can also be formulated to suit a variety of uses. For example, if you want to create a stiff scaffold to help a broken bone heal, you can add more bone mineral particles to the ink.

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3. Ultrasonic 3D printing medical experiments

At present, the Duke University team has used ultrasonic 3D printing technology to realize three different types of medical experiments.

The first experiment challenges traditional major surgical procedures: using ink to seal animal hearts. When an animal has non-valvular atrial fibrillation, the heart stops beating properly, causing blood to pool in the organ. Traditional treatment usually requires open heart surgery to seal the left atrial appendage to reduce the risk of blood clots and heart attacks.

In this experiment, a catheter was used to deliver ultrasonic ink to the left atrial appendage of the experimental goat's heart. Focused ultrasound waves from the ultrasound probe then pass through 12 millimeters of tissue, hardening the ink without damaging any surrounding organs.

Once printed, the ink securely bonds to the heart tissue, making it flexible yet tough enough to withstand the intensity of exercise that mimics a beating heart.

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The second experiment involved minor orthopedic repair surgery. In this experiment, the team removed part of the bone from a chicken leg and then injected ultrasonic ink mixed with the sample's skin and muscle tissue layers into the area where the bone was missing. After the ink hardened, the resulting material bonded seamlessly to the bone and was incompatible with the bone. It can negatively affect any surrounding tissue.

The third experiment is about the delivery of therapeutic drugs: chemotherapy drugs are first added to the sonic ink and then delivered to liver tissue samples. A probe is then used to harden the sonic ink into a hydrogel, which slowly releases the chemotherapy drug and diffuses into the liver tissue requiring treatment.

4. The future of ultrasonic 3D printing

Because the penetration depth of ultrasonic waves is 100 times higher than the depth of light, ultrasonic ink can be delivered to deep tissues, bones, and organs in living organisms with very high spatial precision and achieve "air-to-air printing." This effect cannot be achieved by light-based 3D printing methods. It is also an innovation of 3D printing technology in the field of medicine (especially minimally invasive surgery in surgery and other directions).

Although there is still a long process of research and development, clinical research, etc., before the practical application of this technology, its medical experimental results are enough to prove its broad market prospects.

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