Directly Printable Flexible Strain Sensors for Bending and Contact Feedback of Soft Actuators.

Khaled Elgeneidy,Gerhard Neumann,Niels Lohse,Michael Jackson

doi:10.3389/frobt.2018.00002

Abstract

This paper presents a fully printable sensorized bending actuator that can be calibrated to provide reliable bending feedback and simple contact detection. A soft bending actuator following a pleated morphology, as well as a flexible resistive strain sensor, were directly 3D printed using easily accessible FDM printer hardware with a dual-extrusion tool head. The flexible sensor was directly welded to the bending actuator’s body and systematically tested to characterize and evaluate its response under variable input pressure. A signal conditioning circuit was developed to enhance the quality of the sensory feedback, and flexible conductive threads were used for wiring. The sensorized actuator’s response was then calibrated using a vision system to convert the sensory readings to real bending angle values. The empirical relationship was derived using linear regression and validated at untrained input conditions to evaluate its accuracy. Furthermore, the sensorized actuator was tested in a constrained setup that prevents bending, to evaluate the potential of using the same sensor for simple contact detection by comparing the constrained and free-bending responses at the same input pressures. The results of this work demonstrated how a dual-extrusion FDM printing process can be tuned to directly print highly customizable flexible strain sensors that were able to provide reliable bending feedback and basic contact detection. The addition of such sensing capability to bending actuators enhances their functionality and reliability for applications such as controlled soft grasping, flexible wearables, and haptic devices.

Highlights

AND LITERATURE REVIEWSoft pneumatic actuators are being increasingly adopted in a wide range of applications that benefit from their inherently safe bodies and passive adaption to variations (Rus and Tolley, 2015; Hughes et al, 2016)
Examples of their diverse applications include an assistive soft glove for hand rehabilitation (Polygerinos et al, 2015), a soft robotic gripper for underwater sampling of delicate species (Galloway et al, 2016), a soft mobile robot that can adapt to varying environmental conditions (Tolley et al, 2014), an autonomous soft robotic fish capable of fast body motion (Marchese et al, 2014), a soft anthropomorphic hand that can achieve complex grasp types (Deimel and Brock, 2016), and a soft manipulator inspired by the octopus arms for minimally invasive surgeries (Cianchetti et al, 2014)
Our approach yields an all-printable sensorized soft actuator that can be customized based on the application needs

Summary

Introduction

Soft pneumatic actuators are being increasingly adopted in a wide range of applications that benefit from their inherently safe bodies and passive adaption to variations (Rus and Tolley, 2015; Hughes et al, 2016). Examples of their diverse applications include an assistive soft glove for hand rehabilitation (Polygerinos et al, 2015), a soft robotic gripper for underwater sampling of delicate species (Galloway et al, 2016), a soft mobile robot that can adapt to varying environmental conditions (Tolley et al, 2014), an autonomous soft robotic fish capable of fast body motion (Marchese et al, 2014), a soft anthropomorphic hand that can achieve complex grasp types (Deimel and Brock, 2016), and a soft manipulator inspired by the octopus arms for minimally invasive surgeries (Cianchetti et al, 2014). For seamless integration of sensors into soft-bodied actuators, innovative solutions for flexible and soft sensors are required for many interesting applications, as outlined in a recent review (Amjadi et al, 2016)

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Conclusion