The intersection between nanoscience and additive manufacturing technology has resulted in a new field of printable and flexible electronics. This interesting area of research tackles the challenges in the development of novel materials and fabrication techniques towards a wider range and improved design of flexible electronic devices. This work presents the fabrication of a cost-effective and facile flexible piezoresistive pressure sensor using a 3D-printable carbon nanotube-based nanocomposite. The carbon nanotubes used for the development of the material are multi-walled carbon nanotubes (MWCNT) dispersed in polydimethylsiloxane (PDMS) prepolymer. The sensor was fabricated using the direct ink writing (DIW) technique (also referred to as robocasting). The MWCNT-PDMS composite was directly printed onto the polydimethylsiloxane substrate. The sensor response was then examined based on the resistance change to the applied load. The sensor exhibited high sensitivity (6.3 Ω/kPa) over a wide range of applied pressure (up to 1132 kPa); the highest observed measurement range for MWCNT-PDMS composite in previous work was 40 kPa. The formulated MWCNT-PDMS composite was also printed into high-resolution 3-dimensional shapes which maintained their form even after heat treatment process. The possibility to use 3D printing in the fabrication of flexible sensors allows design freedom and flexibility, and structural complexity with wide applications in wearable or implantable electronics for sport, automotive and biomedical fields.

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Additive fabrication use for the development of sensing devices with complex geometries is increasing constantly. Novel polymer-based materials with conductive properties are among the most investigated materials for soft electronics. In this study, we developed a fully additive-fabricated flexible contact pressure sensor using multi-material printing. The sensing part is a three-dimensional disc printed by extruding a multi-walled carbon nanotube-polymer composite using a laboratoryscale direct ink writing (DIW) process. The DIW process repeatability was studied, and it shows highly repeatable printing characteristics of the sensors. The pressure sensor response under compressive load was also investigated, showing that the sensor exhibited high sensitivity over a wide range of pressure and sensitivity to small increments of compressive force. The dynamic response of the sensor was also studied for different loading conditions where it showed good dynamic characteristics, and the sensor response-recovery time was 0.02 s.