Abstract
In recent years, soft pneumatic actuators have come into the spotlight because of their simple control and the wide range of complex motions. To monitor the deformation of soft robotic systems, elastomer-based sensors are being used. However, the embedding of sensors into soft actuator modules by polymer casting is time consuming and difficult to upscale. In this study, it is shown how a pneumatic bending actuator with an integrated sensing element can be produced using an extrusion-based additive manufacturing method, e.g., fused deposition modeling (FDM). The advantage of FDM against direct printing or robocasting is the significantly higher resolution and the ability to print large objectives in a short amount of time. New, commercial launched, pellet-based FDM printers are able to 3D print thermoplastic elastomers of low shore hardness that are required for soft robotic applications, to avoid high pressure for activation. A soft pneumatic actuator with the in situ integrated piezoresistive sensor element was successfully printed using a commercial styrene-based thermoplastic elastomer (TPS) and a developed TPS/carbon black (CB) sensor composite. It has been demonstrated that the integrated sensing elements could monitor the deformation of the pneumatic soft robotic actuator. The findings of this study contribute to extending the applicability of additive manufacturing for integrated soft sensors in large soft robotic systems.
Highlights
The integration of piezoresistive elastomer strain sensors in soft robotic actuators enables the monitoring of the deformation and motion of the robotic modules
Bucking occurred for the Fused deposition modeling (FDM) printed thermoplastic elastomer (TPS) strips at 57% strain
For the bending actuator, a negative piezoresistive behavior of the sensor was observed because tIhne sthenissosrtueldemy,eTntPwSatsenusseildeisntrciopmsparnesdsioansmofotdpen. eTuhme raetsiucl-tbsaasreedprboemnidsiinngg, baucttuthaetor with integsreantseodr rpesipezonosreeshiasstitvoebeseimnspilnegmeenletemdeinnttos awnearcetusauticocneaslsgfourliltyhmfatboriaccahtieevdeuclsoinsegdalomopulti-materiaalupteolnloemt-bouasesdoftFrDobMotpicrsitnrtuecrtu
Summary
The integration of piezoresistive elastomer strain sensors in soft robotic actuators enables the monitoring of the deformation and motion of the robotic modules. Integrating piezoresistive elastomer-based sensing elements in soft robots using conventional casting methods is time consuming and difficult for automatized fabrication. FDM is compatible with conductive composites based on thermoplastic elastomers and carbon fillers [3]. It is well-known that in order to achieve good piezoresistive properties, a high concentration of conductive filler is required [4]. Because of high filler concentration, the filaments become brittle and commercial FDM printers cannot be used anymore. Commercial launched, pellet-based printers are able to print brittle materials and can be used to fabricate soft robotic actuators with integrated sensing elements
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