A Mechanized Air-Atomized Spray Coating Method for Fabricating Flexible Nanocomposite Piezoresistive Strain Sensors

Nanocomposite piezoresistive strain sensors have offered new avenues for strain measurement of structures with significant deformations, large geometries, or complex contours. The affordable and efficient spray coating technique, especially the air-atomized spray coating method, has considerable potential for batch production of such sensors. However, one of the most popular ways to fabricate sensors is manual spray coating, which not only has a low transfer efficiency (TE), resulting in material waste and environmental pollution, but also makes it challenging to precisely control the homogeneity of sensor coatings, leading to inconsistent quality of existing sprayed sensors. Therefore, a mechanized air-atomized spray coating method is proposed to actualize the stable batch production of sprayed sensors, and spraying parameters are then determined to establish proper process conditions. Carbon black (CB) nanoparticle-reinforced polyvinyl pyrrolidone (PVP) nanocomposites are prepared to fabricate CB/PVP strain sensors to validate the proposed method. Compared with the manual spray coating, the proposed method can manufacture CB/PVP coatings with uniform thickness distribution and micro-morphology. Additionally, the mechanical and electrical properties of CB/PVP nanocomposites are subsequently investigated to verify the consistency of coating quality using nanoindentation and four-probe techniques, respectively. Furthermore, the superior sensitivity and large strain range of CB/PVP strain sensors are evaluated by uniaxial tensile testing. In conclusion, the mechanized air-atomized spray coating method is not only time-saving, inexpensive, and straightforward to implement, but also features wide applicability due to minor requirements for nanocomposites, thus laying a foundation for batch production and popularization of nanocomposite piezoresistive strain sensors.