Question: How the steerable needle makes the material around it bend and break? (general concept)

Matthew Oldfield answered on 6 Mar 2016:

This is a short question with a very big answer. I will try to keep it brief though!

The needle is very soft so we try to make it bend rather than the material around it. It is more like a piece of string than a normal metal needle. If you push a stiff needle into tissue it stretches and pulls the tissue a lot. We try to use a soft needle so that the tissue doesn’t stretch. As the front of the needle steers along a path, the back of the needle follows that path a bit like a worm. We’ve done some experiments to show that this really does happen!

The needle has a sharp point. That is what breaks the material that it is pushing through. This is like a normal medical needle. If you stretch something enough it will normally break. The front of the needle stretches the material around it until it separates – a bit like pushing your finger into a bowl of jelly!

We can alter the shape of the needle tip as we push it in. This is what makes the needle steer. It is a bit like a rudder used for steering a boat but at the front rather than at the back.

All three of these things make our needle work in its particular way. It was my boss who had the idea that they could be combined and used for surgery.