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Pan Y, Liu XJ, Zhao H. Stretchable and conformable variable stiffness device through an electrorheological fluid. SOFT MATTER 2022; 18:9163-9171. [PMID: 36377854 DOI: 10.1039/d2sm01362b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Stiffness variations extend creatures' functions and capabilities to deal with complex environments. In this study, we proposed an electrorheological fluid-based variable stiffness device, named VSERF, made up of soft materials. Our device is soft, thin, and stretchable so that it can conform to surfaces with complex morphologies. The stiffness of the VSERF device can be continuously, independently, and reversibly adjusted by applying an electric field. It achieves 14.8-times compressive stiffness variation and 3.5-times tangential stiffness variation when the electric field intensity increases from 0 V mm-1 to 750 V mm-1. The VSERF device is able to return to its initial shape after removing the external force and electric field, allowing it to be reused. The effects of stretching and bending on the device's capability of stiffness variations are investigated experimentally and the results show that the stiffness variation is unaffected by a stretching strain of up to 20% and a bending curvature of up to 50 m-1. Finally, we show that the VSERF device is capable of conforming to complex surfaces (coral stones, pencils, and 3D printed cubes) in its inactive state, hanging on them with a weight of up to 80 g (19 times of its own weight) in its active state, and detaching when the electric field is removed. The device's short-term and long-term stabilities are experimentally investigated as well. The demonstration of the VSERF's attaching and detaching ability shows that the stiffness-variation device's adaptability to complex environments can be improved.
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Affiliation(s)
- Yiyi Pan
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Tribology in Advanced Equipment, Beijing 100084, China
- Beijing Key Lab of Precision/Ultra-Precision Manufacturing Equipment and Control, Beijing 100084, China.
| | - Xin-Jun Liu
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Tribology in Advanced Equipment, Beijing 100084, China
- Beijing Key Lab of Precision/Ultra-Precision Manufacturing Equipment and Control, Beijing 100084, China.
| | - Huichan Zhao
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Tribology in Advanced Equipment, Beijing 100084, China
- Beijing Key Lab of Precision/Ultra-Precision Manufacturing Equipment and Control, Beijing 100084, China.
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Chellattoan R, Lubineau G. A Stretchable Fiber with Tunable Stiffness for Programmable Shape Change of Soft Robots. Soft Robot 2022; 9:1052-1061. [PMID: 35049362 DOI: 10.1089/soro.2021.0032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
All soft robots require the same functionality, that is, controlling the shape of a structure made from soft materials. However, existing approaches for shape control of soft robots are primarily dominated by modular pneumatic actuators, which require multichambers and complex flow control components. Nature shows exciting examples of manipulation (shape change) in animals, such as worms, using a single-chambered soft body and programmable stiffness changes in the skin; controlling the spatial distribution of changes in stiffness enables achieving complex shape evolutions. However, such stiffness control requires a drastic membrane stiffness contrast between stiffened and nonstiffened states. Generally, this is extremely challenging to accomplish in stretchable materials. Inspired by longitudinal muscle fibers in the skin of worms, we developed a new concept for fabricating a hybrid fiber with tunable stiffness, that is, a fiber comprising both stiff and soft parts connected in a series. A substantial change in membrane stiffness was then observed by the locking/unlocking of the soft part. Our proposed hybrid fiber cyclically produced a membrane stiffness contrast of more than 100 × in less than 6 s using an input power of 3 W. A network of these hybrid fibers with tunable stiffness could manipulate a single-chambered soft body in multiple directions and transform it into a complex shape by selectively varying the stiffness at different locations.
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Affiliation(s)
- Ragesh Chellattoan
- Mechanics of Composites for Energy and Mobility Laboratory, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Gilles Lubineau
- Mechanics of Composites for Energy and Mobility Laboratory, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
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Novel bio-inspired variable stiffness soft actuator via fiber-reinforced dielectric elastomer, inspired by Octopus bimaculoides. INTEL SERV ROBOT 2021. [DOI: 10.1007/s11370-021-00388-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Levine DJ, Turner KT, Pikul JH. Materials with Electroprogrammable Stiffness. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2007952. [PMID: 34245062 DOI: 10.1002/adma.202007952] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/19/2021] [Indexed: 05/18/2023]
Abstract
Stiffness is a mechanical property of vital importance to any material system and is typically considered a static quantity. Recent work, however, has shown that novel materials with programmable stiffness can enhance the performance and simplify the design of engineered systems, such as morphing wings, robotic grippers, and wearable exoskeletons. For many of these applications, the ability to program stiffness with electrical activation is advantageous because of the natural compatibility with electrical sensing, control, and power networks ubiquitous in autonomous machines and robots. The numerous applications for materials with electrically driven stiffness modulation has driven a rapid increase in the number of publications in this field. Here, a comprehensive review of the available materials that realize electroprogrammable stiffness is provided, showing that all current approaches can be categorized as using electrostatics or electrically activated phase changes, and summarizing the advantages, limitations, and applications of these materials. Finally, a perspective identifies state-of-the-art trends and an outlook of future opportunities for the development and use of materials with electroprogrammable stiffness.
