Self-encapsulated hollow microstructures formed by electric field-assisted capillarity

Hollow microstructures serve many useful applications in the fields of microsystems, chemistry, photonics, biology and others. Current fabrication methods of artificial hollow microstructures require multiple fabrication steps and expensive manufacturing tools. The paper reports a unique one-step fabrication process for the growth of hollow polymeric microstructures based on electric field-assisted capillary action. This method demonstrates the manufacturing of self-encapsulated microstructures such as hollow microchannels and microcapsules of around 100-μm height from an initial polymer thickness of 22 μm. Microstructure caps of several microns thickness have been shown to keep their shape under bending or delamination from the substrate. The inner surface of hollow microstructures is shown to be smooth, which is difficult to achieve with current methods. More complicated structures, such as a microcapsule array connected with hollow microchannels, have also been manufactured with this method. Numerical simulation of the resist growth process using COMSOL Multiphysics finite element analysis software has resulted in good agreement between simulated and experimental results on the overall shape of the resulting structures. These results are very positive and demonstrate the speed, versatility and cost-effectiveness of the method.