Electrolyte Solutions to Improve the Performance of Electroactive Polymers used in Infusion Pumps

Abstract

Tucson/San Diego-based company Medipacs, Inc. has developed a novel approach to their infusion pump design: the utilization of electroactive polymer materials to serve as mechanical actuators in portable, disposable infusion pumps. Already in working order, Medipacs' electroactive polymer's design is continually perfected in order to both maximize the polymer's mechanical output as well as uncover the full spectrum of design applications for the polymer. As Medipacs' polymer readily swells while submerged in an electrolyte solution at a low pH, the ions that make up the electrolyte solution are not the only important quality; the concentration of the electrolyte solution is also significant as too high or too low of an electrolyte concentration can hinder polymer expansion. The study at hand investigated not only the cause of a surprising improvement in polymer actuation during the utilization of a new (proprietary) electrolyte over the previously used electrolyte, sodium perchlorate, but also looked to further improve actuation through the investigation of additional electrolytes: citric acid, sodium hydrogen sulfate, and sodium nitrate. A passive swelling test that utilized pH changes to facilitate swelling, and an active swelling test that used an electrical current to facilitate swelling were both used; a polymer known to swell in an alkaline solution was also incorporated into the study for comparison. Preliminary results suggest that an electrolyte solution with many acid-dissociation constants facilitates the greatest swelling of Medipacs' polymer, although more experiments are needed to evaluate the ability to electrochemically control such electrolytes.