smarTubes
Reaching deep into the lung with curved tubes.
While working for Philips Electronics North America, I worked with a team to design and build a new technology to deliver therapies deep into the lung. The idea was to use pre-curved tubes that could be pushed through each other to follow a preset path (determined from an MR or CT image) through the bronchial tree.
Nested Cannulas are curved tubes that are pushed through each other to reach deeply into the lung.
When I built the first set of these bad boys with Nitonol, it quickly became apparent that when you place nested tubes of opposite curvature inside of each other they really don’t like it; they twist along their length to avoid the high potential energy. My solution (patented by Philips, here) was to use non circular tubes that could interlock to stop them from rotating inside of each other.
Interlocking schemes for the tubes prevent them from rotating inside of each other, the prototype used the square tubes in the center.
I built a set of (tiny) interlocked square tubes. What did we learn: forcing things to do what you want can cause a whole lot of friction! It was quite hard to insert the tubes with opposite curvature through each other.
A physical set of three nested cannulas that I built from polycarbonate. The outer diameter of the largest cannula was 2.35mm.
My second invention on nested cannulas (also Patented by Philips, here) was to introduce helical tubes into the mix.
Helical tubes improve the reach of the interlocked nested cannulas; changes in pitch allow for subtle shifts in the nested tubes end point.