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Sensors detect a change in a physical parameter around them and convert it to a measurable signal that can be construed and analyzed for further applications such as automation, wearable devices, human-machine interfaces, and medical devices, among countless other applications. For example, sensors in the biomedical field help to detect the physiological course of a body. Conventionally sensors are produced using photolithography and screen printing. These conventional methods are limited by the complexity and flexibility in manufacturing the sensors. But, additive manufacturing presents a flexible option to produce the sensors and integrate them into structures as a single unit. This paper shows an extrusion-based 3D printing method to print sensors using conductive filaments. A comb-shaped capacitive sensor was 3D printed using commercially available conductive filament on a 3D printed PLA substrate. Printing two different materials with different properties always remains a challenge in FDM, so this paper also explains the stepwise process for printing a conductive composite material along with a thermoplastic. Further experimental characterization of the filament and sensor was also performed. This paper compares the electrical properties of the feedstock and 3D printed parts to understand the impact of extrusion on the material. A custom-made experimental setup was designed to characterize the sensor. One of the challenges is the low melting point of 3D printed parts, limiting their use to low-power applications. However, most biomedical sensing applications are low power, so these sensors remain suitable for such applications. Hence, in the end, the authors have explored the viability of the integration of these 3D printed sensors with medical implants to manufacture smart biomedical devices.
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