A thermo-sensitive hydrogel actuator in dry environment

Thermo-sensitive hydro gel has hydrophilic 3-dimensional structure whose volume is expanded at lower critical solution temperature (LCST) and contracted below the critical temperature. However, the usage of hydro gel is limited because it needs to contain hydro ions in 3-diemnsional structure in order to initiate the volumetric change.¹ Therefore; the hydro gel has been used only with a drug-delivery system and a passive valve in aqueous environments. In this paper, we proposed and demonstrated the new structure of poly N-isopropylacrylamide (NIPAAm) hydrogel actuator as shown in Fig.1. Fig.2. shows 3D molding structure fabricated by standard photolithography process which can contain water inside of itself in order to be used in dry environments independently. First swelling rate of synthesized NIPAAm polymer in water was measured and plotted as shown in Fig. 3 which volume changed 1000% respectively. And we will compare the basic characteristics of the NIPAAm actuator such as the working cycle and response time in dry and aqueous environment.² In addition, unlike imprecise weigh measurement method; swelling/deswelling ratio of NIPAAm will be presented by exact volume measurement as shown in Fig. 4. Hot-plate was used to heat up a NIPAAm actuator since a micro heater system was not finally integrated with the NIPAAm actuator. However, heater integrated NIPAAm actuator will be presented with expecting to experiment on basic characteristics with it. Finally, we will develop the NIPAAm actuator with optimized structure which could have local deformation by its own heating system.