Polymer gels with engineered environmentally responsive microstructural surface patterns

Abstract

A class of hydrogels with microstructural surface arrays has been synthesized. The sputter-depositing method is used to imprint the surface of an N-isopropylacrylamide (NIPA) gel with a square array of a gold thin film. The periodicity of the array is about 20 μm and can be varied as a function of temperature or electric field. As the periodicity of the gel surface pattern changes in responsive to the external stimuli, the light diffraction pattern changes accordingly. It is demonstrated that the deformation of a gel under external force can be easily monitored using the gel with the periodic surface array. The temperature-responsive NIPA polymer gel is also deposited on the surface of another non- responsive gel using the method of photosensitized solution polymerization. The patterned area can be rendered invisible reversibly by switching the temperature above or below the low critical solution temperature of the NIPA gel. Furthermore, the patterned area can also change its hydrophilicity with the environment. The gels with engineered microstructural surface patterns may find applications in sensor and display technology.