Page 407 - IJB-9-3

International Journal of Bioprinting

RESEARCH ARTICLE
A bioinspired 3D-printable flexure joint with

cellular mechanical metamaterial architecture
for soft robotic hands

Alireza Mohammadi *, Elnaz Hajizadeh , Ying Tan , Peter Choong ,
1
2
1
1
Denny Oetomo 1
1 1Department of Mechanical Engineering, The University of Melbourne, Parkville, VIC 3010, Australia
2 Department of Surgery of University of Melbourne at St. Vincent’s Hospital, Fitzroy, VIC 3065,
Australia
(This article belongs to the Special Issue: Mechanical Behaviors of 3D/4D Printing Biomaterials
and Smart Structures)

Abstract

Compliant flexure joints have been widely used for cable-driven soft robotic hands
and grippers due to their safe interaction with humans and objects. This paper
presents a soft and compliant revolute flexure joint based on the auxetic cellular
mechanical metamaterials with a heterogeneous structure. The heterogeneous
architecture of the proposed metamaterial flexure joint (MFJ), which is inspired by the
human finger joints, provides mechanically tunable multi-stiffness bending motion
and large range of bending angle in comparison to conventional flexure joints. The
multi-level variation of the joint stiffness over the range of bending motion can be
tuned through the geometrical parameters of the cellular mechanical metamaterial
*Corresponding author:
Alireza Mohammadi unit cells. The proposed flexure joints are 3D printed with single flexible material in
(alirezam@unimelb.edu.au) monolithic fashion using a standard benchtop 3D printer. The application of the MFJ
Citation: Mohammadi A, is demonstrated in robotic in-hand manipulation and grasping thin and deformable
Hajizadeh E, Tan Y, et al., 2023, objects such as wires and cables. The results show the capability and advantages of
A bioinspired 3D-printable flexure joint the proposed MFJ in soft robotic grippers and highly functional bionic hands.
with cellular mechanical metamaterial
architecture for soft robotic hands. Int
J Bioprint, 9(3): 696.
https://doi.org/10.18063/ijb.696 Keywords: Soft robotics; Mechanical metamaterial; Architectured materials; 3D printing;
Additive manufacturing; Prosthetic hands
Received: October 22, 2022
Accepted: December 19, 2022
Published Online: March 1, 2023 1. Introduction
Copyright: © 2023 Author(s).
This is an Open Access article Compliant flexure joints are mechanisms that transfer force, motion, or energy through
distributed under the terms of the elastic deformation of their flexure elements, resulting in relative motion between two
Creative Commons Attribution links . Comparing to traditional joints, the compliant joints are hinge-less and can be
[1]
License, permitting distribution,
and reproduction in any medium, fabricated as a monolithic structure, which reduces friction, wear, and backlash in the
provided the original work is mechanism and enables compact and lightweight design . In soft robotic applications,
[2]
properly cited. the compliant flexure joints are manufactured with soft and flexible materials. The
Publisher’s Note: Whioce inherent material compliance in addition to compliant flexure joint designs provides
Publishing remains neutral with safer, cheaper, and simpler mechanisms (and consequently simpler control structures)
regard to jurisdictional claims in
[3]
published maps and institutional compared to their rigid counterparts . Due to these advantages, compliant flexure joints,
affiliations. in particular revolute pairs, have been widely used for soft robotic fingers with applications

Volume 9 Issue 3 (2023) 399 https://doi.org/10.18063/ijb.696