Bending of N-Isopropylacrylamide Gel Under the Influence of Infrared Light

摘要

A CO2 infrared laser has been used to irradiate a straight cylindrical N-isopropylacrylamide gel. It is found that the infrared laser not only induces the volume phase transition in the gel, but also causes the gel to bend toward the laser beam. When the laser is blocked, the gel becomes straight again. The transition between the straight and the bending gel is fully reversible. The maximum bending strain of the gel is comparable to that obtained for poly(vinyl alcohol)-poly(sodium acrylate) copolymer gel under the influence of an electric field. The bending effect has been systematically studied as a function of CO2 laser power, time, and the sample cell temperature. The relaxation behavior for the gel restoring its original shape after blocking the infrared irradiation follows an exponential form. It is suggested that the bending effect is caused by a temperature gradient which produces an osmotic pressure difference between the front surface area of the gel and the remainder of the gel.