Researchers at Rice University have developed a method to 3D print soft structures that can reversibly change their shape in response to external stimuli, such as heat or an electric current. The researchers have dubbed their technique “reactive 4D printing” and it could have potential in creating adaptive biomedical implants that can respond to external stimuli for increased therapeutic functionality.
Soft robotic implants have significant therapeutic potential, as they more naturally blend with the soft tissues of the body than rigid implants, and could interact with and manipulate tissues with less risk of irritation or damage. Soft robots are also of interest to biomedical researchers as their flexibility means that they can change their shape significantly, allowing them to fulfill a wide variety of therapeutic roles.
However, so far, soft robotic implants cannot change their inherent configuration, but rather can bend or otherwise distort, typically in response to gas or fluid-mediated actuation. In particular, the concept of an autonomous conformational shape change following the application of an external stimulus has not yet been realized.
This latest research could change that. These researchers have developed a technique to 3D print soft structures that can undergo drastic shape changes in response to a variety of stimuli, including stress, heat, and an electric current. The technique could provide additional flexibility for implanted soft robots, and unlock new functionality.
“These materials, once fabricated, will change shape autonomously,” said Rafael Verduzco, a researcher involved in the study. “We needed a method to control and define this shape change. Our simple idea was to use multiple reactions in sequence to print the material and then dictate how it would change shape. Rather than trying to do this all in one step, our approach gives more flexibility in controlling the initial and final shapes and also allows us to print complex structures.”
The technique relies on printing the material with one set of chemical links that dictate its original form. Then a second set of chemical links is introduced by physically manipulating the object and using UV light to cure it while it is in this altered state, forming a second set of chemical links. The object can then transition between these two forms on the application of heat, an electrical current, or mechanical stress.
“There were a lot of parameters we had to optimize – from the solvents and catalyst used, to degree of swelling, and ink formula – to allow the ink to solidify rapidly enough to print while not inhibiting the desired final shape actuation,” said Morgan Barnes, another researcher involved in the project. “Future work will further optimize the printing formula and use scaffold-assisted printing techniques to create actuators that transition between two different complex shapes. This opens the door to printing soft robotics that could swim like a jellyfish, jump like a cricket or transport liquids like the heart.”
See a video about the technique below.
Study in Applied Materials and Interfaces: Reactive 3D Printing of Shape Programmable Liquid Crystal Elastomer Actuators
Via: Rice University