A study conducted by a team of researcher from the Innovative Center for Flexible Devices, School of Materials Science and Engineering at Nanyang Technological University in Singapore focused on thermal extrusion 3D printing (some call it 4D printing) of devices which change shape when reacting to light.
Compared with traditional stimuli-responsive devices with simple planar or tubular geometries, 3D printed stimuli-responsive devices not only intimately meet the requirement of complicated shapes at macrolevel but also satisfy various conformation changes triggered by external stimuli at the microscopic scale. However, their development is limited by the lack of 3D printing functional materials.
The paper demonstrated the 3D printing of photoresponsive shape memory devices through combining fused deposition modeling printing technology and photoresponsive shape memory composites based on shape memory polymers and carbon black with high photothermal conversion efficiency. External illumination triggers the shape recovery of 3D printed devices from the temporary shape to the original shape.
The effect of materials thickness and light density on the shape memory behavior of 3D printed devices is quantified and calculated. Remarkably, sunlight also triggers the shape memory behavior of these 3D printed devices. This facile printing strategy would provide tremendous opportunities for the design and fabrication of biomimetic smart devices and soft robotics.
The Innovative Centre for Flexible Devices (iFlex) was set up in January 2017 in collaboration with Stanford University in the United States, focusing on flexible electronic research. The two universities will host joint doctoral and postdoctoral positions.
Professor Chen Xiaodong, Director of iFlex, said one focus of the programme is to find simple, scalable and sustainable methods to 3D-print flexible electronics. But this is no simple matter. The ink used, for instance, must not only conduct electricity, but also be stretchable and stable at temperature extremes.
NTU has also been making electronics stretchable as well as bendable, which are important to allow them to attach to surfaces like skin. Researchers have managed to make stretchable capacitors – devices that can store and discharge electricity – by giving them a zigzag shape that can shrink and expand like an accordion.