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Design and Characterization of Electrically Driven-Bioinspired Soft Actuator based on Silicon- Ethanol Composite

Authors:
Amir Hossein Ebrahimi at Ferdowsi University Of Mashhad
Amir Hossein Ebrahimi
Hojat Zamyad at Ferdowsi University Of Mashhad
Hojat Zamyad
Javad Safaie at Ferdowsi University Of Mashhad
Javad Safaie
Samaneh Sahebian at Ferdowsi University Of Mashhad
Samaneh Sahebian
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Abstract

Manufacturing soft robots to mimic the natural movements of living organisms by controllable external stimuli required actuation systems like pneumatic, hydraulic, electrical, magnetic, and memory actuators. Inspired by natural muscles, a fast-responsive soft robot was fabricated by a polymer composite with a phase-change fluid as a secondary phase. The synthesis actuator can displace up to 25% (normal muscle tension), with a power equivalent to 12W. The microstructural observations show that the second phase is homogeneously distributed within microcapsules of less than 20 µm in size across the matrix. The stability of the internal temperature of the actuator in the range of 60-70°C during successive excitation cycles and the ability to achieve the desired amount of displacement allows the use of this soft robot in many areas.
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 
Design and Characterization of Electrically Driven-Bioinspired Soft Actuator based on Silicon-
Ethanol Composite
A. H. Ebrahimi H. Zamyad J. Safaie S. Sahebian
Abstract
Manufacturing soft robots to mimic the natural movements of living organisms by controllable external stimuli
required actuation systems like pneumatic, hydraulic, electrical, magnetic, and memory actuators. Inspired by
natural muscles, a fast-responsive soft robot was fabricated by a polymer composite with a phase-change fluid as
a secondary phase. The synthesis actuator can displace up to 25% (normal muscle tension), with a power
equivalent to 12W. The microstructural observations show that the second phase is homogeneously distributed
within microcapsules of less than 20 µm in size across the matrix. The stability of the internal temperature of the
actuator in the range of 60-70°C during successive excitation cycles and the ability to achieve the desired amount
of displacement allows the use of this soft robot in many areas.
Key Words Soft Robot, Artificial Muscle, Phase Change Fluid, Silicon, Ethanol




Email: S.Sahebian@um.ac.ir
DOI: 10.22067/jmme.2021.69610.1010


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

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
[1, 2]

  
    
[3]


  

[4,5]






[6,8]
  
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                                                    
 


  [9]

 
    
     
[10-12]
  
                        

     




                            
[13]

  
[14]




                           
  
   
[15,16]






    
                                       
                                            



[17-20]


[21-
25]Miriyev


 


[26]
   
   
    
  
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
    
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    
    
  
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                PMMA  
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Ωm 

  




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


 
  
FESEM,
MIRA3 TESCANKv
        
   



     R&S NGPV
Rohde & Schwarz

VA12W   

 pt1000 
   
Canon

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 


 
                  
 
ml 
 

 

  

     







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 
  



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                                       
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                                      



 
  

  



 
                                                 
C°

   






  

  


  

   
  

Miriyev    


[26]

 





 
   


  
                                                
 W 
 MiriyevW[26]


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


  
                                          
     
3.67gr                                     



 


   








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 
   











°C
                                       

   



 
 
mm
mm

 

gr
%
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

soft gripper




    
  
      


    


 
  
bending soft actuator
VA













 



  

                                                   
 s 
                                             




  





   



