3D printing uses computer control to fuse layers of polymers or powders into a three-dimensional object. Rutgers University researchers found a way to add to a fourth dimension – time – to the manufacturing process.
The Rutgers-made material reacts to heat, morphing its shape depending on the temperature.
Take the 3D-printed chess piece in the video below. The object contains a temperature-responsive, water-containing hydrogel – a material common in everyday objects, including Jell-O, contact lenses, and diapers.
As the temperature around the object increases beyond 32 degrees Celsius, the hydrogel expels water and shrinks. Conversely, a decrease in temperature returns the chess piece to its original size.
The Rutgers University–New Brunswick engineers, including assistant professor and senior author of the 4D study Howon Lee, used a lithography-based technique to print layers of a special resin. The resin consists of the hydrogel; a binding element; a chemical that facilitates light-activated bonding; and a dye that controls light penetration.
The measurements of the hydrogel-created objects range from the width of a human hair to a length of several millimeters. By adjusting temperatures, the engineers also discovered the ability to program motion within areas of a 3D-printed object.
Because the material easily carries liquids, the technology may someday support the delivery and targeted release of drugs to the body. The 4D printed objects’ adaptability also enables the development of “living” structures in human organs and tissues.
“The full potential of this smart hydrogel has not been unleashed until now,” said Lee in a Rutgers press release.
Lee spoke with Tech Briefs about the flood of manufacturing possibilities.
Tech Briefs: What is “4D” printing exactly?
Prof. Howon Lee: When a 3D-printed object is designed and manufactured to change shape over time, it’s called 4D printing, with the 4th dimension being time.
Tech Briefs: What are the advantages of having hydrogel in a printed object?
Lee: Hydrogels are polymeric materials which contain a significant amount of water. There are special kinds of hydrogels that can regulate their water content depending on environmental conditions such as temperature. In this work, we 3D printed a temperature-responsive hydrogel, so 3D-printed objects can change size and shape when the temperature changes.
Tech Briefs: What is different about how these objects are made compared to conventional 3D-printing manufacturing processes?
Lee: In conventional 3D printing, what is most important is to form a desired shape. However, in our study, we also studied how to control the shape and size of the printed object using the printing process parameters. Since this hydrogel swells or shrinks depending on temperature, it is important to control how much it swells, how much it shrinks, and at what temperature it shifts shape. We demonstrated all these in our study.
Tech Briefs: Why is this level of control so important, and what does this level of control enable?
Lee: Without knowing how much you can increase/decrease the size of a 3D-printed object, you cannot say you can “control” its size and shape. Simply observing size change is not science, but a quick demo or a small toy. With full control of size and shape, you can create a motion, program some functions, or make it work just like a robot.
Tech Briefs: What applications are possible?
Lee: Possible applications include soft robotic microdevices, targeted drug delivery, and tissue scaffolds mimicking active bodily functions – all of which are exciting to us.
What do you think? Will 4D printing improve medical and robotics applications? Share your thoughts below.
The study’s lead author is Daehoon Han, a doctoral student in the Department of Mechanical and Aerospace Engineering at Rutgers–New Brunswick. Co-authors include Zhaocheng Lu, another doctoral student, and Shawn A. Chester, an assistant professor at New Jersey Institute of Technology.