We’ve been working on a reusable insulin patch pump for the past year, and I wanted to share some of the engineering lessons learned so far. Insulin micro-dosing is mechanically non-trivial: basal delivery can be fractions of a unit per hour, boluses involve larger step changes, and everything has to stay within ISO tolerances while attached to a moving human body for several days.

Some interesting constraints we ran into:

- dose accuracy limits from ISO 11608 (both basal and bolus) - fluidic compliance and variable back-pressure under skin - reservoir deformation and head-pressure drift over time - motor torque margins at low battery voltages - thermal variation (skin vs ambient) affecting fluid and mechanics - occlusion detection without continuous pressure sensing

It’s one of those devices that looks like simple consumer hardware from the outside, but internally mixes fluidics, precision mechanics, biocompatible materials, power constraints, and regulatory requirements.

Happy to share more details in the comments about actuator choices, reservoirs, failure modes, materials, test rigs, or regulatory constraints.