Multi-Material 3D Printed Bendable Smart Sensing Structures

This paper presents a novel additive manufacturing method to obtain bendable smart sensing structures having printed strain sensors and interconnects to gain access to embedded electronic components. The presented smart structure is obtained by simultaneous printing of functional materials along with conventional polymer-based 3D printing materials. To this end, a low-cost open-source 3D printer was augmented with a silver palladium metallic paste extruder. The strain sensors in the presented 3D printed smart structure are particularly useful for wearable motion sensing applications such as knee joint motion analysis. The printed interconnects allow for electrical connection with the Light Emitting Diodes (LEDs) embedded within the 3D printed structure. With electronic components embedded in the flexible 3D printed structure, this work also demonstrates a novel method for soft packaging of electronic and sensing components. The electrical tests conducted on the smart structure show excellent electrical continuity. The 3D printed strain sensors, tested in static and dynamic bending conditions, showed a linear response of resistance. Under no strain, the resistance of the sensor was measured to be 0.9671 n (resistivity of 9.671×10
^-6
Ω.m) and during testing it exhibited a gauge factor of 1. Multi-material additive manufacturing demonstrated in this paper opens a new direction for fabrication of complex 3D structures with embedded sensors and electronics and offers significant advantages for rapid prototyping and packaging.