Imagine smart materials that can change from stiffness like wood to become soft as a sponge – and also change the shape.
The engineers of Rutgers-New Brunswick University have created flexible, lightweight materials with 4D printing, which could lead to better absorption of impacts, airplane or wing modifications, wireless robotics and small implantable biomedical devices. Their research is published in the magazine Horizonts of materials.
3D printing, also known as additive production, converts digital plans into physical objects by building them layer by layer. 4D printing is based on this technology, with one big difference: it uses special materials and sophisticated models for printing objects that change shape with environmental conditions, such as a temperature that acts as a trigger, said senior author Howon Lee, Assistant Professor at the Mechanical and space engineering. Time is the fourth dimension, which allows them to be transformed into a new form.
"We believe that this interconnected science of materials, mechanics and 3D printing will create a new path to a wide range of interesting applications that will improve technology, health, safety and quality of life," said Lee.
Engineers have created a new class of "metamaterials" – materials that are designed to have unusual and contradictory properties that can not be found in nature. The word metamaterial derives from the Greek word "meta", which means "higher" or "beyond".
Previously, the shapes and properties of metamaterials after manufacture were irreversible. But Rutgers engineers can adjust their plastic-like materials with heat so they remain rigid when struck or become soft as a shock-absorbing sponge.
The accuracy can be set more than 100 times at room temperature (73 degrees) and 194 degrees Fahrenheit, allowing excellent control over shock absorption. Materials can be transformed for different purposes. They can be temporarily reshaped in any deformed form and returned to their original shape after heating.
Materials can be used in aircraft or wings that change shape and improve performance, and in light structures that collapse for space launch and transform into a space for a larger structure such as a solar collector.
Soft robots made of soft, flexible and rubberized materials inspired by an octopus could have variable flexibility or stiffness that is adapted to the environment and work. Small devices inserted or inserted into people for diagnosis or treatment can be temporarily made soft and adaptable for minimal invasive and less painful insertion into the body, Lee said.
The main author of the study is Chen Yang, a doctoral student at Lee's Laboratory. Co-authors include Manish Boorugu, Andrew Dopp, Jie Ren, Raymond Martin and Daehoon Han – all present or former Rutgers – and Professor Wonjoon Choi at the Korean University.