Fused filament fabrication for one shot additive manufacturing of capacitive force sensors

Additive manufacturing (AM) technologies have been largely used for the sensor fabrication: fused filament fabrication (FFF) technology is very appealing for the fabrication of embedded piezoresistive sensors into 3D printed structures (such as strain gauges) leading to the fabrication of smart objects. 3D printed structures with embedded sensors can be exploited for the fabrication of biosensor, pushing AM technologies towards a new biomanufacturing paradigm. In the present paper, a new kind of sensor has been fabricated through FFF technology and characterized: capacitive sensor for force/pressure detection. The advantages in the exploitation of FFF for capacitive sensors are several: i) only one manufacturing process is involved, ii) no-assembly tasks are required and, iii) they can be easily integrated into any kind of structure. Two commercial materials (conductive and flexible thermoplastic) have been used to fabricate the sensors in a monolithic way: a robust printing strategy has been used for the electrodes fabrication and three different infill patterns have been studied for the dielectric separator layer. The sensors have been characterized in a range of force of [0, 400] N showing good sensitivity and repeatability: this work paves the way for a large exploitation of FFF in the field of capacitive sensors.