Smart biopolymer films show the autonomous response to external stimuli available in the surrounding atmosphere, such as humidity, water, vapour, light, heat, magnetic and electric fields. These stimuli-responsive systems have several applications ranging from soft robotics to targeted drug delivery. This work is based on water-responsive stimuli where a thin film bends (similar to well-known bimetallic strip) when one surface of the film is exposed to water. The fundamental mechanism for this bending is the development of a concentration gradient through the thickness which induces the eigen-strains in the thin film. However, when these films are immersed in water, both the top and bottom surfaces (through the thickness) are exposed to water resulting in no bending deformation thus making them not suitable for underwater applications. Because the concentration gradient develops from both the top and bottom surfaces which cancel the development of asymmetric concentration gradient through thickness resulting in no net bending deformation in this responsive layer. To mitigate this problem we propose a bilayer thin film which is made of hydrophilic (Chitosan) and hydrophobic (PMMA) biopolymers with a tunable interface to achieve the desired response. The hydrophilic polymer acts as the active layer and responds to water; on the other hand, the hydrophobic layer acts as a passive layer when submerged under water. The desired curvature and the speed of folding (actuation speed) can be controlled through the interface of the hydrophobic and hydrophilic layers. In this work, four types of interfaces, namely, strong, weak, weaker, and no interface (weakest interface) have been designed by changing the concentration of the bonding agent. The strong interface has the highest interfacial strength and hence gives permanent folding. Based on the experimental observations, a finite element model is developed incorporating the coupled chemo-mechanical behavior to mimic the self-folding in the bilayer thin film structure. We developed two methodologies to have a better understanding of the folding mechanism by altering the interface. We will discuss these two methodologies in this seminar.