### Scientists Replicate Shark Intestines to Develop Advanced Tesla Valves
In a pioneering study, researchers at the University of Washington have adeptly replicated the distinctive spiral formations present in shark intestines through the use of 3D-printed pipes. These biologically inspired designs have shown improved control over fluid flow when compared to conventional Tesla valves, especially when created from flexible polymers. The findings, published in the *Proceedings of the National Academy of Sciences* (PNAS), pave the way for novel applications in microfluidics, engineering, and medicine.
#### The Tesla Valve: An Overview of Its History
Nikola Tesla, the Serbian-American inventor, secured a patent for the “valvular conduit” in 1920. This innovative design features a pipe that facilitates fluid flow mainly in one direction without requiring movable components. Tesla’s valve is composed of a series of interlinked, asymmetrical, tear-shaped loops that generate considerable resistance to flow in one direction while permitting relatively unobstructed flow in the opposite direction.
In his patent, Tesla asserted that water would traverse 200 times slower in the non-preferred direction than in the favored one. Although this may have been an overstatement, a 2021 investigation by New York University researchers evaluated a Tesla valve and determined that water moved approximately two times slower in the non-preferred direction. The valve’s performance enhances at elevated flow rates, where it produces turbulent flows that serve as a “plug,” effectively inhibiting reverse flow.
Tesla’s valve has been utilized in microfluidics and various domains where managing fluid flow sans moving parts is beneficial. However, nature, particularly shark intestines, may provide an even more effective alternative.
#### Shark Intestines: Nature’s Own Tesla Valves
Sharks have captivated scientists not only for their hunting capabilities but also for their distinctive internal structure. In 2020, researchers from Japan developed 3D representations of catshark intestines, uncovering a scroll-like spiral configuration. A year later, a different team utilized CT scans to examine the intestines of several shark species, concluding that these spirals operate similarly to naturally occurring Tesla valves.
The design of shark intestines aims to optimize nutrient absorption while regulating the movement of digested content. The spiral configuration allows food to progress efficiently in one direction, akin to Tesla’s valvular conduit. This revelation captivated researchers, who recognized the potential for bio-inspired design.
#### Replicating Shark Intestines with 3D Printing
The research group at the University of Washington, directed by postdoctoral researcher Ido Levin, aimed to decipher how shark intestines achieve their flow asymmetry. “Flow asymmetry in a pipe without movable flaps has immense technological promise, yet the underlying mechanism was unclear,” Levin noted. The team sought to identify which components of the intestine’s makeup contributed to the flow asymmetry and which merely facilitated nutrient absorption.
To investigate this, Levin and his team 3D-printed pipes with internal helical designs that replicated the spirals observed in shark intestines. They adjusted aspects such as the number of turns and the pitch angle of the helix. The initial prototypes, constructed from rigid materials, yielded the desired flow asymmetry, matching or surpassing the performance of traditional Tesla valves.
#### The Significance of Soft Materials
Although the rigid 3D-printed pipes were effective, the research team acknowledged that shark intestines are not composed of rigid substances—they are supple and flexible. This flexibility likely plays a vital role in the intestines’ capacity to regulate fluid flow. Motivated by this insight, the researchers chose to explore soft, deformable polymers.
By utilizing the softest commercially available polymers that could be 3D-printed, the researchers produced a fresh set of pipes. These flexible pipes exhibited seven times greater performance in flow asymmetry than any earlier Tesla valve findings. Since shark intestines are approximately 100 times softer than the polymers employed in this study, the researchers anticipate even greater performance with upcoming materials, such as hydrogels.
#### Prospects and Future Endeavors
The success of these bio-inspired valves unlocks a multitude of potential applications. The 3D-printed pipes, being three-dimensional, can handle larger fluid volumes, making them apt for a wide array of industrial and commercial applications. The capability to manage fluid flow without moving components is notably advantageous in sectors like engineering, medicine, and microfluidics.
Alshakim Nelson, a co-author of the research and a specialist in polymer development, highlighted the broader significance of the study. “Chemists have already been driven to create polymers that are simultaneously soft, strong, and printable. The potential application of these polymers to manage flow in domains ranging from engineering to medicine enhances that drive.”
The next hurdle for the team is to discover even softer materials that can endure high deformation while sustaining their structural integrity. Hydrogels, which are currently being researched for 3D printing, could provide a promising avenue. As the landscape of 3D printing technology progresses, the researchers are
