SLA 3D printing technology for the first time to achieve 4D printing!

As 3D Printing technology is becoming more and more known, the concept of 4D printing has also been initiated from time to time. The so-called 4D printing is actually a 3D printing of smart materials with shape memory, such as shape memory polymers (SMPs). Usually, after the material is created into a new shape, it is subject to external stimuli, such as Heat, stress, etc. will return to their original shape.

Recently, a group of researchers at the Casali Applied Chemistry Center at the Hebrew University in Jerusalem introduced 4D printing into the field of flexible electronics. More importantly, the researchers used a PLA 3D printer to print shape memory polymers. Prior to this, scientists used 4D printing to either use a low-end extrusion printer or a high-end multi-material inkjet 3D printer. Researchers at the Casali Center used an Asiga Pico Plus39 DLP light-cured 3D printer to print SMPs at a higher resolution than the 3D printers we typically use.

“In addition,” the project's researcher Michael Layani said: “Before this, the structure of 4D printing was mainly based on its sensitive parts, which means that its entire structure is only a small piece of reactivity, so its shape memory behavior. It is limited and can only be carried out along a specific execution route, and our structure is completely free to program its shape memory path."

In a recent paper titled "Advanced Materials" called "3D Printing of Shape Memory Polymers for Flexible Electronic Devices," the researchers explained how they would SMPs are used in the field of flexible electronics.

In this study, scientists have developed a process that creates structures with full motion capabilities, rather than only specific parts that can move. They created a custom heated resin barrel in which the printing platform of the Asiga 3D printer was lowered layer by layer. By layer-by-layer curing with UV light at the bottom, they are able to avoid the inhibition of oxygen molecules. In addition, the researchers downloaded some open source STL files on the web for printing test models such as a bird, an Eiffel tower and a vascular stent.

These 3D printed models were rigid and waxy at room temperature, and the researchers used a heat gun to heat them above the melting point, which became soft and reshaped. The researchers then changed their shape and cooled it below the melting point temperature to resolidify it. But when they are heated again, the memory is triggered and the model returns to its original shape.

Researchers say that when this technology is applied to flexible electronic circuits, SMPs can be integrated into conductive materials to trigger their mobility. For example, a flat SMP circuit, printed with conductive silver nanoparticle ink, can trigger its motion by applying and de-energizing the voltage, causing the circuit to turn on and off.

"The response can be used for soft robots, minimally invasive medical devices, sensors, and the manufacture of wearable electronic products," the researchers said. "The use of 3D printing technology overcomes the difficult-to-machine nature of thermoset resins and makes other technologies difficult. The complex geometry that is achieved."

Below is a video of a dragon that the researchers used to print the image, which returned to its original shape at 70 °C. Note that the speed in the video is 16 times the actual speed: