What if a 3D printing defect could become the key to developing a new technology? This is the proposal of a group of researchers at Hanyang University in South Korea, who took advantage of overcuring to create adhesive surfaces inspired by geckos. Using the DLP process, they have managed to replicate anisotropic structures similar to those of the legs of these reptiles, known for their ability to adhere to and detach from surfaces.
The hope is that these structures could be useful for applications like soft robotics, biomedical devices and systems that serve to manipulate objects. The study was published in the journal Mirosystems & Nanoengineering and involved several departments at the Korean university.
Explanation of the process for obtaining and testing anisotropic structures (photo credits: Kim, S., Kim, J., Seo, S. et al.).
For those who don’t know, the DLP 3D printing process involves selectively solidifying resins using light. However, one of its main challenges with it is overcuring, which occurs when the light reaches further than expected and hardens the part in unwanted areas. Normally, this is considered a defect as the accuracy of the structure is altered.
However, in this study it was decided to change this conception. The researchers used overcuring strategically to form inclined microstructures inspired by the adhesive legs of geckos. By controlling the printing direction and light exposure time, they were able to induce a perfect tilt in microscopic abutments from simple digital models.
Why Create These Anisotropic Structures Inspired by Geckos?
The legs of geckos are covered with tiny structures called setae, which in turn branch into micro spatulae. This arrangement allows them to adhere firmly to smooth surfaces, without suction. So their secret lies in the slanted orientation of the fibers, which allows them to stick to something firmly when pressure is applied in one direction, but come off easily with a little twist.
Mimicking that same logic, the team processed the printed microstructures using a double-molding technique, transforming them into surfaces capable of sticking in a gecko-like fashion. The new printed surfaces replicate the adhesion and are ideal for applications such as grippers that need to handle delicate objects without damaging them.
To demonstrate the feasibility of the method, the team fabricated a mechanical module incorporating these anisotropic structures. Their prototype was able to attach to different materials and release them easily with controlled movement. Furthermore, when comparing the new structures with those fabricated by traditional methods, better stability was observed, while reducing the complexity of the fabrication process. Thus, the use of overcuring as a design parameter made it possible to eliminate costly intermediate steps, making the process more efficient. Who would have guessed?
Photos of functional anisotropic structures (photo credits: Kim, S., Kim, J., Seo, S. et al.).
The study demonstrates how a defect can become an advantage when rethought from a creative point of view. By reinterpreting overcuring as a design tool, the researchers overcame the technical limitations of the DLP process, opening a new avenue for fabricating advanced structures.
The development of gecko-inspired robotic grippers is just one example of the potential of this technique. In the future, its application could extend to fields such as soft robotics, precision medical devices or even industrial assembly systems. You can find more information about the technique HERE.
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