Sensor/actuator based on a smart hydrogel/conducting polymer nanocomposite

C.R RIVAROLA; R. RIVERO; M.A MOLINA; M.V MARTINEZ; P.C CAVALLO; M.C MIRAS; C.A BARBERO

Praga

Congreso; 3rd International Conference on Materials and Applications for Sensors and Transducers, IC-MAST; 2013

Nanocomposites are produced by in-situ formation of conductive polymers (polyaniline, polypyrrole) inside smart hydrogel (based on poly(N-isopropylacrylamide), PNIPAM) matrix. Scanning electron microscopy of the nanocomposite shows the formation of nanodomains of the conducting polymer inside the gel, instead of an interpenetrated network. The thermosensitivity of the smart hydrogel is unaffected by the presence of the conducting polymer, in agreement with the presence of separated conductive polymer/hydrogel domains. On the other hand, the temperature for phase transition of the smart hydrogel (32-33 oC for PNIPAM) can be easily tuned to be closer to the human basal temperature by copolymerization with acrylamides bearing hydrophilic groups. The nanocomposite is an electronic conductor due to the presence of the conductive polymer. The resistance decreases linearly with pressure, suggesting a mechanism where conductive polymer nanodomains create conducting paths by touching, when pressure is applied. In that way, an electronic pressure sensor is built. The conductive polymer absorbs electromagnetic radiation (light, microwaves) and heats up driving the phase transition of the smart hydrogel matrix. In the way, the volume collapse and the internal solution is expelled. Based on such phenomena, an electric switch driven by microwaves and a remotely driven drug release device are built.