Fabrication of Artificial Muscle Based Valves for Controlled Drug Delivery

Abstract

Artificial muscle is defined here as a blend of a hydrogel and a redox polymer, which dramatically swells and shrinks under chemical and/or electrical stimuli. Whereas inorganic actuators usually will not change size more than 7%, hydrogel actuators can change size easily by 100%. Hydrogel actuators commonly lack fast response and are difficult to control. In order to circumvent these shortcomings, super porous hydrogels and artificial muscle blends have been investigated in this study. A super porous hydrogel with 200 ~ 500 tm diameter pores can swell over 1000% (w/w) in 3 min when the dry gel is immersed into deionized water. The artificial muscle blend of poly(2-hydroxyethyl)methacrylate (PHEMA) and polyaniline displays significant swelling and shrinking upon applying an electrochemical bias (from −0.2 V to +0.8 V (vs. SCE)). In this type of artificial muscle, polyaniline, a redox polymer (a mixed ion and electron conductor), acts as the “electronic backbone” for transferring electrons from a metal contact throughout the muscle, while PHEMA, a hydrogel (an ion conductor), is responsible for most of the swelling and shrinking. The artificial muscle valves are being integrated as actuators into a drug delivery system, which includes a drug reservoir lined with the micromachined polymer valves, a microprocessor, micro battery and a biosensor. The sensor can monitor a biostimulus (e.g. glucose) and send a signal to the delivery system via an electronic circuit. The transmitted signal will trigger the opening and closing of the artificial muscle controlling the rate of drug release (e.g. insulin) from the drug reservoir.