November 25, 2015

On a recent tour of medtech scene in Holland, we stopped off at TU Delft where teams of professors and graduate students are designing tools to improve how various surgical techniques are performed. Just like we are at Medgadget, the folks at TU Delft believe that technology defines what clinicians are actually able to do. They see their work less as mechanical and electrical engineering and more as patient-centered healthcare. There’s a number of research teams at the university working on different medical challenges and we had the opportunity to take a look at what some of them are up to.

tu-delft-surgicalA good deal of work is being done to improve how existing surgical procedures are performed by making rigid tools flexible and steerable. Knee arthroscopies and minimally invasive surgeries on other organs are common these days, but they’re done using tools that don’t wrap around the ligament being worked on. Instead, the surgeon has to push and rotate tools in a rather unnatural ways with the hope of reaching the tissue that needs to be excised. Invariably, the result is that too often a considerable part of tissue that should be removed remains in place after the procedure. This is where creative mechanical engineering comes in. One of the teams at TU Delft developed an arthroscopy tool that has a snake-like tip capable of bending in surprising ways.

MultiFlexcable-ringThe so-called MultiFlex is an example of the bio-inspired approach that is at the heart of many of the tools being built at TU Delft. It takes ideas from octopus tentacles that have a bunch of muscle rods near the perimeter that work together to flex the tentacle well enough to be featured in horror movies. Fear not, unlike in the movies, the instrument is not autonomous and works in direct response to the operator’s hand movements.

Currently the handle controls the tip of the instrument. You squeeze and push it and simply shape it to take on the shape of the tip. It’s not exactly intuitive because the handle’s shape has to actually be reverse of the tip (that’s how the mechanics are working out right now), and it’s not yet gentle enough to not damage nearby tissue. Those things will certainly be addressed and the technology is poised to find its way into a surgical robot that will be able to safely move around fragile anatomy.

It’s important to note that bio-inspiration is not bio-mimetics, as only certain characteristics taken from nature and used as examples to build new mechanisms. Metal wires, gears, and other more traditional components are still at the core of each device, but are made to work together to produce new capabilities that may have seemed impossible using conventional configurations.

The mechanism that moves the MultiFlex is called a cable-ring, which has a couple helical springs, with rods in between, that work together to flex the multi-steerable instrument.

One major problem the cable-ring design overcomes is present in existing robotic surgery instruments, such as Intuitive Surgical’s EndoWrist, that rely on metal cables wrapped around 2mm wide gears to aim the tip of an instrument. Because the cables are forced to bend to such a degree, they eventually break, and so require regular maintenance after about fifteen procedures. The MultiFlex has no points where the metal wires wrap around and forced to move against.

The MultiFlex isn’t in its final prototype configuration quite yet, as it relies on a somewhat non-intuitive control mechanism that would force the surgeon to think more about the handle than the procedure being performed. Though there’s considerable work to be done before we see the device in production, the fundamental breakthrough of building a flexible and steerable instrument seems to have been achieved.

Link: TU Delft…


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