Induced by a Single Ar Laser Beam

The samples used for the single laser beam irradiation experiments were the same as those discussed in Section 5.4.1. An Ar laser at 488 nm was used as the light source, and the linearly polarized laser beam was spatially filtered, expanded, and collimated. The intensity of the laser beam was 150mW/cm, and the incident laser beam was perpendicular to the wafer surfaces containing the colloids. The experiments were carried out at room temperature under an ambient condition. In a typical case, colloidal spheres of BP-AZ-CA were used for the test, and the result is as follows. 

The exact mechanism of the deformation induced by the laser single beam is still not clear. In the experiment, the light intensity of the spatially filtered and collimated laser beam (1.5 cm in diameter) should be uniform in submicrometer size. This phenomenon has been further confirmed in another type of colloid composed of well-defined polymeric chains (Lambeth and Moore, 2007). Such observations carmot be directly explained by using the gradient force of the laser irradiation. More investigations, both through theoretical and experimental approaches, seem to be required to understand this unusual photoresponsive elfect. 

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