Articulating Colonoscopy Snare
Project lead on a five-person team. A 3.4 mm steerable sheath that gives a colonoscopy snare 360° of angular access independent of the scope — small enough to pass down the 3.6 mm working channel of an adult colonoscope.
- Role
- Project lead
- Organisation
- UCLA Bionics Lab
- Dates
- Jan 2026 – May 2026
- Status
- Complete — working prototype
- Tags
- Medical device · Pull-wire actuation · Nitinol · Prototyping
- Outer diameter
- 3.4 mm — about a plastic straw
- Fits
- 3.6 mm adult colonoscope working channel
- Articulation
- 360° of angular access at the distal tip
- Actuation
- Two pull wires on spools, vertical handle
- Control
- Single-handed, independent of the scope
- Team
- Five people — I grew into the lead role
Prototype in motion
Why it exists
A colonoscope is steerable. The snare that comes out of the end of it is not — it can only be pushed straight out of the working channel. To reach a polyp, the physician has to aim the entire scope, and the scope is too large to point precisely at a small target.
The result is that some polyps are difficult to reach, and when the snare is extended it frequently sits in front of the camera and blocks the view of the thing being removed. The goal was a snare that can be aimed independently of the scope it came out of.
Requirements
Fit inside the 3.6 mm working channel of an adult colonoscope — this is the constraint everything else bends around. Be controllable one-handed by a physician who is already operating the scope with the other. Deliver full 360° of angular access at the tip.
My role
I did not start as team lead; I grew into it. I ran research and development and prototyping, and I owned communication in both directions — gathering requirements from the physicians who would use the device and keeping our PI current on where the project stood.
How it works
The design is a steerable sheath that passes down the colonoscope's working channel, with the snare running through the sheath's own lumen. Once the sheath is protruded past the end of the scope, its distal section — deliberately flexible — can be deflected independently of the scope.
Deflection comes from two pull wires anchored at the tip and wound on spools in a vertical handle. Tensioning one wire bends the tip toward it; combined with rotation, that gives the snare 360° of angular access to point at a polyp the scope itself cannot aim at.
Key decisions
Build a steerable shaft, or integrate one
- Fabricate a braided multi-lumen shaft in-house — needs reflow equipment the lab does not have
- A custom machined articulating tip
- Buy an off-the-shelf steerable sheath and build the integration around it
Off-the-shelf steerable sheath as the actuation platform, with custom integration of the snare through its lumen.
I spent a long stretch of the project reading how commercial catheters and steerable sheaths are actually built, and that research is what produced the answer: the in-house route was blocked by equipment we were never going to have. Buying the sheath changed the question from “can we manufacture a 3.4 mm braided shaft” to “does the clinical idea work” — which is the question that actually mattered, and the one a working prototype could answer.
Driving the distal tip
- A thumb gimbal on the handle
- A motorised drive
- Pull wires on spools, driven from a vertical handle
Two pull wires wound on spools.
The gimbal could not convert the small thumb motions available into enough deflection at the tip. The motorised approach grew large and complex quickly, and this has to sit in a physician's hand alongside a scope they are already driving. Pull wires are what commercial steerable devices use, they work one-handed, and — critically — they scale down to 3.4 mm.
What went wrong
The early prototypes were around 10 mm — nearly three times too large to enter the channel, and scaling down was not a matter of shrinking the model. Without the ability to reflow braided shafts in-house, there was no clear path from a 10 mm proof of principle to something that fits a colonoscope.
That constraint is what drove the research into commercial steerable sheath construction, and that research is what unblocked the project.
Result
A working proof-of-concept prototype at 3.4 mm outer diameter with full 360° angular access, small enough to pass down an adult colonoscope's working channel, plus a prototype developed toward animal trials. Testing focused on confirming the snare deploys reliably through the sheath and that the assembly holds its size and performance.
Design artifacts
A photo of the prototype next to a ruler or a straw would still land the 3.4 mm point instantly. One shot, next time you have the device in hand.