Jan 31, 2018 | By Tess

A team of engineers from Rutgers University-New Brunswick in New Jersey have demonstrated a novel method for 4D printing structures from smart hydrogel materials. The process, which is capable of 3D printing hydrogel structures that change shape (hence the 4D) when exposed to different temperatures, could be used in the development of tissue engineering, soft robots, and drug delivery applications.

A study detailing the research project was recently published in the journal Scientific Reports and was led by Howon Lee, an assistant professor in the department of Mechanical and Aerospace Engineering at Rutgers.

Hydrogel materials, which are basically water-based gels, are becoming increasingly important in the field of additive manufacturing, especially for certain biomedical applications. Scientists and engineers alike are quickly discovering the potentials of being able to create structures from hydrogels for biomedical devices, implants and more.

3D printing, as it turns out, is one of the most promising avenues for manipulating hydrogel materials. As the Rutgers researchers have shown, it is even possible to 3D print high-resolution hydrogel structures which can change their shape and size depending on the temperature.

A key element of the research study was the smart hydrogel used by the researchers, which they say can provide structural rigidity in certain organs and could be an effective vehicle for delivering and releasing drugs into the body. The 3D printable material could also be adapted for use in soft robotics, flexible sensors and actuators, biomedical devices, and to promote cell growth.

Interestingly, the hydrogel material used in the study is a relatively common one, and has been used by scientists for decades for various purposes. Still, and as the Rutgers team points out, no one has ever 4D printed the material before now.

“The full potential of this smart hydrogel has not been unleashed until now," explained Howon Lee. “We added another dimension to it, and this is the first time anybody has done it on this scale. They're flexible, shape-morphing materials. I like to call them smart materials.”

In 3D printing the hydrogel, the engineers used a lithography-based process which builds up objects by depositing layers of a resin and then curing them with UV light. To make the hydrogel printable, it was combined with a binder chemical, and a photosensitive chemical, which enabled the resin to solidify when subjected to light.

The researchers also developed a way to control how the 3D printed hydrogel object would shrink or grow when exposed to certain conditions. For instance, if the 3D printed structure is placed in temperatures below 32°C (90°F) is will absorb water from the environment and grow in size. When the temperature rises above 32°C, however, the hydrogel gradually shrinks as it loses water.

“If you have full control of the shape, then you can program its function,” Lee commented. “I think that's the power of 3D printing of shape-shifting material. You can apply this principle almost everywhere.”

Also worth mentioning is the scale at which the smart hydrogel material can be 3D printed. According to the research team, it is capable of printing objects measuring as small as the width of a human hair and up to “several millimeters” in length.

Ultimately, the goal is to use the 4D printing method and hydrogel to create “living” structures which could be either implanted in human organs or tissues, used for drug delivery, or in soft robotics.



Posted in 3D Printing Application



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