Syringe Pump Wire Actuator

This project was completed at Fractyl Health and involves proprietary information. I will do my best to explain it without revealing any confidential information: A gene therapy virus needed to be injected into a catheter inserted into an endoscope during an animal study. For this reason, the virus could not travel through an IV extension from a syringe pump to the catheter because of the cost associated with the wasted virus in the dead volume of the IV extension. Therefore I was tasked with creating a device that could be remotely actuated by the syringe pump and transmit that force to a syringe attached directly to the catheter.

The basic concept is similar to this image of a motorized syringe actuator however a wire was used to mechanically transmit the force from a syringe pump to the plunger.

Previous designs had utilized a wire inside of a tube that was pushed to actuate the plunger on the syringe. However, this did not transmit the force evenly and skipped while the linear syringe pump was engaged. I decided to use an off-the-shelf throttle cable for the smoothest possible actuation which would be pulled by the syringe pump instead of pushed to more evenly transmit power. I used SLA 3D printing I create a snap-fit housing for a system of two racks and a pinion gear. These mechanically translated the pulling force into a pushing force on the plunger of the syringe. After iterating on the tolerances for the housing and the gears testing confirmed that the plunger was pressed smoothly and linearly.