A multi-material robotic finger with integrated proprioceptive and tactile capabilities produced with a circular process

When developing or designing biomimetic robotic fingers with rigid and soft components and integrated sensors, fabrication is often a bottle-neck when assembling and casting processing techniques are used. This study introduces a thermoplastic multi-material fabrication approach that allows the printing of fingers with incorporated sensing elements in a single shot. Thermoplastics and thermoplastic elastomers based materials have been selected to demonstrate the circular fabrication process. To exhibit the potential of the method, a sensorized multi-material finger was fabricated using polypropylene (PP) for the rigid bone, styrene-based tri-block co-polymer (TPS) for the soft skin and resistive composites based on TPS and carbon black (CB) for the sensing. The 3D printer was equipped with combined pellet- and filament-based extruders to enable the combined fabrication processing of the materials without additional assembling. This allowed the exploration of a range of designs with different geometric and infill properties. To demonstrate the circular process, the fabricated fingers were recycled and the mechanical properties did not result in a visible degradation. The described multi-material fabrication of soft robotic components allows time efficiency of the production method and the reusability of the materials, which contribute to establishing a sustainable circular process in the future.