Delivering Precise Drug Doses
I led a blank-slate design effort for a novel mechanism which delivers a small but precise bolus dose of liquid drug to a patient from a wearable delivery device. The design process was very thorough - our team posed over a dozen prototypes and downselected to three for prototyping using Pugh matrix methodology.
I executed the detail design process on one of the concepts that I originated, sourcing custom parts from three suppliers and commodity components online.
My design features a spring-loaded piston with a custom overmolded seal, nested inside a rotary cam mechanism.
A micromachined rack and gear converts input translational motion into rotation of the mechanism, which loads and delivers the dose when actuation force is applied to the input rack. I designed custom sliding face seals that wipe across the underside of the rotating mechanism, controlling the hydraulic connectivity between the pump piston and draw/dispense lines with high precision.
This design was highly constrained in multiple dimensions: overall size, cost, force to actuate, ease of assembly, and above all, patient safety. I performed comprehensive static force balance analysis to correctly tolerance interference fits, drive sliding contact dimensions, and size the antagonistic springs which support dose and seal functions.
When components arrived, I assembled and tested 10 replicates of the design and delivered them to the client. Their rigorous internal testing demonstrated that my design reduced dose variability from 6.6% to 1.0%, and it was granted US Pat. 11007317.
