Flexible polymer micropattern with thermochromic property

3D micropatterns with diverse functionalities have attracted significant attention in various fields including sensor, display, and biomedical fields. In this study, we suggest a facile 3D micropatterning process using flexible polymer microfiber displaying thermochromic property. 3D structure composed of thermoplastic polyurethane microfibers were stably manufactured by charge reversed electrohydrodynamic jetting method using a conventional 3D printer. After introducing commercial thermochromic pigments into polymer microfiber, vivid color changes were clearly observed with naked eye in 3D structures reversibly depending on the temperature changes and structure diversity. Multiple color transitions in a single structure can also be expressed by simply mixing different colored thermochromic pigments with different color change temperature, and same process can be implemented through the fabrication of biphasic microfiber that can utilize material diversity. Moreover, desired pattern can be highlighted or concealed by using same colored pigments that have different thermochromic temperature, and color transition occurred stably even in the stretched states. Not only by direct heating process, other stimuli such as electric energy can cause thermochromic reaction by Joule heating. In addition, simultaneous addition of UV-responsive material can further expand the scope of applications to anti-counterfeiting and encryption. These thermochromic flexible patterns, which can be fabricated as desired pattern, are expected to be applied in diverse areas such as attachable patch, sensor and anti-counterfeiting.