I. Introduction
The prehensile nature of hands and feet of the primates, with an opposable thumb and toe, respectively, helps them to firmly hold and maneuver on the irregular surfaces of the trees and the branches [1], [2]. The prehensility function is crucial for stable locomotion, brachiation, suspension, foraging and so on, as described in [3]. Various robot designs have been proposed in the literature to emulate the biological systems, which are majorly composed of dedicated mechanisms for achieving locomotion and manipulation capability to suit different tasks and environments. Since our objective is functional mimicking of the prehensility found in primates and increasing versatility, our design approach does not involve replicating the biological form of the primate's hand. Instead, the prehensile functionality has been accomplished by introducing a pair of opposing spring-loaded shape conformable gripping surfaces that can passively conform to the object or substrate for improved stability, as shown in Fig. 1. The shape conformity enables it to grasp a substrate with different geometrical shapes and sizes and performs arm swinging motion without affecting the contact.