Researchers Develop Process Flow to Guide 3D Printing in Soft Robotics Field

Soft robotics is a growing field within Artificial Intelligence. These systems are able to safely adapt to complex environments, and they can have various designs and length scales, from meters to sub micrometers. 

The soft robots that are on the millimeter scale have special importance, since they are able to consist of a combination of miniature actuators controlled by pneumatic pressure. These soft robots are useful for navigating complex confined areas, and the manipulation of small objects. 

One of the consequences of scaling down soft pneumatic robots to millimeters is that they then have finer features. These are reduced by more than one order of magnitude. This design requires a great amount of delicacy when creating them through traditional means such as molding and soft lithography. There are some new technologies like digital light processing (DLP) that produce high theoretical resolutions, but it is still hard to do without clogging. Successful examples of 3D printing miniature soft pneumatic robots do not happen often. 

Researchers from Singapore and China, mainly from the Singapore University of Technology and Design (SUTD), Southern University of Science and Technology (SUSTech), and Zhejiang University (ZJU), have created a generic process flow to guide DLP 3D printing of miniature pneumatic actuators for soft robots. These have an overall size of 2-15 mm. The research was published in Advanced Materials Technologies. 

“We leveraged the high efficiency and resolution of DLP 3D printing to fabricate miniature soft robotic actuators,” said Associate Professor Qi (Kevin) Ge from SUSTech, lead researcher of the research project. “To ensure reliable printing fidelity and mechanical performance in the printed products, we introduced a new paradigm for systematic and efficient tailoring of the material formulation and key processing parameters.”

The way DLP 3D printing works is photo-absorbers are added into polymer solutions. This enhances the printing resolutions in lateral and vertical directions. Increasing the amount will cause rapid degradation in the material’s elasticity. The elasticity is extremely important for soft robots to sustain large deformations. 

“To achieve a reasonable trade-off, we first selected a photo-absorber with good absorbance at the wavelength of the projected UV light and determined the appropriate material formulation based on mechanical performance tests. Next, we characterized the curing depth and XY fidelity to identify the suitable combination of exposure time and sliced layer thickness,” explained co-first author Yuan-Fang Zhang from SUTD.

“By following this process flow, we are able to produce an assortment of miniature soft pneumatic robotic actuators with various structures and morphing modes, all smaller than a one Singapore Dollar coin, on a self-built multimaterial 3D printing system. The same methodology should be compatible with commercial stereolithography (SLA) or DLP 3D printers as no hardware modification is required,” said corresponding author Professor Qi Ge from SUSTech.

On top of all of this, the researchers also developed a soft debris remover that has a continuum manipulator and a 3D printed miniature soft pneumatic gripper. It is capable of navigating through a confined space and collecting small objects that are in difficult places to reach. 

These new developments will help in the process of 3D printing miniature soft robots with complex geometries and sophisticated multimaterial designs. The integration of printed miniature soft pneumatic actuators into a robotic system will provide many opportunities. These new technologies can be applied to applications like jet-engine maintenance and minimally invasive surgery, and they will continue to be developed so that they can benefit many more areas. 

See more from the Singapore University of Technology and Design, where you can find information on current research being done in these fields.