# Soft Robotic Gripper with Chambered Fingers for Performing In-Hand Manipulation
## 1 Introduction  
Among many developments in the robotics field, the emergence of soft robotics has dispelled the conventional notion that a robot should be made of rigid materials. Soft robotics have mainly been inspired by muscular hydrostats or hydrostatic skeletons, which are found in the structures of plants and animals such as octopus, snout, snails, and so on [1]. The soft robot is operated pneumatically, hydraulically, or through variable length tendons, by exploiting the soft material's mechanical properties [2; 3]. Hard robots have features that pose risks to safety, and design structure flaws including heaviness, high cost, and low thermodynamic efficiency. Soft robots are capable of avoiding these limitations [4; 5; 6]. Soft robotics can be used in many fields. An assembled soft robotics gripper made by Soft Robotics Inc. is already being used in the food industry [7]. Depending on the application, a soft robotics gripper can be fabricated by putting several fingers together or fabricated as a single component. Researchers from Harvard have made a starfish-like soft gripper, which is inflated by a single air source. In that study, pneumatic networks called Pneunet chambers were developed, and inflating combinations of the chambers creates complex actuation [8]. All of the elements in this type of robot are actuated simultaneously because they are all supplied by a single air source. Another study presented a soft gripper, which was made by assembling soft actuators that can grasp various objects. This actuator has a bellow, and the study demonstrated a novel approach to actuation based on bellows geometry [9]. The most important factors for a soft actuator that are used in a soft robotic gripper are the air chamber's geometric shape and number of elements as well as the gripper's own structure [10; 11]. Researchers have investigated the structure of air chambers and performed a comparison using FEM analysis, finding that the biggest deformation occurred when the top wedged angle was 30\({}^{\circ}\). Also, a comparison of the width of the actuators determined that the thinnest one, at 0.012 m, was easier to actuate during inflation and deflation [12]. However, more air chambers will produce a higherdegree of freedom. If we apply pressure to all three chambers in a finger simultaneously, the finger will stretch. If one is filled with air, the finger bends, but if two chambers are inflated, it will bend in another direction [13,14]. Considering the material properties of soft actuators, a number of studies have demonstrated that the FEM method is the most appropriate method for analyzing their performance [15,16]. The soft robotic actuator is also more capable of mimicking the manipulation of a human hand compared to a hard robot [17]. Humans have the ability to grasp an object by using the fingers and palm and can translate it from finger to palm or from palm to the fingers, as well as rotate the object. This overall activity is known as \"In-Hand Manipulation\" [18,19]. In a previous study, researchers developed a soft robotics gripper with three chambers on each soft finger and with the help of flexible sensors, the gripper was able to identify an object's shape, resulting in reliable grasping [20]. Even though some studies have investigated soft robotics grippers with multiple chambers, few studies have examined how changing a longitudinal chamber's location and separation can affect the motion of a soft finger and gripper. In this work, we present a soft robotic gripper, which is able to grasp an object and rotate it (in-hand manipulation) effectively using a combination of three inflatable chambers in a finger. Initially, we compared models with two types of cross-sections and with different chamber locations. As a result, we chose a trapezoid cross-sectioned finger with asymmetrically located chambers. Secondly, we designed a soft gripper, consisting of three soft fingers; each soft finger contains three chambers.