3D printing is producing more products in our lives every day. In 2017 a 3D printed bike bridge opened in the Netherlands. A 3D printed fighting robot was introduced at CES 2018. The U.S. Army even started implementing 3D printers to print drones within 24 hours. Now there is a new printing process on the market: 4D printing.
4D printing doesn't require a new type of printer. It is actually a 3D-printing process developed by Rutgers engineers that they call ‘4D printing.' This process uses shape-shifting smart gel for the development of living structures like human organs, human tissues, soft robots, targeted drug delivery, flexible sensors and actuators, biomedical devices and platforms for cells to grow in the body. 4D printing uses a hydrogel to 3D print objects that have the ability to shapeshift with changes in temperature.
Hydrogels maintain their shape and density even when they are filled with water. The smart gel used in the 4D-printing process is good for printing live organs and other healthcare items because they contain water molecules when they are put into the body.
Rutgers-New Brunswick engineers teamed up with the New Jersey Institute of Technology to create their smart gel and 4D-printing process. Hydrogel has been used for many years in biomedical and motion fields but it has never been used in 3D printing before.
To develop their method, the research team turned to a lithography-based printing technique. This technique is fast and cheap while still being able to 3D print many materials with a hydrogel resin with binder and bonding chemicals that develop with light, and a dye that controls the light intake of the printed material.
The team was able to control hydrogel growth by focusing on temperature. Temperatures below 32 degrees Celsius cause the hydrogel to retain water and grow. At temperatures above 32 degrees Celsius, the gel emits water and shrinks.
The paper on this technique was published in Scientific Reports.