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mmmm


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Improving the Actuation Speed and Multi-Cyclic Actuation Characteristics of Silicone/Ethanol Soft Actuators
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  • Jul 2020
The actuation of silicone/ethanol soft composite material-actuators is based on the phase change of ethanol upon heating, followed by the expansion of the whole composite, exhibiting high actuation stress and strain. However, the low thermal conductivity of silicone rubber hinders uniform heating throughout the material, creating overheated damaged areas in the silicone matrix and accelerating ethanol evaporation. This limits the actuation speed and the total number of operation cycles of these thermally-driven soft actuators. In this paper, we showed that adding 8 wt.% of diamond nanoparticle-based thermally conductive filler increases the thermal conductivity (from 0.190 W/mK to 0.212 W/mK), actuation speed and amount of operation cycles of silicone/ethanol actuators, while not affecting the mechanical properties. We performed multi-cyclic actuation tests and showed that the faster and longer operation of 8 wt.% filler material-actuators allows collecting enough reliable data for computational methods to model further actuation behavior. We successfully implemented a long short-term memory (LSTM) neural network model to predict the actuation force exerted in a uniform multi-cyclic actuation experiment. This work paves the way for a broader implementation of soft thermally-driven actuators in various robotic applications.
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Low-Voltage-Driven Large-Amplitude Soft Actuators Based on Phase Transition
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A Focus on Soft Actuation
Article
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  • Oct 2019
The present editorial paper analyzes the hundred recent research works on soft actuation to understand the current main research focus in the light of the grand challenges in the field. Two characteristic paper types were obtained: one focuses on soft actuator design, manufacturing and demonstration, while another includes in addition the development of functional materials. Although vast majority of the works showcased soft actuation, evaluation of its robustness by multi-cyclic actuation was reported in less than 50% of the works, while only 10% described successful actuation for more than 1000 cycles. It is suggested that broadening the research focus to include investigation of mechanisms underlying the degradation of soft functional material performance in real cyclic actuation conditions, along with application of artificial intelligence methods for prediction of muscle behavior, may allow overcoming the reliability issues and developing robust soft-material actuators. The outcomes of the present work might be applicable to the entire soft robotics domain.
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Conductive Fabric Heaters for Heat-Activated Soft Actuators
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We examine electrically conductive fabrics as conductive heaters for heat-activated soft actuators. We have explored various fabric designs optimized for material properties, heat distribution and actuation/de-actuation characteristics of the soft actuators. We implemented this approach in the silicone/ethanol composite actuators, in which ethanol undergoes a thermally-induced phase change, leading to high actuation stress and strain. Various types of conductive fabrics were tested, and we developed a stretchable kirigami-based fabric design. We demonstrate a fabric heater that is capable of cyclic heating of the actuator to the required 80 °C. The fabric with the special kirigami design can withstand temperatures of up to 195 °C, can consume up to 30 W of power, and allows the actuator to reach >30% linear strain. This technology may be used in various systems involving thermally-induced actuation.
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Control Strategies for Soft Robotic Manipulators: A Survey
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  • Jan 2018
With the rise of soft robotics technology and applications, there have been increasing interests in the development of controllers appropriate for their particular design. Being fundamentally different from traditional rigid robots, there is still not a unified framework for the design, analysis, and control of these high-dimensional robots. This review article attempts to provide an insight into various controllers developed for continuum/soft robots as a guideline for future applications in the soft robotics field. A comprehensive assessment of various control strategies and an insight into the future areas of research in this field are presented.
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Additive Manufacturing of Silicone Composites for Soft Actuation
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  • Dec 2019
Elastomer composites have proven to be promising functional materials for soft actuators. Direct manufacturing of these materials is a practical prerequisite for Soft Robotics applications, where form and function are intricately entangled. In this article we show a multimaterial printer and associated processes for in situ fabrication of silicones and silicone-based elastomer composites for soft actuators. We discuss the fabrication process for both the silicone/ethanol composite material and encapsulating silicone skin using an inline passive mixing system, followed by characterization of the rheological and mechanical properties of the printed materials for various print modalities. Rheological study revealed the conditions, allowing continuous 3D printing of both small and big items out of silicone rubber and silicone/ethanol composite. Anisotropic mechanical properties allow for the design of functional characteristics of soft actuators by choosing print design modalities. We demonstrate a single-print-job additive manufacturing of functional multimaterial systems for soft actuation, and suggest that the developed processes will allow us to design soft robots with a broad range of actuation characteristics.
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Programmable Soft Robotics Based on Nano-Textured Thermo-Responsive Actuators
Article
  • Dec 2018
Soft robotic systems are increasingly emerging as robust alternatives to conventional robotics. Here we demonstrate the development of programmable soft actuators based on volume expansion/retraction accompanying liquid-vapor phase transition of a phase change material confined within an elastomer matrix. The combination of a soft matrix (a silicone-based elastomer) and the embedded ethanol-impregnated polyacrylonitrile nanofiber (PAN NF) mat makes it possible to form a sealed compound device that can be operated by changing the actuator temperature above/below than the boiling point of ethanol. The thermo-responsive actuators based on this principle demonstrate excellent bending ability at a sufficiently high temperature (> 90 °C) - comparable with compressed air based soft actuators. The actuator mechanism presented herein is easy to manufacture, easy to automate and recyclable. Finally, the actuation mechanism can be incorporated in wide variety of shapes and configurations making it possible to obtain tunable and programmable soft robots that could find application in wide variety of industrial applications.
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Rejuvenation of soft material–actuator
Article
  • Mar 2018
Akin to the natural tissues, soft artificial muscles possess a life cycle limited by aging and degradation phenomena. Here, we propose a rejuvenation method aimed at silicone-ethanol soft composite actuators, in which ethanol escape occurs during prolonged actuation, thus compromising their performance. The rejuvenation is achieved by immersion of the material–actuator in ethanol, allowing its diffusion into the silicone-based material until saturation. Repeatable rejuvenation of a soft robot, based on the soft material–actuator, resulted in retention of up to 100% of its functionality. Thus, we suggest that this method may be used for the rejuvenation of soft artificial muscles and material–actuators.
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Functional properties of silicone/ethanol soft-actuator composites
Article
  • Feb 2018
  • Mater Des
In the present work, we assess functional properties of silicone/ethanol elastomer composites, recently suggested by us as a novel approach to soft actuation. Our approach allows replacement of massive actuation solutions by self-contained composite material, thus making its detailed characterization extremely important. Here, we describe the composite actuation mechanism using microstructural, thermal and compositional analysis of the material comprising of 0–20 vol% ethanol. As a part of our investigation, we also performed mechanical testing aimed at determining the optimal composition, force and strain characteristics for soft actuation. Specifically, we examined the material performance in different soft actuation scenarios pertinent to the soft robotics applications, namely unidirectional piston-like actuator, and radially expanding McKibben artificial muscle. The results were compared in terms of the maximal force and strain developed in the linear portion of the force/time and strain/time scale. The effects of sample size and internal temperature on the mechanical properties of the material were also investigated. Based on the characterization findings, we formulated operational recommendations for utilizing the composites as soft actuators, and drew directions for the further research.
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Artificial Muscles: Mechanisms, Applications, and Challenges
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The area of artificial muscle is a highly interdisciplinary field of research that has evolved rapidly in the last 30 years. Recent advances in nanomaterial fabrication and characterization, specifically carbon nanotubes and nanowires, have had major contributions in the development of artificial muscles. However, what can artificial muscles really do for humans? This question is considered here by first examining nature's solutions to this design problem and then discussing the structure, actuation mechanism, applications, and limitations of recently developed artificial muscles, including highly oriented semicrystalline polymer fibers; nanocomposite actuators; twisted nanofiber yarns; thermally activated shape-memory alloys; ionic-polymer/metal composites; dielectric-elastomer actuators; conducting polymers; stimuli-responsive gels; piezoelectric, electrostrictive, magnetostrictive, and photostrictive actuators; photoexcited actuators; electrostatic actuators; and pneumatic actuators.
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