Five key materials engineering components and how each component impacted the working performance of a polymer
actuator material are investigated. In our research we investigated the change of actuation performance that occurred
with each change we made to the material. We investigated polymer crosslink density, polymer chain length, polymer
gelation, type and density of reactive units, as well as the addition of binders to the polymer matrix. All five play a
significant role and need to be addressed at the molecular level to optimize a polymer gel for use as a practical actuator
material for biomedical and industrial use.
KEYWORDS: Actuators, Polymers, Polymeric actuators, Sensors, Control systems, Electrodes, Control systems design, Prototyping, Human-machine interfaces, Magnetic sensors
The concept is simple, within the pump a pH responsive polymer actuator swells in volume under electrically controlled
stimulus. As the actuator swells it presses against a drug reservoir, as the reservoir collapses the drug is metered out to
the patient. From concept to finished product, engineering this smart system entailed integration across multiple fields of
science and engineering. Materials science, nanotechnology, polymer chemistry, organic chemistry, electrochemistry,
molecular engineering, electrical engineering, and mechanical engineering all played a part in solutions to multiple
technical hurdles. Some of these hurdles where overcome by tried and true materials and component engineering, others
where resolved by some very creative out of the box thinking and tinkering. This paper, hopefully, will serve to
encourage others to venture into unfamiliar territory as we did, in order to overcome technical obstacles and successfully
develop a low cost smart medical device that can truly change a patient's life.
Electroactuated polymer (EAP) hydrogels based on JEFFAMINE® T-403 and ethylene glycol glycidyl ether (EGDGE)
are used in an infusion pump based on the proprietary Pulse Actuated Cell System (PACS) architecture in development
at Medipacs LLC. We report here significant progress in optimizing the formulation of the EAP hydrogels to
dramatically increase hydrolytic stability and reproducibility of actuation response. By adjusting the mole fraction of
reactive components of the formulation and substituting higher molecular weight monomers, we eliminated a large
degree of the hydrolytic instability of the hydrogels, decreased the brittleness of the gel, and increased the equilibrium
swelling ratio. The combination of these two modifications to the formulation resulted in hydrogels that exhibited
reproducible swelling and deswelling in response to pH for a total period of 10-15 hours.
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