Jan 12, 2018 | By Julia

Despite the impressive strides the medical industry has taken in the field of surgical technology, doctors are still wrestling with a fundamental problem: that of soft tissue grip. As an ongoing issue in minimally invasive surgery, our current model of manipulating soft tissue without slipping revolves around the use of clunky grasping instruments with high pinch forces. These instruments leave a lot to be desired, and rely entirely on the steadiness of a surgeon’s hands in order to be successful. But that could soon be about to change, thanks to one ambitious engineering student and a bit of 3D printing.

Tim van Broekhoven is a recent graduate of the Delt University of Technology (TU Delft) in the Netherlands, and the bright mind behind an innovative new answer to soft tissue grip. For his Master’s thesis in engineering, van Broekhoven sought to overcome the current problems seen in manipulating soft tissue during surgery. Although the issue itself is nothing new, where the engineering student turned to for inspiration is innovative to say the least.

“In nature, several animals employ adhesion in order to grip on, not only hard, but also soft substrates,” van Broekhoven explains in his abstract. “Among these animals, geckos and tree frogs are of special interest for engineered gripping systems, because of their high body mass.” The TU Delft grad goes on to describe how the toe pads of geckos and tree frogs are particularly relevant here, as the primary means through which these creatures sit, climb, and hop around their environment without slipping. The inner workings of these toe pads exhibit natural evolution at its finest: characterized by a microscopic hierarchical pillar structure, the soft toe pads also possess a network of stiff inner fibers; all of it contributes to enhanced friction, or grip, between the animals’ feet and an external surface. Perhaps most exciting, however, is that this structure can be mimicked, facilitating a man-made way to achieve the adhesive grip exhibited by these tiny creatures.

In his thesis, titled “On the Mimicking of Geckos and Tree Frogs for Adhering to Soft Substrates,” van Broekhoven goes on to investigate this mechanism by way of 3D printing. The basic aim, he writes, was to investigate whether reinforcing a soft pad with stiff fibers increases friction of soft substrates as opposed to a pad without fibers. In order to test his hypothesis, van Broekhoven conducted three separate experiments. In the first experiment, he created a specialized polydimethylsiloxane (PDMS) pad which encapsulated 3D printed fibers in order to test the composite’s adhesion and friction forces. In Experiment 2, stiffer 3D printed fibers were used in a similar PDMS pad. Finally, in the last experiment, van Broekhoven used a carbon fiber fabric in the PDMS pad. In all three experiments, both hard and soft gelatin substrates of various stiffness degrees came into play, with the soft gelatines functioning as “phantoms” of human soft tissue.

The results indicated that, regardless of substrate type, adding 3D printed fibers with varying degrees of stiffness to a PDMS pad reduced peak friction force. The carbon fiber fabric, on the other hand, significantly increased peak friction force, as compared with a PDMS pad without fibers. All in all, van Broekhoven concludes that the results from this research are “promising for developing fiber-reinforced composites that can grip to soft substrates, including minimally invasive grasping instruments for soft-tissue grip.”



Posted in 3D Printing Application



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