Programmable Multistable Mechanisms for Safe Surgical Puncturing

We present novel medical devices for safe surgical puncturing, in particular a cannula for the treatment of retinal vein occlusion (RVO). This passive mechanical device has an adjustable stroke and exerts a puncturing force independent of operator applied displacement. The innovative feature of this tool is that puncturing stroke is decoupled from operator input thereby minimizing the possibility of overpuncturing. This is achieved using our concept of stability programming, where the user modifies the mechanism strain energy as opposed to imposing direct displacement which is the case for standard bistable mechanisms. Ultra-fast laser three-dimensional (3D) printing is used to manufacture the needle in glass. A microfluidic channel is integrated into the needle tip for drug injection. Numerical simulations and experimental measurements validate the mechanical stability behavior of the puncture mechanism and characterize its puncturing stroke and force.