Rutgers University engineers have invented a new 4D shape-shifting smart gel that could benefit soft robots and medical applications.
The 4D printing approach involves printing a 3D object with a hydrogel that changes shape over time when temperatures change, said senior author of the study and assistant professor Howon Lee.
The Rutgers findings demonstrates fast, scalable, high-resolution 3D printing of hydrogels, which remain solid and retain their shape despite containing water.
According to the researchers, the smart gel could provide structural rigidity in soft robotics, and enable new applications in flexible sensors and actuators, biomedical devices and platforms or scaffolds for cells to grow, Lee said.
“The full potential of this smart hydrogel has not been unleashed until now,” said 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.”
The Rutgers team made use of a lithography-based technique that’s fast, inexpensive and can print a wide range of materials into a 3D shape. It involves printing layers of a special resin to build a 3D object.
The resin consists of the hydrogel, a chemical that acts as a binder, another chemical that facilitates bonding when light hits it and a dye that controls light penetration.
The engineers learned how to precisely control hydrogel growth and shrinkage. In temperatures below 32 degrees Celsius (about 90 degrees Fahrenheit), the hydrogel absorbs more water and swells in size. When temperatures exceed 32 degrees Celsius, the hydrogel begins to expel water and shrinks.
The objects they can create with the hydrogel range from the width of a human hair to several millimeters long. The engineers also found that they can grow one area of a 3D-printed object – creating and programming motion – by changing temperatures.
“If you have full control of the shape, then you can program its function,” Lee said. “I think that’s the power of 3D printing of shape-shifting material. You can apply this principle almost everywhere.”
Image/video and content credits: Daehoon Han/Rutgers University–New Brunswick