Bioinspired Robotic Fingers Based on Pneumatic Actuator and 3D Printing of Smart Material

Abstract

In this article, we have proposed a novel robotic finger design principle aimed to address two challenges in soft pneumatic grippers-the controllability of the stiffness and the controllability of the bending position. The proposed finger design is composed of a 3D printed multimaterial substrate and a soft pneumatic actuator. The substrate has four polylactic acid (PLA) segments interlocked with three shape memory polymer (SMP) joints, inspired by bones and joints in human fingers. By controlling the thermal energy of an SMP joint, the stiffness of the joints is modulated due to the dramatic change in SMP elastic modulus around its glass transition temperature (T). When SMP joints are heated above T, they exhibit very small stiffness, allowing the finger to easily bend around the SMP joints if the attached soft actuator is actuated. When there is no force from the soft actuator, shape recovery stress in SMP contributes to the finger's shape restoration. Since each joint's rotation can be individually controlled, the position control of the finger is made possible. Experimental analysis has been conducted to show the finger's variable stiffness and the result is compared with the analytical values. It is found that the stiffness ratio can be 24.9 times for a joint at room temperature (20°C) and at an elevated temperature of 60°C when air pressure p of the soft actuator is turned off. Finally, a gripper composed of two fingers is fabricated for demonstration.

Principles and methods for stiffness modulation in soft robot design and development

“…The whole hyper-redundant arm could be printed with a consumer-grade 3D printer. In their subsequent research, variable stiffness soft fingers were developed using SMP for stiffness tuning and bending shape control [13,14]. They attempted heating SMP materials with integrated pin heaters [13] and with conductive elastomers [14].…”

“…In their subsequent research, variable stiffness soft fingers were developed using SMP for stiffness tuning and bending shape control [13,14]. They attempted heating SMP materials with integrated pin heaters [13] and with conductive elastomers [14]. The main novelty of using conductive elastomers was that they could not only provide Joule heating for the SMP part but also enable the finger joint with position feedback capability.…”

“…What's more, we will also present a possible alternative for stiffness modulation in soft robotic design and development. Gripper [13], robotic origami [15], legged robot [22] and load bearing functional part [16,23] Viscosity-based methods Electric/magnetic field Viscosity change ERF, MRF, electroactive gel…”

Performance Optimization of Polymer Fibre Actuators for Soft Robotics

“…The rise of the 3D printer and drops in the cost of traditional manufacturing methods have led to significant expansion in the soft-robotics industry [13][14][15][16][17][18][19][20]. The commercial space has rapidly adopted pneumatic claws where there is a demand for delicate handling of goods, like the handling of fruits and delicate parcels.…”

Low Cost Soft Robotic Gloves for At-home Rehabilitation and Daily Living Activities

“…SMA actuators have high operating temperatures ranging from (100°C-500°C). Complex design of SMA actuators made it difficult to use in rehabilitation purposes and daily living activities [64][65][66][67][68]. Pneumatic actuators were selected due to higher stiffness, low weight and simpler design as compared to above mentioned actuators.…”