Research Projects

Kirigami is a Japanese art which involves strategically placed incisions on a planar sheet of a material, e.g. paper, metal foil, polymeric films, graphene and graphene oxide films, CNT nano-sheets and hydrogels. When an un-stretchable two-dimensional sheet decorated with parallel and/or cross incisions are subjected to uni-axial and/or bi-axial extension, it stretches out in a way that the portion of it, in-between the incisions, bends out-of-plane leading to a three-dimensional structure. On release of the load, the sheet shrinks back, although not completely to its original state. In essence, the kirigami incisions turns the 2D sheet into a three-dimensional stretchable, flexible material with negative Poisson ratio (auxetic). Kirigami inspired designs have been explored for many scientific and engineering applications, e.g. for fabricating engineering structures, which are ultra-light yet strong and possess excellent ability to absorb shock via redistribution of stresses, for making exotic optical materials: ones with transparency dynamically variable via adjustable diffraction of light, and materials having dynamically varying yet pigment-less color (structural color), materials having enhanced heat transfer efficiency and minimized thermal expansion, and even for making state-of-the-art applications like robotic skin for gripping and crawling. However, use of kirigami patterns in applications that directly involve phenomena at the surface of a material or at the interface of two different phases/materials have been minimal. In few applications where kirigami inspired designs have been used for this purpose, it is the easy stretchability and bendability of the material, that has been of primary interest. For example, adhesion of a pressure sensitive adhesive to a curved adherent surface has been facilitated by the kirigamy inspired design of the backing layer, and not the actual glue film per se. Similarly, in a fog collector, kirigami designs have been deployed to influence the air-flow pattern to increase the probability of collision of drops with the collector surface; the interface itself has not been altered by the kirigami design. Nor has there been any attempt to integrate kirigami designs with interfacial effects pertaining to soft materials like elastocapillary effect, surface instabilities, self-organization, surface defects and defect induced heterogeneous nucleation. In fact, when integrated with these effects Kirigami-inspired meta-structures can enhance and direct, both spatially and temporally, liquid spreading, wetting, drop motion, heat dissipation and mass and heat transfer between phases, which are of relevance in host of practical applications. It is to address these knowledge gaps, there is a need to work on this rich field of research, integrate it with conventional methods of surface and interfacial engineering and exploit its dynamic tunability to direct variety of interfacial effects and engineering applications.