A Sensorized Soft Pneumatic Actuator Fabricated with Extrusion-Based Additive Manufacturing

Antonia Georgopoulou,Frank Clemens,Lukas Egloff,Bram Vanderborght

doi:10.3390/act10050102

Abstract

Soft pneumatic actuators with a channel network (pneu-net) based on thermoplastic elastomers are compatible with fused deposition modeling (FDM). However, conventional filament-based fused deposition modeling (FDM) printers are not well suited for thermoplastic elastomers with a shore hardness (Sh < 70A). Therefore, in this study, a pellet-based FDM printer was used to print pneumatic actuators with a shore hardness of Sh18A. Additionally, the method allowed the in situ integration of soft piezoresistive sensing elements during the fabrication. The integrated piezoresistive elements were based on conductive composites made of three different styrene-ethylene-butylene-styrene (SEBS) thermoplastic elastomers, each with a carbon black (CB) filler with a ratio of 1:1. The best sensor behavior was achieved by the SEBS material with a shore hardness of Sh50A. The dynamic and quasi-static sensor behavior were investigated on SEBS strips with integrated piezoresistive sensor composite material, and the results were compared with TPU strips from a previous study. Finally, the piezoresistive composite was used for the FDM printing of soft pneumatic actuators with a shore hardness of 18 A. It is worth mentioning that 3 h were needed for the fabrication of the soft pneumatic actuator with an integrated strain sensing element. In comparison to classical mold casting method, this is faster, since curing post-processing is not required and will help the industrialization of pneumatic actuator-based soft robotics.

Highlights

Based on the stress-strain curve (Figure 3a), it was seen that for all the different fibers, there was a characteristic necking around the yield point. This response has been seen before for composites based on thermoplastic elastomer (TPE) with high carbon black concentration [30] and it is worth mentioning that such a high loading is needed to achieve sufficient sensor properties [30]
The mechanical and electrical behavior do not correlate with the shore hardness of the SEBS matrix
A possible explanation could be found in the carbon black distribution inside the SEBS

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Soft robotics are increasing in popularity compared to their rigid counterparts and can be used in applications that require the careful manipulation of sensitive objects, safe interaction with the user and complex motion [1,2]. Pneumatic soft actuators are a type of soft robot modules in which the inflation of hollow sections, which are connected through a channel system (pneu-net), results in a bending of the elastomeric structure [3]. Very large deformations are exerted on the elastic inflatable actuators and to avoid high pressure, elastomers with low shore hardness, such as silicone elastomers, are preferred [4]

Methods

Results

Conclusion