Abstract
Carbon nanotube sponges were successfully fabricated by freeze-drying method. The carbon nanotube was made hydrophilic by acid treatment then dispersed in water with PVA (0, 0.1, 1 wt%). The mixture was frozen under different condition to form different sized ice grains. The ice in the frozen solid was removed by sublimation without melting under low pressure that left a structure of carbon nanotube sponge. The cell size of the carbon nanotube sponges can be controlled by freezing condition and the amount of polymer addition. A minimum of 3 mg/mL CNTs was found to be needed to form a stable network structure. The strength and stiffness of the sponge increase with the density of CNTs and the amount of polymer addition. The MWNT sponges have very low stiffness and large flexibility. The electrical resistance of MWNTs sponge is very sensitive to its strain. About fivefold to tenfold of conductance change was observed in the compressive strain range between 23 and 69 %. Since the MWNT sponges have very low stiffness, high conductance/pressure ratio and excellent flexibility, artificial tactile pressure sensor arrays could be made by an integrated sponge. The two-point discrimination ability of 1 mm thick F801 sponge is proved to be smaller than 1 mm which is much more sensitive than 2-3 mm of ordinary human skin.