Magnetically controllable colloidal photonic crystals: unique features and intriguing applications

Magnetically induced self-assembly is a very powerful method that can quickly, efficiently and reversibly assemble magnetic colloidal particles into ordered structures with tunable photonic properties. The recent developments in the techniques have enabled convenient modulation of photonic properties and easy fabrication of sophisticated photonic structures. As a result, various practical applications such as magnetically controlled display units, photonic humidity sensors, reusable photonic paper/ink, photonic anti-counterfeiting, high resolution full-color photonic printing and invisible photonic printing have been demonstrated. In this feature article, we will describe these recent advances, with special focus on magnetically induced self-assembly of colloidal particles into 1D chainlike photonic structures, and discuss the emerging applications of this new technique.