Imaging 

3D Printing 

Gallery 

Contact 

Team 

Research 

Publications 

News 

 

News Story

Link to 3D Printing News Stories3DP-News.html
Research Highlights Home PageHighlights.html
Link to 3D Printing Publications3DP-Pubs.html

A tapeworm-inspired tissue-anchoring mechanism for medical devices:
Paving the way for new diagnostic and surgical tools with reduced tissue irritation at the site of attachment

    Today, ingestible devices are often used to study and treat hard-to-reach tissues in the body. Swallowed in pill form, these capsules can pass through the digestive tract, snapping photos or delivering drugs. While in their simplest form, these devices are passively transported through the gut, there are a wide range of applications where robust device attachment to soft or flexible surfaces is also needed. While there has been a rich history of biologically inspired solutions to these problems, ranging from cocklebur-inspired Velcro to slug-inspired medical adhesives, the development of on-demand and reversible attachment mechanisms that can be incorporated into millimeter-scale devices for biomedical sensing and diagnostics represents a persistent challenge. To address these concerns, a new interdisciplinary effort led by SEAS Professor Robert Wood and Dr. James Weaver (from Harvard’s Wyss Institute) provides a design path forward. Reported this week in PNAS Nexus, this new study draws design inspiration from an unexpected source, the world of parasites.

Figure 1: Parasite biodiversity, illustrating the wide range of different length-scale- and tissue-specific attachment organs that are ripe for investigation.  In these illustrations, hooks are denoted in blue and suckers in red.


    Mimicking both the morphology and functionality of these complex biological structures is an incredibly challenging problem, and requires expertise from a wide range of fields including robotics, microfabrication, medical device design, and invertebrate zoology” said Wood, the Harry Lewis and Marlyn McGrath Professor of Engineering and Applied Sciences at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and one of the paper’s corresponding authors.


    To realize these millimeter-scale design and manufacturing efforts, which were ultimately inspired by the hook-like attachment organs of several intestinal tapeworm species (Figure 2), the authors employed a multi-material layer-by-layer fabrication method inspired by methods employed in the printed circuit board industry.  This fabrication approach is largely material agnostic, and as such, polymer, metal, and ceramic components can readily be incorporated into the functional devices to meet the specific application at hand.  Furthermore, due to its rapid turnaround time and the small size of the fabricated devices, this manufacturing approach provides an excellent low-waste prototyping platform during the device research and development phases of a project. 


    One of the key design features of the mechanism is its radially symmetrical architecture, which allowed for the creation of a biologically accurate range of motion from simple planar components.

Figure 2: A comparison between the tapeworm deployable hook array that provided the motivation for the present study (left two images), and the resulting millimeter-scale engineering analog (right two images).


“Employing relatively simple linkage mechanisms allows for the use of laminate manufacturing processes, which offers several advantages over conventional fabrication approaches”, said Gabriel Maquignaz, a visiting graduate student from EPFL, and the paper’s first author. 


“For example, the devices can be manufactured flat and then quickly and easily folded into their final 3D geometries using a largely automated pop-up book-like process”, said Mike Karpelson, a senior staff electrical engineer at SEAS, and an expert in this fabrication workflow. 


    The final device design contains rigid stainless steel structural components adhesively bonded to polymer hinges.  The entire device measures less than 5 mm in diameter when deployed, and weighs only 44 mg. When it comes in contact with a tissue surface (Figure 3), a trigger mechanism is activated which causes the anchoring hooks to rotate out of plane and penetrate the adjacent soft tissue.  Since each hook follows a curved trajectory, it only punctures the skin immediately along the path of penetration (as is the case for the tapeworm hooks) causing minimal tissue damage. Because of the device’s small size and its integrated elastomer spring, the hooks can be deployed in less than 1 millisecond (Figure 4).  The authors further add that since the precision of the manufacturing process is largely limited by the resolution of the laser used in cutting the components, and the thickness of the constituent materials, the fabricated devices could be further scaled down in size as needed for future iterations.


Figure 3: Flow chart illustrating the mechanism of action of the tapeworm-inspired tissue anchoring mechanism.  Upon contact with a tissue surface (in this case, the intestinal lining), the small protruding trigger posts (top right image) are depressed, rapidly deploying the curved array of hooks which penetrate the tissue surface (right bottom three images).


“We’re really excited about applying the lessons learned from these studies to further broaden the design space to include other parasitic bodyplans, and other biological tissues and therapeutic applications.”, said Rachel Zoll, a doctoral candidate at SEAS specializing in biomedical device design, and the article’s second author.

Figure 4: High-speed video (8000 frames per second) showing hook deployment in the tapeworm-inspired mechanism.  Normally this would occur once the device contacts a tissue surface, but for clarity, here it was triggered from above with a pair of forceps. The entire deployment process takes less than 1 millisecond.


“One of the most intriguing aspects of this research effort is that it provides a much-needed experimental testbed for exploring how parasite holdfast anatomy influences human pathology at the point of attachment.”, said Armand Kuris, a parasitology professor at UC Santa Barbara, who was not involved in the study. “This represents a largely unexplored aspect of medical parasitology, and I’m eager to see where this research leads.”


    Beyond the biomedical applications that were the primary focus of the article, the authors also envision the utilization of this technology in non-medical applications ranging from reversibly adhesive tags for wildlife monitoring, to sensing platforms for textile-based materials.

"Parasitic species have a rather dubious reputation with the general public due to their often terrifying body forms and unfamiliar lifecycles that seem straight out of science fiction movies”, said Weaver. “Despite this fact, it is important to realize that these species are particularly well adapted for anchoring into a wide range of different host tissue types using a remarkably diverse set of species- and tissue-specific attachment organs (Figure 1). These features make them ideal model systems for the development of application-specific synthetic tissue anchoring mechanisms for biomedical applications.”

Article Link

TW_files/pgae495.pdf

Design and fabrication of a parasite-inspired,millimeter-scale tissue anchoring mechanism Gabriel Maquignaza, Rachel Zoll, Michael Karpelson, James C. Weaver, and Robert J. Wood PNAS Nexus, December 3, 2024.

TW_files/pgae495_1.pdf