Research On Preparation Techniques Of Inverse Opal Hydrogel Photonic Crystals

There are many natural opal photonic crystals in the world, which display vivid colour. They have attracted great interests and attention. The inverse opal can be obtained by replacing the particles in the opal with pore. It possesses characteristics of good connectivity, high porosity and strong periodicity. It has been widely studied to construct inverse opal hydrogels(IOHs) combining intelligent hydrogels that can response quickly to external stimuli with inverse opal recently.The measurement of temperature has always been a focus. As the development of engineering, the environment that we measure temperature is becoming more complicate, sometimes outdoor, sometimes in a narrow space, sometimes even in fluid environment which may corrode sensor. It is very difficult to measure temperature through traditional temperature sensor in environment mentioned before. In this paper, we prepare a novel material which is sensitive to temperature. Because the material possesses the characteristic of small size and portability, so it can overcome traditional sensor’s shortcoming, and measure temperature rapidly in complicated environment. It has potential applications in the preparation of new sensor.First, preparing colloidal crystal template using gravity sediment method and vertical deposition method, in which it is proved that vertical deposition method is much better than gravity sediment method. Changing the concentration of monodispersed silica nanospheres, well-structured template with about 20 layers has been formed when the concentration is 3.5wt%.The template is placed under 500℃ for 120 minutes to improve its strength. When the rising time from room temperature to 500°C is 150 minutes, it is clear that template is divided into many blocks by cracks formed in the heat treatment. When the rising time is increased to 300 minutes or 500 minutes, the number of cracks decrease dramatically, template’s ordering and integrity are improved. What’s more important, sinter necks have been formed in the heat treatment.Three different ways are used to prepare IOHs. The natural infiltration method is very difficult to obtain IOHs. The pressure method construct porous structure with only one layer, and there are many defects like fracture, unevenness and impurity. The sandwich method can prepare smooth, well-structured three dimensional IOHs through pressure and capillary force. In the removal of template, it is very important to control the corrosion time. If the time is too short, template can’t be corroded completely, but if it is too long, IOHs could be destroyed. As the cross-linker’s proportion in precursor solution decreases, the speed that hydrogels response to external stimuli will become faster, but unfortunately the mechanical strength will be impaired. On the contrary, if cross-linker’s proportion in precursor solution increases, the response speed may become a little slower, though the mechanical strength get improved greatly. Opal hydrogels and IOHs are placed into deionized water in various temperature. It is found two kinds of hydrogels both shrink as temperature rise, but the speed and amplitude that IOHs shrink are larger than opal hydrogels because of the porous structure. The diameters of IOHs in two different temperature are measured repeatedly. The deviation of diameter is small, which means the IOHs possess repeatability.