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Affiliation(s)
- David J Levine
- Department of Mechanical Engineering & Applied Mechanics, 220 S. 33rd St., Philadelphia, PA, 19104, USA
| | - Kevin T Turner
- Department of Mechanical Engineering & Applied Mechanics, 220 S. 33rd St., Philadelphia, PA, 19104, USA
| | - James H Pikul
- Department of Mechanical Engineering & Applied Mechanics, 220 S. 33rd St., Philadelphia, PA, 19104, USA
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Zhang Y, Zhang W, Yang J, Pu W. Bioinspired Soft Robotic Fingers with Sequential Motion Based on Tendon-Driven Mechanisms. Soft Robot 2021; 9:531-541. [PMID: 34115957 DOI: 10.1089/soro.2021.0009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The conformability is yet a challenge for most soft robotic grippers due to the continuous motion and deformation of these machines under external force. Herein, inspired by the movement mechanism of human fingers, we propose a novel tendon-driven soft robotic finger with a preprogrammed bending configuration and a human finger like sequential motion that can be obtained by matching the stiffness gradient of the finger joints with three-dimensional (3D) printing technology. The contents of this article are organized as follows. First, the effect of the anisotropy caused by 3D printing filling direction on the mechanical property is investigated by tensile test. Then, kinematic, stiffness, and fingertip trajectory models are established to analyze the influence of the cross-section thickness and width on the bending and bearing capacity of the finger joint. Furthermore, several experiments are conducted on a self-built experimental platform to evaluate the advantages of sequential motion induced by stiffness gradients. Results reveal that soft robotic fingers with sequential motion show excellent conformability on the object surfaces with various curvatures and outperform nonsequential motion fingers with larger envelop range. Without changing motion trajectories of the fingertip, the deformability of the finger can be tuned by adjusting only the stiffness of the joint. Besides, a two-finger gripper is developed, which presents the capability of grasping objects with different shapes and weights in practical applications. The sequential motion mechanism proposed in this study shows promising potential in soft grippers and robotic design.
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Affiliation(s)
- Yin Zhang
- School of Aeronautics and Astronautics, Sichuan University, Chengdu, China
| | - Wang Zhang
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Jialong Yang
- School of Aeronautics and Astronautics, Sichuan University, Chengdu, China
| | - Wei Pu
- School of Aeronautics and Astronautics, Sichuan University, Chengdu, China
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Wang D, Xu H, Wang J, Jiang C, Zhu X, Ge Q, Gu G. Design of 3D Printed Programmable Horseshoe Lattice Structures Based on a Phase-Evolution Model. ACS APPLIED MATERIALS & INTERFACES 2020; 12:22146-22156. [PMID: 32320209 DOI: 10.1021/acsami.0c04097] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
By 3D printing lattice structure with active materials, the structures can exhibit shape and functional changes under external stimulus. However, the programmable shape changes of the 3D printed lattice structures are limited due to the complex geometries, nonlinear behaviors of the active materials, and the diverse external stimuli. In this work, we propose a design framework combining experiments, theoretical modeling, and finite element simulations for the controllable shape changes of the 3D printed horseshoe under thermal stimulus. The theoretical model is based on a phase evolution model that combines the geometrical nonlinearity and the material nonlinearity. Results show that the shapes with positive or negative Poisson's ratio and bending intermediate shapes can be programmed by tuning the geometrical parameters and the temperature distribution. This work provides a method to aid the design of 3D printed functional lattice structures and have potential applications in soft robotics, biomedicine, and energy absorbing fields.
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Affiliation(s)
- Dong Wang
- Robotics Institute and State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Haipeng Xu
- Robotics Institute and State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jinqiang Wang
- Robotics Institute and State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Chengru Jiang
- Robotics Institute and State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiangyang Zhu
- Robotics Institute and State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qi Ge
- Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Guoying Gu
- Robotics Institute and State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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