Potential of thermo-sensitive hydrogel as an actuator

Abstract

To use poly-N-Isopropylacrylamide (PNIPAAm) as an actuator, we investigated its general characteristics such as swelling/deswelling ratio, response time and swelling force. Through out the variation, a change in volume of over 600% of PNIPAAm and a force generation of gram force order was obtained. Furthermore, we measured the significant change of friction caused by phase transition phenomena that is hydrophobic and hydrophilic. Surface condition that influences friction force can be reversed from swelling phase to deswelling phase by controlling the temperature of PNIPAAm. To verify the potential application of PNIPAAm using this characteristic, we compared its friction force under glass and small-intestine tissue of a pig. It was found that the level of friction differs significantly depending on phase change of PNIPAAm. Based on this knowledge, we could conclude that PNIPAAm can be applied to the stopping mechanism of in-body locomotion in order to replace the clamping mechanism of in body robot for locomotion on the gastrointestinal tract.